Effects of High Iodine Containing Low Osmolar Contrast Agent (Visipaque) on Thyroid Function Tests

Objective: Investigating high iodine containing low osmolar contrast agent (visipaque) effects on thyroid function tests and thyroid sonography characteristics. Methods: 65 euthyroid cases and 92 controls composed the samples in baseline. Thyroid function tests, Urine Iodine Concentration (UIC) and thyroid sonography were conducted for both groups before and 1 and 3 months after angiography. Serum levels of T4, T3, T3RU, TSH, TPO-Ab and UIC were measured, and hypo/heyperthyroidism prevalence was compared between groups. Results: Mean T3, T4 and TSH changes 1 month after angiography were insignificant in both groups (P: 0.61, P: 0.4 and P: 0.14, P: 0.23 in cases and controls for T3 and T4). Medians among cases and controls were 12.8 and 16.75 μg/dl, respectively, at baseline. These values varied to 28.45 and 15.2μg/dl, and 12.95 and 14.2μg/dl 1 month and 3 months after angiography in case and control groups, respectively. UIC increase one month after angiography was significant among cases (P=0.002). TPO- Ab+ were same 3 months after angiography. Thyroid volume changes were significant among cases (P<0.001) and insignificant among controls (P=0.680). No significant difference was seen between cases and controls in overt hypothyroidism, however, a considerable change were seen in thyroid volume and UIC one month after angiography among cases. The hypothyroidism rate among cases was insignificant which may be either related to few cases or short half-life of visipaque (2.1 hour) so that 97% of injected dose was excreted in urine within 24 hours. Conclusion: Thyroid function test is not recommended before angiography in patients without previous thyroid records