Preserving cardiovascular benefits of hormone replacement therapy.

In the premenopausal period, the risk of heart disease is considerably lower in women than in men; however, in the postmenopausal period, when estrogen levels are considerably lower, women's risk of heart disease increases dramatically and approaches that of men. Numerous animal studies, using a variety of models, also confirm estrogen's cardioprotective effect. Although the results of numerous population-based, observational studies have demonstrated a lower risk of heart disease in women who receive estrogen replacement therapy, evidence from prospective, randomized clinical trials is scant. The Postmenopausal Estrogen/Progestin Intervention (PEPI) trial evaluated cardiovascular risk factors, not events, in a large, prospective, randomized trial and found that estrogen improved lipid profiles and other known risk factors. In addition, the PEPI trial compared several estrogen/progestogen treatment regimens, including both medroxyprogesterone acetate (MPA) and micronized progesterone (MP), and found that combined hormone replacement therapy regimens including MP attenuated the beneficial effects of estrogen less than those containing MPA. In the Heart and Estrogen/Progestin Replacement Study (HERS), however, which prospectively evaluated whether estrogen and MPA use reduced the number of nonfatal myocardial infarctions and cardiovascular events, no effect was seen. Although HERS was a null trial, the vast literature base showing a cardioprotective effect should not be discounted. Further research will be required before blanket recommendations on the cardioprotective effects of hormone therapy can be made.