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Amiodarone-induced thyroid disorders

Background

Overview

Definition
Amiodarone, an iodinated benzofuran, is a potent antiarrhythmic medication that can alter thyroid hormone metabolism and may precipitate hypothyroidism or hyperthyroidism.
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Pathophysiology
Amiodarone-induced thyroid disorders are caused by either deiodination, which releases large amounts of iodine that can impair thyroid function, or by direct cytotoxicity on thyroid cells by amiodarone or its metabolite.
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Epidemiology
The prevalence of thyroid dysfunction in patients taking amiodarone ranges from 5% to 14%.
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Disease course
Amiodarone-associated hypothyroidism is similar to iodine-induced hypothyroidism and typically presents with symptoms such as fatigue, weight gain, and cold intolerance. It can also lead to myxedema coma, severe bradycardia, prolonged atrioventricular conduction, peripheral edema, and severe muscle cramps. On the other hand, amiodarone-associated hyperthyroidism, or thyrotoxicosis, presents with symptoms such as weight loss, palpitations, heat intolerance, muscle weakness, anorexia, restlessness, tremor, and congestive HF.
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Prognosis and risk of recurrence
The prognosis of amiodarone-induced thyroid disorders is generally favorable. Most patients can recover thyroid function once amiodarone is stopped, but some may require long-term management due to persistent thyroid dysfunction.
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Guidelines

Key sources

The following summarized guidelines for the evaluation and management of amiodarone-induced thyroid disorders are prepared by our editorial team based on guidelines from the European Thyroid Association (ETA 2018) and the American Thyroid Association (ATA 2016). ...
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Screening and diagnosis

Indications for screening: as per ATA 2016 guidelines, consider monitoring thyroid function tests before and within the first 3 months following the initiation of amiodarone therapy and at 3-6-month intervals thereafter.
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Diagnostic investigations

Laboratory tests: as per ATA 2016 guidelines, consider obtaining thyroid function tests to identify disorders associated with iodine-induced hyperthyroidism (type 1 amiodarone-induced thyrotoxicosis), specifically including toxic nodular disease and previously occult Graves' disease, in clinically stable patients with amiodarone-induced thyrotoxicosis.
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Medical management

Management of hyperthyroidism, withdrawal of amiodarone: as per ETA 2018 guidelines, view patients with amiodarone-induced thyrotoxicosis as at risk of emergency treatment at any time due to the increased mortality and morbidity, particularly in the elderly and/or if a reduced LV dysfunction is present.
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More topics in this section

  • Management of hyperthyroidism (antithyroid drugs)

  • Management of hyperthyroidism (sodium perchlorate)

  • Management of hyperthyroidism (corticosteroids)

  • Management of hyperthyroidism (radioactive iodine)

  • Management of hyperthyroidism (thyroidectomy)

  • Management of hypothyroidism