Fibroblast growth factor 23

Fibroblast growth factor 23 or FGF23 is a is_associated_with::protein that in humans is encoded by the FGF23 is_associated_with::gene. FGF23 is a member of the is_associated_with::fibroblast growth factor (FGF) family which is responsible for is_associated_with::phosphate metabolism.

Function
The main function of FGF23 seems to be regulation of phosphate concentration in plasma. FGF23 is secreted by Osteocytes in response to elevated is_associated_with::Calcitriol. FGF23 acts on the kidneys, where it decreases the expression of NPT2, a sodium-phosphate cotransporter in the proximal tubule. Thus, FGF23 decreases the reabsorption and increases excretion of phosphate. FGF23 may also suppress 1-alpha-hydroxylase, reducing its ability to activate is_associated_with::vitamin D and subsequently impairing calcium absorption.

Clinical significance
FGF23 is located on is_associated_with::chromosome 12 and is composed of three is_associated_with::exons. Mutations in FGF23 that render the protein resistant to proteolytic cleavage leads to increased activity of FGF23 and the renal phosphate loss found in the human disease is_associated_with::autosomal dominant hypophosphatemic rickets. FGF23 is also overproduced by some types of is_associated_with::tumors, such as the is_associated_with::benign is_associated_with::mesenchymal is_associated_with::neoplasm is_associated_with::Phosphaturic mesenchymal tumor causing is_associated_with::tumor-induced osteomalacia, a is_associated_with::paraneoplastic syndrome. Loss of FGF23 activity is thought to lead to increased phosphate levels and the clinical syndrome of familial tumor is_associated_with::calcinosis. This gene was identified by its mutations associated with autosomal dominant hypophosphatemic rickets. Prior to discovery in 2000, it was hypothesized that a protein existed which performed the function of FGF23. This putative protein was known as phosphatonin.