Iodide contrast used to sharpen some diagnostic images seem to have an unrecognized dark side. A study published in the Archives of Internal Medicine was based on 20-year follow-up data of nearly 2,000 people who had undergone CT scans, cardiac catheterization or angiograms. People who later developed thyroid disease, with their thyroid glands becoming overactive or underactive, were two to three times more likely than other patients to have received iodide-containing contrast material. Although this type of reaction has been previously reported from Europe, this study is the largest as well as the most recent in the U.S. to document the link between iodide exposure and thyroid dysfunction.
The authors warn that their findings should not keep people from getting needed diagnostic work-ups. An accompanying editorial urges doctors to keep the patient’s broad health picture in mind when ordering tests. Those who may be especially susceptible to thyroid problems should be monitored closely for some time after an unavoidable iodide exposure. Patients who have such tests should be alert for symptoms of over or underactive thyroid function.