Levonorgestrel/estradiol oral contraceptives affect brachial artery peak response during flow‐mediated dilation

Abstract

We investigated brachial artery responsiveness in two groups of females using different doses of combined monophasic levonorgestrel (LNG)/ethinyl estradiol (EE) oral contraceptives (OCs). We examined brachial artery peak responses during the active pill phase (AP) compared to placebo pill phase (PP) of the cycle. In Group A, active pills contained 0.10 mg LNG/ 0.02 mg EE. Group B active pills contained 0.15 mg LNG/ 0.03 mg EE. In both groups, placebo pills did not contain exogenous hormone. We tested the brachial artery using flow-mediated dilation (FMD) and nitroglycerin (NTG) to measure endothelium-dependent and endothelium-independent vasodilation, respectively. 12 women (18–26 yr) have completed the study, 8 in Group A and 4 in Group B. All subjects participated on two study days, once during the AP (days 5–7 of week 3) and once during PP (days 5–7 of week 4). Heart rate and blood pressure were continuously monitored while using high resolution Doppler ultrasound and automated wall tracking software to record brachial artery diameters, FMD, NTG dilation, and blood velocity each visit. There was a difference in FMD in Group A between AP and PP (5.16 ± 0.63% vs 7.23 ± 0.92%; p=0.024) but no difference in Group B between AP and PP (7.31 ± 0.29% vs 7.37 ± 0.93%; p=0.927). There were no differences in baseline diameters or shear rate between visits or groups (p>0.05). There were no differences in NTG dilation between groups or between AP and PP in either group (p>0.05). These data suggest that exogenous hormones can change vascular responsiveness during OC use and this response may be dose dependent. Supported by ACSM Grant #442981