The Characteristics of Amiodarone-induced Thyrotoxicosis in a Moderate Iodine Deficit Area

Introduction: Amiodarone (AMI), a class III anti-arrhythmic drug, is associated with a number of side effects, including thyroid dysfunction (both hypo- and hyperthyroidism), which is due to amiodarone's high iodine content and its direct toxic effect on the thyroid. Objective: To evaluate the incidence of Amiodarone induced thyrotoxicosis (AIT) (type, rate of occurrence) and to identify the risk factors involved in its occurrence. Material and method: We examined patients treated with amiodarone, between January 2002 and December 2011, who presented to our Department of Endocrinology Târgu Mures for thyroid dysfunctions. Results: The retrospective study included 87 patients with thyroid dysfunctions; 58 (66.7%) patients had AIT and 29 (33.3%) had Amiodarone induced hypothyroidism (AIH). In the AIT group: 35 were women (60.3%), 23 were men (39.7%); the average age was 61.60 ± 12.39 years. Risk factors identified for the AIT group were male gender (RR = OR = 3.8; Chi-squer = 5.7, p = 0.004) and pre-existing thyroid abnormalities (RR = 2.5, Chi-square = 4.1, p = 0.005). The thyroid dysfunction occurrence was heterogeneous (0.2-183 months). The patients with previous thyroid abnormalities developed earlier thyroid dysfunction compared to those with an apparently normal thyroid gland (22.25 ± 4.14 months versus 32.09 ± 7.69 months, p = 0.02, T test). Conclusion: In the context of the specific iodine geoclimatic intake and the area of origin, amiodarone - induced thyroid dysfunction spectrum is dominated by thyrotoxicosis. Screening and monitoring of thyroid function for patiens under chronic amiodarone treatment is necessary