Endocrine Abstracts

Background: Amiodarone is a commonly used antiarrhythmic drug, but because of its abundance with iodine and a direct toxic effect on the thyroid, it can have side effects like hypo- and hyperthyroidism. There are two types of amiodarone-induced thyrotoxicosis (AIT). We present a case which demonstrates the importance of timely diagnosis and appropriate treatment of amiodarone-induced thyrotoxicosis in patients with serious cardiac comorbidities.

Case presentation: A 74-year-old male with a history of a thyroid checkup in 2019 after accidental finding on CT, when neck ultrasound (US) and scintigraphy were performed (ultrasound showed a multinodular goiter; scintigraphy showed several warm nodules), hypertension, paroxysmal atrial fibrillation, implanted mechanical aortic valve because of aortic regurgitation, left ventricular hypertrophy, and reduced ejection fraction, was referred to our clinic because of hyperthyroidism. Four months prior to this visit amiodarone was discontinued by his cardiologist after five years of use. At the time of amiodarone discontinuation the patient had a thyroid stimulating hormone (TSH) level below the lower reference limit and no hypermetabolic symptoms. No thyrostatic treatment was initiated nor was he referred to an endocrinologist. The patient developed symptoms of hyperthyroidism two months later; TSH was suppressed. His primary care physician started him on 10 mg of thiamazole daily. After two more months, the patient’s state worsened. He was referred to an otorhinolaryngologist who advised the patient to visit our clinic. US was repeated, confirming the presence of multinodular goiter, no signs of gland destruction were present, and vascularisation was neither increased nor absent. At that point urgent restoration of stable clinical state was necessary because the patient had cardiac decompensation and overt hyperthyroidism with suppressed TSH and high free thyroxine (FT4) level, as well as prolonged prothrombin time due to coumarin use. After cardiac recompensation, normalization of the coagulogram, and reduction of the FT4 level under full thiamazole dose (which stayed slightly above the upper reference limit), thyroidectomy was performed. Significant clinical and laboratory improvement followed.

Conclusions: AIT has been associated with increased morbidity and mortality, especially in older patients with impaired left ventricular function. The importance of regular monitoring of thyroid status in amiodarone users and rapid recovery and stable maintenance of euthyroidism when necessary, should be emphasized to both endocrinologists and non-endocrinologists.