TUESDAY, Jan. 24 (HealthDay News) -- Iodinated contrast media (ICM), a substance commonly used in imaging procedures such as CT scans and cardiac catheterization, may affect patients' thyroid function, according to a new study in the Jan. 23 issue of the Archives of Internal Medicine.

After examining two decades of patient information from 1990 through 2010, researchers from Brigham and Women's Hospital, Massachusetts General Hospital and Harvard Medical School found people who have been exposed to ICM are at greater risk for hyperthyroidism.

Hyperthyroidism, also called "overactive thyroid," occurs when the thyroid gland makes too much thyroid hormone. Two dozen symptoms that can be associated with the condition include difficulty concentrating, fatigue, weight loss, clammy skin and increased sweating, itching and hair loss.

There was no association between ICM and hypothyroidism, or an underactive thyroid.

The researchers concluded that since ICM is widely used, more studies are needed to confirm their findings and determine exactly why and how this substance affects thyroid function.

In commenting on the study, Dr. Elizabeth Pearce of Boston University School of Medicine, wrote that patients who may be more vulnerable to thyroid problems, such as those with underlying unstable heart disease, should have their thyroid function monitored after iodine exposure.

More information

The U.S. National Institutes of Health provides more information on hyperthyroidism.