Aim: This study was designed to show the effect of a nonionic contrast medium (Iomeprol-300; CM) on the intrathyroidal iodine concentration with and without a concomitant medication with perchlorate (1380 mg/d) to block the thyroidal iodine uptake.
Volunteers and methods: Twelve volunteers recieved 100 ml Iomeprol-300 intravenously and the perchlorate prophylaxis mentioned above. Another 12 volunteers got 100 ml Iomeprol-300 only. By means of X-ray-fluorescence-analysis the intrathyroidal iodine concentration was determined in advance as well as 0.2, 1, 3, 5, 7, 24, 48, 72, and 96 hours after the application of the CM.
Results, conclusion: The intrathyroidal iodine concentration did not change in the group of volunteers on perchlorate medication. Without perchlorate the intrathyroidal iodine concentration decreased after the application of the CM when it was initially high (722 +/- 66 microg/ml before, 670 +/- 65 microg/ml after CM; p = 0.046) and increased in case of a low initial concentration (327 +/- 40 microg/ml before, 381 +/- 25 microg/ml after CM; p = 0.046). The effect is significant but its magnitude is too small to be harmful for a patient with a healthy thyroid. The oral application of 1.4 g/d perchlorate inhibits the thyroidal iodine uptake and the intrathyroidal iodine concentration is unaffected by the application of a CM.