Ovarian cycle and sympathoexcitation in premenopausal women

The influence of the ovarian cycle on muscle sympathetic nerve activity (MSNA) remains controversial. Some studies report an increase of resting MSNA during the mid luteal (ML) phase of the ovarian cycle compared with the early follicular phase, whereas other studies do not. These inconsistent findings may be attributable, in part, to the 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 (ΔE(2)) and progesterone (ΔP). Multiple regression analysis of data from previous studies with complete recordings of mean arterial pressure, MSNA, E(2), and P during both early follicular and ML phases were available from 30 eumenorrheic women (age, 28 ± 1 years; body mass index, 23 ± 0 kg/m(2)). ML phase increased E(2) (37 ± 2 to 117 ± 9 pg/mL; P<0.001), P (1 ± 0 to 11 ± 1 ng/mL; P<0.001), and MSNA (12 ± 1 to 15 ± 1 bursts/min; P=0.02), but did not alter mean arterial pressure (83 ± 2 to 83 ± 2 mm Hg; P=0.91). ΔMSNA was correlated with ΔE(2) (r=-0.50, P=0.003) and ΔE(2)/ΔP (r=-0.52, P=0.002) but not ΔP (r=0.21, P=0.13). There was no association between Δmean arterial pressure and ΔE(2) (r=-0.13, P=0.49), ΔP (r=-0.04, P=0.83), or ΔE(2)/ΔP (r<0.01, P=0.98). In conclusion, sympathoexcitation during the ML phase of the ovarian cycle seems to be dependent, in part, on the degree of sex steroid surges. This dynamic interaction among E(2), P, and MSNA likely explains previously reported inconsistencies in the field; it remains possible that other sex steroids, such as testosterone, might explain further variance.