Which paraneoplastic syndrome is caused by ectopic secretion of parathyroid hormone-related peptide (PTHrP) and is classically associated with squamous cell carcinoma of the lung?
- A Syndrome of inappropriate antidiuretic hormone secretion (SIADH)
- B Cushing syndrome from ectopic ACTH
- C Humoral hypercalcemia of malignancy ✓
- D Lambert-Eaton myasthenic syndrome
Correct answer: C. Humoral hypercalcemia of malignancy
Explanation
Humoral hypercalcemia of malignancy (HHM) is the most common paraneoplastic cause of hypercalcemia, typically due to PTHrP secretion by squamous cell carcinomas (especially lung). PTHrP binds the PTH receptor, stimulating osteoclastic bone resorption and renal calcium reabsorption. SIADH is classically associated with small cell lung carcinoma; ectopic ACTH with small cell and bronchial carcinoids; Lambert-Eaton with small cell carcinoma (antibodies against VGCC).
Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.