Preparation with iopanoic acid rapidly controls thyrotoxicosis in patients with amiodarone-induced thyrotoxicosis before thyroidectomy

Abstract

Background. Amiodarone-induced thyrotoxicosis (AIT) may develop either in apparently normal glands (type II AIT) or in the presence of thyroid abnormalities (type I AIT). Sometimes AIT is resistant to conventional treatment. Thyroidectomy was used in patients with AIT, but in patients who are thyrotoxic it may be hazardous. Methods. Seven patients with AIT (6 type I and 1 type II, 5 men, 2 women, mean age 70 years [range, 60-82 years]) were prepared for total thyroidectomy with a short course of iopanoic acid (1 g/day orally for a mean of 13 days), an oral iodinated cholecystographic agent inhibiting 5'-deiodinase and causing a reduction in the peripheral conversion of thyroxine to triiodothyronine. Mean thyroid volume was 64 mL (range, 10-145 mL). Results. Mean serum-free triiodothyronine levels decreased from 20 ± 16.7 pmol/L to 6 ± 2 pmol/L (P =.0004), whereas serum-free thyroxine values remained unchanged. Euthyroidism was rapidly (7-20 days) restored, allowing an uncomplicated total thyroidectomy in all patients and the ability to continue amiodarone therapy in 6 patients. None had increased surgical bleeding, recurrent nerve palsy, or hypoparathyroidism. No cardiovascular complications occurred. Conclusions. Iopanoic acid is an effective drug allowing rapid control of hyperthyroidism in AIT. (Surgery 2002;132:1114-8.)