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

Cota Ancuța-Elena,Pașcanu Ionela,Căpraru Oana-Maria

doi:10.2478/amma-2013-0045

Cota Ancuța-Elena, Pașcanu Ionela + Show 1 more

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https://doi.org/10.2478/amma-2013-0045

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Abstract

Abstract 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

Highlights

Amiodarone (AMI), a class III anti-arrhythmic drug, is associated with a number of side effects, including thyroid dysfunction, which is due to amiodarone's high iodine content and its direct toxic effect on the thyroid
Risk factors identified in the Amiodarone induced thyrotoxicosis (AIT) group were: male gender (RR = OR = 3.8; Chi-square = 5.7; p = 0.004) and pre-existing thyroid abnormalities (RR = 2.5; Chi-square = 4.1; p = 0.005)
Pre-existing thyroid abnormalities in our group were significant: 29 (76.31%) patients with type I AIT had a previous history of thyroid patology like diffuse goiter in 2 cases (6.9%), nodular goiter in 26 cases (89.7%) and Graves-Basedow disease in 1 case (3.4%)

Summary

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. A 200 mg AMI tablet contains 75 mg of iodine, from which 6 mg are released per day, causing an overload 50–100 times greater than the WHO daily iodine recommendation (0.15–0.3 mg/day). This amount disturbs the complex physiology of the thyroid gland and has a direct toxic effect on thyrocytes [3,4,5]. Amiodarone induced thyrotoxicosis (AIT) has an incidence of 2–23%, with a higher frequency in iodine-deficient areas (2–13% in the U.S, 9.6% in Italy) [6,7,8].

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