Chronic administration of amiodarone and thyroid function: A follow-up study

Abstract

In order to evaluate the effects of amiodarone on thyroid function in chronically treated patients, 43 consecutive patients, who had been taking a mean weekly dose of 1420 ± 488 mg for more than 9 months (mean 16.5 months), were studied. In a first evaluation, three patients with hypothyroidism and two with hyperthyroidism were discovered. In the remaining 38 patients, mean T 4 (131 ± 38 nmol/L) and rT 3 (0.85 ± 0.3 nmol/L) levels were significantly higher than reference values ( p < 0.05 and p < 0.001, respectively), and mean T 3 levels (1.89 ± 0.73 nmol/L) were significantly lower ( p < 0.001). Thirteen patients showed hyperresponsiveness to thyrotropin-releasing hormone (TRH) stimulation testing. In a second evaluation, performed 12 to 18 months later, two new cases of hypothyroidism were discovered. T 3 levels showed significantly lower values ( p < 0.02) than in the first evaluation, whereas basal thyroid-stimulating hormone levels and levels 30 and 60 minutes after TRH stimulation were significantly higher than those in the first evaluation ( p < 0.001). Five new hyperresponders to TRH were found. In the present series, the progressive appearance of clinical thyroid dysfunction with an elevated total incidence (16%) is demonstrated. Moreover, a progressively high prevalence of hyperresponsiveness to TRH stimulation is shown. These findings indicate that chronic amiodarone administration may carry a high risk of thyroid dysfunction.