Phosphate homeostasis, monitoring and managment of hyperphosphatemia in patients with the Chronic Kidney diseases

5. Fibroblast growth factor 23 (FGF23)

FGF23 is a phosphatonin that is produced primarily by osteocytes and to a lesser extent, by osteoblasts. It is a hormone that consists of 251 amino acid residues, including a signal peptide comprising 24 amino acids.

It inhibits renal tubular reabsorption of phosphate. FGF23 exerts its effects by binding to the FGFR1-Klotho complex. Alpha Klotho serves as a co-receptor. FGF23 suppresses NPT2a and NPT2c expression at the proximal renal tubules, thereby inhibiting renal phosphate reabsorption.FGF23 also reduces the circulatory level of 1,25(OH)2D by decreasing the expression of 1-alpha-hydroxylase and increasing the expression of 24-hydroxylase.