Interleukin-6 is higher in naturally menstruating women as compared to oral contraceptive pill users during the low hormone phase
Endogenous sex hormone concentrations vary between healthy naturally menstruating (non-OCP) and oral contraceptive pill-using (OCP) women, as well as across cycles. The aim of this study was to investigate potential differences in concentrations of inflammatory cytokine, interleukin-6 (IL-6), vasoconstrictive substance, endothelin-1 (ET-1), and measures of vascular function among relatively lower and higher hormone phases of non-OCP and OCP. Concentrations of estrogen, progesterone, IL-6 and ET-1 and measures of vascular function were collected in 22 women (22±1 y, OCP: n=12) during the early follicular (EF, ≤5 days of menstruation onset) and early luteal (EL, 4±2 days post-ovulation) phases of non-OCP and were compared to the placebo pill (PP, ≤5 days of PP onset) and active pill (AP, ≤5 days of highest dose AP) phases of OCP. Vascular function was assessed via brachial artery flow-mediated dilation (%FMD). Concentrations of endogenous estrogen and progesterone were higher in the EL phase as compared to the EF phase of non-OCP (p=0.01) but were similar between phases of OCP (p>0.05). IL-6 was higher in non-OCP during the EF phase as compared to the EL phase as well as compared to OCP during the PP phase (p=0.002) but was similar between groups during the EL and AP phases, respectively (p>0.05). Concentrations of ET-1 and measures of %FMD were similar between groups and unaffected by phase (p>0.05). Thus, there exists variation in inflammation between young, healthy non-OCP and OCP during the lower hormone phase, despite similarities in vascular function and concentrations of ET-1 between groups and phases.