Amiodarone treatment and thyroid disorders

Amiodarone is a benzofuranic iodine-rich antiarrhythmic drug used in the treatment of severe tachyarrhythmias, especially ventricular. Drug causes many adverse effects including thyroid disorders in 14-18% of patients: amiodarone induced thyrotoxicosis type I and type II (AIT I, AIT II) and amiodarone induced hypothyroidism (AIH). AIT occurs more frequently in geographical areas with low iodine intake, whereas AIH is more frequent in iodine-sufficient areas. AIH may appear both in normal thyroid gland and Hashimoto's disease. AIT I occurs most often on the basis of Greave's disease or goiter. In contrast to AIT, AIH does not cause difficulties with diagnosis and treatment. In order to differentiate between AIT I and AIT II such methods as USG, CFDS, RAIU, MIBI and IL-6 are used. Increased vascularization showed in CFDS, increased MIBI uptake in scintigraphy, increased 131I uptake in RAIU in some cases are typical for AIT I. In opposition to AIT I, all this parameters are decreased in AIT II and it is possible that the level of serum IL-6 is increased. However, the usefulness of IL-6 is controversial. After diagnosis discontinuation of amiodarone should be taken into consideration. In addition, AIT I is preferably treated with methimazole and potassium perchlorate. AIT II is treated with glucocorticoids. In the case of unclear diagnosis and mixed types of AIT the combination of all foregoing drugs should be instituted. If the case is refractory, thyreidectomy should be taken into consideration, especially if a patient suffers from left ventricular systolic dysfunction. RIT--radioiodine therapy is also possible.