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Post-radioiodine hypothyroidism — SCE Endocrinology MCQ

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EasyThyroidPost-radioiodine hypothyroidismSCE Endocrinology

A 24-year-old woman has fatigue and weight gain 6 months after radioactive iodine for Graves' disease. TSH is 32 mU/L and free T4 is 6 pmol/L. She asks why symptoms appeared after apparently successful treatment. What is the underlying pathophysiology?

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Correct answer: A — Loss of thyroid hormone production after radioiodine-mediated follicular destruction

Radioiodine ablates thyroid follicular tissue and can lead to permanent hypothyroidism requiring levothyroxine. Pituitary suppression would produce low or inappropriately normal TSH, not high TSH. The pearl is that hypothyroidism after definitive Graves' treatment is expected and monitored for.

Reference: NICE NG145, BNF