Effectiveness of radioiodine (131-I) as definitive therapy in patients with autoimmune and non-autoimmune hyperthyroidism

Abstract

We evaluated the outcome of radioiodine (RAI) therapy in 100 consecutive patients treated in the period 2000-2001 for hyperthyroidism due to Graves' disease (GD), toxic adenoma (TA) and toxic multinodular goiter (TMG). Thyroid function was measured before and after therapy every 3-6 months up to 3 yr. Three years after therapy, 75% of TA patients were euthyroid, 18.7% were hypothyroid and 6.3% hyperthyroid. Of the TMG patients, 62.2% were euthyroid, 18.9% were hypothyroid and 18.9% hyperthyroid. In GD patients euthyroidism was achieved in 12.9% of the patients, hypothyroidism in 74.2% and hyperthyroidism persisted in 12.9%. Definitive hypothyroidism was significantly higher in GD (p<0.0001) than in TA and TMG patients. Overall, positive effect of RAI (definitive hypothyroidism or euthyroidism) was very high: 93.7% in TA, 81.1% in TMG and 87.1% in GD patients. Thyroid volume reduction was observed in all patients, but was higher in GD patients (mean reduction of 76%) and in TA patients (mean nodule reduction of 69%). In TMG, mean reduction was of 32%. The median activity of RAI received by the 86 cured patients was 555 MBq (15 mCi) compared to 407 Mbq (11 mCi) received by the 14 patients who remained hyperthyroid. No influence was found between outcome and clinical parameters at the moment of 131-I therapy. In conclusion, our results indicate that RAI therapy is highly effective and safe for the control of hyperthyroidism.