Estrogens and progestins: Background and history, trends in use, and guidelines and regimens approved by the US Food and Drug Administration

The US Food and Drug Administration (FDA) approved marketing of diethylstilbestrol in 1941 and conjugated equine estrogens (CEE) in 1942 for treament of menopausal symptoms. Estrogen sales doubled and tripled in the mid-1960s to mid-1970s until 1975, when reports of increased endometrial cancer in estrogen users resulted in a dramatic decline. Estrogen use increased again, with evidence of protective effects of progestins on estrogen-induced endometrial changes, combined with a 1982 report that Premarin (conjugated estrogen tablets; Wyeth Pharmaceuticals Inc., Philadelphia, PA) retained bone mass and a 1984 National Institutes of Health (NIH) Consensus Conference on Osteoporosis statement that estrogens were the most effective means for preventing bone loss. Despite conflicting 1985 reports regarding the relation between estrogens and coronary heart disease (CHD), many published observations of reduced CHD risk in estrogen users—reinforced by 1995 clinical trial findings of favorable lipoprotein changes in women assigned to CEE with or without a progestin—promoted increased use through the 1990s. By 2001, approximately 15 million US women were using estrogen therapy with or without progestins. The 2002 Women’s Health Initiative (WHI) clinical trial finding of greater harm than benefit of combined CEE plus a progestin resulted in a precipitous decrease in estrogen and progestin use and a serious reevaluation of menopausal hormone therapy, as well as increased interest in alternative approaches to managing menopausal symptoms, including use of “bioidentical” hormones. FDA guidelines regarding treatment indications for vasomotor symptoms, vaginal atrophy, and osteoporosis prevention have resulted in approval of several estrogen (and progestin) formulations, doses, and routes of administration, thereby providing many options for women who seek conventional therapy.