A 45-year-old woman has a serum calcium of 11.4 mg/dL, phosphorus 2.1 mg/dL, PTH 145 pg/mL (normal 15–65), and 24-hour urine calcium 380 mg/day. She is asymptomatic. Which finding would be the strongest indication for parathyroidectomy?

• A Serum calcium 1 mg/dL above upper limit of normal
• B 24-hour urine calcium > 400 mg/day
• C Age less than 50 years
• D T-score of −2.6 at lumbar spine on DXA ✓

Explanation

Per the 2022 Fourth International Workshop guidelines for asymptomatic primary hyperparathyroidism, surgical indications include: serum calcium >1 mg/dL above ULN, eGFR <60 mL/min, T-score ≤−2.5 at any site or Z-score ≤−2.5 in premenopausal women, vertebral fracture on imaging, or age <50. A T-score of −2.6 (≤−2.5) meets this criterion. Urine calcium >400 mg/day is a surgical indication but her level is only 380 mg/day. Age <50 is an independent indication regardless of calcium level.

Reference: Harrison's Principles of Internal Medicine, 21st ed.

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Written and medically reviewed by the StethoPrep medical team.