Brachial artery endothelial function is stable across a menstrual and oral contraceptive pill cycle but lower in premenopausal women than in age-matched men.

Sex hormone concentrations differ between men, premenopausal women with natural menstrual cycles (NAT), and premenopausal women using oral contraceptive pills (OCP), as well as across menstrual or OCP phases. This study sought to investigate how differences in sex hormones, particularly estradiol, between men and women and across cycle phases might influence brachial artery endothelial function. Fifty-three healthy adults (22 ± 3 yr, 20 men, 15 NAT women, and 18 second-, third-, or fourth-generation OCP women) underwent assessments of sex hormones and endothelial [flow-mediated dilation (FMD) test] and smooth muscle [nitroglycerin (NTG) test] function. Men were tested three times at 1-wk intervals, and women were tested three times throughout a single menstrual or OCP cycle (NAT: menstrual, midfollicular, and luteal phases and OCP: placebo/no pill, "early", and "late" active pill phases). Endogenous estradiol concentration was comparable between men and women in their NAT menstrual or OCP placebo phase ( P = 0.36) but increased throughout a NAT cycle ( P < 0.001). Allometrically scaled FMD did not change across a NAT or OCP cycle but was lower in both groups of women than in men ( P = 0.005), whereas scaled NTG was lower only in NAT women ( P = 0.001). Changes in estradiol across a NAT cycle were not associated with changes in relative FMD ( r2 = 0.01, P = 0.62) or NTG ( r2 = 0.09, P = 0.13). Duration of OCP use was negatively associated with the average relative FMD for second-generation OCP users only ( r = -0.65, P = 0.04). Our findings suggest that brachial endothelial function is unaffected by cyclic hormonal changes in premenopausal women but may be negatively impacted by longer-term use of second-generation OCPs. NEW & NOTEWORTHY We demonstrate that brachial artery flow-mediated dilation does not change across a menstrual or oral contraceptive pill cycle in premenopausal women but is lower in women than in men. Although unaffected by within-cycle changes in estradiol, brachial flow-mediated dilation is negatively correlated with duration of oral contraceptive pill use for second-generation pills.

Effect of sex, menstrual cycle phase, and monophasic oral contraceptive pill use on local and central arterial stiffness in young adults.

Arterial stiffness is associated with increased cardiovascular disease risk. Previous sex-based investigations of local and central stiffness report inconsistent findings and have not controlled for menstrual cycle phase in women. There is also evidence that sex hormones influence the vasculature, but their impact on arterial stiffness across a natural menstrual (NAT) or oral contraceptive pill (OCP) cycle has been understudied. This study sought to 1) examine potential sex differences in local and central stiffness, 2) compare stiffness profiles between NAT and OCP cycles, and 3) investigate the relationship between duration of OCP use and arterial stiffness. Sex hormone concentrations, ß-stiffness index (local stiffness), and carotid-femoral pulse wave velocity [cfPWV (central stiffness)] were assessed in 53 healthy adults (22 ± 3 yr old, 20 men, 15 NAT women, and 18 OCP women). All participants were tested three times: men on the same day and time 1 wk apart, NAT women in menstrual, midfollicular and luteal phases of the menstrual cycle, and OCP women in placebo, early active and late active pill phases. ß-Stiffness was higher in men than NAT and OCP women ( P < 0.001), whereas cfPWV was similar between groups ( P = 0.09). ß-Stiffness and cfPWV did not differ across or between NAT and OCP cycles ( P > 0.05 for both) and were not associated with duration of OCP use (ß-stiffness: r = 0.003, P = 0.99; cfPWV: r = -0.26, P = 0.30). The apparent sex differences in local, but not central, stiffness highlight the importance of assessing both indexes in comparisons between men and women. Furthermore, fluctuating sex hormone levels do not appear to influence ß-stiffness or cfPWV. Therefore, these stiffness indexes may need to be assessed during only one cycle phase in women in future investigations. NEW & NOTEWORTHY We observed higher local, but not central, arterial stiffness in men than women. We also demonstrated that there are no differences in arterial stiffness between naturally cycling women and women who use monophasic oral contraceptive pills, and that the duration of oral contraceptive pill use does not influence arterial stiffness.