Abstract
Amiodarone, an iodinated benzofuran derivative, is used for treatment of refractory cardiac arrhythmias. Certain features of the drug's structure resemble those of the biologically active thyroid hormone, triiodothyronine (T3). In addition, the drug has a variety of complex effects on thyroid hormone physiology, including a number of possible antagonistic effects on thyroid hormone function at the cellular level. The drug occasionally causes clinically overt hyperthyroidism and hypothyroidism. We review these effects and discuss their clinical implications.