What is the basis for the determining sex from position of adult pelvis?

What is the basis for the determining sex from position of adult pelvis?

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I've read that a person with enough knowledge of anatomy can tell the difference between a "woman" who is a slim man that is very good with makeup and an actual woman.

They usually claim to be able to tell the difference between the two by certain things like digit ratios and pelvic position. Is there any basis to these claims? The one I'm specifically interested in is the "position of the pelvis", as that is the most recent example of the claim I've seen. This is a direct quote from a novel that I'm reading.

EDIT: it looks like I phrased the question badly. As anongoodnurse stated, I'd like to know if there's any basis for telling if a living person is a man or a woman by looking at them.

An example is if you dress up a slim man with a feminine looking face, get a make up artist to make the face look like a very attractive woman, and put that man in a little black dress, would a person knowledgeable about human anatomy, for example a GP MD, OBGYN, mortician, or Sherlock Holmes (kidding), is there any basis for that person to be able to say: "nope, that's a dude".

"Position of the pelvis" is pretty vague, but there are very clear differences in pelvic morphology between females and males. This sexual dimorphism looks like:

Female pelves are wider and flatter, which I think you could tell from surface anatomy. Of course if you could palpate, then you could tell for sure.

Sex differences in humans

Sex differences in humans have been studied in a variety of fields. Sex determination occurs solely by the presence or absence of a Y chromosome. Phenotypic sex refers to an individual's sex as determined by their internal and external genitalia, expression of secondary sex characteristics, and behavior. [1]

The sex of the individual can be defined in different ways, giving rise to different conceptual frameworks about what determines sex. [2] Sex differences generally refer to traits that are sexually dimorphic. A subset of such differences is hypothesized to be the product of the evolutionary process of sexual selection. [3] [4]

Patient discussion about sex

Q. Is it safe to have sex with my pregnant wife? My wife and I are 4 months pregnant and are expecting our first baby. Can we have sex? I am afraid it will harm the baby.

Q. sex after giving birth My baby (Shelly) is three months now. Me and my husband tried having sex a couple of times since she was born, but the intercourse just hurts too much. Is this normal? I heard that sometimes when you get cuts during the birth they sew you too tight. Can it be the case? And if so, is this permanent or will it get better?

A. as long as the wound is already recovered, I think you can start the sexual activities. But again it depends on every person, I think scoote had given us a good example for that.
In case you still feel some discomfort and even hurt sensation down there, it is advisable to go see your doctor, just to check.

Meanwhile, enjoy your life and my greeting for baby Shelly..

Q. Is it safe to have sex with a woman with cancer of the uterus? My 45-years old wife was told she have cancer in the uterus, and will have an operation soon. Meanwhile, should we use a condom during sex? Can the tumor pass from her to me (like AIDS or HPV)?

The Philosophical Contradictions of the Transgender Worldview

People say that we live in a postmodern age that has rejected metaphysics. That’s not quite true. We live in a postmodern age that promotes an alternative metaphysics. As I explain in When Harry Became Sally, at the heart of the transgender moment are radical ideas about the human person—in particular, that people are what they claim to be, regardless of contrary evidence. A transgender boy is a boy, not merely a girl who identifies as a boy. It’s understandable why activists make these claims. An argument about transgender identities will be much more persuasive if it concerns who someone is, not merely how someone identifies. And so the rhetoric of the transgender moment drips with ontological assertions: people are the gender they prefer to be. That’s the claim.

Transgender activists don’t admit that this is a metaphysical claim. They don’t want to have the debate on the level of philosophy, so they dress it up as a scientific and medical claim. And they’ve co-opted many professional associations for their cause. Thus the American Psychological Association, in a pamphlet titled “Answers to Your Questions about Transgender People, Gender Identity, and Gender Expression,” tells us, “Transgender is an umbrella term for persons whose gender identity, gender expression, or behavior does not conform to that typically associated with the sex to which they were assigned at birth.” Notice the politicized language: a person’s sex is “assigned at birth.” Back in 2005, even the Human Rights Campaign referred instead to “birth sex” and “physical sex.”

The phrase “sex assigned at birth” is now favored because it makes room for “gender identity” as the real basis of a person’s sex. In an expert declaration to a federal district court in North Carolina concerning H.B. 2, Dr. Deanna Adkins stated, “From a medical perspective, the appropriate determinant of sex is gender identity.” Dr. Adkins is a professor at Duke University School of Medicine and the director of the Duke Center for Child and Adolescent Gender Care (which opened in 2015). Adkins argues that gender identity is not only the preferred basis for determining sex, but “the only medically supported determinant of sex.” Every other method is bad science, she claims: “It is counter to medical science to use chromosomes, hormones, internal reproductive organs, external genitalia, or secondary sex characteristics to override gender identity for purposes of classifying someone as male or female.”

This is a remarkable claim, not least because the argument recently was that gender is only a social construct, while sex is a biological reality. Now, activists claim that gender identity is destiny, while biological sex is the social construct.

Adkins doesn’t say whether she would apply this rule to all mammalian species. But why should sex be determined differently in humans than in other mammals? And if medical science holds that gender identity determines sex in humans, what does this mean for the use of medicinal agents that have different effects on males and females? Does the proper dosage of medicine depend on the patient’s sex, or on his or her gender identity?

But what exactly is this “gender identity” that is supposed to be the true medical determinant of sex? Adkins defines it as “a person’s inner sense of belonging to a particular gender, such as male or female.” Note that little phrase “such as,” implying that the options are not necessarily limited to male or female. Other activists are more forthcoming in admitting that gender identity need not be restricted to the binary choice of male or female, but can include both or neither. The American Psychological Association, for example, defines “gender identity” as “a person’s internal sense of being male, female, or something else.”

Adkins asserts that being transgender is not a mental disorder, but simply “a normal developmental variation.” And she claims, further, that medical and mental health professionals who specialize in the treatment of gender dysphoria are in agreement with this view.

Transgender Catechism

These notions about sex and gender are now being taught to young children. Activists have created child-friendly graphics for this purpose, such as the “Genderbread Person.” The Genderbread Person teaches that when it comes to sexuality and gender, people have five different characteristics, each of them falling along a spectrum.

There’s “gender identity,” which is “how you, in your head, define your gender, based on how much you align (or don’t align) with what you understand to be the options for gender.” The graphic lists “4 (of infinite)” possibilities for gender identity: “woman-ness,” “man-ness,” “two-spirit,” or “genderqueer.”

The second characteristic is “gender expression,” which is “the way you present gender, through your actions, dress, and demeanor.” In addition to “feminine” or “masculine,” the options are “butch,” “femme,” “androgynous,” or “gender neutral.”

Third is “biological sex,” defined as “the physical sex characteristics you’re born with and develop, including genitalia, body shape, voice pitch, body hair hormones, chromosomes, etc.”

The final two characteristics concern sexual orientation: “sexually attracted to” and “romantically attracted to.” The options include “Women/Females/Femininity” and “Men/Males/Masculinity.” Which seems rather binary.

The Genderbread Person tries to localize these five characteristics on the body: gender identity in the brain, sexual and romantic attraction in the heart, biological sex in the pelvis, and gender expression everywhere.

The Genderbread Person presented here is version 3.3, incorporating adjustments made in response to criticism of earlier versions. But even this one violates current dogma. Some activists have complained that the Genderbread Person looks overly male.

A more serious fault in the eyes of many activists is the use of the term “biological sex.” Time magazine drew criticism for the same transgression in 2014 after publishing a profile of Laverne Cox, the “first out trans person” to be featured on the cover. At least the folks at Time got credit for trying to be “good allies, explaining what many see as a complicated issue,” wrote Mey Rude in an article titled “It’s Time for People to Stop Using the Social Construct of ‘Biological Sex’ to Defend Their Transmisogyny.” (It’s hard to keep up with the transgender moment.) But Time was judged guilty of using “a simplistic and outdated understanding of biology to perpetuate some very dangerous ideas about trans women,” and failing to acknowledge that biological sex “isn’t something we’re actually born with, it’s something that doctors or our parents assign us at birth.”

Today, transgender “allies” in good standing don’t use the Genderbread Person in their classrooms, but opt for the “Gender Unicorn,” which was created by Trans Students Educational Resources (TSER). It has a body shape that doesn’t appear either male or female, and instead of a “biological sex” it has a “sex assigned at birth.” Those are the significant changes to the Genderbread Person, and they were made so that the new graphic would “more accurately portray the distinction between gender, sex assigned at birth, and sexuality.”

According to TSER, “Biological sex is an ambiguous word that has no scale and no meaning besides that it is related to some sex characteristics. It is also harmful to trans people. Instead, we prefer ‘sex assigned at birth’ which provides a more accurate description of what biological sex may be trying to communicate.” The Gender Unicorn is the graphic that children are likely to encounter in school. These are the dogmas they are likely to be catechized to profess.

While activists claim that the possibilities for gender identity are rather expansive—man, woman, both, neither—they also insist that gender identity is innate, or established at a very young age, and thereafter immutable. Dr. George Brown, a professor of psychiatry and a three-time board member of the World Professional Association for Transgender Health (WPATH), stated in his declaration to the federal court in North Carolina that gender identity “is usually established early in life, by the age of two to three years old.” Addressing the same court, Dr. Adkins asserted that “evidence strongly suggests that gender identity is innate or fixed at a young age and that gender identity has a strong biological basis.” (At no point in her expert declaration did she cite any sources for any of her claims.)

Transgender Contradictions

If the claims presented in this essay strike you as confusing, you’re not alone. The thinking of transgender activists is inherently confused and filled with internal contradictions. Activists never acknowledge those contradictions. Instead, they opportunistically rely on whichever claim is useful at any given moment.

Here I’m talking about transgender activists. Most people who suffer from gender dysphoria are not activists, and many of them reject the activists’ claims. Many of them may be regarded as victims of the activists, as I show in my book. Many of those who feel distress over their bodily sex know that they aren’t really the opposite sex, and do not wish to “transition.” They wish to receive help in coming to identify with and accept their bodily self. They don’t think their feelings of gender dysphoria define reality.

But transgender activists do. Regardless of whether they identify as “cisgender” or “transgender,” the activists promote a highly subjective and incoherent worldview.

On the one hand, they claim that the real self is something other than the physical body, in a new form of Gnostic dualism, yet at the same time they embrace a materialist philosophy in which only the material world exists. They say that gender is purely a social construct, while asserting that a person can be “trapped” in the wrong gender. They say that there are no meaningful differences between man and woman, yet they rely on rigid sex stereotypes to argue that “gender identity” is real, while human embodiment is not. They claim that truth is whatever a person says it is, yet they believe there’s a real self to be discovered inside that person. They promote a radical expressive individualism in which people are free to do whatever they want and define the truth however they wish, yet they try ruthlessly to enforce acceptance of transgender ideology.

It’s hard to see how these contradictory positions can be combined. If you pull too hard on any one thread of transgender ideology, the whole tapestry comes unraveled. But here are some questions we can pose:

If gender is a social construct, how can gender identity be innate and immutable? How can one’s identity with respect to a social construct be determined by biology in the womb? How can one’s identity be unchangeable (immutable) with respect to an ever-changing social construct? And if gender identity is innate, how can it be “fluid”? The challenge for activists is to offer a plausible definition of gender and gender identity that is independent of bodily sex.

Is there a gender binary or not? Somehow, it both does and does not exist, according to transgender activists. If the categories of “man” and “woman” are objective enough that people can identify as, and be, men and women, how can gender also be a spectrum, where people can identify as, and be, both, or neither, or somewhere in between?

What does it even mean to have an internal sense of gender? What does gender feel like? What meaning can we give to the concept of sex or gender—and thus what internal “sense” can we have of gender—apart from having a body of a particular sex? Apart from having a male body, what does it “feel like” to be a man? Apart from having a female body, what does it “feel like” to be a woman? What does it feel like to be both a man and a woman, or to be neither? The challenge for the transgender activist is to explain what these feelings are like, and how someone could know if he or she “feels like” the opposite sex, or neither, or both.

Even if trans activists could answer these questions about feelings, that still wouldn’t address the matter of reality. Why should feeling like a man—whatever that means—make someone a man? Why do our feelings determine reality on the question of sex, but on little else? Our feelings don’t determine our age or our height. And few people buy into Rachel Dolezal’s claim to identify as a black woman, since she is clearly not. If those who identify as transgender are the sex with which they identify, why doesn’t that apply to other attributes or categories of being? What about people who identify as animals, or able-bodied people who identify as disabled? Do all of these self-professed identities determine reality? If not, why not? And should these people receive medical treatment to transform their bodies to accord with their minds? Why accept transgender “reality,” but not trans-racial, trans-species, and trans-abled reality? The challenge for activists is to explain why a person’s “real” sex is determined by an inner “gender identity,” but age and height and race and species are not determined by an inner sense of identity.

Of course, a transgender activist could reply that an “identity” is, by definition, just an inner sense of self. But if that’s the case, gender identity is merely a disclosure of how one feels. Saying that someone is transgender, then, says only that the person has feelings that he or she is the opposite sex. Gender identity, so understood, has no bearing at all on the meaning of “sex” or anything else. But transgender activists claim that a person’s self-professed “gender identity” is that person’s “sex.” The challenge for activists is to explain why the mere feeling of being male or female (or both or neither) makes someone male or female (or both or neither).

Gender identity can sound a lot like religious identity, which is determined by beliefs. But those beliefs don’t determine reality. Someone who identifies as a Christian believes that Jesus is the Christ. Someone who identifies as a Muslim believes that Muhammad is the Final Prophet. But Jesus either is or is not the Christ, and Muhammad either is or is not the Final Prophet, regardless of what anyone happens to believe. So, too, a person either is or is not a man, regardless of what anyone—including that person—happens to believe. The challenge for transgender activists is to present an argument for why transgender beliefs determine reality.

Determining reality is the heart of the matter, and here too we find contradictions. On the one hand, transgender activists want the authority of science as they make metaphysical claims, saying that science reveals gender identity to be innate and unchanging. On the other hand, they deny that biology is destiny, insisting that people are free to be who they want to be. Which is it? Is our gender identity biologically determined and immutable, or self-created and changeable? If the former, how do we account for people whose gender identity changes over time? Do these people have the wrong sense of gender at some time or other? And if gender identity is self-created, why must other people accept it as reality? If we should be free to choose our own gender reality, why can some people impose their idea of reality on others just because they identify as transgender? The challenge for the transgender activist is to articulate some conception of truth as the basis for how we understand the common good and how society should be ordered.

As I document in depth in When Harry Became Sally, the claims of transgender activists are confusing because they are philosophically incoherent. Activists rely on contradictory claims as needed to advance their position, but their ideology keeps evolving, so that even allies and LGBT organizations can get left behind as “progress” marches on. At the core of the ideology is the radical claim that feelings determine reality. From this idea come extreme demands for society to play along with subjective reality claims. Trans ideologues ignore contrary evidence and competing interests they disparage alternative practices and they aim to muffle skeptical voices and shut down any disagreement. The movement has to keep patching and shoring up its beliefs, policing the faithful, coercing the heretics, and punishing apostates, because as soon as its furious efforts flag for a moment or someone successfully stands up to it, the whole charade is exposed. That’s what happens when your dogmas are so contrary to obvious, basic, everyday truths. A transgender future is not the “right side of history,” yet activists have convinced the most powerful sectors of our society to acquiesce to their demands. While the claims they make are manifestly false, it will take real work to prevent the spread of these harmful ideas.

Related Posts

I have personally experienced gender dysphoria, and I explored transition in my early twenties. I&hellip


We thank the Center for Academic Research and Training in Anthropology, the Primate Research Institute of the University of Kyoto, F. Zachos (Mammal Collection, Natural History Museum Vienna), M. Häusler, C. Fornai and V. Krenn (University of Zurich and University of Vienna) for access to the chimpanzee pelves. We thank H. Reynolds for sharing the human landmark data. B.F. and P.M. acknowledge support from the Austrian Science Fund FWF (Elise Richter grant no. V-826 to B.F., grant no. P29397 to P.M.). N.D.S.G. was funded by a postdoctoral fellowship from the Konrad Lorenz Institute. E.Z. was supported by an Erasmus+ student exchange fellowship from the European Union.

Adult Positions

These are the Adult Official Positions of the ISCD as updated in 2019.

Indications for Bone Mineral Density (BMD) Testing

  • Women aged 65 and older
  • For post-menopausal women younger than age 65 a bone density test is indicated if they have a risk factor for low bone mass such as:
    • Low body weight
    • Prior fracture
    • High risk medication use
    • Disease or condition associated with bone loss
    • Low body weight
    • Prior fracture
    • High risk medication use
    • Disease or condition associated with bone loss

    Women discontinuing estrogen should be considered for bone density testing according to the indications listed above.

    Reference Database for T-Scores

    • Use a uniform Caucasian (non-race adjusted) female normative database for women of all ethnic groups.*
    • Use a uniform Caucasian (non-race adjusted) female reference for men of all ethnic groups.*
    • Manufacturers should continue to use NHANES III data as the reference standard for femoral neck and total hip T-scores.
    • Manufacturers should continue to use their own databases for the lumbar spine as the reference standard for T-scores.
    • If local reference data are available they should be used to calculate only Z-scores but not T-scores.

    *Note: Application of recommendation may vary according to local requirements.

    Central DXA for Diagnosis

    • The WHO international reference standard for osteoporosis diagnosis is a T-score of -2.5 or less at the femoral neck.
      • The reference standard from which the T-score is calculated is the female, white, age 20-29 years, NHANES III database.
      • In certain circumstances the 33% radius (also called 1/3 radius) may be utilized.

      *Note: Other hip regions of interest, including Ward’s area and the greater trochanter, should not be used for diagnosis. Application of recommendation may vary according to local requirements.

      • Skeletal sites to measure
        • Measure BMD at both the PA spine and hip in all patients.
        • Forearm BMD should be measured under the following circumstances:
          • Hip and/or spine cannot be measured or interpreted.
          • Hyperparathyroidism
          • Very obese patients (over the weight limit for DXA table)
          • Use PA L1-L4 for spine BMD measurement.
          • Use all evaluable vertebrae and only exclude vertebrae that are affected by local structural change or artifact. Use three vertebrae if four cannot be used and two if three cannot be used.
          • BMD based diagnostic classification should not be made using a single vertebra.
          • If only one evaluable vertebra remains after excluding other vertebrae, diagnosis should be based on a different valid skeletal site.
          • Anatomically abnormal vertebrae may be excluded from analysis if:
            • They are clearly abnormal and non-assessable within the resolution of the system or
            • There is more than a 1.0 T-score difference between the vertebra in question and adjacent vertebrae.
            • Use femoral neck or total proximal femur, whichever is lowest.
            • BMD may be measured at either hip.
            • There are insufficient data to determine whether mean T-scores for bilateral hip BMD can be used for diagnosis.
            • The mean hip BMD can be used for monitoring, with total hip being preferred.
            • Use 33% radius (sometimes called one-third radius) of the non-dominant forearm for diagnosis. Other forearm ROI are not recommended.

            Fracture Risk Assessment

            • A distinction is made between diagnostic classification and the use of BMD for fracture risk assessment.
            • For fracture risk assessment, any well-validated technique can be used, including measurements of more than one site where this has been shown to improve the assessment of risk.

            Use of the Term “Osteopenia”

            • The term “osteopenia” is retained, but “low bone mass” or “low bone density” is preferred.
            • People with low bone mass or density are not necessarily at high fracture risk.

            BMD Reporting in Postmenopausal Women and in Men Age 50 and Older

            BMD Reporting in Females Prior to Menopause and in Males Younger Than Age 50

            • Z-scores, not T-scores, are preferred. This is particularly important in children.
            • A Z-score of -2.0 or lower is defined as “below the expected range for age” and a Z-score above -2.0 is “within the expected range for age.”
            • Osteoporosis cannot be diagnosed in men under age 50 on the basis of BMD alone.
            • The WHO diagnostic criteria may be applied to women in the menopausal transition.

            Z-Score Reference Database

            • Z-scores should be population specific where adequate reference data exist. For the purpose of Z-score calculation, the patient’s self-reported ethnicity should be used.

            Serial BMD Measurements

            • Serial BMD testing in combination with clinical assessment of fracture risk, bone turnover markers, and other factors including height loss and trabecular bone score, can be used to determine whether treatment should be initiated in untreated patients, according to locally applicable guidelines.
            • Serial BMD testing can monitor response to therapy by finding an increase or stability of bone density.
            • Serial BMD testing should be used to monitor individuals following cessation of osteoporosis pharmacologic therapy.
            • Serial BMD testing can detect loss of bone density, indicating the need for assessment of treatment adherence, evaluation of secondary causes of osteoporosis, and re-evaluation of treatment options.
            • Follow-up BMD testing should be done when the results are likely to influence patient management.
            • Intervals between BMD testing should be determined according to each patient’s clinical status: typically one year after initiation or change of therapy is appropriate, with longer intervals once therapeutic effect is established.
            • In conditions associated with rapid bone loss, such as glucocorticoid therapy, testing more frequently is appropriate.

            Phantom Scanning and Calibration

            The Quality Control (QC) program at a DXA facility should include adherence to manufacturer guidelines for system maintenance. In addition, if not recommended in the manufacturer protocol, the following QC procedures are advised:

            • Perform periodic (at least once per week) phantom scans for any DXA system as an independent assessment of system calibration.
            • Plot and review data from calibration and phantom scans.
            • Verify the phantom mean BMD after any service performed on the densitometer.
            • Establish and enforce corrective action thresholds that trigger a call for service.
            • Maintain service logs.
            • Comply with government inspections, radiation surveys and regulatory requirements.

            Precision Assessment

            • Each DXA facility should determine its precision error and calculate the LSC.
            • The precision error supplied by the manufacturer should not be used.
            • If a DXA facility has more than one technologist, an average precision error combining data from all technologists should be used to establish precision error and LSC for the facility, provided the precision error for each technologist is within a pre-established range of acceptable performance.
            • Every technologist should perform an in vivo precision assessment using patients representative of the clinic’s patient population.
            • Each technologist should do one complete precision assessment after basic scanning skills have been learned (e.g., manufacturer training) and after having performed approximately 100 patient-scans.
            • A repeat precision assessment should be done if a new DXA system is installed.
            • A repeat precision assessment should be done if a technologist’s skill level has changed.
            • To perform a precision analysis:
              • Measure 15 patients 3 times, or 30 patients 2 times, repositioning the patient after each scan.
              • Calculate the root mean square standard deviation (RMS-SD) for the group.
              • Calculate LSC for the group at 95% confidence interval.
              • Lumbar Spine: 1.9% (LSC=5.3%)
              • Total Hip: 1.8% (LSC=5.0%)
              • Femoral Neck: 2.5% (LSC=6.9%)
              • Retraining is required if a technologist’s precision is worse than these values.

              Cross-Calibration of DXA: Changing Hardware or Systems

              • When changing hardware, but not the entire system, or when replacing a system with the same technology (manufacturer and model), cross-calibration should be performed by having one technologist do 10 phantom scans, with repositioning, before and after a hardware change.
                • If a greater than 1% difference in mean BMD is observed, contact the manufacturer for service/correction.
                • Scan 30 patients representative of the facility’s patient population once on the initial system and then twice on the new system within 60 days.
                • Measure those anatomic sites commonly measured in clinical practice, typically spine and proximal femur.
                • Facilities must comply with locally applicable regulations regarding DXA.
                • Calculate the average BMD relationship and LSC between the initial and new machine using the ISCD DXA Machine Cross-Calibration Tool (
                • Use this LSC for comparison between the previous and new system. Inter-system quantitative comparisons can only be made if cross-calibration is performed on each skeletal site commonly measured.
                • Once a new precision assessment has been performed on the new system, all future scans should be compared to scans performed on the new system using the newly established intra-system LSC.

                Cross-Calibration of DXA: Adding Hardware or Systems

                • When adding a DXA scanner with the same technology (manufacturer and model) of the original (index) scanner, for the purpose of allowing patients to be scanned across devices, cross-calibration should be performed by scanning one spine phantom on both the index scanner, and on the additional scanner(s) on 20 different days to establish the respective mean BMD values. If a greater than 0.5% difference in mean BMD is observed between devices, contact the manufacturer for service/correction to return the additional machines to match the index scanner calibration and verify the new calibration with the same process.
                  • Certain additional conditions that may apply are:
                    • When the DXA scanners are installed in the same building or campus and using the same technologists, then the original LSC of the index scanner can be used for inter-scanner comparisons or
                    • When the systems are installed in geographically distinct locations, or using different technologists, or seeing a different patient population, then precision studies must be done at each site and an average LSC of all the individual technologist precision assessments can be calculated. Use the ISCD positions on calculating an LSC when multiple technologists are using a single scanner.
                    • One scanner should be designated the index (gold standard) device. Each additional different technology device should be cross-calibrated to the index device.
                    • Scan a minimum of 30 patients, representative of the facility’s patient population twice on the index system and twice on the new system within 60 days. Individual patients may be measured on both scanners the same day, or ideally on different days, but no more than 30 days apart for any one patient.
                    • Measure those anatomic sites commonly measured in clinical practice, typically spine and proximal femur(s).
                    • Calculate the average LSC between the index and new machine using the ISCD DXA Machine Cross-Calibration Tool
                    • Use the average LSC for comparison between the two systems. Inter-system quantitative comparisons can only be made if cross-calibration is performed for each skeletal site commonly measured for monitoring.
                    • Once the in vivo cross-calibration equivalence is established, the long term-stability of all the systems must be carefully monitored with frequent scanning of a suitable external phantom on all cross-calibrated devices. Stability of a running average of phantom BMD on each system should be within 0.5% of the value established at the time of the cross-calibration.
                    • Inter-machine LSC should not be applied to patients who have both scans done on a single device. A separate intra-machine LSC, established using the duplicate scans on the second device during the generalized LSC (gLSC) process should be used for any patient having both scans on a single device.
                    • Facilities must comply with locally applicable regulations regarding DXA.

                    BMD Comparison Between Facilities

                    • It is not possible to quantitatively compare BMD or to calculate a LSC between facilities without cross-calibration.
                    • Patients should return to the same DXA device that was used to perform their most recent prior study, provided that the facility in vivo precision and LSC values are known and do not exceed established maximum values.

                    Vertebral Fracture Assessment Nomenclature

                    • Vertebral Fracture Assessment (VFA) is the correct term to denote densitometric spine imaging performed for the purpose of detecting vertebral fractures.

                    Indications for VFA

                    • Lateral Spine imaging with Standard Radiography or Densitometric VFA is indicated when T-score is < -1.0 and of one or more of the following is present:
                      • Women age ≥ 70 years or men ≥ age 80 years
                      • Historical height loss > 4 cm (>1.5 inches)
                      • Self-reported but undocumented prior vertebral fracture
                      • Glucocorticoid therapy equivalent to ≥ 5 mg of prednisone or equivalent per day for ≥ 3 months

                      Methods for Defining and Reporting Fractures on VFA

                      • The methodology utilized for vertebral fracture identification should be similar to standard radiological approaches and be provided in the report.
                      • Fracture diagnosis should be based on visual evaluation and include assessment of grade/severity. Morphometry alone is not recommended because it is unreliable for diagnosis.
                      • The Genant visual semi-quantitative method is the current clinical technique of choice for diagnosing vertebral fracture with VFA.
                      • Severity of deformity may be confirmed by morphometric measurement if desired.

                      Indications for Following VFA with Another Imaging Modality

                      • The decision to perform additional imaging must be based on each patient’s overall clinical picture, including the VFA result.
                      • Indications for follow-up imaging studies include:
                        • Lesions in vertebrae that cannot be attributed to benign causes
                        • Vertebral deformities in a patient with a known history of a relevant malignancy
                        • Equivocal fractures
                        • Unidentifiable vertebrae between T7-L4
                        • Sclerotic or lytic changes, or findings suggestive of conditions other than osteoporosis

                        Note: VFA is designed to detect vertebral fractures and not other abnormalities.

                        Serial Lateral Imaging

                        • Repeat VFA or radiographic lateral spine imaging in patients with continued high risk (e.g., historical height loss > 4 cm (>1.5 inches), self-reported but undocumented vertebral fracture, or glucocorticoid therapy equivalent to ≥ 5 mg of prednisone or equivalent per day for greater than or equal to three months).

                        DXA to Detect Abnormalities in the Spectrum of AFF

                        • Femur DXA images should be reviewed for localized cortical abnormalities in the spectrum of AFF.
                        • When using DXA systems to detect abnormalities in the spectrum of AFF, scanning methods that generate bilateral full-length femur images (FFI) should be used. The FFI report should state the absence or presence of abnormalities in the spectrum of AFF. If a focal cortical thickening is present on the lateral cortex, the report should state whether a lucent line is seen. Consider additional imaging when clinically appropriate.
                        • Consider bilateral FFI for detecting abnormalities in the spectrum of AFF in patients who are receiving bisphosphonate or denosumab therapy or discontinued it within the last year, with a cumulative exposure of 3 or more years, especially those on glucocorticoid therapy.

                        Baseline DXA Report: Minimum Requirements

                        • Demographics (name, medical record identifying number, date of birth, sex)
                        • Requesting provider
                        • Indications for the test
                        • Manufacturer and model of instrument used
                        • Technical quality and limitations of the study, stating why a specific site or ROI is invalid or not included
                        • BMD in g/cm2 for each site
                        • The skeletal sites, ROI, and, if appropriate, the side, that were scanned
                        • The T-score and/or Z-score where appropriate
                        • WHO criteria for diagnosis in postmenopausal females and in men age 50 and over
                        • Risk factors including information regarding previous non-traumatic fractures
                        • A statement about fracture risk. Any use of relative fracture risk must specify the population of comparison (e.g., young- adult or age-matched). The ISCD favors the use of absolute fracture risk prediction when such methodologies are established.
                        • A general statement that a medical evaluation for secondary causes of low BMD may be appropriate
                        • Recommendations for the necessity and timing of the next BMD study

                        Follow-Up DXA Report

                        • Statement regarding which previous or baseline study and ROI is being used for comparison
                        • Statement about the LSC at your facility and the statistical significance of the comparison
                        • Report significant change, if any, between the current and previous study or studies in g/cm2 and percentage.
                        • Comments on any outside study including manufacturer and model on which previous studies were performed and the appropriateness of the comparison
                        • Recommendations for the necessity and timing of the next BMD study

                        DXA Report: Optional Items

                        • Recommendation for further non-BMD testing, such as X-ray, magnetic resonance imaging, computed tomography, etc
                        • Recommendations for pharmacological and non-pharmacological interventions
                        • Addition of the percentage compared to a reference population
                        • Specific recommendations for evaluation of secondary osteoporosis

                        DXA Report: Items That Should Not Be Included

                        • A statement that there is bone loss without knowledge of previous bone density
                        • Mention of “mild”,”moderate”, or “marked” osteopenia or osteoporosis
                        • Separate diagnoses for different ROI (e.g., osteopenia at the hip and osteoporosis at the spine)
                        • Expressions such as “She has the bones of an 80-year-old,” if the patient is not 80 years old
                        • Results from skeletal sites that are not technically valid
                        • The change in BMD if it is not a significant change based on the precision error and LSC

                        Components of a VFA Report

                        • Patient identification, referring physician, indication(s) for study, technical quality, and interpretation
                        • A follow-up VFA report should also include comparability of studies and clinical significance of changes, if any.
                        • VFA reports should comment on the following:
                          • Unevaluable vertebrae
                          • Deformed vertebrae, and whether or not the deformities are consistent with vertebral fracture
                          • Unexplained vertebral and extra-vertebral pathology

                          Trabecular Bone Score (TBS)

                          • TBS is associated with vertebral, hip and major osteoporotic fracture risk in postmenopausal women.
                          • TBS is associated with hip fracture risk in men over the age of 50 years.
                          • TBS is associated with major osteoporotic fracture risk in men over the age of 50 years.
                          • TBS should not be used alone to determine treatment recommendations in clinical practice.
                          • TBS can be used in association with FRAX and BMD to adjust FRAX-probability of fracture in postmenopausal women and older men.
                          • In patients receiving anti-fracture therapy:
                            • The role of TBS in monitoring anti-resorptive therapy is unclear.
                            • TBS is potentially useful for monitoring anabolic therapy.

                            Hip Geometry

                            • Hip axis length (HAL) derived from DXA is associated with hip fracture risk in postmenopausal women.
                            • The following hip geometry parameters derived from DXA (CSA, OD, SM, BR, CSMI, NSA) should not be used to assess hip fracture risk.
                            • Hip geometry parameters derived from DXA (CSA, OD, SM, BR, CSMI, HAL, NSA) should not be used to initiate treatment.
                            • Hip geometry parameters derived from DXA (CSA, OD, SM, BR, CSMI, HAL, NSA) should not be used for monitoring.

                            General Recommendations for Non-Central DXA Devices: QCT, pQCT, QUS, and pDXA

                            The following general recommendations for QCT, pQCT, QUS, and pDXA are analogous to those defined for central DXA technologies. Examples of technical differences amongst devices, fracture prediction ability for current manufacturers and equivalence study requirements are provided in the full-text documents printed in the Journal of Clinical Densitometry.

                            • Bone density measurements from different devices cannot be directly compared.
                            • Different devices should be independently validated for fracture risk prediction by prospective trials, or by demonstration of equivalence to a clinically validated device.
                            • T-scores from measurements other than DXA at the femur neck, total femur, lumbar spine, or one-third (33%) radius cannot be used according to the WHO diagnostic classification because those T-scores are not equivalent to T-scores derived by DXA.
                            • Device-specific education and training should be provided to the operators and interpreters prior to clinical use.
                            • Quality control procedures should be performed regularly.

                            Baseline Non Central DXA Devices (QCT, pQCT, QUS, pDXA) Report: Minimum Requirements

                            • Date of test
                            • Demographics (name, date of birth or age, sex)
                            • Requesting provider
                            • Names of those receiving copy of report
                            • Indications for test
                            • Manufacturer, and model of instrument and software version
                            • Measurement value(s)
                            • Reference database
                            • Skeletal site/ROI
                            • Quality of test
                            • Limitations of the test including a statement that the WHO diagnostic classification cannot be applied to T-scores obtained from QCT, pQCT, QUS, and pDXA (other than one-third (33%) radius) measurements
                            • Clinical risk factors
                            • Fracture risk estimation
                            • A general statement that a medical evaluation for secondary causes of low BMD may be appropriate
                            • Recommendations for follow-up imaging

                            Note: A list of appropriate technical items is provided in the QCT and pQCT sections of the full text documents printed in the Journal of Clinical Densitometry.

                            Non Central DXA Devices (QCT, pQCT, QUS, pDXA) Report: Optional Items

                            • Report may include the following optional item:
                              • Recommendations for pharmacological and non-pharmacological interventions

                              QCT and pQCT

                              • Acquisition
                                • With single-slice QCT, L1-L3 should be scanned with 3D QCT, L1-L2 should be scanned.
                                • QCT acquisition of the proximal femur should extend from the femoral head to the proximal shaft.
                                • For density-based QCT measurements the in-scan calibration phantom can be replaced by asynchronous calibration if scanner stability is maintained.
                                • Opportunistic CT to screen for patients with low BMD or low bone strength of the spine or proximal femur is possible only if validated machine-specific cutoff values and scanner stability have been established.
                                • Femoral neck and total hip T-scores calculated from 2D projections of QCT data are equivalent to the corresponding DXA T-scores for diagnosis of osteoporosis in accordance with the WHO criteria.
                                • Spinal trabecular BMD as measured by QCT has at least the same ability to predict vertebral fractures as AP spinal BMD measured by central DXA in postmenopausal women. There is lack of sufficient evidence to support this position for men.
                                • There is lack of sufficient evidence to recommend spine QCT for hip fracture prediction in either women or men.
                                • Total femur trabecular BMD measured by QCT predicts hip fractures as well as hip BMD measured by DXA in postmenopausal women and older men.
                                • pQCT of the forearm at the ultra-distal radius predicts hip, but not spine, fragility fractures in postmenopausal women. There is lack of sufficient evidence to support this position for men.
                                • Central DXA measurements at the spine and femur are the preferred method for making therapeutic decisions and should be used if possible. Where QCT and DXA are both available and provide comparable information, DXA is preferred to limit radiation exposure.
                                • However, if central DXA cannot be done, pharmacologic treatment can be initiated if the fracture probability, as assessed by QCT of the spine or pQCT of the radius using device specific thresholds, and in conjunction with clinical risk factors, is sufficiently high.
                                • Trabecular BMD of the lumbar spine measured by QCT can be used to monitor age-, disease-, and treatment-related BMD changes.
                                • Integral and trabecular BMD of the proximal femur measured by QCT can be used to monitor age- and treatment-related BMD changes.
                                • Trabecular and total BMD of the ultra-distal radius measured by pQCT can be used to monitor age-related BMD changes.
                                • Vertebral strength as estimated by QCT-based FEA predicts vertebral fracture in postmenopausal women.
                                • Vertebral strength as estimated by QCT-based FEA is comparable to spine DXA for prediction of vertebral fractures in older men.
                                • Femoral strength as estimated by QCT-based FEA is comparable to hip DXA for prediction of hip fractures in postmenopausal women and older men.
                                • FEA cannot be used to diagnose osteoporosis using the current WHO T-score definition.
                                • Vertebral or femoral strength as estimated by QCT-based FEA can be used to initiate pharmacologic treatment using validated thresholds and in conjunction with clinical risk factors.
                                • Vertebral or femoral strength as estimated by QCT-based FEA can be used to monitor age- and treatment-related changes.
                                • For QCT using whole body CT scanners the following additional technical items should be reported:
                                  • Tomographic acquisition and reconstruction parameters
                                  • kV, mAs
                                  • Collimation during acquisition
                                  • Table increment per rotation
                                  • Table height
                                  • Reconstructed slice thickness, reconstruction increment
                                  • Reconstruction kernel
                                  • Tomographic acquisition and reconstruction parameters
                                  • Reconstructed slice thickness
                                  • Single / multi-slice acquisition mode
                                  • Length of scan range in multi-slice acquisition mode
                                  • Acquisition
                                    • The only validated skeletal site for the clinical use of QUS in osteoporosis management is the heel.
                                    • Validated heel QUS devices predict fragility fracture in postmenopausal women (hip, vertebral, and global fracture risk) and men over the age of 65 (hip and all non-vertebral fractures), independently of central DXA BMD.
                                    • Discordant results between heel QUS and central DXA are not infrequent and are not necessarily an indication of methodological error.
                                    • Heel QUS in conjunction with clinical risk factors can be used to identify a population at very low fracture probability in which no further diagnostic evaluation may be necessary. (Examples of device-specific thresholds and case findings strategy are provided in the full text documents printed in the Journal of Clinical Densitometry.)
                                    • Central DXA measurements at the spine and femur are preferred for making therapeutic decisions and should be used if possible. However, if central DXA cannot be done, pharmacologic treatment can be initiated if the fracture probability, as assessed by heel QUS, using device-specific thresholds and in conjunction with clinical risk factors, is sufficiently high. (Examples of device-specific thresholds are provided in the full-text documents printed in the Journal of Clinical Densitometry.)
                                    • QUS cannot be used to monitor the skeletal effects of treatments for osteoporosis.
                                    • Fracture Prediction
                                      • Measurement by validated pDXA devices can be used to assess vertebral and global fragility fracture risk in postmenopausal women, however, its vertebral fracture predictive ability is weaker than central DXA and heel QUS. There is lack of sufficient evidence to support this position for men.
                                      • Radius pDXA in conjunction with clinical risk factors can be used to identify a population at very low fracture probability in which no further diagnostic evaluation may be necessary. (Examples of device-specific thresholds and case findings strategy are provided in the full-text documents printed in the Journal of Clinical Densitometry.)
                                      • The WHO diagnostic classification can only be applied to DXA at the femur neck, total femur, lumbar spine and the one-third (33%) radius ROI measured by DXA or pDXA devices utilizing a validated young-adult reference database.
                                      • Central DXA measurements at the spine and femur are the preferred method for making therapeutic decisions and should be used if possible. However, if central DXA cannot be done, pharmacologic treatment can be initiated if the fracture probability, as assessed by radius pDXA (or DXA) using device specific thresholds and in conjunction with clinical risk factors, is sufficiently high. (Examples of device-specific thresholds are provided in the full text documents printed in the Journal of Clinical Densitometry.)
                                      • pDXA devices are not clinically useful in monitoring the skeletal effects of presently available medical treatments for osteoporosis.

                                      Body Composition

                                      • Indications
                                        • DXA total body composition with regional analysis can be used in the following conditions:
                                          • In patients living with HIV to assess fat distribution in those using anti-retroviral agents associated with a risk of lipoatrophy (currently stavudine [d4T] and zidovudine [ZDV, AZT])
                                          • In obese patients undergoing bariatric surgery (or medical, diet, or weight loss regimens with anticipated large weight loss) to assess fat and lean mass changes when weight loss exceeds approximately 10%. The impact on clinical outcomes is uncertain.
                                          • In patients with muscle weakness or poor physical functioning to assess fat and lean mass. The impact on clinical outcomes is uncertain.
                                          • No phantom has been identified to remove systematic differences in body composition when comparing in-vivo results across manufacturers.
                                          • An in vivo cross-calibration study is necessary when comparing in vivo results across manufacturers.
                                          • Cross-calibrating systems of the same make and model can be performed with an appropriate whole body phantom.
                                          • Changes in body composition measures can be evaluated between two different systems of the same make and model if the systems have been cross-calibrated with an appropriate total body phantom.
                                          • When changing hardware, but not the entire system, or when replacing a system with the same technology (make and model), cross-calibration should be performed by having one technologist do 10 whole body phantom scans, with repositioning, before and after a hardware change. If a greater than 2% difference in mean percent fat mass, fat mass or lean mass is observed, contact the manufacturer for service/correction.
                                          • No total body phantoms are available at this time that can be used as absolute reference standards for soft-tissue composition or bone mineral mass.
                                          • The Quality Control (QC) program at a DXA body composition facility should include adherence to manufacturer guidelines for system maintenance. In addition, if not recommended in the manufacturer protocol, the following QC procedures are advised:
                                            • Perform periodic (at least once per week) body composition phantom scans for any DXA system as an independent assessment of system calibration.
                                            • Plot and review data from calibration and body composition phantom scans.
                                            • Verify the body composition phantom mean percent fat mass and tissue mass after any service performed on the densitometer.
                                            • Establish and enforce corrective action thresholds that trigger a call for service.
                                            • Maintain service logs.
                                            • Comply with radiation surveys and regulatory government inspections, radiation surveys and regulatory requirements.
                                            • For adults total body (with head) values of BMI, BMD, BMC, total mass, total lean mass, total fat mass, and percent fat mass should appear on all reports.
                                            • Total Body BMC as represented in the NHANES 1999-2004 reference data should be used when using DXA in 4-compartment models.
                                            • DXA measures of adiposity and lean mass include visceral adipose tissue (VAT), appendicular lean mass index (ALMI: appendicular lean mass/ht2), android/gynoid percent fat mass ratio, trunk to leg fat mass ratio, lean mass index (LMI: total lean mass/ht2), fat mass index (FMI: fat mass/ht2) are optional. The clinical utility of these measures is currently uncertain.
                                            • When comparing to the US population, the NHANES 1999-2004 body composition data are most appropriate for different races, both sexes, and for ages from 8 to 85 years. [Note: Reference to a population does not imply health status.]
                                            • Both Z-scores and percentiles are appropriate to report if derived using methods to adjust for non-normality.
                                            • The use of DXA adiposity measures (percent fat mass or fat mass index) may be useful in risk-stratifying patients for cardio-metabolic outcomes. Specific thresholds to define obesity have not been established.
                                            • “Low lean mass” could be defined using appendicular lean mass divided by height squared (ALM/height2) with Z-scores derived from a young adult, race, and sex-matched population. Thresholds for low lean mass from consensus guidelines for sarcopenia await confirmation.

                                            DXA in Patients with Spinal Cord Injury

                                            • All adults with spinal cord injury resulting in permanent motor or sensory dysfunction should have a DXA scan of the total hip, proximal tibia and distal femur, as soon as medically stable.
                                            • In adults with SCI, total hip, proximal tibia and distal femur bone density should be used to diagnose osteoporosis, predict lower extremity fracture risk and monitor response to therapy when normative data are available.
                                            • Serial DXA assessment of treatment effectiveness among individuals with SCI should include evaluation at the total hip, distal femur, and proximal tibia, following a minimum of 12 months of therapy at 1- to 2-year intervals. Segmental analysis of total hip, distal femur and proximal tibia sub-regions from a whole-body scan should not be used for monitoring treatment.
                                            • There is no established threshold BMD value below which weight-bearing activities are absolutely contraindicated. BMD and clinical risk factors should be used to assess fracture risk prior to engaging in weight-bearing activities.

                                            DXA in Transgender and Gender Non-conforming Individuals

                                            • Baseline BMD testing is indicated for Transgender and Gender Non-Conforming (TGNC) individuals if they have any of the following conditions:
                                              • History of gonadectomy or therapy that lowers endogenous gonadal steroid levels prior to initiation of hormone therapy.
                                              • Hypogonadism with no plan to take gender-affirming hormone therapy.
                                              • Existing ISCD indications for BMD testing, such as glucocorticoid use and hyperparathyroidism, apply.
                                              • Low bone density as defined by current ISCD guidelines.
                                              • Individuals taking treatment to suppress puberty, such as GnRH analogs.
                                              • Non-adherence with or inadequate doses of gender-affirming hormone therapy.
                                              • Plan to discontinue gender-affirming hormone therapy.
                                              • Presence of other risks for bone loss or fragility fracture.
                                              • Bone mineral density testing intervals should be individualized based on each patient’s clinical status: typically, every one to two years until BMD is stable or improved is appropriate, with longer intervals thereafter.
                                              • T-scores should be calculated using a uniform Caucasian (non-race adjusted) female normative database for all transgender individuals of all ethnic groups we recommend using a T-score of <-2.5 or less for diagnosis of osteoporosis in all TGNC individuals age 50 years or older, regardless of hormonal status.
                                              • Calculate Z-scores using the normative database that matches the gender identity of the individual.
                                              • If requested by the ordering provider, Z-scores may also be calculated using the normative database that matches the sex recorded at birth.
                                              • In gender-nonbinary individuals, the normative database that matches the sex recorded at birth should be used.
                                              • Gender data should be obtained on the intake questionnaire.

                                              Peri-prosthetic and Orthopedic Uses of DXA

                                              • Bone health assessment should be considered in patients prior to elective orthopedic and spine surgery. BMD should be measured in those meeting ISCD or regional indications for DXA testing.
                                                • Routine DXA scans should include PA lumbar spine and hip.
                                                • Forearm DXA should be considered in patients having upper limb surgery.
                                                • VFA should be considered in patients having spine surgery.
                                                • Diabetes mellitus (long term duration of diabetes (>10yrs) and poor control)
                                                  • Trabecular bone score measurement should be obtained in patients with diabetes, if available.
                                                  • After total hip arthroplasty, Gruen zones are recommended at the femur and the DeLee / Charnley or Wilkinson method are recommended at the pelvis.
                                                  • Modifications of ROI based on patient conditions and implant geometry are acceptable.
                                                  • A Dorr classification of B or C.
                                                  • A Cortical Index of less than 0.4 measured at 10 cm below the mid lesser trochanter.

                                                  DXA Nomenclature

                                                  • DXA – not DEXA.
                                                  • T-score – not T score, t-score, or t score
                                                  • Z-score – not Z score, z-score, or z score

                                                  DXA Decimal Digits Preferred number of decimal digits for DXA reporting:

                                                  • BMD: (example, 0.927 g/cm2)
                                                  • T-score: (example, -2.3)
                                                  • Z-score: (example, 1.7)
                                                  • BMC: (example, 31.76 g)
                                                  • Area: (example, 43.25 cm2)
                                                  • % reference database: (example, 82%)


                                                  • AFF – atypical femur fracture
                                                  • ALMI – appendicular lean mass index
                                                  • BMC – bone mineral content
                                                  • BMD – bone mineral density (equivalent to areal BMD, aBMD)
                                                  • BMI – body mass index
                                                  • BR – buckling ratio
                                                  • CSA – Cross Sectional Area
                                                  • CSMI – cross-sectional moment of inertia
                                                  • DXA – dual-energy X-ray absorptiometry
                                                  • FEA – Finite element analysis
                                                  • FMI – fat mass index
                                                  • HAL – hip axis length
                                                  • ISCD – International Society for Clinical Densitometry
                                                  • LMI – lean mass index
                                                  • LSC – least significant change
                                                  • NHANES III – National Health and Nutrition Examination Survey III
                                                  • NSA – neck shaft angle
                                                  • OD – outer diameter
                                                  • PA – posterior anterior
                                                  • pDXA – peripheral dual-energy x-ray absorptiometry
                                                  • pQCT – peripheral quantitative computed tomography
                                                  • QC – quality control
                                                  • QCT – quantitative Computed Tomography
                                                  • QUS – quantitative Ultrasound
                                                  • ROI – region(s) of interest
                                                  • SCI – spinal cord injury
                                                  • SM – section modulus
                                                  • SSI – strain strength index
                                                  • TBLH – total body less head
                                                  • TBS – trabecular bone score
                                                  • TGNC – transgender and gender non-conforming
                                                  • VAT – visceral adipose tissue
                                                  • VFA – Vertebral Fracture Assessment
                                                  • vBMD – volumetric BMD
                                                  • WHO – World Health Organization

                                                  © Copyright ISCD, June 2019. Supersedes all prior “Official Positions” publications.
                                                  Approved and Accepted by the ISCD Board on May 28, 2019

                                                  Sex Essential Reads

                                                  The Psychology of Erotic Dreams

                                                  Why Has Partner Sex Declined and Celibacy Risen in the Past 20 Years?

                                                  The hypothalamus of female rodents has greater levels of methylation than males: that is, more genes are suppressed. Giving such females testosterone postnatally reduces this. In other words, some of the methylation markers are removed, releasing those genes to become active. Such females behave more like males. Furthermore, giving a drug to little males that prevents de-methylation results in them behaving more like females.

                                                  In seems that the brain may develop with a number of genes in the neurons of the hypothalamus suppressed: If this is left unaltered, then the individual will develop as a female. This agrees with the long-standing view that the "default" condition is female. However, testosterone is able to remove selected methylation tags, thus releasing genes that determine male-like behavior. Now we need to know exactly what these genes do and, even more difficult, why they should specify gender. But it’s a start, and this breakthrough may be a door to a much greater understanding of how sexuality develops and what influences it.

                                                  Of course, there’s another major question: Does this apply to humans? From what we know, we can prophesy that it likely does, but that sexuality in humans in all its forms will also be greatly influenced by social and experiential factors to an extent, perhaps, not so apparent in other species—but which may also involve epigenetic events.

                                                  Anatomy May Be Key to Female Orgasm

                                                  THURSDAY, April 21, 2016 (HealthDay News) -- Despite what's often portrayed in movies and on TV, most women can't orgasm with penetration alone during sexual intercourse.

                                                  And simple anatomy is to blame, a new evidence review suggests.

                                                  Each woman's ability to orgasm during sex depends almost wholly on physical development that occurred while she was still in the womb, according to the review authors.

                                                  During gestation, the clitoris begins to drift up and away from the vaginal opening, the researchers said.

                                                  But among women whose clitoris drifted too far up, it may be very difficult or even impossible to have an orgasm during sex, because traditional lovemaking doesn't provide enough friction to stimulate the clitoris, said Dr. Maureen Whelihan. She's an obstetrician and gynecologist in West Palm Beach, Fla., and an expert with the American College of Obstetricians and Gynecologists.

                                                  "It's not her fault. She was born that way," said Whelihan, who was not involved with the research but reviewed the findings.

                                                  The researchers said they have figured out the distance between a woman's clitoris and her urinary opening that can predict whether she will be able to orgasm during sex, without any additional stimulation.

                                                  The "magic number" is 2.5 centimeters -- slightly less than 1 inch, said Elisabeth Lloyd, who was not involved with the new study. Lloyd is an affiliated faculty scholar with the Kinsey Institute for Research in Sex, Gender and Reproduction at Indiana University-Bloomington.

                                                  "It's so strong a correlation that if you give us a woman who has a distance of 3 centimeters, we can very reliably predict she won't have orgasm with intercourse," Lloyd said. "Women can do this measurement themselves or with their partner, to help explain their own sexual experience."

                                                  Other factors, such as penis size, the skill of the sexual partner or the intensity of desire "might have some effect, but it really is the anatomical distance that seems to be predictive," Lloyd said.

                                                  Exposure to male hormones in the womb increases the amount of drift, Lloyd said. "If she's exposed to a lot of androgen, the clitoral bud migrates far away," she said.

                                                  Between 70 percent to 90 percent of women are unable to achieve orgasm with penetration alone, Whelihan said.

                                                  "Of those that claim they can have purely vaginal orgasms, 90 percent of them say they have to be on top," she added. "Guess what? When you're on top, sitting on the partner's erection and grinding on his abdomen, it's really not just a vaginal orgasm. You're rubbing your clitoris on his abdomen or pelvis."

                                                  Nine out of 10 women in her practice have had an orgasm during their life, Whelihan said, but nearly all needed direct clitoral stimulation to achieve it.

                                                  What about the G-spot, the erogenous area purported to exist inside the vagina? Autopsies haven't consistently supported the existence of the G-spot, the evidence review said.

                                                  A majority of sex experts don't believe there is such a thing, Whelihan said. "According to most of the experts, we believe if the G-spot exists then it only exists in a few women," she said.

                                                  Couples determined to achieve female orgasm during intercourse should start paying more attention to the clitoris, Lloyd and Whelihan said.

                                                  Couples can use positions where the female is on top, which allows the woman to get more friction against her clitoris. Or they can use a sexual position that allows either the man or the woman to rub the clitoris during sex, either with fingers or a sex toy, Whelihan said.

                                                  "There are many ways to have an orgasm where she's having hers while he's having his," she said. "Couples should not focus on something that will never change anatomically, and instead find ways to allow for some type of clitoral stimulation during penetration."

                                                  However, couples also should remember that orgasm with intercourse is not necessary for a woman to have a healthy or enjoyable sex life, Lloyd added.

                                                  "I think this approach is traditional, and it's very common, but it's problematic. We've learned in our research there are so many women who do not have orgasm with intercourse on a regular basis," Lloyd said. "To put this banner of healthiness as having orgasm with intercourse kind of stacks the deck against these women who, because of their anatomy, cannot have orgasm with intercourse."

                                                  The evidence review was conducted by Leslie Hoffman of the department of anatomy at Indiana University School of Medicine, and colleagues. The report was published online April 4 in the journal Clinical Anatomy.

                                                  Reconstruction of a historical case

                                                  From the combined genotyping and DNA quantification results, we conclude that Foekje Dillema was a 46,XX/46,XY mosaic, with equal numbers of both genetic cell types at least in her skin (online supplementary data). In the fetal gonads of a 46,XX/46,XY mosaic, the tissue ratio of XX:XY cells will push the bipotential gonads to become either ovaries or testes, or both. A preponderance of 46,XX cells in fetal gonads can lead to the development of ovaries, but with some 46,XY testis tissue present in one or both of these ovaries. Such an ovotestis condition, which can also occur in the form of a complete ovary and a complete testis on either side, has been referred to with the term true hermaphroditism.11 12 The most common karyotype found in true hermaphroditism is 46,XX, followed by 46,XX/46,XY chimerism and mosaicism.12 We would like to emphasise that the term hermaphrodite, as well as other terms such as intersex, need to be replaced by the DSDs classification proposed by consensus in 2006,13 for the simple reason that the terms hermaphrodite and intersex cannot, and should not, be applied to human individuals. Instead, a true hermaphrodite is correctly referred to as either a female or male individual with ovotesticular DSD.13 When ovotestis formation is confined to only one of the gonads, the other gonad and the ovarian part of the ovotestis can function as steroidogenic ovarian tissue.11 12 The testicular part of the fetal ovotestis will produce anti-Müllerian hormone, insulin-like factor 3 and testosterone,14 acting towards regression of Müllerian ducts, initiation of testis descent and partial virilisation by circulating androgens, respectively, but none of these effects might reach a level where overt fetal virilisation leads to the birth of a boy. Hence, an individual with ovotesticular DSD often is raised as a girl,12 and also experiences a female gender identity (described below).

                                                  The X:Y ratio in the adult skin, as we obtained from Dillema's clothes, does not provide any information about the ratio in her fetal gonads. However, Foekje Dillema was formally registered as a female at birth, and she was raised as a girl, according to all accounts, including those available from her family. Hence, she is unlikely to have been exposed to a markedly elevated level of testosterone during fetal development. From all available data, including the present DNA evidence, we deduce that Dillema had an ovotesticular DSD with a predominance of ovarian tissue. At the onset of puberty, gonadotropic stimulation of the gonads most likely led to marked activation of steroidogenesis – the production of both oestradiol and testosterone in Dillema's case of ovotesticular DSD. From photographs, it is evident that from puberty she had breast development, but personal accounts also indicate that she showed some facial hair growth.1 Hyperandrogenism from puberty may have contributed to Dillema's athletic performance.

                                                  The Human Tail and Other Tales of Evolution

                                                  Editor’s Note: First published in St. Louis MetroVoice 4, no. 1 (January 1994).

                                                  In the May 20, 1982, issue of The New England Journal of Medicine, Dr. Fred Ledley, M.D. presented a clinical case report titled “Evolution and the Human Tail.” Ledley’s report concerned a baby born with a two-inch long fleshy growth on its back, bearing a superficial resemblance to a tail. Ledley strongly implied that this growth (called a caudal appendage) was essentially a “human tail,” though he admitted that it had virtually none of the distinctive biological characteristics of a tail!

                                                  All true tails have bones in them that are a posterior extension of the vertebral column. Also, all true tails have muscles associated with their vertebrae, which permit some movement of the tail. Ledley conceded that there has never been a single documented case of an animal tail lacking these distinctive features, nor has there been a single case of a human caudal appendage having any of these features. In fact, the caudal appendage Ledley described is merely a fatty outgrowth of skin that wasn’t located in the right place on the back to be a tail! Still, Ledley saw his caudal appendage as providing compelling proof for the evolution of man from our monkey-like ancestors. He said that

                                                  even those of us who are familiar with the literature that defined our place in nature (Darwinism)—are rarely confronted with the relation between human beings and their primitive ancestors on a daily basis. The caudal appendage brings this reality to the fore and makes it tangible and inescapable.

                                                  Is there any branch of science, other than evolution , where such trivial data can be extrapolated into such profound and “inescapable” facts?

                                                  The “human tail” is just one example of what evolutionists call a “vestigial organ.” As the name suggests, these organs are supposed to represent useless remnants of what were once functional and useful organs in our primitive ancestors. As recently as 1971, the Encyclopedia Britannica claimed that there were more than 100 vestigial organs in man. Even critically important organs such as the thymus and parathyroid glands were once considered to be vestigial simply because their functions were not understood. As biomedical science has progressed, there are fewer and fewer claims of function-less organs. Despite their diminishing numbers, vestigial organs are still mentioned in textbooks as one of the strongest evidences for evolution and against intelligent design by a Creator. The most frequently cited examples of vestigial organs in man are the coccyx and the appendix.

                                                  The human coccyx, or “tail bone,” is a group of four or five small vertebrae fused into one bone at the lower end of our vertebral column. Most of us never really think about our “tail bone” until we fall on it. Evolutionists are dead certain that the coccyx is a vestige of a tail left over from our monkey-like ancestors. The coccyx does occupy the same relative position at the end of our vertebral column as does the tail in tailed primates, but then, where else would it be? The vertebral column is a linear row of bones that supports the head at its beginning and it must end somewhere. Wherever it ends, evolutionists will be sure to call it a vestigial tail.

                                                  Most modern biology textbooks give the erroneous impression that the human coccyx has no real function other than to remind us of the “inescapable fact” of evolution . In fact, the coccyx has some very important functions. Several muscles converge from the ring-like arrangement of the pelvic (hip) bones to anchor on the coccyx, forming a bowl-shaped muscular floor of the pelvis called the pelvic diaphragm. The incurved coccyx with its attached pelvic diaphragm keeps the many organs in our abdominal cavity from literally falling through between our legs. Some of the pelvic diaphragm muscles are also important in controlling the elimination of waste from our body through the rectum.

                                                  Another common evolutionary claim found in textbooks is that the human appendix is really a vestigial cecum left over from our plant-eating evolutionary ancestors. The cecum is a blind-ending pouch near the beginning of the large intestine, which provides additional space for digestion. In some plant-eating animals, such as cows, the cecum contains special bacteria that aid in the digestion of cellulose. The appendix is clearly not a vestigial cecum because almost every mammal has a cecum and many of these also have an appendix! Man, for example, has both a cecum and an appendix—neither is vestigial or useless. The appendix, like the once “vestigial” tonsils and adenoids, is a lymphoid organ (part of the body’s immune system) that makes antibodies against infections in the digestive system. Believing it to be a useless evolutionary “leftover,” many surgeons once removed even the healthy appendix whenever they were in the abdominal cavity. Today, removal of a healthy appendix under most circumstances would be considered medical malpractice.

                                                  There are organs in the body that have no known function in the adult but are still not vestigial in the evolutionary sense. For example, poorly developed and inactive mammary glands are found in adult males of all mammals, including man. Even evolutionists do not believe that these rudimentary glands are vestigial mammary glands left over from female ancestors of males, nor do they believe that males once nursed their young. There is a much better explanation for the male mammary gland. Males and females develop from nearly identical embryos, which, at an early stage of development, become either male or female under the influence of genes in the sex chromosomes. The same parts of an embryo may produce either male or female sex organs and mammary glands. In humans, almost every component of female sex organs can be found in a rudimentary form in the male and the reverse is also true. Thus, the presence of rudimentary organs in the adult do not tell us something about evolution , but rather tell us something about embryology.

                                                  In conclusion, the “vestigial” status of many organs has often been merely a way of covering up our ignorance of their true function. Unfortunately, there is little inclination to investigate the functional significance of organs believed to be “useless.” There are now few, if any, organs that are considered to be functionless in both embryo and adult. Even if vestigial organs were to exist, they would not provide evidence for evolution but rather for devolution. The problem for evolutionists is not how useful organs are lost, but how evolution produces new useful organs with all their integrated complexity. It is here that we find evolutionary tales.

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