THE INFLUENCE OF AMIODARONE ON THYROID FUNCTION – A CASE REPORT

Abstract

Amiodarone is an antiarrhythmic drug, commonly used in the treatment of ventricular and supraventricular arrhythmias. It can cause many side effects, including thyroid dysfunction, which can lead to either hypo- or hyperthyroidism. There are two types of amiodarone-induced hyperthyroidism. Type 1 affects patients with preexisting thyroid pathology and is the consequence of iodine excess. Type 2 is not related to preexisting thyroid pathology and is characterised by the presence of destructive thyroid inflammation. A 55-year old male was admitted to our hospital because of chest pain. He was diagnosed with atrial fibrillation and three vessel coronary artery disease, serum TSH concentration was normal. The patient later underwent coronary artery bypass surgery and was subsequently prescribed amiodarone. Two years later he became hyperthyroid, thyroid ultrasonography was consistent with autoimmune thyroid disease, however thyroid autoantibodies were negative. Amiodarone was discontinued and antithyroid drugs were introduced, leading to remission of hyperthyroidism. One month after the discontinuation of the antithyroid drugs the patient had a primary cardiac arrest, there were signs of diffuse ischemic cerebral injury. Due to nonsustained ventricular tachycardias an implantable cardioverter defibrillator was inserted, the patient was again prescribed amiodarone, and after three years of continuous amiodarone treatment hyperthyroidism recurred. As amiodarone discontinuation in conjunction with antithyroid drugs and high-dose glucocorticoid treatment did not result in remission, total thyroidectomy was safely performed. Pathohistological examination of the thyroid revealed pathologic changes consistent with amiodarone-induced hyperthyroidism type 2. Substitution therapy with levothyroxine was introduced on the 17th postoperative day. Peroral glucocorticoid therapy is the first line treatment of type 2 amiodarone-induced hyperthyroidism. However, in a selected group of patients, where medication therapy is unsuccessful, total thyroidectomy is an effective and safe modality, despite high-dose glucocorticoid treatment and other possible comorbidities. Furthermore, total thyroidectomy makes continuous amiodarone therapy possible, when it is necessary. It is important to keep in mind that high serum concentrations of free triiodothyronine and free thyroxine may persist for several days after total thyroidectomy.