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Lithium-induced hypothyroidism — USMLE Step 3 MCQ

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HardPsychiatryLithium-induced hypothyroidismUSMLE Step 3

A patient with bipolar I disorder remains euthymic on lithium. They have polyuria, fine tremor and newly elevated TSH with low free T4; lithium level and creatinine are therapeutic. What is the best management?

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

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Correct answer: D — Start levothyroxine and continue lithium with renal and thyroid monitoring

Explanation lettering: D = shown as A · A = shown as B · E = shown as D · B = shown as E

When lithium is effective, hypothyroidism is generally treated while lithium is continued and monitored. B risks relapse. C can precipitate mania. D worsens toxicity. E does not correct the endocrine adverse effect.

Reference: American Psychiatric Association, Bipolar Disorder Practice Guideline: https://www.psychiatry.org/psychiatrists/practice/clinical-practice-guidelines