Effect of iodinated contrast media on thyroid function in adults

Abstract

Excess free iodide in the blood (ingested or injected) may cause thyrotoxicosis in patients at risk. Iodinated contrast medium solutions contain small amounts of free iodide and may be of significance for patients at risk. The free iodide may also interfere with nuclear medicine diagnostic studies and treatment. Therefore the Contrast Media Safety Committee of the European Society of Urogenital Radiology reviewed the literature on this subject in order to prepare guidelines. A report and guidelines were prepared based on an extensive Medline search. The report was discussed with the participants attending the Tenth European Symposium on Urogenital Radiology, Uppsala, Sweden, September 2003. Contrast medium induced thyrotoxicosis is rare. Contrast medium injection does not affect thyroid function tests (e.g., T3, T4, TSH) in patients with a normal thyroid. Routine monitoring of thyroid function tests before contrast medium injection in patients with a normal thyroid is not indicated even in areas where there is dietary iodine deficiency. Patients at risk of developing thyrotoxicosis after contrast medium injection are patients with Graves' disease and patients with multinodular goiter with thyroid autonomy, especially elderly patients and patients living in areas of iodine deficiency. Patients at high-risk should be carefully monitored by endocrinologists after contrast medium examinations. Prophylaxis in these groups is not generally recommended, although it may offer some protection in selected high-risk individuals. The free iodide load of contrast media injections interferes with iodide uptake in the thyroid and therefore compromises diagnostic thyroid scintigraphy and radio-iodine treatment of thyroid malignancies for 2 months after administration of contrast media. Simple guidelines on the subject are proposed.

Side Effects of Radiographic Contrast Media: Pathogenesis, Risk Factors, and Prevention

“…A dose of contrast media used in typical radiological procedure contains about 13500  μ g of free iodide [9] and 15 to 60 g of bound iodine [9, 10] that may be liberated as free iodide in the body [9, 11]. This is actually an acute iodide load of 90 to several hundred thousand times the recommended daily intake of iodide (150  μ g) [12].…”

Thyrotoxicosis in a 13‐year‐old girl following pituitary adenectomy for Cushing′s disease

“…Unlike our case, both of these cases postulate an antibody‐positive thyroid dysfunction, and therefore, this pediatric case is unique. Iodinated contrast medium is known to induce thyrotoxicosis in adults but is very rare 13, 14, 15. In this case, the first symptoms of thyrotoxicosis developed approximately 2 months after the use of iodinated contrast medium, and according to Conn et al.…”

“…Contrast medium injection does however not affect thyroid function tests (TFT) in patients with a normal thyroid. Patients at risk of developing thyrotoxicosis after contrast medium injection are patients with Grave′s disease and multinodular goiter with thyroid autonomy, especially elderly patients and patients living in areas of iodine deficiency 13, 17. Iceland is considered an area without iodine deficiency, and it has been established that the girl did not have Grave′s disease as she was antibody negative.…”

Characteristics of incidentally found thyroid nodules in computed tomography: comparison with thyroid scintigraphy

“…A 200-ml dose of a contrast medium containing 35 μg/ml provides 7,000 μg free iodide, equivalent to 45 times the recommended daily intake [14]. Our hypothesis was that iodine containing contrast media for chest CT accumulates in the thyroid due to the act of iodination, and this process could influence the HU values of the thyroid.…”