Diagnosis of hyperparathyroidism in patients with urolithiasis using measurement of serum immunoreactive parathyroid hormone and serum calcium.

Serum immunoreactive PTH (iPTH) was measured in 74 patients with urolithiasis and correlated to the corresponding serum calcium values. Serum iPTH was measured using a rooster antibovine iPTH antiserum which crossreacted with the human hormone within the 44-68 amino acid residue region. Sixty-six of these patients had normal serum iPTH and calcium concentrations. Their calcium values varied from 2.2 mmol/l to 2.6 mmol/l and their serum iPTH concentrations were less than 0.6 micrograms/l. The remaining 8 patients with urolithiasis were judged to have primary hyperparathyroidism because of an abnormal iPTH/calcium relationship. These patients had serum calcium concentrations varying from 2.6 mmol/l to 3.4 mmol/l and iPTH concentrations between 0.35 micrograms/l and 3.03 micrograms/l. The diagnosis was verified histologically in 7 patients after operation. In the last patient iPTH was reduced from 1.01 micrograms/l to 0.21 micrograms/l after surgery, and serum calcium changed from 2.6 mmol/l to 2.2 mmol/l. The combined evaluation of serum iPTH and calcium may improve the diagnosis for hyperparathyroidism and was in our series helpful in making a correct diagnosis in 2 out of 7 patients who had histologically verified disease. In addition, iPTH measurements are valuable to rule out hyperparathyroidism as the cause of hypercalcaemia.