• C Henzen, M Buess, and L Brander.
• Medizinische Klinik, Kantonsspital Luzern. chr.henzen.irm@bluewin.ch
• Swiss Med Wkly. 1999 May 1; 129 (17): 658-64.

AbstractIodine-induced thyrotoxicosis or "jodbasedow phenomenon" has been reported throughout the world since iodine has been administered to treat endemic goitre. Nowadays, iodinated radiocontrast agents and the antiarrhythmic drug amiodarone are the most common sources of excess iodine load subsequently leading to iodine-induced thyrotoxicosis, especially in elderly patients with underlying goitre. The aim of the study was to identify the number of cases of iodine-induced thyrotoxicosis among patients with thyrotoxicosis in a large urban hospital. Over an 18-month period thyrotoxicosis has been diagnosed in a total of 39 patients. Eight patients with iodine-induced thyrotoxicosis (5 female, 3 male; mean age 60.6 years) have been identified (20%). In all patients with iodine-induced thyrotoxicosis, iodine exposure with a mean iodine dose of 21.5 g was documented 2 to 16 weeks before diagnosis (iodinated radiocontrast agents in 5 patients, amiodarone in 2 patients, kelp tablets in 1 patient). Clinical features were predominantly tachyarrhythmias and heart failure, while 6 of 8 patients had goitre (thyroid volume 31 to 193 ml). Thyroid antibodies were not detected. Diagnosis was confirmed in 5 of 8 patients with increased urinary iodine concentrations (3436 to > 6000 nmol/24 h), and in 3 of 8 patients with a low tracer uptake in thyroid scintigraphy (1 to 4%). Treatment consisted of methimazole in all patients, additional tional beta-blockers and lithium in 4 patients, and prednisone in 5 patients. The mean treatment ment duration was 9.2 months, and patients became euthyroid after a mean treatment duration of 6.4 weeks. One patient (with still elevated free thyroxine levels) died of myocardial infarction 4 weeks after antithyroid drug therapy had been installed. The incidence, mechanisms and features of iodine-induced thyrotoxicosis are discussed. Iodine-induced thyrotoxicosis is a common disease, and the recognition and treatment of iodine-induced thyrotoxicosis, particularly in elderly patients and patients with goitre, are of clinical importance.

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