Initially Suspected Anaphylaxis Following Iodinated Contrast: Jod-Basedow Phenomenon in a 73-Year-Old Female Without a History of Thyroid Dysfunction

The Jod-Basedow phenomenon (JB phenomenon), also referred to as “iodine-induced hyperthyroidism,” rarely occurs. Radiological imaging using iodinated contrast contains a dose of 300 to 1221 mg of iodine per kilogram, which can transiently induce clinically significant hyperthyroidism (referred to as Jod-Basedow Syndrome) in euthyroid patients. Hence, the reporting of such events is important for clinicians to be aware of, to prevent unnecessary iodine-based imaging. Underlying thyroid abnormalities, including latent Graves’ disease, autoimmune thyroiditis, use of iodine-containing foods or medications, such as amiodarone, and Lugol’s iodine have been shown to increase the risk of JB phenomenon. In terms of the pathophysiology of the JB phenomenon, when iodine exposure is in excess, increased iodine leads to increased hormone synthesis, and with an absence of auto-regulation, this can lead to thyrotoxicosis. In this case report, we describe the iodine-induced JB phenomenon in a 73-year-old female with no prior thyroid dysfunction, who was initially admitted for pyelonephritis and was eventually transferred to the intensive care unit secondary to suspected anaphylaxis.