Methimazole for Prevention of Iodinated Contrast Media-Induced Exacerbation of Thyrotoxicosis in Susceptible Patients.

OBJECTIVE

Iodinated contrast media (ICMs) are widely used in a variety of examinations and procedures. The aim of the current study was to investigate the efficacy of methimazole (MMI) in prevention of thyrotoxicosis after ICM exposure.

METHODS

A retrospective cohort study included patients aged ≥18 years admitted to a tertiary medical center who underwent ICM examination or procedure and received MMI prior to iodine exposure.

RESULTS

A total of 179 patients with 202 hospitalizations were included. The mean age was 72.3 ± 13.5 years (female, 64%). Nearly all patients (99%) had a history of thyroid disease, and 91% were treated with MMI prior to admission. Seventy-five patients had low thyroid-stimulating hormone (TSH) levels prior to ICM exposure. In this high-risk group, MMI led to normalization of TSH after discharge in 19%, and 64% remained with low TSH levels after discharge but with a small median difference in free thyroxine levels of -0.5 (interquartile range [IQR], -5.9 to 5.2) pmol/L. In the 8 patients with dose increase during hospitalization, treatment with MMI was beneficial with a median free thyroxine decrease of -6.2 (IQR, -9.2 to -1) pmol/L and TSH increase of 0.2 (IQR, 0.02-0.7) mIU/L. In 110 patients with normal TSH levels before admission, with MMI treatment, most (71%) remained euthyroid after discharge, 13% had low TSH levels, and 9% had high TSH levels. In the 15 patients with high TSH levels prior to admission, the TSH levels of only 2 patients normalized, 47% remained with high TSH levels, and 27% had low TSH levels after discharge.

CONCLUSION

In patients with pre-existing thyrotoxicosis treated with antithyroid drugs, MMI therapy before ICM exposure prevented exacerbations. In patients with low TSH levels before admission, increasing the dose of MMI before exposure led to improvement in thyroid functions after discharge.