[AMIODARONE AND THE THYROID FUNCTION].

Amiodarone is a benzofuran derivative that contains up to 40% of iodine. Amiodarone is used for treatment and prevention of life threatening supraventricular and ventricular tachyarrhythmias. The effects on thyroid gland vary from abnormalities in thyroid function tests to overt amiodarone induced hypothyroidism (AIH) and thyrotoxicosis (AIT). Patients with AIH are treated with L-thyroxine and may continue treatment with amiodarone. Two different forms of AIT have to be distinguished: amiodarone induced hyperthyroidism (AIT I) and thyroiditis (AIT II). AIT I is treated with antithyroid drugs, while total thyroidectomy and iodine-131 are used for definitive treatment. AIT II is treated with glucocorticoids. Patients with AIT have to stop treatment with amiodarone. Dronedarone is a less potent antiarrhythmic agent with structural and pharmacological properties similar to amiodarone. Dronedarone is devoid of iodine with fewer adverse effects and therefore it may be used in high risk patients for development of AIT or AIH.