CST3 and polycystic ovary syndrome: The IVW analysis showed that PCOS and some indicators have causal relationship such as fibroblast growth factor 23 (1.205, 95% CI, 1.031-1.409; P = 0.019), creatinine (0.012, 95% CI, 1.001-1.023; P = 0.035), cystatin C (1.024, 95% CI, 1.006-1.042; P = 0.009).