ENHANCED SUSCEPTIBILITY TO AMIODARONE-INDUCED HYPOTHYROIDISM IN PATIENTS WITH THYROID AUTOIMMUNE-DISEASE

Background: The iodine-rich antiarrhythmic drug, amiodarone, can induc e both thyrotoxicosis and hypothyroidism, the former being more freque nt in iodine-deficient areas, the latter in iodine-sufficient areas. I n this study we evaluated prospectively thyroid function in amiodarone -treated patients with positive or negative baseline thyroid autoantib ody test results who resided in a moderately iodine-deficient area of Italy. Subjects: Two groups of patients received long-term amiodarone treatment: Group 1 included 13 patients with negative thyroid autoanti body test results. Group 2 consisted of seven patients with positive t hyroid autoantibody test results and thyroid ultrasound patterns compa tible with Hashimoto's thyroiditis. The control group (group 3) includ ed 16 untreated euthyroid patients with Hashimoto's thyroiditis. All s ubjects resided in a mildly iodine-deficient area of Italy (Southern S ardinia) and had low urinary iodine values. Patients in groups 1 and 2 had markedly elevated urinary iodine excretion during treatment. The follow-up period ranged from 6 to 29 months in group 1, from 4 to 9 mo nths in group 2, and from 12 to 55 months in group 3. Results: Two (15 %) of 13 patients in group 1 with nodular goiter developed thyrotoxico sis. No patient in this group developed circulating thyroid autoantibo dies. Five (71%) of seven patients in group 2 became hypothyroid after 4 to 9 months of amiodarone treatment associated with a rise in serum thyroid autoantibody levels. No patient in group 3 became hypothyroid . Conclusions: (1) Amiodarone administration can cause both thyrotoxic osis and hypothyroidism (2) Hypothyroidism is far more frequent in pat ients with preexisting thyroid autoimmune disease. (3) Amiodarone can modify the natural history of Hashimoto's thyroiditis. (4) Circulating thyroid autoantibodies do not appear in amiodarone-treated patients w ho have negative test results prior to therapy.