Is low radioactive iodine uptake really an adverse factor in the outcome of radioiodine therapy of Graves disease

1564 Objectives High 24 hrs RAIU has conventionally been considered to be a requisite for favorable outcome of radioiodine therapy.Few recent studies have challenged this concept and suggested the contrary.With a power of 95% and alpha 0.01 we aimed to analyze the exact role of 24hr RAIU in the outcome of radioiodine therapy of Graves disease. Methods 633 patients of Graves disease treated with a fixed dose of 185MBq(5mCi)radioiodine were followed up every 3 monthly for 12 months.Patients were divided into 2 groups-(1)≤50% RAIU and (2)>50% RAIU (lab normal 15-35% at 24 hrs).Success of first dose of 131I was defined as a biochemical as well as clinical euthyroid or hypothyroid status during 12 months post therapy follow up without need for any further therapy.Any biochemical or clinical hyperthyroidism at 12 months was treated as 1st dose failure.Gland size,duration of disease,treatment with antithyroid drugs and its duration were the other factors considered in the analysis. Results 175 patients had an RAIU ≤ 50% and 458 patients had RAIU >50%.First dose success rate in group 1 was 81.7% and in group 2 it was 68.55% which was statistically significant. Conclusions Low 24hr RAIU(≤50%) is associated with a significantly better outcome than high 24hr RAIU (>50%) in patients of Graves disease treated with a fixed dose of 185MBq(5mCi) radioiodine