Estrogen improves endothelium-dependent, flow-mediated vasodilation in postmenopausal women

* Objective: To assess the effect of estrogen replacement therapy on endothelium-dependent vasodilation in postmenopausal women. * Design: Double-blind, placebo-controlled, crossover trial. * Setting: University medical center. * Patients: 13 postmenopausal women aged 44 to 69 years (average age, 55 [+ or -] 7 years). * Intervention: Patients were randomly assigned to receive placebo, oral estradiol at a dose of 1 mg/d, and oral estradiol at a dose of 2 mg/d. Each treatment phase lasted 9 weeks. * Measurements: High-resolution ultrasonography was used to measure vascular reactivity in a peripheral conduit vessel, the brachial artery. Endothelium-dependent vasodilation was determined by measuring the change in brachial artery diameter during increases in flow induced by reactive hyperemia. Endothelium-independent vasodilation was measured after sublingual nitroglycerin was administered. * Results: Flow-mediated, endothelium-dependent vasodilation of the brachial artery was greater when patients received estradiol (13.5% and 11.6% for 1-mg and 2-mg doses, respectively) than when patients received placebo (6.8%; P < 0.05 for each dose compared with placebo). In contrast, estrogen administration had no effect on endothelium-independent vasodilation as assessed by sublingual nitroglycerin. * Conclusion: Short-term estrogen replacement therapy improves flow-mediated endothelium-dependent vasodilation in postmenopausal women. This improvement may be mediated by a direct effect of estrogen on vascular function or may be induced through modification of lipoprotein metabolism.
Short-term treatment with estrogen replacements may improve dilation of the vessels of the heart in postmenopausal women, thus minimizing their risk of cardiovascular problems. A study of 13 postmenopausal women, aged 44 to 69, with high levels of cholesterol found that daily administration of estradiol (a form of estrogen) at a 1 milligram (mg) or 2 mg dose increased flow-mediated vasodilation in the brachial (arm) artery after nine weeks of treatment. High-resolution ultrasonography was used to measure changes in the diameter of the brachial artery. No major change in the total cholesterol level was noted with estrogen treatment. No specific dose of estrogen was recommended, although the study did conclude that estrogen replacement therapy improved the function of the blood vessels of the heart. Lower doses may be optimal because high doses of estrogen may increase the risk of endometrial cancer.