The female hormone system is determined by a regulatory circuit consisting of the hypothalamus, pituitary gland (hypophysis) and the ovaries (ovaries). The female ovaries are the central organ for the production of the female sex hormones estradiol and progesterone as well as for female fertility. Only a functioning interaction between the ovaries, the hypothalamus, the pituitary gland (hypophysis) and the uterus ensures unimpaired fertility.
The female sex hormones estradiol and progesterone belong to the class of steroid hormones that are produced from cholesterol. This class of hormones are able to overcome cell membranes and can thus unfold their effect by binding to receptors inside the cell. Usually hormones act by binding to receptors on the cell surface, as they are not able to cross cell membranes.
As these steroid hormones are well soluble in fat but poorly soluble in water, they are mostly bound to proteins for transport in the blood. Only 1% of the estrogens and 2% of the progesterone are freely available, can overcome cell membranes and develop their effect. Therefore, the free hormones are also called biologically active.
Among the proteins to which the steroid hormones are bound are sex hormone-binding globulin (SHBG), albumin and transcortin (CBG). For the production of the female sex hormones, but also of other hormones, the hormones from the hypothalamus and pituitary gland are crucial. Stimulating (“releasing”) or inhibiting (“inhibiting”) hormones are produced in certain areas of the hypothalamus regardless of sex and are responsible for the release of hormones from the front lobe of the pituitary gland, also known as the adenohypophysis.
Hormones whose release is influenced by stimulating (“releasing”) or inhibiting hormones from the hypothalamus: the gonadotropins LH (luteinizing hormone) and FSH (follicle-stimulating hormone), growth hormone (somatotropin or HGH/GH), PRL (prolactin), ACTH (adrenocorticotropic hormone) and TSH (thyroid stimulating hormone). Finally, prolactin is also produced in the frontal lobe of the pituitary gland. Its release is mainly triggered by a stimulating hormone, Thyrotropin Releasing Hormone (TRH) from the hypothalamus.
The biochemical messenger dopamine, on the other hand, inhibits the release of prolactin. Dopamine is the most important regulator of prolactin release and is therefore also known as the prolactin inhibiting factor. Two other hormones are produced directly in the hypothalamus and transported to the posterior lobes of the pituitary gland, also known as the neurohypophysis.
These include the hormones ADH (antidiuretic hormone), which is responsible for the regulation of the water balance, and oxytocin, which is responsible for contractions, milk injection and milk release in pregnant women. After transport to the posterior lobe of the pituitary gland, the two hormones are stored there and released as required. In the following, the hormones that play a special role in the female organism are discussed in detail. It should be noted that all these hormones are also present in the male organism and also play a specific role.
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