CST3 and chronic kidney disease: For the horizontal pleiotropy, we found that there was no evidence between PCOS and serological indicators of CKD: fibroblast growth factor 23 (P= 0.971), creatinine (P = 0.212), cystatin C (P= 0.357), estimated glomerular filtration rate (P= 0.180), β2-microglobulin (P = 0.600), except for urinary albumin-to-creatinine ratio (P= 0.046).