[The value of the parathyrin-related protein (PTH-RP) in the diagnosis of cancer-associated hypercalcemia].

BACKGROUND

The parathyrine related protein (PTH-RP) is very similar, both in structure and in function, to the PTH and is considered as a mediator in humoral hypercalcemia in cancer. The aim of this study was to know the clinical value of PTH-RP measurement.

METHODS

Serum PTH-RP concentrations were studied in 22 healthy subjects, 13 patients with primary hyperparathyroidism, 9 patients with solid neoplasms and normocalcemia, 26 patients with solid neoplasms and hypercalcemia and 4 patients with hematologic neoplasms and hypercalcemia. The PTH-RP was quantified by a competitive radioimmunoassay technique using a specific antibody of the PTH-RP 1-40 fragment. Intact parathyrine (i-PTH) was quantified by an IRMA method using 2 polyclonal antibodies (INCSTAR).

RESULTS

Fifteen (68%) of the healthy controls presented undetectable serum 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 normocalcemia or in those with hematologic neoplasms and hypercalcemia. High values of PTH-RP were observed in 8 out of 9 (88%) of the patients with solid neoplasms and hypercalcemia with bone metastasis and in 7 out of 11 (63%) of the patients with bone involvement.

CONCLUSIONS

Serum parathyrine-related protein was found to be high in a large proportion of patients with solid neoplasms and hypercalcemia. Serum PTH-RP determination is useful in the clinical investigation of patients with hypercalcemia. Even in patients with bone metastasis, hypercalcemia may have a humoral background.