Estrogen replacement therapy has been shown to reduce the risk of coronary heart disease (CHD) in women, especially in women who have a history of this disease. Hulley and colleagues report the results of the Heart and Estrogen/progestin Replacement Study (HERS), which evaluated postmenopausal women with heart disease to see if therapy with estrogen plus progestin lowered the risk of events associated with coronary heart disease.

Postmenopausal women younger than 80 years who had established coronary heart disease were randomized to receive either conjugated equine estrogen plus progestin or a placebo daily. Women were excluded from the study if they had had an event associated with their coronary disease in the previous six months.

Baseline physical examination included a breast examination, Papanicolaou smear, endometrial evaluation, mammogram and an electrocardiogram. A lipid profile was also performed. Patients were examined every four months. After one year, many of the baseline studies were repeated. Outcome measures were nonfatal myocardial infarction or death as the result of coronary heart disease.

Of the 2,763 women enrolled in the study, 1,380 received hormone replacement therapy (HRT) and 1,383 received placebo. The average length of follow-up was 4.1 years. More women in the treatment group experienced events associated with coronary heart disease in the first year of treatment, although this early increase did not continue throughout the follow-up period. Overall, coronary heart disease events occurred in 172 women in the treatment group and in 176 women in the control group. These differences were not statistically significant. However, women in the treatment group did experience significant increases in the risk of gallbladder disease and venous thromboembolism.

The authors conclude that the use of estrogen-progestin replacement therapy in postmenopausal women for secondary prevention of coronary heart disease is unwarranted. However, women who are already receiving therapy should continue it, as the reduction of events associated with heart disease is favorably affected after several years of treatment. In a related editorial, Petitti underscores the efficacy of estrogen replacement therapy for bone and menopausal symptoms and stresses that no woman, even those with coronary heart disease, should stop hormone replacement therapy solely on the basis of the HERS study results.