SummaryIntroduction We previously reported that granulocyte colony-stimulating factor (G-CSF) plays a critical role in ovulation, suggesting that neutrophils may maintain ovulation. We assessed myeloperoxidase (MPO), a major and specific enzyme of neutrophils, in women with abnormal and normal menstrual cycles to clarify the relationship between MPO and ovulation. Methods We analyzed MPO activity in blood neutrophils of women with abnormal menstrual cycles (indicative of anovulation, n = 12) and age- and body mass index-matched normal menstrual cycles (indicative of ovulation, n = 24) using two parameters as a marker of MPO, Neut X and mean peroxidase index (MPXI). Results MPO of women with abnormal menstrual cycles was significantly lower than that of women with normal menstrual cycles [Neut X: 62.6 ± 1.1 (mean ± standard error of the mean) vs. 66.2 ± 0.3, P = 0.009; MPXI: −0.54 ± 1.66 vs. 4.91 ± 0.53, P = 0.008]. Among women with normal menstrual cycles, MPO was highest in the follicular phase (Neut X: 67.0 ± 0.3; P = 0.033). Conclusion The difference in MPO between women with abnormal and normal menstrual cycles and the upregulation of MPO before ovulation suggest that neutrophils and MPO are closely related to ovulation.
