How the Dose of Iodine-131 Should be Determined in the Treatment of Graves' and Toxic Nodular Hyperthyroidism

Abstract

Despite the wide use of radioiodine treatment for hyperthyroidism, the best approach to radioiodine dose selection in the treatment remains controversial. The objective of our study was to evaluated factor affected treatment of hyperthyroidism with radioactive I-131, the result of radioactive iodine treatment in our department and the average number of radioiodine treatment.
Material and Method : A database of 387 patients were retrospectively reviewed. The therapeutic activity administered was calculated by the equation

The thyroid gland weight was estimated by palpation.
Results : The failure rates of I131 treatments of Graves' disease in our study for first dose, second dose and third dose are 43.51%, 33.98% and 12%, respectively. The failure rates of I131 treatments of toxic nodular goiter in our study for first dose, second dose and third dose are 39.22%, 58.82% and 33.33%, respectively. The average number of treatments of Graves' disease and Toxic nodular goiter were 1.45 and 1.58, respectively. There was not a significant between Graves' disease and Toxic nodular goiter in the averge number treatments. The %24 hr. I-131 uptake and gland weight were higher in the group of Graves' disease patients who had hyperthyroidism in comparison with Graves' disease patients who developed euthyroidism and hypothyroidism. The gland weight was higher in the group of toxic nodular patients who had hyperthyroidism in comparison with toxic nodular patients who developed euthyroidism.
Discussion : The factors affecting the treatment of hyperthyroidism by the equation in this study are Thyroid gland weight and %24 hr. I-131 uptake. Large thyroid gland mass had a lower success rate from radioiodine treatment than small thyroid gland mass. The mean I-131 24 hours uptake of the patients with persistant hyperthyroid for Graves' disease and Toxic nodular goiter is significantly higher than the mean percent uptake of I131 of the patients who developed euthyroid and hypothyroid. The description this finding may be from the administration I-131 dose is inversely proportional to the measured 24 hours radioiodine uptake.