Calcium and Parathyroid USMLE Step 1 Practice Question
A 55-year-old man with primary hyperparathyroidism (serum calcium 11.8 mg/dL, PTH 145 pg/mL) undergoes cervical exploration. Intraoperative findings reveal no abnormal gland in the inferior parathyroid bed. Chest CT demonstrates a 1.2-cm hyperdense lesion in the anterior mediastinum. The patient denies neck trauma and takes no medications affecting calcium metabolism. Which embryologic structure most commonly gives rise to ectopic inferior parathyroid glands found in the mediastinum?
Answer choices
- AUltimobranchial body
- BThird pharyngeal pouchCorrect answer
- CSecond pharyngeal pouch
- DFourth pharyngeal pouch
- EFirst pharyngeal pouch
- FDorsal wing of the second pharyngeal pouch
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