FGF-23 is a hormone that is secreted by osteoblasts within the bones. This protein works with the kidneys to help regulated levels of phosphate in the blood/serum. The kidney gets rid of excess phosphate by excreting it in urine. When more phosphate is needed, the kidney reabsorb phosphate into the bloodstream. FGF-23 signals the kidneys to stop reabsorbing phosphate into the bloodstream. This fibroblastic growth factor binds to a receptor protein called FGF receptor 1. These receptors span the membrane of kidney cells. The binding of the protein and the receptors stimulates a signal cascade that stops phosphate reabsorption into the bloodstream.

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Why measure FGF-23?

Phosphate plays a critical role in the formation and growth of bones in children and for maintaining bone strength in adults. An imbalance in levels of FGF-23 in the body causes high or low levels of phosphate in the bloodstream. Low levels of phosphate in the blood can result in hypophosphatemia rickets or osteomalacia, which is a weakening of the bone which can cause bone pain and fractures. High levels of phosphate in the blood can indicate kidney disfunction.

Check out our two kits used for measuring FGF-23: