(HealthDay News) – Exposure to iodinated contrast media (ICM), which are frequently used during imaging procedures, is associated with changes in thyroid function, specifically an increased risk of developing incident hyperthyroidism and incident overt hypothyroidism, according to a study published in the Jan. 23 issue of the Archives of Internal Medicine.

Connie M. Rhee, MD, from Harvard Medical School in Boston, and colleagues conducted a case-control study of patients treated over 20 years who did not have preexisting thyroid conditions. ICM exposure was assessed using claims data for contrast-enhanced computed tomography or cardiac catheterization. Incident hyperthyroid or hypothyroid cases were defined by a change in thyrotropin level from normal (at baseline) to low or high (follow-up measurement). Controls were selected using an incidence density sampling approach and were matched to cases on the basis of age, sex, race/ethnicity, estimated glomerular filtration rate, follow-up thyrotropin measurement date, and interval between baseline and the follow-up thyrotropin measurement date.

The researchers found 178 and 213 incident hyperthyroid and hypothyroid cases, respectively, who were matched to 655 and 779 euthyroid controls. ICM exposure was significantly associated with incident hyperthyroidism (odds ratio [OR] 1.98) but not with incident hypothyroidism (OR 1.58). In secondary analysis, iodinated contrast media exposure was associated with incident overt hyperthyroidism (follow-up thyrotropin level ≤0.1 mIU/L; OR 2.50) and with incident overt hypothyroidism (follow-up thyrotropin level >10 mIU/L; OR 3.05).

“Iodinated contrast media exposure is associated with subsequent development of incident hyperthyroidism and incident overt hypothyroidism,” the authors write.

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