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Primary hyperparathyroidism — USMLE Step 3 MCQ

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ModerateInternal Medicine (chronic management)Primary hyperparathyroidismUSMLE Step 3

A 59-year-old woman has recurrent calcium oxalate kidney stones and constipation. Calcium is 11.4 mg/dL, phosphate is low, and intact parathyroid hormone is elevated. Which of the following is the most likely diagnosis?

Educational content. Not a substitute for clinical judgement or local policy.

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Correct answer: A — Primary hyperparathyroidism

Elevated calcium with inappropriately high PTH, low phosphate, and kidney stones suggests primary hyperparathyroidism.

Reference: Endocrine Society hyperparathyroidism guidance