PTH Regulation by the Klotho/FGF23 Axis in CKD

Secondary hyperparathyroidism (SHPT) is an important complication of chronic kidney disease (CKD) and end-stage renal disease (ESRD), particularly among patients receiving dialysis. Downregulation of the parathyroid hormone (PTH), vitamin D (VDR), and calcium-sensing receptors (CaR) represent critical steps that lead to abnormalities in mineral metabolism, including high phosphate, low calcium, and vitamin D deficiency. Circulating fibroblast growth factor 23 (FGF23) concentration increases in CKD and the complex klotho-FGF receptor decreases in hyperplastic parathyroid glands of uremic patients, contributing to SHPT. In this chapter, we describe the parathyroid glands physiology and its normal and pathological regulation by the FGF23/Klotho axis in CKD.