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Estrogens

The chemical nature: these are derivatives of cholesterol and:

1) there are 3 double bonds in A-ring

2) estrone has 1 OH-group (in C3); estradiol has 2 OH-groups in C3 and C17; estriol has 3 OH-groups in C3, C16 and C17

The physiologic action: despite total physiologic action estrogens exert specific influence on female body:

1) they promote formation and function of female genitals

2) they evoke increase of uterus due to growth of stroma of myometrium and endometrium

3) they enhance growth of salpinx, vagina, mammary glands

4) they take part in regulation of function of mammary glands

5) they regulate mensis with follicle-stimulating hormone, luteinizing hormone and progestrone: first days after mensis the level of FSH is increased. It results in maturation of follicles. Follicles produce estradiol and proliferation of endometrium occurs. In the middle of menstrual cycle LH is increased. Under influence of LH the final maturation of follicles occurs and then ovulation proceeds. After ovulation follicle is converted to yellow body. After formation of yellow body the estrogens secretion stops and secretion of progesterone beginns.

The chemical nature of progestrone this hormone has double bond between C4 and C5 like glucocorticoids and ketogroup in C3. Therefore it possesses weak action of glucocorticoids

The mechanism of action: 2-nd one. This hormone may be formed in placenta, gonads, adrenal cortex. But only progestrone of yellow body exits in blood.

The physiologic action: this is “hormone of pregnancy” because it prepares uterus for implantation of embryo and promotes the formation of placenta, growth of mammary glands, deminishes irritability of muscles of uterus, increase of excretion of potassium and retards sodium and chlorine in blood, hampers ovulation.

If the pregnancy beginns so development of embryo occurs; if the pregnancy doesn’t occur so degeneration of yellow body proceeds and mensis beginns again

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