In mouse models, loss of PHEX function or increased FGF-23 production inhibits mineralization mainly, but not only, because of hypophosphatemia due to decreased renal Pi reabsorption, secondary to the decreased abundance of the brush border membrane (BBM)-associated Na-Pi cotransporter proteins [20,75,76,77,78] and the decreased intestinal absorption of phosphate [79]. The gene discussed is PHEX; the disease is hypophosphatemia.