Objective      To determine the clinical therapeutic effect of

131

-iodine (

131

I) at 2 different doses on the treatment of Graves’ hyperthyroidism

and investigate the influence factors and complications.       Methods      A randomized controlled trial was conducted on 652 Graves’ hyperthyroidism patients who were admitted in our hospital from September 2006 to June 2010. These patients were prospectively assigned into 2 matched groups

low-dose group (n=330

receiving a calculated dose of

60-100 μCi(2.22-3.70 MBq)/g

131

I)

and conventional dose group (n=322

receiving 80-120 μCi(2.96-4.44 MBq)/g

131

I ). Patients were followed up for 12 months and considered as in remission when they were in a stable euthyroid state. Primary efficiency and incidence of hypothyroidism were compared between the 2 groups. Prednisone was given to 8 patients with infiltrative ophthalmopathy at a daily dose of 0.5 mg/kg for 1 month during radioiodine therapy.       Results      The remission rate was lower in low dose group (80.0%) than in the conventional dose group (82.9%)

but no difference was found. The incidence of hypothyroidism was significantly lower in the low dose group than the conventional dose group (12.1% vs 16.8%

P0.05). There was no correlation among clinical features

thyroid uptake

antibody levels

and serum hormones levels with outcome. For the patients having infiltrative ophthalmopathy

their symptoms did not become severer. No any new case of infiltrative ophthalmopathy was observed in the 2 group during treatment.       Conclusion      Low-dose and conventional dose have no difference in primary remission rate; but the former results in significant lower incidence of hypothyroidism. In the treatment of Graves’ hyperthyroidism with

131

I

appropriately reducing conventional dose of

131

I might be more reasonable for better outcome.