[Amiodarone-induced hyperthyroidism].

Amiodarone is extensively used in cardiology practice because of its excellent antiarrhythmic properties. It produces alterations in thyroid functional because it contains 37% iodine and it is structurally similar to the thyroid hormones. Amiodarone inhibits 5'-deiodinase in the liver. The incidence of amiodarone-induced hyperthyroidism is between 6% and 12% of treated patients. The figures for pediatric patients are similar. Determination of tri-iodothyronine (T3), thyroxine (T4) and thyroid-stimulating hormone (TSH) plays an important role in the diagnosis and follow-up of thyroid alterations. Treatment options in amiodarone-induced hyperthyroidism in children include thionamide, potassium perchlorate, and prednisone. We present the case of hyperthyroidism secondary to amiodarone in a 10-year-old boy with Marfan's syndrome who was admitted several times for crises of paroxysmal supraventricular tachycardia and atrial fibrillation. After amiodarone treatment he presented a clinical and analytical picture of hyperthyroidism with very low TSH levels and increased free-T4 levels. Thyroid echography and scintigraphy were normal. Treatment with thiamazole did not alter the clinical picture, which returned to normal after prednisone administration. Currently, prednisone is being slowly withdrawn.Amiodarone. Hyperthyroidism. Antiarrhythmics.