A physician-validated, board-style question from the Active Transport QBank. Try it, then check the reasoning for every option.
A 55-year-old man presents to the physician with tiredness, lethargy, bone pain, and colicky right abdominal pain for 1 month. He has no comorbidities. He does not have any significant past medical history. His height is 176 cm (5 ft 7 in), weight is 88 kg (194 lb), and his BMI is 28.47 kg/m2. The physical examination is normal, except for mild right lumbar region tenderness. Laboratory studies show:
Hemoglobin 13.5 g/dL
Serum TSH 2.2 mU/L
Serum calcium 12.3 mg/dL
Serum phosphorus 1.1 mg/dL
Serum sodium 136 mEq/L
Serum potassium 3.5 mEq/L
Serum creatinine 1.1 mg/dL
Urine calcium Elevated
An ultrasound of the abdomen reveals a single stone in the right ureter without hydroureteronephrosis. Clinically, no evidence of malignancy was observed. An X-ray of the long bones reveals diffuse osteopenia with subperiosteal bone resorption. The serum parathyroid hormone level is tested and it is grossly elevated. What is the most appropriate next step in his management?
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A
99mTc sestamibi scan with ultrasound of the neckCorrect. After biochemical confirmation of primary hyperparathyroidism, dual-modality 99mTc sestamibi scan plus neck ultrasound is the preferred preoperative localization strategy.
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B
CT scan of the neckIncorrect. CT scan is reserved for cases where sestamibi/ultrasound are nondiagnostic or for ectopic glands; it is not first-line.
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C
Bone scan (DEXA)Incorrect. DEXA assesses bone density (useful for baseline assessment of bone disease) but does not localize the abnormal gland.
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D
Sestamibi scan onlyIncorrect. Sestamibi alone is less accurate than dual-modality imaging combining sestamibi with ultrasound.
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E
Serum 1,25-dihydroxyvitamin D levelIncorrect. Vitamin D testing helps distinguish primary from secondary hyperparathyroidism but is not the next step for surgical localization once primary hyperparathyroidism has been biochemically confirmed.
↑ Tap an answer to reveal the reasoning
Answer: A. A middle-aged man with hypercalcemia, hypophosphatemia, hypercalciuria, a kidney stone, subperiosteal bone resorption with osteopenia, and a grossly elevated PTH has primary hyperparathyroidism, most likely from a parathyroid adenoma (~85% of cases). The classic mnemonic — "stones, bones, abdominal groans, psychiatric overtones" — fits: nephrolithiasis, lytic bone disease with subperiosteal resorption (seen on hand X-rays in advanced cases), and constitutional symptoms.
Once primary hyperparathyroidism is biochemically confirmed (elevated calcium with elevated PTH), the next step is preoperative localization of the abnormal parathyroid gland. The combination of 99mTc-sestamibi scan plus high-resolution neck ultrasound is the modern dual-modality approach, with sensitivity around 95% for adenoma localization. Sestamibi is concentrated by mitochondrion-rich parathyroid adenomas and persists after thyroid washout. Ultrasound provides anatomic correlation.
Definitive treatment is parathyroidectomy. Bone density (DEXA) may be obtained for baseline but does not localize disease. CT or 4D-CT is used when sestamibi/ultrasound are nondiagnostic.
**Why each option:**
**A.** Correct. After biochemical confirmation of primary hyperparathyroidism, dual-modality 99mTc sestamibi scan plus neck ultrasound is the preferred preoperative localization strategy.
**B.** CT scan is reserved for cases where sestamibi/ultrasound are nondiagnostic or for ectopic glands; it is not first-line.
**C.** DEXA assesses bone density (useful for baseline assessment of bone disease) but does not localize the abnormal gland.
**D.** Sestamibi alone is less accurate than dual-modality imaging combining sestamibi with ultrasound.