Calcium and Parathyroid USMLE Step 1 Practice Question
A 19-year-old man with MEN1 syndrome undergoes parathyroidectomy with cryopreservation for recurrent primary hyperparathyroidism. Postoperatively, he presents with tetany, paresthesias, and positive Chvostek sign. Vital signs show HR 102, RR 18, BP 128/76. Laboratory studies reveal ionized calcium 3.2 mg/dL (normal 4.5-5.3), phosphate 5.2 mg/dL, magnesium 1.8 mg/dL, and PTH <5 pg/mL. Urinary calcium is normal. Which mechanism best explains his acute hypocalcemia?
Answer choices
- AHypomagnesemia from operative blood loss
- BThyroid hormone suppression of calcium reabsorption
- CTertiary hyperparathyroidism reversal
- DInadequate cryopreservation of parathyroid tissue
- EHungry bone syndrome with rapid mineral uptake by previously hyperstimulated osteoblastsCorrect answer
- FAcute hypoalbuminemia reducing protein-bound calcium and total serum calcium concentration
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