Gonadotropin secretion in response to low and high doses of LRF in normal and hypogonadal women (functional disparity of the gonadotrophs)

Abstract

A comparison was made of gonadotropin release after an iv bolus of large (150 mug) and small (10 mug) doses of LRF during various phases of the menstrual cycle and in primary hypogonadal women. Gonadotropin release was quantitatively similar to small and large doses of LRF in hypogonadal women with low estradiol levels. In contrast, normal women from the early to late follicular phase of the cycle, the gonadotropin response to a small dose of LRF (10 mug) was not as great as that observed with a large dose of LRF (150 mug) and did not elicit the augmented gonadotropin response of the late follicular phase. During the mid-luteal phase, a significant enhancement of responses to small doses of LRF was observed. The sustained gonadotropin release induced by the large dose of LRF in the late follicular phase was no longer apparent during the mid-luteal phase, although the dose-related discrimination of LH release was maintained. These dose-related disparities in the gonadotropin release to LRF might represent functional expressions of the two-pool dynamics of the gonadotrophs induced by ovarian steroids.