Abstract
Amiodarone is a widely used antiarrhythmic drug, [for cardiac arrhythmia], which contains 75 mg of I- per 200 mg of active substance. Eight patients receiving long-term amiodarone therapy experienced hypothyroidism. Of these patients 7 had no previous history of thyroid dysfunction or goiter. Antithyroid antibodies were absent and standard perchlorate discharge tests were positive in 7 patients when hypothyroidism was diagnosed. In 1 patient, amiodarone therapy was withdrawn; over the next 9 mo., the hypothyroidism resolved and results of the perchlorate discharge test reverted to normal. Amiodarone-induced hypothyroidism is similar to previously described I--induced hypothyroidism. It may develop in the absence of a previous history of thyroid disease and all patients receiving long-term amiodarone therapy should therefore be regularly monitored for hypothyroidism.