Estrogens

The most active estrogen in the human body is estradiol, followed by estrone and estriol. Estrogens are produced mainly by granulosa cells of the ovary. The secretion of estrogen is enhanced in response to the release of FSH from the pituitary gland. In the hypothalamus and gonadotrophs of the anterior lobe of the pituitary gland, the increased level of estradiol in the blood suppresses the secretion of GnRH and FSH, in addition, the follicular cells produce inhibin, which inhibits the secretion of FSH.

Estradiol in serum

Estradiol is the main estrogen representative with the highest biological activity. Estrone is formed from estradiol by an enzymatic route and has less pronounced biological activity( due to its low ability to bind to cell receptors).During pregnancy, estrone can be detected in increasing concentrations. In this case, the hormone is synthesized from DHEAS, which is formed in the adrenal cortex of the fetus. Thus, estrone is one of the indicators characterizing the state of the fetus.

In the female body, estradiol is synthesized in the ovaries, in the envelope and granulosa cells of the follicles. In the luteal phase of the menstrual cycle, estradiol is synthesized exclusively by the cells of the follicle shell, while the granulosa cells luteinize and switch to the synthesis of progesterone. At the onset of pregnancy, the massive production of estrogens is performed by the placenta. Other places for the synthesis of estrogen, especially estrone in postmenopause, include the adrenal cortex and peripheral fat tissue, because of their ability to aromatize androgens. Determination of the concentration of estradiol is necessary for assessing the function of the ovaries. Reference values ​​of es-traidiol concentration in blood serum are given in the table.

Reference values ​​for estradiol concentration in blood serum

Table Reference values ​​for serum estradiol concentration

Fig. Changing the concentration of estradiol in the blood serum during the normal menstrual cycle

There is no reliable evidence of estrogen secretion in the male body, usually they are formed from testosterone.

Organs of estrogen in women include the uterus, vagina, vulva, fallopian tubes and mammary glands. Estrogens are responsible for the development of secondary sexual characteristics and determine the characteristic physical and mental characteristics of women. Estrogens cause the closure of epiphysical growth points.

Changes in the concentration of estradiol during the normal menstrual cycle are reflected in Fig. The level of estradiol remains low in the beginning and middle of the follicular phase of the menstrual cycle.3-5 days before the peak of LH, the level of estradiol begins to increase and reaches its maximum values ​​approximately 12 hours before the peak of LH.After a sharp drop to the lowest values ​​observed 48 hours after the peak of LH, the level of estradiol begins to rise again( biphasic progression).The maximum concentration is achieved on the 9th day after ovulation, and then at the end of the cycle the concentration of the hormone again falls as the yellow body is atresy.

Low concentration of estradiol in the blood is characteristic of diseases of the hypothalamus or pituitary gland;a high concentration is observed with escrogensecretory tumors or follicular ovarian cysts, in such cases an excess of estradiol inhibits the secretion of LH and FSH, leading to anovulation. The main diseases and conditions in which the concentration of estradiol in the blood can vary are shown in the table.

Fig. Change in serum estradiol concentration during the normal menstrual cycle

Table Diseases and conditions in which the serum estradiol concentration changes

Table Diseases and conditions in which the serum estradiol concentration changes