131I therapy and Graves' disease in a long term observation: euthyroidism is a suitable goal. Our experience.

OBJECTIVE: The aim of the study was to verify early and definitive outcome of radioiodine therapy in patients with Graves' disease, administering 131I calculated dose to pursue euthyroidism. PATIENTS AND METHODS: We retrospectively analyzed 639 patients affected by Graves' disease and treated by one or more 131I calculated doses. Results dose by dose are reported. As to the first administration, outcome is related to parameters used to calculate dose and to patients' available features. Failures and hypothyroidism onset are evaluated. RESULTS: A mean dose of 10 mCi shows great effectiveness: 75% of patients were cured after one administration, 88% after two. Of the failures, 84.1% occurred in a mean time of 0.34±0.23 years and were more frequent for larger glands, accelerated intra-gland radioiodine turnover, ophtalmopathy, administration of antithyroid drugs until 131I therapy. Of hypothyroid patients, 39.8% were diagnosed within the first year. After a sharp initial rise, hypothyroidism occurred at a slower rate, with estimated yearly increases of 3.8% until 10 years and of 1.8% later. In still followed up patients, euthyroidism was observed in about half the population after 10 years and in a third after 25 years. CONCLUSIONS: 131I can be the first line treatment for Graves' disease in small-medium thyroids. Calculated doses can achieve a high amount of long term euthyroid patients. Similar results could be expected by fixed doses of 10 mCi.