Compensated Low-Dose ^131I Therapy of Graves' Disease

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Abstract
To minimize the high rate of residual thyrotoxicosis encountered in low-dose 131I therapy of Graves'' disease, 62 patients were treated with a low-dose 131I protocol that includes a compensation for thyroid size. Dose varied between 40 .mu.Ci retained/g for glands of normal size to 100 .mu.Ci/g for glands of 100 g or greater. Mean dose was 51.9 .mu.Ci/g. At 1 yr after therapy, 66.1% of subjects were euthyroid, 9.7% hypothyroid, and 24.2% hyperthyroid, a significant improvement (P < 0.01) over the previous experience using 50 .mu.Ci/g independent of gland size. Several factors, other than 131I dose, which might influence the outcome of therapy, were investigated. Initial free thyroxine index observed before therapy was found to have prognostic significance. Hypothyroidism developed only in patients having an initial free thyroxine index of 22.5 or less (about 2.5 times the upper limit of normal in the laboratory).