A 68-year-old heavy smoker presents with a cavitating lung mass in the right upper lobe on imaging. Labs show serum calcium of 13.2 mg/dL with suppressed PTH. Which paraneoplastic mediator is responsible for the hypercalcemia?

• A Parathyroid hormone (PTH)
• B Prostaglandin E2
• C Calcitriol (1,25-dihydroxyvitamin D)
• D Parathyroid hormone-related peptide (PTHrP) ✓

Explanation

Squamous cell carcinoma of the lung is the classic cause of PTHrP-mediated humoral hypercalcemia of malignancy. PTH is suppressed. Calcitriol-mediated hypercalcemia is seen in sarcoidosis and lymphoma. Prostaglandin E2 is a less common mediator. The central cavitating upper lobe mass in a smoker strongly favors squamous cell carcinoma.

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.