Calcium and Parathyroid USMLE Step 1 Practice Question
A 72-year-old woman with minimal sun exposure presents with diffuse bone pain and progressive proximal muscle weakness. Vital signs show BP 128/76 mmHg, HR 88/min, RR 16/min, temp 37°C. Laboratory studies reveal calcium 7.2 mg/dL, phosphate 2.1 mg/dL, alkaline phosphatase 95 U/L, and PTH 156 pg/mL. Serum 25-hydroxyvitamin D is 18 ng/mL. Cognitive function remains intact. Which diagnosis best explains these findings?
Answer choices
- AHumoral hypercalcemia of malignancy
- BPseudohypoparathyroidism
- CPrimary hyperparathyroidism
- DVitamin D deficiency causing osteomalaciaCorrect answer
- EFamilial hypocalciuric hypercalcemia
- FOncogenic osteomalacia from tumor-secreted FGF-23
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