Abstract

Amiodarone is a widely used antiarrhythmic agent for the management of cardiac arrhythmias. Its high iodine content can significantly affect thyroid function, occasionally leading to amiodarone-induced thyrotoxicosis (AIT). We report a case of mixed-type AIT that developed during chronic amiodarone therapy. A 68-year-old male patient with a medical history of hypertension and Type 2 diabetes mellitus had an implantable cardioverter-defibrillator (ICD) placed approximately 2.5 years ago due to non-sustained ventricular tachycardia (VT) and non-ischemic dilated cardiomyopathy. During follow-up, the patient experienced ICD shocks. Thyroid function tests at that time were within normal limits, and oral cordarone was initiated at a dose of 200 mg twice daily. His other medications included delix 5 mg once daily, saneloc 100 mg once daily, forxiga 10 mg once daily, aldactone 25 mg once daily, and janumet 50/1000 mg once daily. Recently, the patient presented with complaints of right arm tremor, fatigue, and palpitations. Laboratory evaluation revealed thyroid stimulating hormone <0.01 mU/L, sT4 77.7 ng/dL, and sT3 4.6 ng/dL. Thyroid ultrasonography demonstrated a normal gland volume, heterogeneous parenchyma, and normal vascularity. With a preliminary diagnosis of mixed-type AIT, the patient was admitted to the endocrinology service. Cordarone was discontinued, and thyromazole was initiated at 20 mg/day. Due to inadequate clinical response, Prednol 32 mg/day was added, and the thyromazole dose was increased to 40 mg/day. As thyroid function failed to improve, total thyroidectomy was planned. Plasmapheresis was performed preoperatively. The patient was subsequently scheduled for further evaluation regarding VT ablation. AIT presents significant diagnostic and therapeutic challenges. Regular thyroid function monitoring, a multidisciplinary approach, and close collaboration between cardiologists and endocrinologists are essential for effective management.