Leg microvascular function remain robust throughout the female menstrual cycle

Abstract

BACKGROUNDThe female menstrual cycle (MC) is characterized by fluctuating concentrations of estrogen and progesterone. While the impact of these vasoactive sex hormones on macrovascular function has received considerable attention, little is known about their influence on the microvasculature. Since the microvasculature ultimately determines skeletal muscle perfusion, a thorough understanding of the influence sex hormones have on microvascular function is needed. It was therefore the purpose of this study to investigate microvascular function, as assessed via the passive leg movement technique (PLM), of eumenorrheic females at three unique gonadal hormone profiles.METHODSSix healthy females (age: 22 ± 2 years; height: 168 ± 2 cm; weight: 59 ± 2 kg) were studied during the early follicular (EF; days 1‐4), late follicular (LF; days 8‐12), and mid luteal (ML; days 8‐10 post luteinizing hormone peak) phases of their MC. Venous blood was collected and analyzed for estrogen and progesterone concentrations. For each visit, subjects arrived at the laboratory in a fasted, rested state and at the same time of day. Passive leg movement (1 Hz for one minute; 90‐degree range of motion at the knee) was performed in a seated position. At rest and during PLM, leg blood flow (femoral artery; QL) was measured with Doppler ultrasound, while heart rate (HR), cardiac output (CO), and mean arterial pressure (MAP) were continuously measured via Finapress.RESULTSAll females presented traditional patterns of hormonal variation throughout the MC. Estrogen (EF: 144 pg/mL, LF: 239 pg/mL, ML: 359 pg/mL) was different at each phase (p < 0.05), while progesterone was similar during EF and ML (~0.2 ng/mL; p = 0.2), but significantly higher during ML (~6.8 ng/mL, p = 0.02). The area under the curve (AUC) for QL (~170 mL, p = 0.7) during the 1 min PLM, and the increase in QL from rest to the peak response to PLM (QLΔpeak; ~540 mL/min, p = 0.3) were not different at any phase of the MC. Furthermore, MAP AUC (~1.0 mL), MAPΔpeak (~6 mmHg), and therefore leg vascular conductance (VC) AUC (~1.9 mL/mmHg) and VCΔpeak (~6.5 mL/min/mmHg), did not change throughout the MC (p > 0.3). Finally, COΔpeak (~0.6 L/min) and HRΔpeak (~7 bpm) remained similar throughout the MC (p > 0.4).SUMMARY & CONCLUSIONDespite significant differences in venous estrogen and progesterone concentrations during EF, LF, and ML, the hyperemic response to PLM was unchanged at each phase, indicating that microvascular function remain consistent throughout the MC. In addition, both the MAP and the central hemodynamic response to PLM was similar at each stage of the MC. These findings suggest that a tight control of the MC may no longer be considered critical for studies focusing on microvascular function. These new insights might, ultimately, facilitate the involvement of females in future investigations.