Therapeutic Response to Radioactive Iodine Treatment in Graves' Disease / 대한내분비학회지

ABSTRACT

BACKGROUND: Prediction of therapeutic response to radioactive iodine (RAI) in Graves disease is poorly understood. Although thyrotropin binding inhibitor immunoglobulin (TBII) level is a strong index for relapse after antithyroid drug treatment, conflicting results are described regarding its prognostic significance in Graves disease treated with RAI. This study is to evaluate possible prognostic factors including TBII wbich affect the outcome of RAI therapy in Graves disease. METHODS: Two hundred and one patients with Graves disease who were followed for over 12 months after RAI treatment were studied retrospectively. The subjects were divided into hypothyroid, euthyroid and hyperthyroid groups, based on the thyroid function evaluated at 12 months after RAI therapy. We evaluated the association of clinical parameters including patients age, goiter size, degree of hyperthyroidism and TBII index with outcome of RAI treatment. RESULTS: In Graves disease, response rate to RAI was 70.1% (hypothyroid 22.4% and euthyroid 47.7%) until 12th month. The mean age of hypothyroid group was 40+/-11 years, significantly older than that other groups (euthyroid 33+/-12, hyperthyroid 35+/-13, p<0.05). Initial level of thyroid function, duration of antithyroid drug treatment prior to RAI, goiter size and dosage of RAI were not significantly different between the groups. There were 61 patients who had both TBII tests before and after RAI. Twelve had negative TBII and 49 had positive TBII before RAI admini-stration. The rate of unremitted hyperthyroidism after RAI therapy was significantly lower in patients with negative TBII than in those with positive TBII prior to RAI treatment( 0% versus 46.9%, p<0.05). CONCLUSION: Graves patients with positive TBII prior to RAI therapy were associated with lower therapeutic response to RAI than those with negatve TBII. And old age was associated with the development of early hypothyroidism after RAI therapy. These results suggest these factors be also considered in the treatment of Graves disease with RAI.