Menstrual cycle and sympathetic neural activity in humans: A retrospective study

Abstract

Some studies report an increase of resting muscle sympathetic nerve activity (MSNA) during the midluteal (ML) phase of the menstrual cycle when compared to the early follicular phase (EF), while others do not. The inconsistent findings may be due, in part, to variable surges in estradiol and progesterone. We tested the hypothesis that the degree of sympathoexcitation during the ML phase (ΔMSNA) is associated with changes in estradiol (ΔE2) and progesterone (ΔP). Retrospective analysis of previous studies with recordings of mean arterial pressure (MAP), MSNA, E2, and P during both EF and ML phases yielded 30 eumenorrheic women (age, 18–51 yrs). ML phase increased E2 (37±2 to 117±9 pg/ml; p<.001), P (1±0 to 11±1 ng/ml; p<.001), and MSNA (12±1 to 15±1 bursts/min; p=.02), but did not alter MAP (83±2 to 83±2 mmHg; p=.91). ΔMSNA was correlated to ΔE2 (r=−.50, p=.005) and ΔE2/ΔP (r=−.52, p=.004), but not ΔP (r=.21, p=.26). There was no association between ΔMAP and ΔE2 (r=−.13, p=.49), ΔP (r=−.04, p=.83), or ΔE2/ΔP (r<.01, p=.98). In conclusion, sympathoexcitatory responses to the ML phase appear to be associated with the degree of sex steroid surges. While E2 had a stronger influence on MSNA than P, it is worthy to note that a strong association with ΔMSNA persisted when both ΔE2 and ΔP were considered. This dynamic interaction between E2, P, and MSNA likely explains previously reported inconsistencies in the field. Supported by NIH.