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Amiodarone Effect on TFTs — RACP Adult Medicine MCQ

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HardEndocrinologyAmiodarone Effect on TFTsRACP Adult Medicine

A 45-year-old woman on amiodarone for AF has thyroid function tests: TSH 6.5 mU/L (mildly elevated), free T4 18 pmol/L (upper-normal/slightly high), free T3 3.2 pmol/L (normal). She is clinically euthyroid. What is the most likely interpretation?

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Correct answer: B — Euthyroid sick syndrome (non-thyroidal illness)

Amiodarone contains 37% iodine by weight and inhibits peripheral T4-to-T3 conversion. Expected TFT changes in early amiodarone use (first 3 months): elevated T4 and reverse T3, reduced T3, and mildly elevated TSH — this is a pharmacological effect, not thyroid disease. The patient is clinically euthyroid. No treatment is needed. Monitor TFTs 3-6 monthly for true AIT (type 1 or 2) development.

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