Effect of iodinated contrast media on thyroid function in adults

Area of Science:

• Radiology and Nuclear Medicine
• Endocrinology
• Pharmacology

Background:

• Excess free iodide in the blood, whether ingested or injected, poses a risk of thyrotoxicosis in susceptible individuals.
• Iodinated contrast media contain free iodide, which can be significant for at-risk patients and interfere with nuclear medicine studies.
• Thyroid function tests (T3, T4, TSH) are generally unaffected in patients with normal thyroid function following contrast medium injection.

Framework:

• A literature review was conducted by the Contrast Media Safety Committee of the European Society of Urogenital Radiology.
• Guidelines were developed based on an extensive Medline search and discussed at the Tenth European Symposium on Urogenital Radiology.
• The review aimed to address the safety concerns and clinical implications of free iodide in contrast media.

Implementation:

• Contrast medium-induced thyrotoxicosis is rare, but patients with Graves' disease or multinodular goiter with thyroid autonomy are at higher risk.
• Elderly patients and those in iodine-deficient areas are particularly susceptible to thyrotoxicosis after contrast medium administration.
• High-risk patients require careful endocrinological monitoring post-contrast examination; prophylaxis is generally not recommended but may benefit selected individuals.

Implications:

• The free iodide load from contrast media can interfere with thyroidal iodide uptake for up to two months, impacting diagnostic scintigraphy and radio-iodine therapy.
• Routine thyroid function monitoring is not indicated for patients with normal thyroid function before contrast medium injection.
• Guidelines are proposed to manage the risks associated with iodinated contrast media, particularly concerning thyroid function and potential thyrotoxicosis.