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

Abstract

Recent studies have revealed that HRT may increase the risk for atherosclerotic vascular disease (ASVD). 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 17beta-estradiol (E2) gel 0.6 mg/day for 6 months. The control group (n=30) had no treatment for 6 months. 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). 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.