Calcium and Parathyroid USMLE Step 1 Practice Question
A 28-year-old woman undergoes routine laboratory testing and is found to have a serum calcium of 11.1 mg/dL on repeated occasions. She denies polyuria, bone pain, or nephrolithiasis. Vital signs are normal (BP 118/76, HR 72, RR 16, Temp 98.6°F). Serum parathyroid hormone is mildly elevated at 68 pg/mL (normal 15–65), while 24-hour urine calcium excretion is markedly low at 45 mg/day. Serum phosphate and alkaline phosphatase are normal. Which of the following is the most likely diagnosis?
Answer choices
- AFamilial hypocalciuric hypercalcemiaCorrect answer
- BHumoral hypercalcemia of malignancy
- CSarcoidosis
- DPrimary hyperparathyroidism due to adenoma
- EVitamin D intoxication
- FThyrotoxicosis with increased bone turnover
See the full explanation
Get the correct-answer rationale, why each distractor is wrong, the underlying mechanism, and high-yield associations — plus adaptive practice that targets your weak areas — with a free MedBoardPRO account.