Menopause status as the main factor explaining the gender differences of serum nitric oxide concentrations in...

The aim of this study was to investigate whether the observed differences between serum NOx levels of men and women were influenced by the menopausal status of women.

A total of 1,209 eligible subjects, aged 40-60 years, were recruited from among participants of the Tehran lipid and glucose study, and subdivided into three groups: men (n = 457), women with regular cycles (n = 288) and postmenopausal women (n = 464). Serum concentrations of NOx were compared between these groups using Kruskal Wallis-Mann-Whitney U test, followed by Bonferroni correction. ANCOVA was applied for comparison of log-transformed NOx values between groups after adjustment for confounder variables.

The mean (SD) of age and BMI did not differ between studied groups. There were statistically significant differences between the medians (inter-quartile ranges) of serum NOx levels in men, women with regular cycles and the postmenopausal women [26 (20-37), 25.5 (19-39) and 29 (21-43) μmol/L], respectively (P = 0.012). Post hoc pair-wised comparison, adjusted with Bonferroni correction, demonstrated that women with postmenopausal status had higher serum levels of NOx values than those women with regular cycle or men (P = 0.011). The results remained unchanged after further adjustment for potential confounders.

These results provide evidence that differences observed between serum NOx values of middle-aged women and men are more related to menopausal status rather than gender.