WBR1026

Author	[[PageAuthor::Mohamed Moubarak, M.D. [1]]]
Exam Type	ExamType::USMLE Step 3
Main Category	MainCategory::Primary Care Office
Sub Category	SubCategory::Cardiovascular
Prompt	[[Prompt::A 60 year-old female comes to your office complaining of fatigue, lethargy, intolerance of cold and dry skin. These symptoms started gradually over the last month. The patient has a past medical history of hypertension for 15 years which is controlled by Metoprolol and hydrochlorothiazide, thyroiditis which was treated successfully with corticosteroids 3 years ago, and atrial fibrillation 1 year ago which is controlled by amiodarone and warfarin with controlled INR. On examination, the patient has a normal vital signs, no pain or swelling in her neck. Serum TSH is elevated, with low levels of free T4. The patient is diagnosed with Amiodarone-induced hypothyroidism (AIH). What is the best next step in managing this patient?]]
Answer A	AnswerA::Stop amiodarone
Answer A Explanation	[[AnswerAExp::Incorrect Discontinuation of amiodarone may not be applicable in this patient because of the underlying indication for its use]]
Answer B	AnswerB::Start levothyroxine
Answer B Explanation	[[AnswerBExp::Correct Thyroid hormone replacement therapy is the treatment of choice in cases of Amiodarone-induced hypothyroidism (AIH)]]
Answer C	AnswerC::Reassurance and follow up
Answer C Explanation	[[AnswerCExp::Incorrect Amiodarone-induced hypothyroidism (AIH) needs to be treated with thyroid hormone replacement therapy]]
Answer D	AnswerD::Start corticosteroids
Answer D Explanation	[[AnswerDExp::Incorrect There is no indication to use corticosteroids in this patient]]
Answer E	AnswerE::Stop metoprolol
Answer E Explanation	[[AnswerEExp::Incorrect Metoprolol is not the cause of hypothyroidism in this patient.]]
Right Answer	RightAnswer::B
Explanation	[[Explanation::Amiodarone-induced hypothyroidism (AIH) is believed to result from the inability of the thyroid to escape from the Wolff-Chaikoff effect. Amiodarone is a benzofuranic-derivative iodine-rich drug, the large amount of iodide released during the metabolism of amiodarone leads to an adaptive blockage of further thyroidal iodide uptake and thyroid hormone biosynthesis, the so-called Wolff-Chaikoff effect. The reported incidence of AIH varies widely, ranging from 6% in countries with low iodine intake to 13% in countries with a high dietary iodine intake. The risk of developing hypothyroidism is independent of the daily or cumulative dose of amiodarone. However, the risk is greater in the elderly and in female patients, probably as a result of a higher prevalence of underlying thyroid abnormality. The relative risk of developing AIH was found to be 13-fold higher in female patients with positive thyroid microsomal or thyroglobulin antibodies, as compared with men without thyroid antibodies. Reference "Effects of amiodarone on thyroid function.",journal = Ann Intern Med, volume = 126, issue = 1, month = Jan, year = 1997,PMID = 8992925. "Amiodarone and the thyroid: a practical guide to the management of thyroid dysfunction induced by amiodarone therapy.", journal = Heart, volume = 79, issue = 2, month = Feb, year = 1998,PMID = 9538302. "Incidence, predictability, and pathogenesis of amiodarone-induced thyrotoxicosis and hypothyroidism.",journal = Am J Med, volume = 91, issue = 5, month = Nov, year = 1991, PMID = 1951413. Educational Objective: References: ]]
Approved	Approved::No
Keyword	[[WBRKeyword::Amiodarone]]
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