Amiodarone-Induced Thyrotoxicosis Due to Destructive Thyroiditis

Abstract

Amiodarone-induced thyrotoxicosis (AIT) type 1 occurs in subjects with an underlying thyroid disease, whereas type 2 AIT is a form of destructive thyroiditis. Our hypothesis was that the common practice of thyroid testing before prescription of amiodarone would reduce the incidence of pure type 1 AIT, though a stringent classification may be difficult (mixed type AIT). Thyroid testing before and after treatment of AIT (n = 12) and the response to combined antithyroid and glucocorticoid treatment (n = 11) were recorded in a consecutive series of patients seen at a university hospital. Some criteria for type 1 AIT were fulfilled in 3 patients, but the diagnosis of a mixed form AIT was more likely in 2 of these. Type 2 AIT was diagnosed in the other 9 patients, while 6 patients had diffuse hypoechoic goitre. The median time to euthyroidism (defined as normal fT3 concentration) under thionamide and prednisolone (starting dose 20 to 75 mg/d) was 2 months (interquartile range 1 to 2.7 months). Thionamide treatment was stopped after a median duration of 5.7 months (interquartile range 4.2 to 8.7 months) and glucocorticoids were completely withdrawn after 6.7 months (5.5 to 8.7 months). Nowadays, isolated type 1 AIT is rarely found and destructive thyroiditis (as type 2 AIT or mixed form) is the predominant cause of AIT. To accelerate recovery, we prescribed thionamide and glucocorticoids simultaneously as first-line therapy once contraindications for the use of steroids had been ruled out.