[Diagnostic significance of parathyroid hormone-related protein in tumor patients with hypercalcemia]

The clinical utility of measuring parathormone-related protein (PTHrP) was investigated in 94 patients (48 men, 46 women, mean age 56 [18-82] years) with tumour-associated hypercalcaemia, using a radioimmunoassay directed against the middle portion (53-84) of PTHrP (reference range < 5-21 pmol/l). Increased levels of the middle portion of PTHrP were found in 44 of the 73 patients (60%) with hypercalcaemia associated with solid tumours (median 49 [22-333] pmol/l). There was a positive correlation between the serum calcium concentration and the PTHrP (P = 0.018). The frequency of a raised PTHrP, indicating hormone-induced hypercalcaemia, was similar in patients with and without bone metastases (48% vs 66%). Elevated PTHrP was particularly frequent in patients with squamous cell carcinomas (17 out of 21; 81%), while PTHrP levels were normal in 18 out of the 21 patients with hypercalcaemia associated with haematological malignancies. PTHrP levels were normal in 37 out of 38 normocalcaemic tumour patients and in 30 out of 32 patients with primary hyperparathyroidism. Hypercalcaemia associated with benign disease was found in only one case, a female with marked benign breast hypertrophy.--The measurement of PTHrP allows the demonstration of a pathogenetic factor in tumour-associated hypercalcaemia, and differentiation from other causes of hypercalcaemia, in particular primary hyperparathyroidism.