Resistant hyperthyroidism induced by sodium iopodate used as treatment for Graves' disease

Abstract

Sodium iopodate has recently been advocated for long-term control of hyperthyroidism in Graves' disease. Its advantages over conventional therapy are a rapid fall in thyroid hormones and control of symptoms with a simple dosage regime. We report a case in which severe resistant hyperthyroidism developed during treatment of Graves' disease with sodium iopodate. Sodium iopodate may not be suitable for long-term use in all patients with Graves' disease. Sodium iopodate was introduced as a contrast agent for oral cholecystography, but more recently its use has been advocated in the acute and longterm management of thyrotoxicosis (Wu et al. 1987b;Sharp et al. 1981;Shen et al. 1985). We re¬ port a case in which severe resistant hyperthyroid¬ ism developed during treatment of Graves' disCase Report A 36-year-old man was admitted for control of hyperthy¬ roidism. He gave a 3 month history of weight loss, tremor, sweating and frequent defecation. On examination he was severely hyperthyroid, had exophthalmos and a moderate smooth goitre with a bruit. The serum total thyroxine (TT4) and total triiodothyroninie (TT3) meas¬ ured by radioimmunoassay (Seth et al. 1976) were 296 nmol/1 (normal range 65-145) and 8.7 nmol/1 (normal range 1.1-2.8), respectively. Serum thyrotropin using a sensitive assay (Seth et al. 1984) was undetectable (normal range 0.3-5.0 mU/1). Treatment was commenced with 500 mg sodium iopodate (Bilopten*, Schering) once a day and long acting propranolol (Inderai LA®, ICI), 320 mg a day. Within 72 h the TT4 and TT, had fallen to 197 and 2.0 nmol/1, respectively, and his condition improved. A week later he was discharged when the TT4 and TT3 were 168 and 1.9 nmol/1 and his weight had increased by 2 kg.On review 3 weeks after starting treatment with sodium iopodate, TT4 and TT3 were 131 and 3.0 nmol/1 and he had discontinued the propranolol. He defaulted from clinic for 6 weeks, but continued to take the sodium iopo¬ date, receiving further supplies from his general practi¬ tioner. On review he was again severely hyperthyroid and the TT4 and TT3 were 269 and 10 nmol/1. The sodium io¬ podate was stopped and propylthiouracil, 150 mg three times daily, commenced. After 3 weeks there had been no fall in thyroid hormone levels and he was readmitted and the propylthiouracil continued. Over the next 6 weeks in hospital his weight continued to drop and the TT4 and TT3 remained 215 and 8.3 nmol/1. Carbimazole, 15 mg four times daily, was then substituted for the pro¬ pylthiouracil and after 2 weeks the TT4 and TT3 fell to 146 and 5.6 nmol/1, but he remained clinically hyperthy¬ roid and lithium carbonate, 400 mg twice daily, was added to his treatment Two weeks later the TT4 and TT3 were 107 and 3.4 nmol/1. After a further 2 weeks (3 months after starting propylthiouracil) a near total thy¬ roidectomy was performed. Postoperatively he has re¬ quired thyroxine and 1 alpha hydroxycholecalciferol. DiscussionSodium iopodate and similar drugs are iodine con¬ taining agents used for oral cholecystography. When introduced the...

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Resistant Thyrotoxicosis in a Patient with Graves Disease: A Case Report

“…Sodium ipodate has been used for the long-term control of Graves thyrotoxicosis and is believed to cause a more rapid fall in thyroid hormone level and provide an easier control of symptoms. However, it may itself rarely cause severe resistant hyperthyroidism when used in the treatment of Graves disease [9]. …”