[Hormone replacement therapy of menopause, heart and blood vessels].

The incidence of coronary heart disease (CHD) is lower in premenopausal women than in men and post-menopausal women of the same age. The higher CHD rate after menopause is currently attributed to estrogen deficiency: many epidemiological (case-control and prospective) studies have reported a reduced risk (0.5-0.63) of CHD in post-menopausal women receiving hormone replacement therapy (HRT). Moreover, estrogens have multiple effects that would be expected to be cardioprotective, including favorable changes in lipids, endothelial function, vascular reactivity and blood flow. However, the observational studies are subject to several biases that could falsely elevate the apparent benefit of estrogens: women taking estrogens tend to be wealthier, more educated and healthier than untreated women. The american HERS (Heart and Estrogen-progestin Replacement Study; 2.763 women) is a large multicenter randomized study of secondary prevention, designed to evaluate the efficacy of HRT. Results are disappointing, since no reduced risk was observed, and the risk of CHD was even higher in women receiving HRT during the first year: 1.52 (CI 95%: 1.01-2.29). In HERS study, the treatments consisted of conjugated equine estrogens and the synthetic progestin medroxyprogesterone acetate (MPA) which are rarely used in Europe. Indeed, the effects of HRT are not equivalent depending on the dose, the route of administration, the type of progestogen. It should be emphasized that MPA, contrarily to progesterone, inhibits the beneficial effect of estrogens on lipids and experimental atherosclerosis. The route of administration of estrogens is also involved: estrogens alter hemostasis factors, and when orally administered, they have a first pass liver effect, which favors hypercoagulability. It is therefore urgent that Europeans undertake a European "HERS study" in order to investigate the possible beneficial effect of non oral estrogens (gel or patch) associated with natural progesterone.