Parathyroid hormone-related protein (50–69) and response to pamidronate therapy for tumour-induced hypercalcaemia

• Published in: European journal of cancer & clinical oncology Vol. 27; no. 12; pp. 1629 - 1633
• Main Authors: Dodwell, D.J., Abbas, S.K., Morton, A.R., Howell, A.
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 1991
• ISSN: 0277-5379
• DOI: 10.1016/0277-5379(91)90431-C

A region-specific radioimmunoassay has been employed to measure levels of immunoreactive parathyroid hormone-related protein (50–69) (iPTHrP (50–69)) in patients with tumour-induced hypercalcaemia (TIH). This assay is based on an antiserum raised against synthetic human PTHrP (50–69). The assay showed no cross-reactivity with human or bovine parathyroid hormone (1–84). The effect of a single dose (60 mg) of pamidronate was studied in 25 consecutive patients with TIH. All were rehydrated prior to treatment. All but 2 patients (8%) became normocalcaemic after treatment; both of these had very high levels of iPTHrP (50–69). Time to achieve normocalcaemia, as an index of relative resistance to pamidronate, correlated positively with pretreatment level of iPTHrP (50–69). Absence of radiological evidence of bone metastases also predicted relative resistance to pamidronate. In this study, iPTHrP (50–69)-induced osteoclastic bone resorption was a more important mechanism in the causation of TIH than PTHrP-induced renal reabsorption of calcium as assessed by the renal thresholds for calcium and phosphate.