ESTROGEN IMPROVES ENDOTHELIUM-DEPENDENT, FLOW-MEDIATED VASODILATION IN POSTMENOPAUSAL WOMEN

Objective: To assess the effect of estrogen replacement therapy on end othelium-dependent vasodilation in postmenopausal women. Design: Doubl e-blind, placebo-controlled, crossover trial. Setting: University medi cal center. Patients: 13 postmenopausal women aged 44 to 69 years (ave rage age, 55 +/- 7 years). Intervention: Patients were randomly assign ed to receive placebo, oral estradiol at a dose of 1 mg/d, and oral es tradiol at a dose of 2 mg/d. Each treatment phase lasted 9 weeks. Meas urements: High-resolution ultrasonography was used to measure vascular reactivity in a peripheral conduit vessel, the brachial artery. Endot helium-dependent vasodilation was determined by measuring the change i n brachial artery diameter during increases in flow induced by reactiv e hyperemia. Endothelium-independent vasodilation was measured after s ublingual nitroglycerin was administered. Results: Flow-mediated, endo thelium-dependent vasodilation of the brachial artery was greater when patients received estradiol (13.5% and 11.6% for I-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 administratio n 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 eff ect of estrogen on vascular function or may be induced through modific ation of lipoprotein metabolism.