Variations in endothelial function and arterial compliance during the menstrual cycle

Female sex hormones have been implicated in the cardioprotection of premeno pausal women. However, the cardiovascular actions of these hormones and the effects of their natural fluctuations during the menstrual cycle are not f ully understood. We studied changes in vascular function during the menstru al cycle in 15 healthy premenopausal women. Four noninvasive procedures wer e performed during, the early follicular (EF), late follicular (LF), early luteal (EL), and late luteal (LL) phases: flow-mediated dilatation (FMD) of the brachial artery during reactive hyperemia, laser Doppler velocimetry ( LDV) with direct current iontophoresis of acetylcholine (ACh) and nitroprus side, whole body arterial compliance (WBAC), and pulse wave velocity. Hormo ne levels were consistent with predicted cycle phase and showed that all su bjects ovulated during the cycle studied. FMD, LDV with ACh, and WBAC varie d cyclically, with significant increases from the F to LF phase, sharp fall s in the EL phase, and significant recoveries in the LL phase. These change s were most marked for FMD [EF, 8.8 +/- 0.6% (mean +/- SEM); LF, 10.0 +/- 0 .7; EL, 4.2 +/- 0.6; LL, 8.6 +/- 0.9] and the LDV response to ACh (EF, 2.7 +/- 0.2 V/min; LF, 3.3 +/- 0.4; EL, 1.8 +/- 0.3; LL, 2.7 +/- 0.4). WBAC cha nged similarly (EF, 0.58 +/- 0.08 arbitrary units; LF, 0.84 +/- 0.06; EL, 0 .65 +/- 0.05; LL, 0.68 +/- 0.06). Sodium nitroprusside-induced vasodilatati on decreased significantly from EF to EL, with no other significant differe nce, and pulse wave velocity did not vary significantly over the four time points. Conductance and resistance artery endothelial reactivity and smooth muscle sensitivity to nitric oxide and arterial compliance are modulated significa ntly in response to the changing hormonal patterns of the menstrual cycle. These findings emphasize the importance of menstrual phase in the interpret ation of data on endothelial function and may provide insights into the mec hanisms underlying sex differences in cardiovascular risk and other disease processes in premenopausal women.