PROPHYLACTIC APPLICATION OF THYROSTATIC DRUGS DURING EXCESSIVE IODINEEXPOSURE IN EUTHYROID PATIENTS WITH THYROID AUTONOMY - A RANDOMIZED STUDY

In a prospective, randomized study we examined the influence of prophy lactic short-term thyrostatic therapy on thyroid iodine metabolism in patients with euthyroid autonomy undergoing elective coronary angiogra phy. From a total of 1177 patients, 51 fulfilled the criteria of euthy roid autonomy before coronary angiography (negative thyrotropin-releas ing hormone test, 10-min uptake of at least 1.2% Tc-99m and no elevati on of free thyroxine and free triiodothyronine indices) and were rando mized into three groups: group 1 (N = 17) received 20 mg/day of thiama zole and group 2 (N = 17) received 900 mg/day of sodium perchlorate; t hyrostatic therapy was begun on the day before angiography and continu ed for 14 days; group 3 (N = 17) served as controls without treatment. Parameters of thyroid function-free thyroxine (FT4) index and free tr iiodothyronine (FT3) index, thyrotropin (TSH) and delta-TSH-urine iodi ne excretion and Tc-99m uptake were determined before and 30 days afte r coronary angiography. At the end of the study the mean FT4 index and FT3 index were elevated significantly in the control group compared w ith baseline values, but were still within the normal range, In contra st, the mean FT4 index and FT3 index remained unchanged in the treated groups. Four mild cases of hyperthyroidism were observed at the end o f the study: two cases in the control group and one case in each of th e treated groups. Thyrotropin suppression, urine iodine excretion and Tc-99m uptake differed significantly between the treated groups and th e control group. In the treated groups TSH suppression, urine iodine e xcretion and Tc-99m uptake remained unchanged 30 days after coronary a ngiography compared with baseline values. In the control group the deg ree of TSH suppression and the level of urine iodine excretion increas ed (about twofold) significantly after coronary angiography, whereas T c-99m uptake decreased significantly (ca. 50%). In conclusion, short-t erm prophylactic thyrostatic therapy seems to have a protective effect against iodine excess in patients with euthyroid autonomy. However, m ild hyperthyroidism could not be prevented in some cases. Probably a c ombination therapy of thiamazole and perchlorate would be more effecti ve.