Myxedema Coma Precipitated by Iohexol: Case Report and Brief Literature Review on the Wolff–Chaikoff Effect

Background: Failure to escape from the Wolff-Chaikoff effect (WCE) causes hypothyroidism. Methods: This is the first report of myxedema coma after iohexol administration. The failure of the escape phenomenon in this patient was longer than existing reports. Results: The patient received 42,000 mg of iodine in iohexol cumulatively and developed myxedema coma after 16 days. She was subsequently found to have pre-existing primary hypothyroidism that was treated with levothyroxine 50 μg daily, but had defaulted treatment. She was discharged with levothyroxine 100 μg daily and this was weaned to 50 μg daily over 12 months. Conclusions: Iodine-based contrast media (ICM) can aggravate primary hypothyroidism. In severe cases, it may precipitate myxedema coma. Patients with thyroid disorders should be informed to monitor for aggravation of their symptoms after ICM administration. Long-term follow-up of thyroid function may be needed in patients who fail to escape from the WCE.