The Women's Health Initiative trials of menopausal hormone therapy: lessons learned

Objective: The Women's Health Initiative (WHI) assessed oral conjugated equine estrogens (CEE) taken with or without medroxyprogesterone acetate (MPA) for prevention of chronic disease in postmenopausal women aged 50-79 years. Methods: Women with an intact uterus (n = 16,608) were randomized to CEE+ MPA therapy or placebo for a median of 5.6 years; women with hysterectomy (n = 10,739) were randomized to CEE-alone therapy or placebo for a median of 7.2 years. Both cohorts have been followed for 18 years. Results: In the overall study population (mean age, 63 y), neither estrogen-progestin therapy (EPT) nor estrogen-only therapy prevented coronary heart disease or led to a favorable balance of chronic-disease benefits and risks. Subgroup analyses, however, suggest that timing of hormone therapy (HT) initiation influences the relation between HT and coronary risk, as well as its overall benefit-risk balance, with more favorable effects in women who are younger (age < 60 year) or recently menopausal (within 10 year) than in women who are older or further past the menopausal transition. In younger women who entered the trial of estrogen-only therapy with oophorectomy, the intervention was associated with a significant 32% reduction in all-cause mortality over long-term follow-up. Conclusions: WHI findings indicate important differences in HT-related clinical outcomes by age and time since menopause. Systemic HT has an acceptable safety profile for menopause management when initiated among healthy women who are younger (or recently menopausal) and not at elevated risk for cardiovascular disease or breast cancer. Initiation of treatment in older women who are distant from menopause onset, however, should be avoided. Other HT formulations and routes of delivery warrant further study. (WHI clinicaltrials.gov identifier: NCT00000611)