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PTHrP-mediated hypercalcemia — ABIM Board MCQ

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HardEndocrinology/MetabolismPTHrP-mediated hypercalcemiaABIM Board

A 66-year-old with metastatic squamous-cell carcinoma is confused and dehydrated. Corrected calcium is 15.4 mg/dL. Isotonic volume replacement has begun, kidney function permits an intravenous bisphosphonate and there is no contraindication to calcitonin. Which calcium-lowering regimen is appropriate now?

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Correct answer: B — Add calcitonin plus intravenous zoledronic acid as initial severe-hypercalcemia treatment

The best answer is “Add calcitonin plus intravenous zoledronic acid as initial severe-hypercalcemia treatment”. Severe hypercalcemia of malignancy requires a rapidly acting bridge with calcitonin plus durable antiresorptive therapy using an intravenous bisphosphonate or denosumab. Calcitonin is limited to 48 to 72 hours because tachyphylaxis develops. Oral bisphosphonate is too slow, thiazides reduce urinary calcium loss, and the malignant context does not justify delaying urgent treatment for a PTH result.

Reference: Endocrine Society Hypercalcemia of Malignancy Guideline: https://www.endocrine.org/clinical-practice-guidelines/hypercalcemia