Iodine-Based Contrast Media May Disrupt Thyroid Functions In Children Receiving MRI or CT Scans, FDA Warns

Children receiving iodine-based contrast agents to improve the results of medical scans, such as MRIs, X-rays and CT Scans, could experience dangerous decreases in thyroid function, according to a new warning issued by federal regulators.

The FDA released a drug safety communication on March 30, announcing that it will require new label warnings for all iodinated contrast media (ICM) injections for children 3 years old and younger. The agency indicates the injections could temporarily decrease thyroid hormone levels, and could even result in hypothyroidism.

Iodine contrast media include products like Visipaque, Omnipaque, Ultravist, and others that may be administered to help enhance magnetic resonance imaging (MRIs), X-rays and computed tomography scans (CT scans), providing more detailed results that improve the chances of an accurate diagnosis.

The FDA first warned of possible thyroid function problems with children given ICMs in 2015, and called for contrast-agent manufacturers to conduct more research. Since then, six new studies have been published which the agency reviewed before making its latest determination.

According to the FDA’s analysis, most of the decreases were temporary, and required no treatment. The findings indicate the decrease ranges from one percent to 15 percent, and tended to occur more often, and more dramatically, in newborns; especially in those who were born preterm.

Children with heart problems faced the greatest risk of health problems, because they often require very high doses of ICM during heart procedures.

“Our review showed that underactive thyroid or a temporary decrease in thyroid hormone levels were uncommon. However, the conditions should be identified and treated early when needed to prevent potential future complications,” the FDA states in the safety communication. “Newborns, particularly those born premature, and children in their first 3 years with underlying conditions such as heart issues may be higher risk for problems of the thyroid, a gland in the neck that releases hormones that help control many of the body’s functions.”

In addition to new label warnings. The FDA is also recommending monitoring for all children 3 and under who receive ICM injections to check for changes in thyroid hormone levels. The agency warns that if left untreated, the lowered thyroid function could cause cognitive and other developmental problems.

The agency is calling on doctors to evaluate thyroid function within three weeks of a child receiving ICM, and to treat thyroid function as clinically needed.

The FDA is urging healthcare professionals and patients to report any adverse events or side effects related to ICM use to the FDA’s MedWatch adverse event reporting program.