Estrogen replacement therapy and the prevention of coronary heart disease in postmenopausal women

The use of estrogen replacement therapy (ERT) for the prevention of coronar y heart disease (CHD) is discussed. Cardiovascular disease is the number one cause of death in women. It is bel ieved that the loss of estradiol production at menopause increases the risk of CHD. Theoretically, ERT should decreases CHD rusk in postmenopausal lev els the metabolic factors that affect CHD. Many mechanistic studies of the effects of estrogen on lipoproteins, hemostasis, carbohydrate metabolism, a nd vessel wall tone and reactivity support a cardioprotective role for estr ogen. In addition, observational studies have found that ERT, with or witho ut progesterone, significantly reduces the risk of CHD. However, mechanisti c and observational studies can establish only an association, not a cause and effect relationship. Furthermore, bias may influence the risk estimates . The heart and Estrogen/Progestin Replacement Study (HERS), published in 1 998, was the first large, randomized, controlled trial to evaluate the effi cacy of estrogen and progesterone replacement therapy in reducing CHD risk. Overall, the study found that continuous hormone replacement therapy (HRT) in women with CHD did not reduce cardiovascular risk at an average of 4.1 years of follow-up. In addition, there was an early increase in the risk of thromboembolic events. Although many mechanistic and observational studies suggest that ERT reduce s the risk of morbidity and mortality from CHD in postmenopausal women, the only large, randomized, controlled study of this question to date failed t o confirm this. Until data from ongoing studies are available, health care providers must reconsider prescribing ERT or HRT solely for the secondary p revention of CHD.