The history of hormone therapy use and recent controversy related to heart disease and breast cancer arising from prevention trial outcomes.

The reasons for hormone therapy use have changed dramatically over time from being very popular for the purpose of preserving youth in women to menopause-related symptom management, disease prevention, and now back to menopause-related symptom management. Over time, several important risks associated with the use of hormone therapy have become evident, causing dramatic reductions in the use of hormone therapy for periods of time following identification of these risks. Most recently, randomized controlled prevention trials that evaluated hormone therapy for the purpose of reducing or preventing coronary heart disease among women have found that hormone therapy is associated with increased rather than decreased risks for coronary heart disease. The most recent of these trials again identified increased risks for breast cancer associated with estrogen plus progestogen therapy. The evolving evidence base from these randomized controlled prevention trials is complicated and in some cases contradictory. Specifically, the data suggest that the timing of when hormone therapy is initiated once a woman is postmenopausal may influence her risk for developing heart disease and breast cancer. In this article, contradictory evidence is carefully sifted so risks and benefits can be weighed by clinicians when partnering with women to individualize decisions about using hormone therapy.