Hypoparathyroidism was suspected as the etiology of the hypocalcemia because the patient’s intact parathyroid hormone (PTH) level was not elevated (21 ng/L; normal range: 10-65 ng/L) despite the presence of hyperphosphatemia (serum phosphate, 2.7 mmol/L; normal range: 1.16-1.87 mmol/L) and hypocalcemia. This evidence concerns the gene PTH and hyperphosphatemia.