Fibroblast growth factor 23 (FGF23)

Fibroblast growth factor 23 or FGF23 is a protein encoded by the FGF23 gene.

It is is a member of the fibroblast growth factor (FGF) family which aids in phosphate and vitamin D metabolism and regulation.

Chromosome 12 

Its main function is regulation of phosphate concentration in plasma. 

FGF23 is secreted by osteocytes in response to increased calcitriol. 

FGF23 acts on the kidneys, where it decreases a sodium-phosphate cotransporter in the proximal tubule.

Thus, FGF23 decreases the reabsorption of calcium and increases excretion of phosphate. 

FGF23 may suppress 1-alpha-hydroxylase, reducing its ability to activate vitamin D and subsequently impairing calcium absorption.

FGF23 gene is located on chromosome 12 and is composed of three exons. 

FGF23 mutations resist proteolytic cleavage increasing its activity.

 FGF23 excess causes renal phosphate loss and is found in autosomal dominant hypophosphatemic rickets. 

FGF23 is also overproduced by some types of tumors, causing tumor-induced osteomalacia, a paraneoplastic syndrome.

The  mutational loss of FGF23 activity leads to increased phosphate levels and the clinical syndrome of familial tumor calcinosis: autosomal dominant hypophosphatemic rickets.

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