Amiodarone Thyrotoxicosis Type 2 — RACP Adult Medicine MCQ

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HardEndocrinologyAmiodarone Thyrotoxicosis Type 2RACP Adult Medicine

A 55-year-old woman on amiodarone for AF develops thyrotoxicosis (free T4 65 pmol/L, TSH <0.01). She has no goitre and no ophthalmopathy. Thyroid ultrasound shows normal vascularity (no increased flow). She has elevated inflammatory markers (CRP 85). IL-6 is elevated. What is the most likely type of amiodarone-induced thyrotoxicosis?

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Correct answer: C — Dexamethasone IV

Amiodarone-induced thyrotoxicosis type 2 (AIT-2) is a destructive thyroiditis (not excess synthesis). Features: no goitre, normal/reduced thyroid vascularity on Doppler US (vs increased in AIT-1), elevated inflammatory markers (CRP, IL-6), and normal RAIU. Treatment: prednisolone 40 mg daily (dramatic response in AIT-2). AIT-1 (excess synthesis in pre-existing thyroid disease) is treated with antithyroid drugs. Mixed forms are common — combination therapy often given empirically. Among options, dexamethasone/corticosteroid is the key treatment for AIT-2.

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