Differential effects of oral conjugated equine estrogen and transdermal estrogen on atherosclerotic vascular disease risk markers and endothelial function in healthy postmenopausal women

Abstract

BACKGROUND: Recent studies have revealed that HRT may increase the risk for atherosclerotic vascular disease (ASVD). METHODS: We investigated the effects of HRT via different administration routes on the markers for ASVD and endothelial function in healthy postmenopausal women. The oral HRT group (n = 18) received conjugated equine estrogen 0.625 mg/day; the transdermal HRT group (n = 18) received 17 beta-estradiol (E-2) gel 0.6 mg/day for 6 months. The control group (n = 30) had no treatment for 6 months. RESULTS: The C-reactive protein (CRP) rose from 0.129 +/- 0.116 to 0.752 +/- 0.794 mg/dl (P < 0.01) in the oral HRT group but remained unchanged in the transdermal HRT and control groups. The flow-mediated vasodilation (FMD) in the brachial artery was increased significantly by HRT from 6.0% before oral HRT to 14.7% after oral HRT (P < 0.001) and from 5.9% before transdermal HRT to 13.9% after transdermal HRT (P = 0.001). CONCLUSIONS: These data suggest that oral estrogen induces ASVD risk by increasing acute inflammation; however, transdermal estrogen avoids this untoward effect. Additionally, transdermal estrogen exerts a positive effect on endothelial function similar to that of oral estrogen. Therefore, the transdermal route might be favourable in terms of ASVD risks.