Gonadotropin release after administration of LH-RH during early follicular phase

On day 7 of the menstrual cycle 15 ovulatory women received 8 bolus injections of 25 microgram, 100 microgram, or 500 microgram of LH-RH at hourly intervals. With increasing LH-RH doses total LH release increased significantly (P less than 0.05) whereas total FSH release did not differ among the groups. A biphasic release pattern independent of the LH-RH dose administered was obtained for both. After the first three LH-RH injections a stepwise augmentation of gonadotropin release followed by a rapid decline of LH and a more moderate decrease of FSH release were observed. The increase of pituitary sensitivity after repeated LH-RH stimulation may be explained by a self potentiating effect of LH-RH on its own secretion. The decrease in pituitary sensitivity observed with continuing LH-RH stimulation may be due to a refractory effect on the pituitary receptors.