THE VALUE OF THE PARATHYRINE RELATED PROT EIN IN THE DIAGNOSIS OF HYPERCALCEMIA ASSOCIATED TO CANCER

BACKGROUND: The parathyrine related protein (PTH-RP) is very similar, both in structure and in function, to the PTH and is considered as a m ediator in humoral hypercalcemia in cancer. The aim of this study was to know the clinical value of PTH-RP measurement. METHODS: Serum PTH-R P concentrations were studied in 22 healthy subjects, 13 patients with primary hyperparathyroidism, 9 patients with solid neoplasms and norm ocalcemia, 26 patients with solid neoplasms and hypercalcemia and 4 pa tients with hematologic neoplasms and hypercalcemia. The PTH-RP was qu antified by a competitive radioimmunoassay technique using a specific antibody of the PTH-RP 1-40 fragment. Intact parathyrine (I-PTH) was q uantified by an IRMA method using 2 polyclonal antibodies (lNCSTAR). R ESULTS: Fifteen (68%) of the healthy controls presented undetectable s erum PTH-RP concentrations. The serum PTH-RP concentration was normal in all those patients with hyperparathyroidism. Elevated serum PTH-RP values were not found in patients with solid neoplasms and normocalcem ia or in those with hematologic neoplasms and hypercalcemia. High valu es of PTH-RP were observed in 8 out of 9 (88%) of the patients with so lid neoplasms and hypercalcemia with bone metastasis and in 7 out of 1 1 (63%) of the patients with bone involvement. CONCLUSIONS: Serum para thyrine-related protein was found to be high in a large proportion of patients with solid neoplasms and hypercalcemia. Serum PTH-RP determin ation is useful in the clinical investigation of patients with hyperca lcemia. Even in patients with bone metastasis, hypercalcemia may have a humoral background.