Increased serum levels of a parathyroid hormone-like protein in malignancy-associated hypercalcemia

A. A. Budayr, R. A. Nissenson, R. F. Klein, K. K. Pun, O. H. Clark, D. Diep, C. D. Arnaud, G. J. Strewler

Research output: Contribution to journalArticlepeer-review

200 Scopus citations


Study Objective: To measure the serum levels of a newly described parathyroid hormone-like protein (PLP), which was isolated from malignant tumors associated with hypercalcemia, and determine whether PLP is a humoral factor in malignancy-associated hypercalcemia. Design: A cross-sectional study of serum levels of PLP using a newly developed radioimmunoassay. Setting: A university-affiliated Veterans Administration hospital in San Francisco, California, a University hospital in Hong Kong, and a private hospital in Danville, Pennsylvania. Patients: Patients with hypercalcemia (calcium >2.65 mmol/L) and a diagnosis of malignancy were studied. Control groups included normocalcemic patients with malignancy, patients with hyperparathyroidism, and normal subjects. Measurements and Main Results: Serum immunoreactive PLP (iPLP) levels in normal subjects were less than 2.5 pmol eq/L (10 pg/mL), and 68% of subjects had undetectable levels. The serum concentration of iPLP was normal in 15 of 16 hypercalcemic patients with hyperparathyroidism. Serum iPLP was increased (>2.5 pmol eq/L) in 36 of 65 (55%) patients with malignancy-associated hypercalcemia, with a mean value of 6.1 ± 0.9 pmol eq/L (24 pg/mL). In a subgroup of patients with solid tumors, serum iPLP was increased in 30 (71%) of 42 hypercalcemic patients, with a mean value of 6.5 ± 0.9 pmol eq/L. Serum iPLP was elevated in only 3 of 23 normocalcemic patients with cancer. In patients with solid malignancies (n = 59), levels of iPLP were positively correlated with the total serum calcium (r = 0.43, P<0.01). Conclusions: The data indicate a relation between the serum concentration of iPLP and the presence of hypercalcemia in solid malignancies. The results support a role for PLP as a humoral mediator of hypercalcemia in most patients with solid tumors. Measurement of iPLP should be useful in the differential diagnosis of hypercalcemia.

Original languageEnglish (US)
Pages (from-to)807-812
Number of pages6
JournalAnnals of internal medicine
Issue number10
StatePublished - 1989
Externally publishedYes

ASJC Scopus subject areas

  • Internal Medicine


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