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9665390 
Journal Article 
Review 
Approach to the patient with amiodarone-induced thyrotoxicosis 
Bogazzi, F; Bartalena, L; Martino, E 
2010 
Yes 
Journal of Clinical Endocrinology and Metabolism
ISSN: 0021-972X
EISSN: 1945-7197 
95 
6 
2529-2535 
English 
20525904 
WOS:000278444000003 
Amiodarone, a benzofuranic iodine-rich antiarrhythmic drug, causes thyroid dysfunction in 15-20% of cases. Although amiodarone-induced hypothyroidism poses no particular problem, amiodarone-induced thyrotoxicosis (AIT) is a diagnostic and therapeutic challenge. There are two main forms of AIT: type 1, a form of iodine-induced hyperthyroidism, and type 2, a drug-induced destructive thyroiditis. However, mixed/indefinite forms exist that may be caused by both pathogenic mechanisms. Type 1 AIT usually occurs in abnormal thyroid glands, whereas type 2 AIT develops in apparently normal thyroid glands (or small goiters). Diagnosis of thyrotoxicosis is easy, based on the finding of increased free thyroid hormone concentrations and suppressed TSH levels. Thyroid radioactive iodine (RAI) uptake values are usually very low/suppressed in type 2 AIT, most commonly low or low-normal, but sometimes normal or increased in type 1 AIT despite the iodine load. Color flow Doppler sonography shows absent hypervascularity in type 2 and increased vascularity in type 1 AIT. Mixed/indefinite forms may have features of both AIT types. Thionamides represent the first-line treatment for type 1 AIT, but the iodine-replete gland is not very responsive; potassium perchlorate, by inhibiting thyroid iodine uptake, may increase the response to thionamides. Type 2 AIT is best treated by oral glucocorticoids. The response very much depends on the thyroid volume and the severity of thyrotoxicosis. Mixed/indefinite forms may require a combination of thionamides, potassium perchlorate, and steroids. RAI is usually not feasible in AIT due to low RAI uptake values. Thyroidectomy represents a valid option in cases resistant to medical therapy. 
Anti-Arrhythmia Agents; Biomarkers; Iodine Radioisotopes; Technetium Tc 99m Sestamibi; 971Z4W1S09; Amiodarone; N3RQ532IUT; Index Medicus; Thyroid Function Tests; Ultrasonography; Iodine Radioisotopes -- pharmacokinetics; Positron-Emission Tomography; Thyroid Gland -- diagnostic imaging; Thyrotoxicosis -- diagnostic imaging; Amiodarone -- adverse effects; Amiodarone -- therapeutic use; Thyrotoxicosis -- therapy; Thyrotoxicosis -- chemically induced; Anti-Arrhythmia Agents -- therapeutic use; Atrial Fibrillation -- drug therapy; Anti-Arrhythmia Agents -- adverse effects; Atrial Fibrillation -- complications