Radioiodine therapy in patients with Graves' disease

We studied retrospectively 104 patients with Graves' disease who underwent radioiodine therapy between 1983 and 1993. The administered dose varied from 2.0 to 9.0 mCi (74 to 333 MBq). In 1994 and 1998 the patients were asked to answer a questionnaire and were considered to have hypothyroidism when receiving T4 therapy. The importance of radioiodine therapy, its indications and the different methods of calculating the administered activity were studied. The results were compared with the literature. At the end of the evaluation, 62,4% of the patients presented hypothyroidism and 37,6% euthyroidism. There was no significant difference regarding the development of hypothyroidism when sex, number of doses, total activity (mCi), effective radiation (μCi per gram of tissue) and use of antithyroid drugs were considered. In conclusion, the period of time of post-radioiodine therapy is the most important factor in the analysis of the results, which may interfere with the development of hypothyroidism. (author)