Estrogen's role in endometrial cancer.

Data reported since 1975 indicate that the natural hormone estrogen may act as a carcinogen when unopposed by an adequate amount of progesterone. Carcinogenesis may proceed when it is present at a high level for a short time. It is generally accepted that 3 groups of women have been at risk of developing cancer from exogenous estrogen exposure: 1) women who took sequential oral contraceptives; 2) post-menopausal women who received estrogen replacement therapy; 3) girls with ovarian dysgenesis who received unopposed estrogen therapy at puberty. Similarly, 4 groups of women appear to be at risk of developing cancer form endogenous estrogen sources: 1) women with granulosa-cell or theca-cell ovarian tumors; 2) anovulatory women; 3) obese postmenopausal women; 4) women with liver disease. The falling incidence of endometrial cancer associated with diminished estrogen sales is the final proof of an association of estrogen exposure with development of disease.