[Iodinated contrast medium in patients with thyroid disorders]

Adequate intake of iodine is essential for normal thyroid function. However, sudden exposure to high amounts of iodine may cause thyroid dysfunction.

The aims of this paper are to summarize the literature on the effects of iodinated contrast medium (CM) on thyroid function, the risk to develop CM-induced hyper- and hypothyroidism, and to describe procedures for clinical practice regarding diagnosis, prevention, and treatment of CM-induced hyperthyroidism.

The occurrence of CM-induced hyperthyroidism is very rare (<0.5%). In Germany, thyroid function is commonly assessed with laboratory tests (TSH determination) before the use of iodinated CM. Older patients (>60 years) with autonomous thyroid and concomitant cardiac diseases are at particular risk of developing hyperthyroidism. The main focus of prevention is to identify patients at risk of developing iodine-induced hyperthyroidism and carry out further thyroid diagnostic procedures prior to CM use. In these patients, prophylaxis with perchlorate and/or thionamides is recommended or alternatively careful monitoring of the patients after use of CM. In patients with overt hyperthyroidism, the use of CM is contraindicated. Iodine-induced hypothyroidism is predominantly found in regions with sufficient iodine supply and in patients with autoimmune thyroiditis. Free iodide influences iodide uptake into the thyroid and therefore interferes with nuclear diagnostic procedures like thyroid scintigraphy as well as radioactive iodine treatment which may be hampered for 2 months or longer after use of CM.