Progestins secretion

Progesterone is secreted by the corpus luteum, placenta, and in small amounts by the adrenal cortex. Progesterone and its derivatives (ie, the progestins) transform the proliferative endometrium into a secretory endometrium. Progestins are necessary for the development of the placenta and inhibit the secretion of pituitary gonadotropins, which in turn prevents maturation of the ovarian follicle and ovulation. The synthetic progestins are usually preferred for medical use because of the decreased effectiveness of progesterone when administered orally. 

Cervical mucus is secreted by the endocervical glands and is regulated by estrogens and progestins. Under the influence of high levels of estrogen or progesterone, the physicochemical composition of cervical mucus may reduce sperm motility and provide a barrier to fertilization. 

Administration of estrogens and progestins inhibits FSH and LH secretion from the pituitary (feedback inhibition) and hence ovulation. This effect is the action of contraceptive pills. A small amount of the... 

Progesterone (15), the principal progestin in mammals, is secreted primarily by the corpus luteum of the ovary. A main responsibility of progesterone, together with estrogen, is to prepare the endometrium... 

Our data have shown that the non-aromatlsable androgen DHT and progestins can act directly at the pituitary level at physiological concentrations to inhibit spontaneous PRL secretion and reverse the well-known stimulatory effect of E (39, 40, 42, 51). In addition, the effect of E2, DHT and progestins is observed, not only on spontaneous and IRH-induced PRL secretion, but also in the presence of IBMX. This last observation suggests that the marked modulatory effects of sex steroids are exerted at a step following cyclic AMP formation. 

Although the granulosa cell is subject to different varieties of signaling systems, FSH is the most important hormone for its differentiation. Specifically, FSH stimulates the granulosa cells to secrete estrogens and progestins, as well as various nonsteroidal substances [43]. The induction of various hormone receptors in the granulosa cell is also FSH dependent. 

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