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

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 AI T 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 I type H, 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 triiodo thyronine 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.