Antithyroid antibodies during amiodarone treatment.

In 44 euthyroid and goitre-free patients, 23 treated with amiodarone (group A) and 21 treated with other antiarrhythmic drugs (group B), antimicrosomal antibodies and antithyroglobulin antibodies were determined before the beginning of treatment and after 7, 15, 30, 60, and 180 days. In group A, none of the patients had antithyroid antibodies before treatment. 1 of 15 patients (6.7%) had antimicrosomal antibodies (titre 1:100) on day 7 only, and 1 of 18 (5.5%) had antithyroglobulin antibodies (titre 1:80) on day 180. In group B. 1 of 21 patients (4.8%) had antimicrosomal antibodies (IgG class) at titre 1:400 before the beginning of treatment, which was negative on day 180, and 2 of 17 (11.8%) had antimicrosomal antibodies (titre 1:100) on day 60 only. None of these patients showed clinical and/or laboratory signs of hyper- or hypothyroidism. These data indicated that antithyroid antibodies rarely appear in amiodarone-treated patients and do not differ significantly from patients treated with other antiarrhythmic drugs. The role of autoimmunity and the meaning of antithyroid antibodies in the pathogenesis of amiodarone-induced thyroid dysfunction (mainly of hypothyroidism) in patients without pre-existent thyroid diseases is still unclear.