Modulation of pituitary responses to synthetic LH-RH by gonadal steroids in women with secondary amenorrhoea.

LH-RH stimulation tests were performed on two successive days in 25 women with secondary amenorrhoea of probable hypothalamic origin by intravenous injection of 150 mug of synthetic LH-RH. The patients were selected by exclusion of definite pituitary or ovarian disease and in the absence of clinical or laboratory evidence of androgen excess. Five women received successive LH-RH stimulation tests only without administration of steroid hormone. Twenty women were treated with gonadal steroids in addition to the double LH-RH stimulation test by intramuscular injection of the steroid 4 h after the first LH-RH injection. Of these 20, 9 received oestradiol (Oe2), 5 received progesterone (P) and 6 received Oe2 + P. Gonadotrophin responses to LH-RH in successive tests without steroid were not significantly different. Oe2 or P alone each produced suppression of LH and FSH responses to LH-RH in the second test as compared to the first. Combined Oe2 + P produced augmentation or suppression of the second gonadotrophin responses depending on the dose of Oe2 administered. The results demonstrate a direct effect of oestrogen or progesterone alone and in combination on the pituitary responsiveness to LH-RH. The effect of the combined steroids can be modified by variation in the oestrogen: progesterone ratio.