Besides, the prevalence of PCOS was dramatically raised with the quartiles of tryptophan, kynurenine, kynurenic acid, and quinolinic acid levels, while notably reduced with the quartiles of KYN/KYNA before and after adjustment for age, BMI, LH, androstenedione, and AMH (Figures 2C, D; Supplementary Table 3), demonstrating that the abnormal activation of the tryptophan-kynurenine pathway and obviously altered metabolites levels, indeed, profoundly affect the occurrence and development of PCOS. Here, PLOD1 is linked to polycystic ovary syndrome.