Amiodarone-induced thyrotoxicosis

Abstract

Amiodarone-induced thyroid dysfunction occurs in about 15-20% of patients under amiodarone therapy. Amiodarone-induced hypothyroidism (AIH) can develop in patients with an apparently normal thyroid gland or in those with an underlying chronic autoimmune thyroiditis. On a clinical ground, AIH is not challenging and can be easily treated with L-thyroxine therapy. Amiodarone-induced thyrotoxicosis (AIT) can occur in patients with (AIT 1) or without (AIT 2) an underlying thyroid disease. AIT 1 is a true iodine-induced hyperthyroidism occurring in patients with an underlying thyroid autonomy while AIT 2 is a drug-induced destructive thyroiditis. According to the different pathogenetic mechanism, AIT 2 is treated with glucocorticoids while AIT 1 usually responds to thionamides. Thyroidectomy should be considered when AIT represents an imminent risk for cardiac conditions, when patients require a prompt resolution of thyrotoxicosis or when they do not respond to the medical therapy. An effective collaboration between cardiologists and endocrinologists is crucial in each part of the management of AIT patients, including the evaluation of cardiological conditions with regard to thyroid hormone excess and whether, or not, it is necessary to continue amiodarone therapy.