Calcium and Parathyroid USMLE Step 1 Practice Question
A 42-year-old woman on levothyroxine for Hashimoto thyroiditis presents with fatigue, bone pain, and hypercalcemia (11.2 mg/dL). PTH is 9 pg/mL, 1,25-dihydroxyvitamin D is normal, and 25-hydroxyvitamin D is 58 ng/mL. She reports excessive intake of fortified milk and vitamin D supplements. Which of the following is the most likely mechanism of her hypercalcemia?
Answer choices
- AGranulomatous disease concurrent with autoimmune thyroiditis
- BFamilial hypocalciuric hypercalcemia
- CExcess exogenous vitamin D causing unregulated intestinal calcium absorptionCorrect answer
- DThyroid hormone excess from levothyroxine overdose
- EPrimary hyperparathyroidism masquerading as autoimmune thyroiditis
- FLevothyroxine overreplacement causing increased bone turnover and calcium mobilization with suppressed TSH
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