PTH and chronic kidney disease: After adjusting for confounding factors, one increase in CKD stage was associated with an increase of 58.87 pg/mL (95% CI: 38.00, 79.73) in PTH, and associated with an increase of 0.545% (95% CI: 0.096, 1.027) in PI; for every 1 pg/mL increase in PTH was associated with an increase of 0.005% (95% CI: 0.001, 0.009) in PI; the increased PTH mediated 34.4% of the total effect of CKD stages on PI.