Primary and secondary prevention of cardiovascular events through hormone replacement therapy (HRT)

A recently (2002) published, randomised, double blind placebo controlled trial of hormone replacement therapy (HRT), the Women's Health Initiative (WHI), is not consistent with the decrease in cardiovascular disease under CEE/HPA seen in observational primary prevention studies like the Nurses' Health Study. Baseline characteristics of participants like age, body mass index, years since menopause and preexistent cardiovascular diseases may be responsible for the lack of benefit seen in this trial. Clinical outcome data of HRT from randomised trials in secondary prevention of cardiovasular diseases are limited. The first prospective, randomised placebo controlled trial, the Heart and Estrogen/Progestin Replacement Study (HERS) in secondary prevention did not show any difference in CHD events between treatment groups and placebo during a follow up of 4.1 years. However, an increased risk of CHD was seen especially during the first year on HRT, subsequent years showed a decrease in event rate compared with never-users. One explanation for this lack of benefit may be a bi-directional effect of estrogen - early risk and late benefit - especially in an elderly study population with established atherosclerotic lesions. In postmenopausal women, estrogen replacement therapy affects LDL-and HDL-cholesterol levels favorably, causes vasodilatation by activating NOS, inhibits platelet aggregation and proinflammatory cell adhesion on endothelial cells of vascular wall. Estrogen can affect the cardiovascular system adversely by increasing triglycerid levels, CPR and proinflammatory cytokines like tumor necrosis factor a (TNF-alpha). Alternatives to HRT like phytoestrogens act via estrogen a and beta receptor modulation. Phytoestrogens may lo-wer LDL-cholesterol levels without increasing triglyceride levels, they have shown antioxidannt properties as well as favorable effects on vascular reactivity. The importance of HRT and phytoestrogens in primary and secondary prevention of cardiovascular disease remains to be established.