Administering phosphate therapy to individuals affected by XLH increases phosphate wasting and leads to secondary hyperparathyroidism and nephrocalcinosis, where the dose of phosphate correlates with the severity of nephrocalcinosis; low doses of 1,25D are given in combination with phosphate to XLH patients to suppress serum PTH levels [47, 48]. The gene discussed is PTH; the disease is nephrocalcinosis.