Hypothyroidism and Hyperthyroidism in an Adolescent With Complex Congenital Heart Disease Exposed to Iodinated Contrast Media: Case Report.

Introduction: Jod-Basedow syndrome and iodine-induced hypothyroidism are rare but clinically significant complications of iodine exposure. We report a unique case of a 14-year-old boy with congenital heart disease, who developed sequential iodine-induced hypothyroidism due to failure to escape from the Wolff-Chaikoff effect, followed by hyperthyroidism (Jod-Basedow syndrome) after additional exposure to iodinated contrast. Case Presentation: The patient is a 14-year-old male with a history of complex congenital cardiac defects. He underwent a Fontan procedure to manage his single-ventricle physiology, resulting in plastic bronchitis requiring lymphatic intervention and cardiac catheterization. At age 15, he developed hypothyroidism requiring levothyroxine, but 6 months later presented with symptoms and labs confirming hyperthyroidism following CT scan with IV iodinated contrast. Levothyroxine was discontinued, and methimazole was initiated to manage his hyperthyroidism. Conclusion: Iodine-induced hypothyroidism and Jod-Basedow syndrome should be considered potential complications for patients who undergo iodine exposure. This case highlights the importance of vigilant thyroid monitoring in congenital heart disease patients who are undergoing frequent radiation and iodine contrast exposure. In this patient, both his hypothyroidism and hyperthyroidism were successfully managed, but his overall condition deteriorated, ultimately requiring a heart transplant. This case underscores the importance of close monitoring of thyroid hormone levels in complex cardiac patients who undergo repeated exposure to iodinated contrast during procedures and imaging studies.