Correlation of thyroid functions, urinary iodine excretion, Tc99m pertechnetate and i-131 uptakes in patients with multinodular goiter after mandatory iodinization

The aims of this study are 1. to evaluate the association between urine iodine levels and thyroid Tc99m pertechnetate uptake (TcPU) levels in multinodular goiter (MNG) patients, 2. to evaluate TcPU levels in euthyroid, subclinical and clinical hyperthyroid patient groups, 3. by comparing TcPU and I- 131 uptake levels to decide whether TcPU can be used instead of I-131 uptake. 24-74 year old (mean 52.8±11.2) 29 (23 F, 6 M) multinodular goiter patients were included to the study. After taking blood and urine samples, TcPU tests and thyroid scintigraphies were done and the patients were evaluated with thyroid ultrasound. By performing I-131 uptake measurements 4. and 24. hour uptake levels were calculated. In this study, 21 of 29 patients (%72) had urinary iodine level above 100 μg/gr cre that indicates sufficient iodine intake. There was a significant negative correlation between TcPU levels and urine iodine levels as indicated in the literature. According to TSH levels, while 18 patients were euthyroid, 11 were hyperthyroid (6 subclinical, 5 overt clinic). TcPU levels were found to be higher in hyperthyroid patients than euthyroid ones, but this difference was not statistically significant. In 9 euthyroid patients there were hyperactive nodules. There was a significant positive correlation between patients' TcPU and I-131 4. and 24. hour uptake values.In conclusion, our patients' median urinary iodine level was 130 μg/gr cre which was sufficient. After iodinisation, high percentage (%37) of patients were hyperthyroid. We found that half of euthyroid patients had hyperactive nodules which showed the importance of thyroid scintigraphy in the evaluation of multinodular goiter patients. Correlation of TcPU and I-131 uptake levels suggest that TcPU can be used instead of I-131 uptake levels. Our preliminary results suggest that it would be important to evaluate the relationship between urinary iodine and TcPU levels in larger series of MNG patients after mandatory iodinization.