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TSH Recovery Overshoot — RACP Adult Medicine MCQ

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ModerateEndocrinologyTSH Recovery OvershootRACP Adult Medicine

A 50-year-old man recovering from a severe pneumonia has TFTs during recovery: TSH 8.5 mU/L (elevated), free T4 15 pmol/L (normal), free T3 4.5 pmol/L (normal). He has no thyroid disease history. TFTs 2 weeks earlier during acute illness showed TSH 0.2, T4 9, T3 1.5. What is the most likely interpretation?

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

TSH rebound elevation during recovery from non-thyroidal illness is a well-recognised phenomenon. During acute illness, TSH was suppressed (sick euthyroid). During recovery, TSH transiently overshoots above normal (sometimes to 10-20 mU/L) before normalising. This should NOT be treated with levothyroxine. Recheck TFTs in 6-8 weeks — they will normalise. Premature treatment risks iatrogenic thyrotoxicosis.

Reference: eTG Endocrine – 2024 – Non-Thyroidal Illness; Fliers 2015 Review