What causes X-linked hypophosphatemia ?
What causes X-linked hypophosphatemia? X-linked hypophosphatemia (XLH) is caused by mutations in the PHEX  gene on the X chromosome. Nearly 300 PHEX mutations have been associated with XLH. Mutations in this gene lead to an increase in the bodily concentration of fibroblast growth factor 23 (FGF23), a growth hormone that regulates phosphate reabsorption in the kidneys. Too much FGF23 causes phosphate wasting in the kidneys that prevents maintenance of proper phosphate levels in the blood and is responsible for the symptoms of XLH.