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T3 Peripheral Conversion — FRCA Primary MCQ

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ModeratePhysiology - Endocrine & MetabolicT3 Peripheral ConversionFRCA Primary

T3 is predominantly produced by:

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Correct answer: D — Peripheral deiodination of T4

The thyroid produces predominantly T4 (~90 μg/day) with small amounts of T3 (~9 μg/day). T3 is 3-5 times more active than T4. Approximately 80% of circulating T3 comes from peripheral deiodination of T4 primarily in liver and kidneys.

Reference: Power Kam 2018 Principles of Physiology for the Anaesthetist