Abstract

PIP: The effects of 17beta-estradiol on the responsiveness of the pituitary to gonadotropin-releasing hormone (GnRH) and on the rate of disappearance of GnRH were studied in 15 healthy nulliparous women aged 18-21 years. The women were divided into 3 groups: Group 1 received no estradiol, Group 2 received the amount of estradiol needed to achieve a circulating level comparable with that in the late follicular phase, and Group 3 received enough estradiol to achieve a concentration similar to that at midcycle. Following administration of GnRH, a marked increase in both LH and FSH was seen in Group 1 subjects. A smaller increase in LH level was observed in Group 2, and virtually no LH response occurred in Group 3. There was no significant increase in FSH level in either group treated with estradiol. The infusion of estradiol did not affect the maximal plasma concentration of exogenously administered GnRH or its disappearance rate in 4 women studied.