The Incidence and Risk of Inducing Hyperthyroidism Following Amiodarone Treatment

Introduction: Amiodarone, a frequently used antiarrhythmic drug in cardiology, is very efficient in the treatment of ventricular and supraventricular tachiarrithmyas. The iodine content of amiodarone is 39%. Its chemical structure is similar to tyrosine. It is estimated that 1–23% of patients treated with amiodarone can develop hyperthyroidism. The purpose of this study is to assess and monitor the incidence of hyperthyroidism induced by amiodarone in patients admitted for various types of cardiac dysrhythmias, considering that most of the patients included in the study came from an endemic goitre area.
Material and method: One-hundred patients chosen systematically (62 men, 38 women) from 560 patients treated with amiodarone in the January 1st, 2009 – December 31, 2009 period were assessed (clinically, laboratory findings and imaging studies); their mean age was 64 years (range 50–70 years). In order to identify and diagnose hyperthyroidism, a questionnaire (Newcastle index) was used, also urinary iodine dosage, hormonal dosages (T3, T4, TSH) and thyroid imaging (ultrasound, radioactive iodine uptake test) were used.
Results: The incidence of hyperthyroidism induced by amiodarone in this study was 8%. Hyperthyroidism was more frequent in women (6 women vs. 2 men).
Conclusions: Thyroid hormonal levels have to be determined and a clinical or thyroid ultrasound examination should be made prior to initiating a treatment with amiodarone. At the end of the study, 8 patients, most of them female, were diagnosed with hyperthyroidism.