Postmenopausal Hormone Replacement Therapy: How Could We Have Been So Wrong?

While the public is hungry for medical discoveries that will immediately change clinical practice, evidence typically accumulates piecemeal and practice changes slowly. The early stoppage and release of the main results of the estrogen plus progestin component of the Women's Health Initiative (WHI) broke the typical pattern. This very large, methodologically rigorous randomized, controlled trial found that for every 10 000 women taking the hormone combination for 1 year (10 000 person-years), 7 more would have coronary events, 8 more would have strokes, 8 more would have pulmonary emboli, and 8 more would have invasive breast cancer than would 10 000 women taking placebo (1). Benefits of combination hormone therapy were 6 fewer cases of colorectal …