Effect of several estrogens on serum gonadotropin levels in postmenopausal women.

Abstract

To study the effect of several estrogens on serum gonadotropin levels in postmenopausal women blood samples taken from postmenopausal women treated with either ethinyl estradiol mestranol 1-hydroxethinyl estradiol-1.3-diacetate or 17-dioxanyl estradiol for 12-27 days were radioimmunoassayed for serum FSH and LH levels. Doses of 20 mcg/day of ethinyl estradiol began to lower FSH levels on the second day of treatment and lowered LH levels after 13 days. FSH levels stayed suppressed after cessation of the treatment but LH levels rebounded quickly. Ethinyl estradiol at higher doses caused quicker declines in both FSH and LH levels. Mestranol at 50 mcg/day produced significant decreases in FSH and LH levels starting on day 5 of treatment without rebound after cessation of treatment. Hydroxethinyl estradiol at 50 mcg/day caused a stronger decrease in FSH and LH levels than the other estrogens starting on day 2 without rebound. Dioxanyl estradiol at 200 mcg/day failed to inhibit FSH or LH levels in a significant manner and a strong LH rebound was seen within 1 day after cessation of treatment. This LH rebound similar to that seen with ethinyl estradiol at 20 mcg/day is probably due to a drop in the circulating levels of these exogenous estrogens. It is concluded that estrogens of the 17-hydroxy chemical group are necessary to inhibit pituitary gonadotropin secretion. In small doses these estrogens primarily suppress serum FSH only but both FSH and LH at higher doses.