Effect of Several Estrogens on Serum Gonadotropin Levels in Postmenopausal Women

Abstract

Serum follicle-stimulating hormone (FSH) and luteinizing hormone (LH) were determined by radioimmunoassay in postmenopausal women before, during and after the administration of small or moderate doses of ethinyl estradiol, mestranol, 1-hydroxyethinyl estradiol-1.3-diacetate and 17-dioxanyl estradiol. It was found that ethinyl estradiol in small doses (20 µg/day) primarily depresses serum FSH. In larger doses this estrogen and two of its derivatives (mestranol and 1-hydroxyethinyl estradiol-1.3-diacetate) lower both FSH and LH. No LH release is observed during treatment with any of these four estrogens. However, 2-3 days after cessation of treatment with 20 µg/day ethinyl estradiol or 200 µg/day 17-dioxanyl estradiol, there is a marked increase in serum LH concentrations. This rebound is most probably related to the drop in the circulating levels of these exogenous estrogens. It was also observed that the 17 hydroxy group seems to be essential for the inhibition of pituitary gonadotropin secretion.