A 62-year-old man on amiodarone for atrial fibrillation develops weight loss, tremor, and a suppressed TSH. Free T4 is elevated. Colour flow Doppler of the thyroid shows increased vascularity, and interleukin-6 levels are normal. Which statement is correct?

• A This is amiodarone-induced thyrotoxicosis type 2, best treated with glucocorticoids
• B Amiodarone must be stopped immediately before any thyroid treatment
• C Radioiodine ablation is the first-line therapy
• D This is amiodarone-induced thyrotoxicosis type 1, best treated with antithyroid drugs ✓

Explanation

Type 1 AIT is iodine-induced excess hormone synthesis in an underlying nodular goitre or latent Graves disease; it shows increased thyroidal vascularity on Doppler and responds to thionamides (often high dose). Type 2 is destructive thyroiditis with low vascularity and raised IL-6, responding to steroids. Radioiodine uptake is negligible because of iodine load, so ablation fails. Stopping amiodarone alone does not help since its half-life is very long.

Reference: Williams Textbook of Endocrinology, 14th ed.

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Written and medically reviewed by the StethoPrep medical team.