A patient has calcium of 3.1 mmol/L, a suppressed PTH, a lung mass and bone pain. What is the likely mechanism, and what is the initial treatment?
Answer and explanation
Correct answer: C. PTH-related protein secretion, treated with fluid then a bisphosphonate
- Step 1: A suppressed PTH with hypercalcaemia excludes primary hyperparathyroidism and points to a PTH-independent cause. Step 2. Squamous lung tumours secrete PTHrP. Hydration with saline is first, followed by bisphosphonate to inhibit osteoclasts. Answer: PTH-related protein secretion, treated with fluid then a bisphosphonate. Why not the others: Primary hyperparathyroidism has a raised or inappropriately normal PTH. Thiazides raise calcium and are inappropriate. Hypoparathyroidism causes low calcium.
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