Effect of Estrogen Replacement Therapy on Sympathetic Activity in Postmenopausal Women

Abstract

To the Editor: Two recent articles in Circulation described modulations of sympathetic nerve activity to the muscle vascular bed in postmenopausal women on long-term estrogen replacement therapy (ERT). Vongpatanasin et al1 reported a decrease in resting muscle sympathetic nerve activity (MSNA) after transdermal but not oral estrogen administration. Furthermore, the diastolic blood pressure was significantly decreased after transdermal ERT. The authors concluded that the decrease in blood pressure was induced by a fall in MSNA to the muscle vascular bed. These data confirm and extend the results of a recent study that administered 2-day transdermal ERT to postmenopausal women and measured MSNA to the muscle vascular bed in the superficial peroneal nerve using a placebo-controlled, within-subject crossover design.2 In this study, resting MSNA decreased from 37.1±3.1 to 30.1±3.1 bursts/min by the second day of estrogen treatment. Vongpatanasin and colleagues1 show that this effect is sustained for a treatment period of 8 weeks. In the short-term study by Weitz et al,2 however, the identical decrease in MSNA was not accompanied by a fall in blood pressure. This finding casts doubt on the hypothesis that the decrease in blood pressure is the consequence of reduced sympathetic tone to the muscle vascular bed. Rather, other mechanisms, such as direct vascular effects, could account for the …