At Gonadotropins FSH (follicle stimulating hormone) and LH (luteinizing hormone) are produced by the anterior portion of the pituitary and regulate the activity of the ovaries and testes.
These organs, in turn, will produce hormones that will act on the emergence of secondary sexual characters and the process of human reproduction.
In man the FSH stimulates sperm production. O LH acts on the testis favoring testosterone production, the male sex hormone.
In women, the FSH and LH participate in menstrual cycle. In this cycle there will be the formation of oocyte and the production of ovarian hormones. estrogen and progesterone, which prepare the uterus for a possible pregnancy. At puberty, estrogens act on the emergence of secondary sexual characters.
Hormones and their relationship to secondary sex characters
Male sex hormones are collectively called androgens. They are cholesterol-derived steroids. Of them, the best known, is the testosterone. In addition to being necessary for sperm maturation, they act at puberty by giving rise to secondary sexual characteristics such as voice thickening, typical hair distribution, increased skeletal size, and stimulation of muscle biosynthesis of muscle tissue (they are therefore considered anabolic hormones).
In women, estrogens of which the best known is the estradiol, are related to the preparation of the uterus for reproduction and the determination of secondary sexual characteristics such as breast growth, pelvic enlargement and fat deposition in certain places of the organism.
Hormones and the menstrual cycle
The menstrual cycle in women is caused by the alternating secretion of follicle-stimulating and luteinizing hormones, the anterior pituitary (pituitary) (adenohypophysis), and estrogen and progesterone by the ovaries. The cycle of phenomena that induce this alternation has the following explanation:
- At the beginning of the menstrual cycle, ie when menstruation begins, the anterior pituitary secretes larger amounts of follicle stimulating hormone along with small amounts of luteinizing hormone. Together, these hormones promote the growth of various follicles in the ovaries and cause considerable estrogen (estrogen) secretion.
- Estrogen is then believed to have two sequential effects on anterior pituitary secretion. First, it would inhibit the secretion of follicle-stimulating and luteinizing hormones, causing their rates to decline to a minimum around the tenth day of the cycle. Then suddenly the anterior pituitary would begin to secrete very high amounts of both hormones but mainly luteinizing hormone. It is this phase of sudden increase in secretion that causes the rapid final development of one of the ovarian follicles and rupture within about two days.
- The ovulation process, which occurs around the fourteenth day of a normal 28-day cycle, leads to the development of the corpus luteum or yellow body, which secretes high amounts of progesterone and considerable amounts of estrogen.
- O estrogen and the progesterone secreted by the corpus luteum inhibit the anterior pituitary again, decreasing the secretion rate of follicle-stimulating and luteinizing hormones. Without these hormones to stimulate it, the corpus luteum involutes, so that estrogen and progesterone secretion drops to very low levels. This is when menstruation begins, caused by this sudden decline in the secretion of both hormones.
- At this time, the anterior pituitary, which was inhibited by estrogen and progesterone, begins to secrete large amounts of follicle stimulating hormone again, starting a new cycle. This process continues throughout a woman's reproductive life.