[en] Gonadotrophin release was studied after synthetic luteinizing hormone releasing hormone (LH RH) injection in several physiological and experimental conditions. In male subjects, 25 μg of LH RH induced a follicle stimulating hormone (FSH) and luteinizing hormone (LH) release before and during puberty. With higher doses of LH RH, FSH was then released and the LH increment was proportional to the dose. When FSH was released, its increase was always less marked and later than that of LH. In female subjects, 25 μg of LH RH induced marked increase of FSH and a weak increment of LH before puberty. In girls entering puberty, LH response became higher than that of FSH. In eugonadal women, the FSH and LH response, was more marked during luteal phase than during preovulatory phase. Hormonal non sequential contraceptive drugs inhibited FSH and LH response induced by 50 μg of LH RH whereas they could not depress the gonadotrophin response to 100 μg of LH RH. In postmenopausal women, LH only increased after 25 μg of LH RH; pretreatment with 200 μg of ethinyloestradiol for 5 days allowed a release of both FSH and LH. From these data, it may be accepted that gonadotrophin response to LH RH depends on the endocrine equilibrium and on gonadal steroids which could modify the synthesis and/or the release of pituitary gonadotrophin. Furthermore on the basis of selective LH response to small doses of LH RH we may speculate that an FSH releasing factor exists.Gonadotropin release after synthetic LH-RH injection was studied under a variety of experimental conditions. In male subjects, LH-RH (25 mcg) induces release of LH and FSH before and during puberty, but only of LH in adults. Larger doses of LH-RH do induce FSH release, with LH release proportional to LH-RH dose; FSH release is smaller than LH release and follows it. In prepuberal females, LH-RH induces a large release of FSH and a weak release of LH. In puberty, LH response becomes greater than FSH. In eugonadal women, FSH and LH responses are more marked during luteal phase than during preovulatory phase. Nonsequential hormonal contraceptives inhibit FSH and LH response to 50 mcg of LH-RH, but not to 100 mcg. In postmenopausal women, LH increases after 25 mcg of LH-RH; 200 mcg ethinyl estradiol for 5 days permits an increase of both gonadotropins. These results suggest that gonadotropin response to LH-RH depends on endocrine equilibrium and gonadal steroids which may modify the synthesis and/or release of pituitary gonadotropins. On the basis of selective LH response to small doses of LH-RH, ti is speculated that an FSH releasing factor may exist.
