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Amiodarone-induced hypothyroidism — USMLE Step 3 MCQ

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HardInternal Medicine (chronic management)Amiodarone-induced hypothyroidismUSMLE Step 3

A 59-year-old woman has progressive fatigue, constipation, dry skin, and weight gain. TSH is 18 mIU/L and free T4 is low. She started amiodarone 9 months ago for ventricular arrhythmia. Thyroid peroxidase antibody is negative. Which of the following is the most likely diagnosis?

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Correct answer: B — Amiodarone-induced hypothyroidism

Amiodarone's iodine load and direct thyroid effects can cause hypothyroidism, often with elevated TSH and low free T4. Treatment usually involves levothyroxine while assessing the ongoing need for amiodarone.

Reference: American Thyroid Association thyroid disease guidance