Amiodarone-Induced Thyrotoxicosis — RACP Adult Medicine MCQ

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HardEndocrinologyAmiodarone-Induced ThyrotoxicosisRACP Adult Medicine

A 28-year-old woman presents with generalised anxiety, tremor, proximal myopathy, oligomenorrhoea, and heat intolerance. She has been taking amiodarone for 6 months for paroxysmal AF. TSH is <0.01 mU/L and free T4 is 65 pmol/L. Thyroid uptake scan shows low uptake. What is the most likely type of amiodarone-induced thyroid dysfunction?

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Correct answer: C — Amiodarone-induced thyrotoxicosis type 2

Amiodarone-induced thyrotoxicosis (AIT) type 2 is a destructive thyroiditis caused by amiodarone's direct toxic effect on thyroid follicular cells. It is characterised by low thyroid uptake (compared to increased/normal uptake in type 1). Type 2 is treated with prednisolone. Type 1 (excess iodine-mediated) is treated with carbimazole. Mixed forms require combination therapy.

Reference: ETA – 2018 – Amiodarone and Thyroid Guidelines; eTG Endocrine 2024