Changes in pituitary sensitivity to GnRH in estrogen-treated post-menopausal women: evidence that gonadotrophin surge attenuating factor plays a physiological role

BACKGROUND: The purpose of this study was to investigate changes in pituitary response to GnRH in post-menopausal women during substitution treatment with exogenous estrogen and progesterone. METHODS: Seven healthy post-menopausal women (group 1) were treated with various doses of E2 valerate for 43 days, so as the serum concentrations of E2 mimicked those of a follicular (FP-1), a luteal (LP) and a second follicular (FP-2) phase. During the LP, progesterone was also administered. The 30 min response of LH (ΔLH) and FSH (ΔFSH) to GnRH (10 μg i.v.) (pituitary sensitivity) was investigated every 24 h in group 1 and also in seven normally cycling women (group 2) during a spontaneous (control) follicular phase (FP). Based on the hormone profiles, day 32 in group 1 (FP-2) corresponded to day 2 in the spontaneous FP of group 2. RESULTS: Basal FSH concentrations were significantly higher in FP-2 than in the control FP (P