PTH and hyperphosphatemia: The other two related patients showed normal calcium concentrations (2.56 mmol/L and 2.44 mmol/L), mildly lowered parathyroid hormone concentrations (12.3 ng/L and 11.2 ng/L), and elevated phosphate concentrations (3.26 mmol/L and 2.87 mmol/L), suggesting familial hyperphosphatemia.