Biological Chemistry - Berezov, T. T., Korovkin, B. F. 1998

Hormones
Sex Hormones
Female Sex Hormones

Sex Hormones are synthesized primarily in the Gonads of females (Ovaries) and males (Testes); in addition, certain amounts of sex hormones are produced in the Placenta and the adrenal cortex. It should be noted that male gonads produce small amounts of female hormones and, conversely, the ovaries synthesize minor quantities of Male Sex Hormones. This fact is supported by studies of the Chemical Nature of hormones in certain pathological conditions characterized by drastic shifts in The ratio of male to female sex hormone synthesis.

The primary site of Synthesis of Female sex hormones—estrogens (from the Greek oistros, meaning passionate desire)—is the ovaries and the corpus luteum; The formation of these hormones has also been proven in the Adrenal Glands, testes, and placenta. Estrogens were first discovered in 1927 in the urine of pregnant women, and in 1929 A. Butenandt and, simultaneously, E. Doisy isolated estrone from urine, which became the first steroid hormone obtained in crystalline form.

Currently, two groups of female sex hormones are recognized, differing in their chemical Structure and biological function: estrogens (with estradiol as the main representative) and progestins (with progesterone as the main representative). The chemical structures of the principal female sex hormones are presented below:

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The most active estrogen, estradiol, is synthesized predominantly in the follicles; the other two estrogens are derivatives of estradiol and are also synthesized in the adrenal glands and placenta. All estrogens contain 18 carbon atoms. The ovarian secretion of estrogens and progesterone is cyclical, depending on the phase of the Menstrual cycle: During the first phase, primarily estrogens are synthesized, whereas during the second phase, progesterone is predominantly produced.

The precursor of these hormones, like that of corticosteroids in the body, is Cholesterol, which undergoes successive reactions of hydroxylation, oxidation, and side-chain Cleavage to yield pregnenolone. Estrogen synthesis is completed by a unique aromatization reaction of the first ring, catalyzed by the microsomal enzyme complex aromatase. It is hypothesized that the aromatization process involves at least three oxidase reactions, all of which are cytochrome P-450 dependent.

It should be noted that during Pregnancy, yet another endocrine organ Functions in the female body to produce estrogens and progesterone: the placenta. It has been established that the placenta alone cannot synthesize Steroid Hormones, and a functionally competent endocrine organ is most likely the placenta-fetus complex, or fetoplacental unit (from the Latin foetus, meaning fetus). A specific feature of estrogen synthesis is that the starting material—cholesterol—is supplied by the maternal Organism; the placenta carries out the sequential conversion of cholesterol into pregnenolone and progesterone. Further synthesis occurs exclusively in fetal Tissues.

A leading role in regulating the synthesis of estrogens and progesterone is played by pituitary gonadotropic hormones (follitropin and lutropin), which control hormone synthesis indirectly via ovarian Cell receptors, the adenylate cyclase–cAMP system, and most likely through the synthesis of a specific protein. The main biological function of estrogens and progesterone, the synthesis of which begins after the onset of Puberty, is to ensure the reproductive function of the female body. During this period, they induce The Development of secondary sex characteristics and create optimal conditions ensuring the possibility of egg Fertilization following ovulation. Progesterone performs A number of specific functions in the body: it prepares the uterine mucosa for successful embryo implantation in the event of fertilization, and upon the establishment of pregnancy, its primary role is the maintenance of pregnancy; it exerts an inhibitory effect on ovulation and stimulates the development of mammary gland tissue. Estrogens exert an anabolic effect on the body by stimulating Protein Synthesis.

The degradation of estrogens presumably occurs in the Liver, although The Nature of the bulk of their urinary metabolites remains unclear. They are excreted in the urine as sulfuric or glucuronic acid conjugates, with estriol being excreted predominantly as a glucuronide, and estrone as a sulfate ester. Progesterone is first converted in the liver into inactive pregnanediol, which is excreted in the urine as a glucuronide conjugate.

In medical practice, natural hormones and synthetic compounds with estrogenic activity are widely used; unlike natural hormones, these synthetic agents are not degraded in the digestive tract. Synthetic estrogens include diethylstilbestrol and synestrol, which are derivatives of the hydrocarbon stilbene.

Both of these agents, along with several other stilbene derivatives, have also found application in oncological practice: they inhibit the growth of prostate tumors.