Прогестогендер: гормондар және олардың қызметі

Steroid hormone that activates the progesterone receptor
progestogens as hormones

Progestogens, also sometimes written progestagens or gestagens, are a class of natural or synthetic steroid hormones that bind to and activate the progesterone receptors (PR). Progesterone is the major and most important progestogen in the body. The progestogens are named for their function in maintaining pregnancy (i. e., progestational), although they are also present at other phases of the estrous and menstrual cycles. Progestins are synthetic progestogens and are used in medicine. Other endogenous progestogens, with varying degrees of progestogenic activity, include 16α hydroxyprogesterone (16α OHP), 17α hydroxyprogesterone (17α OHP) (very weak), 20α dihydroprogesterone (20α DHP), 20β dihydroprogesterone (20β DHP), 5β dihydroprogesterone (5β DHP) (very weak), 3β dihydroprogesterone (3β DHP), 11 deoxycorticosterone (DOC), and 5α dihydrodeoxycorticosterone (5α DHDOC). They are all metabolites of progesterone, lying downstream of progesterone in terms of biosynthesis.

The major tissues affected by progestogens include the uterus, vagina, cervix, breasts, testes, and brain. The main biological role of progestogens in the body is in the female reproductive system, and the male reproductive system, with involvement in regulation of the menstrual cycle, maintenance of pregnancy, and preparation of the mammary glands for lactation and breastfeeding following parturition in women; in men progesterone affects spermiogenesis, sperm capacitation, and testosterone synthesis. Progestogens also have effects in other parts of the body. Unlike estrogens, progestogens have little or no role in feminization.

Progesterone is produced from cholesterol with pregnenolone as a metabolic intermediate. In the first step in the steroidogenic pathway, cholesterol is converted into pregnenolone, which serves as the precursor to the progestogens progesterone and 17α hydroxyprogesterone. These progestogens, along with another steroid, 17α hydroxypregnenolone, are the precursors of all other endogenous steroids, including the androgens, estrogens, glucocorticoids, mineralocorticoids, and neurosteroids. Thus, many tissues producing steroids, including the adrenal glands, testes, and ovaries, produce progestogens. In some tissues, the enzymes required for the final product are not all located in a single cell. For example, in ovarian follicles, cholesterol is converted to androstenedione, an androgen, in the theca cells, which is then further converted into estrogen in the granulosa cells. Fetal adrenal glands also produce pregnenolone in some species, which is converted into progesterone and estrogens by the placenta (see below). In the human, the fetal adrenals produce dehydroepiandrosterone (DHEA) via the pregnenolone pathway.

Progesterone is the major progestogen produced by the corpus luteum of the ovary in all mammalian species. Luteal cells possess the necessary enzymes to convert cholesterol to pregnenolone, which is subsequently converted into progesterone. Progesterone is highest in the diestrus phase of the estrous cycle.

The role of the placenta in progestogen production varies by species. In the sheep, horse, and human, the placenta takes over the majority of progestogen production, whereas in other species the corpus luteum remains the primary source of progestogens. In the sheep and human, progesterone is the major placental progestogen. The equine placenta produces a variety of progestogens, primarily 5α dihydroprogesterone and 5α,20α tetrahydroprogesterone, beginning on day 60. A complete luteo placental shift occurs by day 120–150.

The endogenous progestogens are naturally occurring pregnane steroids with ketone and/or hydroxyl groups at the C3 and C20 positions.

Progestogens, including both progesterone and progestins, are used medically in hormonal birth control, hormone therapy, to treat gynecological disorders, to suppress sex hormone levels for various purposes, and for other indications.