IODINE-INDUCED HYPERTHYROIDISM DUE TO NONIONIC CONTRAST RADIOGRAPHY IN THE ELDERLY

PURPOSE: To identify the number of cases of hyperthyroidism that follo wed the performance of contrast radiography in elderly patients at a g eriatric hospital in a non-iodine-deficient area and to determine the clinical course of the condition. PATIENTS AND METHODS: All patients o ver a 20-month period with biochemical hyperthyroidism (plasma free th yroxine level greater than 25.0 pmol/L and thyroid-stimulating hormone level less than 0.10 IU/L) were identified. Clinical features of hype rthyroidism and exposure to nonionic contrast media radiographs within the previous 12 months were sought. Follow-up extended from 6 to 22 m onths. RESULTS: A total of 28 patients with hyperthyroidism (aged 70 t o 96 years) were identified. Seven patients (25%) had documented bioch emical development of hyperthyroidism (five) or subsequent hyperthyroi dism (two) 3 to 8 weeks after nonionic contrast media radiography. The four patients who underwent scanning had a multinodular thyroid, and thyroid antibodies were not detected in five of five patients. Althoug h the condition appeared self-limited and six of six patients were eut hyroid after 18 months, the condition was not benign; progress and rec overy were adversely affected by hyperthyroidism. Four patients had a good response to treatment with an antithyroid drug (carbimazole). CON CLUSION: Iodine-induced thyrotoxicosis following contrast radiography was found in 7 of 28 cases of hyperthyroidism seen at a geriatric hosp ital. Although the condition appears ultimately self-limited, pharmaco logic control of severe clinical features may be required. The frequen cy of this condition in a non-iodine-deficient area appears related to the more common occurrence of autonomous thyroid nodules in the elder ly. Because performance of contrast radiography is more common in this age group, the recognition and treatment of iodine-induced thyrotoxic osis are of increasing clinical importance.