Amiodarone-induced thyrotoxicosis: A review

BACKGROUND: Amiodarone-induced thyrotoxicosis (AIT) develops in 3% of amiodarone-treated patients in North America. AIT is classified as type 1 or type 2. Type 1 AIT occurs in patients with underlying thyroid pathology such as autonomous nodular goiter or Graves' disease. Type 2 AIT is a result of amiodarone causing a subacute thyroiditis with release of preformed thyroid hormones into the circulation. OBJECTIVES: To review the literature and present all overview of the differentiation between and management of type I and type 2 AIT METHODS: PubMed, the Cumulative Index to Nursing and Allied Health Literature and Medscape searches of all available English language articles front 1983 to 2006 were performed. Search terms included amiodarone-induced thyrotoxicosis', 'complications', 'management, 'treatment' and 'colour flow Dopper sonography'. RESULTS: There is evidence to suggest that to differentiate between type I and type 2 AIT, I careful history and physical examination should be performed to identify pre-existing thyroid disease. An iodine-131 uptake test and colour flow Doppler sonography should be performed. Patients with type 2 AIT should receive a trial of glucocorticoids, whereas those with type I should receive antithyroid therapy. For patients in whom the mechanism of the thyrotoxicosis is unclear, a combination of prednisone and antithyroid therapy may be considered.