skip to main content

AIT Classification and Treatment — EECC MCQ

Instant feedback + full explanation. One question, done properly.

ModerateCardiac PharmacologyAIT Classification and TreatmentEECC

A 60-year-old man on long-term amiodarone for AF has his thyroid function checked. TSH is 0.01 mU/L (suppressed) with free T4 52 pmol/L (elevated) and free T3 8.5 pmol/L (elevated). He is clinically thyrotoxic. What type of amiodarone-induced thyrotoxicosis (AIT) is this and how is it classified?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: E — AIT is classified as Type 1 (iodine-induced excess thyroid hormone synthesis in pre-existing thyroid disease — treated with thionamides ± perchlorate) or Type 2 (destructive thyroiditis from direct amiodarone toxicity — treated with corticosteroids); mixed forms require combined treatment; colour-flow Doppler ultrasound helps differentiate (increased vascularity in Type 1 vs absent in Type 2)

Amiodarone causes thyroid dysfunction in 15-20% of patients through its high iodine content (75 mg iodine per 200 mg amiodarone tablet). AIT classification: Type 1: excess iodine provides substrate for increased thyroid hormone synthesis in patients with pre-existing thyroid disease (multinodular goitre, Graves' disease); thyroid gland is hypervascular on Doppler; treated with thionamides (carbimazole/methimazole) ± potassium perchlorate (blocks iodine uptake). Type 2: direct toxic effect of amiodarone causing destructive thyroiditis with release of preformed thyroid hormone; thyroid is avascular on Doppler; treated with corticosteroids (prednisolone 40-60 mg tapering). Mixed Type 1+2: common in practice — treated with combined thionamide + corticosteroid. The 2024 ESC AF Guidelines recommend 6-monthly TFT monitoring for all patients on amiodarone and prompt treatment of AIT.

Reference: ESC (2024): AF Guidelines; ETA/ATA AIT Guidelines