Biokinetics of $^{131}I$ after endogenous and exogenous stimulation of TSH in patients with DTC

BACKGROUND: The effective radioiodine treatment of patients with DTC is possible only after raising the TSH value over 30 μUI/ml. This effect might be obtained by either endogenous or exogenous stimulation. The aim of this study was to evaluate differences in 131I biokinetics of selected regions of interest (ROIs) in cases of endogenous and exogenous stimulation. MATERIAL AND METHODS: Two groups of 50 patients were enrolled in the study. All patients were treated with 3.7 GBq of 131I; the first group after thyroid hormone withdrawal (THW), the second group after rhTSH administration (rhTSH). On the basis of post-treatment images, the uptake ratios over selected ROIs (thyroid remnants, mediastinum, liver, stomach, abdomen, and whole-body) were compared between groups. RESULTS: In the case of uptake over the whole-body and the liver, statistically significant higher values were received for the THW group. For the remaining regions, the differences between groups were statistically insignificant, but uptake ratios in the rhTSH group were generally numerically lower compared to the THW group. CONCLUSIONS: The revealed difference in radioiodine biokinetics after thyroid hormone withdrawal or administration of recombinant human TSH may influence many important aspects of patients with DTC treatment, such as the choice of proper therapeutic scheme, the cost of therapy, and the dose assessment.