Draft of the federal clinical recommendations for diagnosisi and treatment of amiodarone-induced thyroid dysfunction

Abstract

Amiodarone is an antiarrhythmic drug that is commonly used for treatment of various supraventricular and ventricular arrhythmias. Amiodarone and its main active metabolite desethylamiodarone have a direct dose-dependent cytotoxic effect on thyroid follicular cells. Consequently, some patients receiving amiodarone may develop thyroid dysfunction: amiodarone-induced hypothyroidism (AIH) or amiodarone-induced thyrotoxicosis (AIT). The diagnosis, classification, and treatment of amiodarone-induced thyroid dysfunction remain to be a challenge to all clinicians deal with this problem. This draft of clinical recommendations was developed by a group of specialists experienced in the diagnosis and treatment of amiodarone-induced thyroid dysfunction. AIH does not require amiodarone withdrawal. Thyroxine treatment is recommended for all patients with manifest AIH, subclinical forms of AIH do not always need its prescription. There are two main types of amiodarone-induced thyrotoxicosis: AIT type 1 (is a hyperthyroidism that develops due to excessive iodine intake in autonomous thyroid nodules or latent Graves ‘ disease) and AIT type 2 (develops due to destructive thyroiditis because of the cytotoxic effect of amiodarone). In addition, there is a mixed form, which has features of both types of AIT. Autonomous AIT 1 is characterized by the presence of one or more «hot» nodules in the thyroid. Elevated TSH receptor antibodies or typical clinical manifestations confirm the diagnosis of diffuse toxic goiter and, consequently, AIT1. Colour-flow Doppler sonography (CFDS) is proposed as the basic method of differential diagnosis of AIT 1 and AIT 2. CFDS «pattern 0», usually indicates AIT 2, the presence of «patterns I-III» mostly typical for AIT 1. The thyreostatics are recommended for AIT 1, oral glucocorticoids for AIT 2 and their combination for a mixed AIT. Emergency thyroidectomy should be applied to patients with deteriorating cardiovascular pathology and ineffective drug therapy. In the absence of clinical suspicion on thyroid dysfunction, thyroid hormones assessment should be done 3 months after the start of amiodarone treatment, thereafter every 6 months.