AIT Type 1 — RACP Adult Medicine MCQ

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HardEndocrinologyAIT Type 1RACP Adult Medicine

A 45-year-old woman on amiodarone for 1 year presents with palpitations, weight loss, and tremor. TSH is <0.01 mU/L and free T4 is 58 pmol/L. She has a pre-existing multinodular goitre. Thyroid uptake scan shows increased uptake in the nodules with suppressed surrounding tissue. What is the most likely type of amiodarone-induced thyroid dysfunction?

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Correct answer: B — Amiodarone-induced thyrotoxicosis type 1

AIT type 1 occurs in patients with pre-existing thyroid disease (multinodular goitre or Graves disease) where excess iodine drives increased thyroid hormone synthesis. Thyroid uptake is normal or increased (unlike type 2). Treatment is carbimazole plus potassium perchlorate (blocks iodine uptake). Amiodarone should be ceased if possible.

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