Estrogen metabolism in normal and neoplastic endometrium.

Studies on normal endometrium at different phases of the menstrual cycle have shown that progesterone and synthetic progestins reduce the levels of estradiol receptors in the tissue and increase the activity of estradiol-17beta-dehydrogenase, an enzyme that converts estradiol to estrone. These effects may account for the antiestrogenic characteristics of the progestins. Similar effects were obtained in some postmenopausal patients with endometrial adenocarcinoma treated for two to 10 days with oral medroxyprogesterone acetate. These results point to the potential usefulness of a short-term, in vivo biochemical test which, combined with histologic observations, may identify patients who are likely to respond to treatment with progestins.