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Drug-induced central hypothyroidism — SCE Endocrinology MCQ

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HardThyroidDrug-induced central hypothyroidismSCE Endocrinology

A 40-year-old woman has progressive fatigue after starting bexarotene for cutaneous T-cell lymphoma. Free T4 is 7 pmol/L and TSH is 0.05 mU/L. Morning cortisol is normal. What is the most likely diagnosis?

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Correct answer: D — Bexarotene-induced central hypothyroidism

Bexarotene-induced central hypothyroidism is best because bexarotene can suppress TSH and increase thyroid hormone metabolism, producing low free T4 with low TSH. The alternatives are less appropriate because Hashimoto's primary hypothyroidism raises TSH; Graves' and thyroiditis raise thyroid hormones; assay interference is possible but the drug exposure provides the best explanation. The SCE teaching point is to integrate the clinical pattern, biochemistry and context rather than treating an isolated result.

Reference: NICE NG145; BNF