A 58-year-old man with a 50 pack-year smoking history presents with hemoptysis and hypercalcemia (serum calcium 13.2 mg/dL). Chest X-ray shows a central hilar mass with cavitation. Biopsy shows keratin pearls and intercellular junctions. Which paraneoplastic hormone is most likely responsible for the hypercalcemia?

• A Parathyroid hormone (PTH)
• B 1,25-dihydroxyvitamin D
• C Calcitonin
• D Parathyroid hormone-related peptide (PTHrP) ✓

Explanation

Squamous cell carcinoma of the lung classically presents as a central cavitary mass in smokers and causes humoral hypercalcemia of malignancy via PTHrP secretion. PTH (option A) would indicate primary hyperparathyroidism. Small cell carcinoma causes SIADH or ACTH-mediated Cushing syndrome, not hypercalcemia. Calcitonin (option C) is produced by medullary thyroid carcinoma and lowers calcium.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.