Calcium and Parathyroid USMLE Step 1 Practice Question
A 66-year-old man with squamous cell carcinoma of the lung presents with constipation, confusion, and dehydration. Vital signs show BP 148/92, HR 102, RR 18, temp 37.2°C. Laboratory studies reveal serum calcium 12.8 mg/dL, phosphate 2.1 mg/dL, and suppressed PTH at 15 pg/mL. Chest X-ray confirms the known malignancy. He denies bone pain or recent thiazide use. Which mediator most likely causes his metabolic abnormality?
Answer choices
- AParathyroid hormone related peptideCorrect answer
- BExcess 1,25 dihydroxyvitamin D from the kidney
- CErythropoietin
- DThyroid stimulating immunoglobulin
- ECalcitonin
- FOsteolytic bone metastases from local osteoclast activation
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