Discriminant factors affecting early outcome of radioiodine treatment for Graves' disease.

Pretreatment clinical, biochemical, iodine-131 (131I) scan and tracer-kinetic parameters were studied in 827 Chinese patients with Graves' disease treated with radioactive iodine. One year after 131I therapy, 56.7% were euthyroid, 33.9% were still thyrotoxic and 9.4% were hypothyroid. Discriminant analysis of all pretreatment variables identified thyroid mass, presenting free thyroxine index and 4 h 131I uptake as the three variables most helpful in discriminating the early outcome group of 131I therapy. The findings suggest that patients with large goitres and severe disease may require higher doses of 131I for treatment of Graves' disease.