The Women's Health Initiative (WHI) assessed the long-term effects of hormone therapy (HT) in postmenopausal women. The WHI started HT treatment on women aged 50-79 years in order to ascertain these effects. The study was ended early, due to findings of increased risk of coronary heart disease, breast cancer, stroke, and thromboembolic complications in women receiving estrogen plus progestin, compared to placebo. An increased risk of thromboembolic complications was also demonstrated in the estrogen only component of the WHI. The WHI results were initially reported for all subjects, and showed little difference when data were not analyzed by age. New WHI sub-analyses stratifying results by age, and an extended follow-up of the WHI offer a more complete picture of the effects of HT, revealing that starting HT in postmenopausal women less than ten years from last menstrual period appears to have less risk. In addition, hysterectomized women treated with estrogen only in the WHI have showed less risk of adverse outcomes than women in the estrogen plus progestin group. In this paper, we review data supporting the use of HT administered to postmenopausal women, showing it to have more benefit than risk for symptom control, prevention of bone mineral loss and fracture, and improvement of the metabolic profile in women who began HT when they were less than 60 years of age and had their last menstrual period less than ten years previous. In hysterectomized women treated with estrogen only, a reduction in breast cancer risk was noted in all age groups. The WHI raised many important questions. Ten years later, some have been answered, including confirmation that HT for most newly menopausal women is safe and effective. The treatment of the aging woman, including hormone treatment after menopause, should remain one of our highest research priorities. This article is part of a Special Issue entitled 'Menopause'.
Keywords: Hormone therapy; Menopause; Women's Health Initiative.
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