However, it is noteworthy that there was a remarkably negative correlation between the expression level and promoter methylation level of BNIP3 in the control group (R = − 0.740, P = 0.001), but this correlation was not found in the PCOS group (R = 0.23, P = 0.923). This evidence concerns the gene BNIP3 and polycystic ovary syndrome.