On a normal diet, Vdr−/− mice were hypocalcemic, hypophosphatemic, had elevated parathyroid hormone (PTH) levels and virtually undetectable fibroblast growth factor (FGF23) levels, while urinary fractional excretion of calcium and phosphate remained relatively high given the hypocalcemia and hypophosphatemia (Fig. 3a, b). This evidence concerns the gene FGF23 and Hypocalcemia.