Risk factors for amiodarone‐induced thyroid dysfunction in Japan

<jats:title>Abstract</jats:title><jats:sec><jats:title>Background</jats:title><jats:p>Amiodarone is associated with a number of significant adverse effects, including elevated transaminase levels, pulmonary fibrosis, arrhythmia, and thyroid dysfunction. Although thyroid dysfunction is considered to be a common and potentially serious adverse effect of amiodarone therapy, the exact pathogenesis remains unknown because of its complex manifestations. Therefore, the prevalence of, and risk factors for, amiodarone‐induced thyroid dysfunction in Japanese patients were investigated in the present study.</jats:p></jats:sec><jats:sec><jats:title>Methods</jats:title><jats:p>A retrospective analysis of patients treated with amiodarone between January 2012 and December 2013 was performed. A total of 317 patients with euthyroidism, or subclinical hyperthyroidism or hypothyroidism, were enrolled in this study.</jats:p></jats:sec><jats:sec><jats:title>Results</jats:title><jats:p>After being treated with amiodarone, 30 (9.5%) and 60 patients (18.9%) developed amiodarone‐induced hyperthyroidism and amiodarone‐induced hypothyroidism, respectively. Ten (33.3%) patients with amiodarone‐induced hyperthyroidism and 40 (66.6%) with amiodarone‐induced hypothyroidism were diagnosed within two years of the initiation of amiodarone therapy. Dilated cardiomyopathy (DCM) [Adjusted odds ratio (OR) 3.30 (95% confidence interval (CI): 1.26–8.90)], and cardiac sarcoidosis [Adjusted OR 6.47 (95% CI: 1.60–25.77)] were identified as predictors of amiodarone‐induced hyperthyroidism. The baseline free thyroxine (T4) level [Adjusted OR 0.13 (95% CI: 0.03–0.68)], and thyroid‐stimulating hormone (TSH) level [Adjusted OR1.47 (95% CI: 1.26–1.74)] were identified as predictors of amiodarone‐induced hypothyroidism.</jats:p></jats:sec><jats:sec><jats:title>Conclusion</jats:title><jats:p>DCM and cardiac sarcoidosis were identified as risk factors for amiodarone‐induced hyperthyroidism. Risk factors for amiodarone‐induced hypothyroidism included higher baseline TSH level and lower baseline free T4 level, suggesting that subclinical hypothyroidism may be a potential risk factor for the development of amiodarone‐induced hypothyroidism.</jats:p></jats:sec>