Iodinated Contrast Media Induced Hyperthyroidism

The proper synthesis of thyroid hormones is dependent on adequate iodine supply. The mean daily iodine intake recommended by World Health Organization is 150 mg. Iodinated contrast medium (ICM) typically contains 13 500 mg of free iodine and 15-60 g of bound iodine, an amount well above acceptable upper level. In a situation of excess iodine, thyroid discontinues the release of hormones (Wolff-Chaikoff effect), which is usually transient, although can persist causing hypothyroidism. Iodine-induced hyperthyroidism (IIH), known as the Jod-Basedow phenomenon is infrequent, but elderly patients and individuals with autonomously functioning nodular goiters are at higher risk of developing this dysfunction. According to recent studies the risk of ICM-induced hyperthyroidism appears to be low. The prevalence has not been well assessed and varies from 1 % to 10 %. Currently, there are no specific guidelines concerning the prophylactic therapy of IIH. American Thyroid Association (ATA) does not recommend routine administration of antithyroid drugs before iodinated contrast medium for all patients, however, advises to consider prophylaxis in patients at high risk of developing IIH or with cardiovascular comorbidities. ATA recommends avoidance of additional iodine and administration of b-blockers alone or with antithyroid drugs as a treatment of IIH, depending on the severity of hyperthyroidism. This study was performed to evaluate the influence of ICM on thyroid status and advantages of prophylactic therapy during ICM exposure in patients with euthyroid goiter and cardiovascular comorbidities. The association between the incidence of IIH and thyroid volume was also assessed.