Calcium and Parathyroid USMLE Step 1 Practice Question
A 64-year-old woman presents with fatigue and bone pain. Vital signs: BP 128/82, HR 88, RR 16, Temp 37.2°C, SpO2 98% on room air. Laboratory studies show serum calcium 10.4 mg/dL, PTH 78 pg/mL, and 1,25-dihydroxyvitamin D elevated at 68 pg/mL (normal 20-50). Chest X-ray demonstrates bilateral hilar lymphadenopathy. Parathyroid imaging is unremarkable. Which diagnosis best explains these findings?
Answer choices
- AVitamin D intoxication from supplements
- BSarcoidosis with extrarenal 1-alpha hydroxylase productionCorrect answer
- CPrimary hyperparathyroidism
- DTertiary hyperparathyroidism
- EHyperthyroidism with secondary PTH elevation
- FGranulomatous tuberculosis with elevated 1,25-dihydroxyvitamin D from activated macrophages
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