Amiodarone-induced thyrotoxicosis type 2 — SCE Endocrinology MCQ

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HardThyroidAmiodarone-induced thyrotoxicosis type 2SCE Endocrinology

A 63-year-old woman taking amiodarone develops weight loss and palpitations. TSH is <0.01 mU/L, free T4 is 55 pmol/L, free T3 is mildly raised, thyroid antibodies are negative and Doppler ultrasound shows low vascularity without nodules. What is the most likely diagnosis?

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Correct answer: D — Type 2 amiodarone-induced thyrotoxicosis

Type 2 amiodarone-induced thyrotoxicosis is best because low vascularity with absent nodular disease supports destructive type 2 amiodarone-induced thyrotoxicosis. The alternatives are less appropriate because type 1 disease is iodine-driven synthesis in abnormal thyroid tissue; Graves' usually has antibodies and vascularity; toxic multinodular disease has nodules; raised free T4 is not subclinical disease. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: European Thyroid Association amiodarone thyroid dysfunction guideline