The regulation of pituitary gonadotropin secretion by the interactions between follicle stimulating hormone-releasing hormone (FSH-RH), luteinizing hormone-RH, and sex steroids is reviewed. Ovarian and testicular sex steroids act to block the further release of LH and FSH, stimulated by LH-RH and FSH-RH, presumably by suppressing the hypothalamic release of gonadotropin-releasing hormones. Studies have shown that receptor sites sensitive to the feedback effect of sex steroids exist primarily in the hypothalamus, though there is some evidence for their existence in the pituitary also. It is also possible that LH and FSH provide inhibitory impulses in a short-loop feedback system. LH-RH, in doses as small as .2 mcg, has been shown to induce a rapid increase in plasma LH. It has been suggested that 1 hypothalamic substance is responsible for the release of both FSH and LH. The stimulatory effect of LH-RH is not blocked by the administration of estrogen-progestogen oral contraceptives (OCs), which suggests that OCs, as well as clomiphene, act principally on the hypothalamus rather than the pituitary. High doses of clomiphene may block FSH and LH release, whereas low doses appear to stimulate their release. It appears that the structure of LH-RH resembles those of thyrotropin-releasing hormone and growth hormone-releasing hormone. Various approaches to fertility control utilizing synthetic LH-RH are discussed.
|Original language||English (US)|
|Number of pages||2|
|Journal||Research in reproduction|
|State||Published - Jul 1 1970|
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