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Thyroid Hormone T3 T4 — FRCA Primary MCQ

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HardPhysiology - Endocrine & MetabolicThyroid Hormone T3 T4FRCA Primary

Which statement about thyroid hormone production and activity is correct?

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

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Correct answer: D — Most circulating T3 is produced by peripheral conversion of T4

The best answer is “Most circulating T3 is produced by peripheral conversion of T4”. Most circulating T3 is generated by peripheral conversion of T4, while the thyroid secretes predominantly T4. TSH is produced by the anterior pituitary, T3 is the more active hormone at nuclear receptors, and thyroid hormones increase basal metabolic rate.

Reference: RCoA, Primary FRCA Syllabus: https://rcoa.ac.uk/sites/default/files/documents/2026-01/Primary-FRCA-Syllabus.pdf