Postmenopausal estrogen replacement therapy appears to reduce the risk of coronary artery disease as well as the mortality associated with cardiovascular disease. The mechanisms for this effect are unclear, although postmenopausal hormone replacement therapy (HRT) reduces low-density lipoprotein cholesterol and increases high-density lipoprotein cholesterol by 10 to 15 percent. A beneficial effect on endothelial function has also been observed. Lim and associates studied the effects of long-term HRT on left ventricular (LV) wall thickness in women.

Twenty women who had been receiving HRT for more than 10 years were compared with 19 healthy control subjects. All of the women were white and postmenopausal. The study excluded women with previously identified heart disease or high blood pressure, or those being treated with cardiac medications. The study subjects and control subjects were matched for age. Complete medical histories were obtained, as well as vital signs and transthoracic echocardiography to measure LV dimensions.

Members of the control group were found to have a significantly greater LV mass adjusted for height. A statistically significant difference between the groups was found in the size of the posterior wall and the septum. Even after adjusting for age, alcohol consumption, body mass index and systolic hypertension, HRT remained a statistically significant variable. There was a nonsignificant trend for more regular exercise among the women who were taking HRT.

The authors conclude that LV dimensions were reduced by 19.7 percent in a small group of women taking HRT for more than 10 years compared with control subjects. Since LV hypertrophy has been shown to be an independent risk factor for mortality associated with cardiovascular causes, this protective effect may explain a part of the beneficial effects of HRT in the reduction of cardiac mortality in women.