Human Fibroblast growth factor 23 is encoded by FGF23 gene in humans. Human fibroblast growth factor 23 belongs to fibroblast growth factor family and is responsible for metabolism of phosphate. The prime function of fibroblast growth factor 23 is regulation of phosphate concentration in plasma. Fibroblast growth factor 23 is secreted in response to increased levels of calcitriol by the Osteocytes. Fibroblast growth factor 23 acts on kidneys and decreases NPT2 expression which is a sodium-phophate cotransporter in proximal tubule. Fibroblast growth factor 23 decreases the reabsorption and increases phospate excretion. It also suppresses 1-alpha-hydroxylase and reduces its ability of Vitamin D activation and impaires calcium absorption.

FGF23 is located on chromosome 12 and consists of three axons. FGF23 mutations lead to resistance of the protein towards proteolytic cleavage which results in elevated activities of FGF23 ans loss of renal phosphate which is observed in autosomal dominant hypophosphatemic rickets disease. Fibroblast growth factor 23 is overproduced by tumors like benign mesenchymal neoplasm , phosphaturic mesenchymal tumor which causes tumor-induced osteomalacia. Fibroblast growth factor 23 activity loss leads to increase in phosphate levels and syndrome of familial tumor calcinosis. The protein has direct effects which include sodium dependent phosphate transport impairement in renal brush border and intestinal membrane vesicles, inhibition fo calcitriol along with stimulation of calcitriol breakdown and inhibition of prathyroid secretion.