A 45-year-old woman is evaluated for osteoporosis. Serum calcium is 11.2 mg/dL, phosphorus 2.4 mg/dL, intact PTH is 95 pg/mL (normal 15–65). 24-hour urine calcium is 340 mg. Dual X-ray absorptiometry (DXA) shows T-score of −2.7 at the lumbar spine. Which feature MOST favors surgical parathyroidectomy in asymptomatic primary hyperparathyroidism per current guidelines?
- A Serum calcium of 11.2 mg/dL
- B T-score of −2.7 at any site ✓
- C 24-hour urine calcium of 340 mg
- D Patient age of 45 years
Correct answer: B. T-score of −2.7 at any site
Explanation
Current Fourth International Workshop guidelines recommend parathyroidectomy in asymptomatic primary hyperparathyroidism when T-score ≤−2.5 at lumbar spine, hip, or distal radius, or presence of vertebral fracture by imaging. Her T-score of −2.7 meets this threshold. Serum calcium meeting criteria requires >1 mg/dL above upper normal (i.e., ≥11.3 mg/dL for most labs with upper limit 10.2 mg/dL), which is borderline here. Urine calcium >400 mg/24h (not 340 mg) and age <50 years are also surgical criteria.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
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Written and medically reviewed by the StethoPrep medical team.