Journal Article

Falsely Elevated Parathyroid Hormone-Related Protein (PTH-RP) in a Patient With Hypercalcemia and Renal Failure

Gifford Lum

in Laboratory Medicine

Published on behalf of American Society for Clinical Pathology

Volume 42, issue 12, pages 726-728
Published in print December 2011 | ISSN: 0007-5027
Published online October 2015 | e-ISSN: 1943-7730 | DOI: http://dx.doi.org/10.1309/LM23TD4IUTAJBJMG
Falsely Elevated Parathyroid Hormone-Related Protein (PTH-RP) in a Patient With Hypercalcemia and Renal Failure

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Humoral hypercalcemia of malignancy (HHM) is the cause of hypercalcemia in the majority of patients with hypercalcemia and cancer. Parathyroid hormone-related protein (PTH-RP) has been identified as the circulating factor that mediates HHM. An N-terminal and a C-terminal PTH-RP are clinically useful assays for screening patients for HHM, and both assays are elevated in such patients. C-terminal PTH-RP depends on glomerular filtration and accumulates in patients with renal failure without malignancy, resulting in falsely-elevated levels, whereas N-terminal PTH-RP is low or undetectable in such patients. We present a case of a patient with renal failure and hypercalcemia who did not have an obvious malignancy and who presented with an elevated C-terminal PTH-RP level and a normal N-terminal PTH-RP. In patients with renal failure and hypercalcemia without cancer, C-terminal PTH-RP may be falsely elevated, especially if the eGFR is <20 mL/minute, and in such patients, N-terminal PTH-RP, because it is less affected by renal function, is the preferred test.

Keywords: PTH-RP; hypercalcemia; false elevation; renal faliure; malignancy; C-terminal PTH-RP; N-terminal PTH-RP

Journal Article.  1826 words. 

Subjects: Chemistry

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