Prediction of therapeutic response to radioactive iodine in Graves' disease using TSH-receptor antibodies and HLA-status.

We have examined the combined usefulness of TSH-receptor antibody detection and HLA status on the therapeutic response to standard doses of radioactive iodine (RAI) in forty-three hyperthyroid Graves' patients. Twenty-three patients had detectable TSH-receptor antibodies as measured by 125I-TSH binding-inhibition (TBI) prior to administration of 7 mCi RAI. Eighteen (78%) of these patients were rendered euthyroid within 3 months. In contrast, twenty patients were TBI negative prior to RAI and sixteen (80%) of these individuals remained hyperthyroid at 3 months and required two, or more, doses of RAI to control their thyroid function. DR3 status alone was not strongly associated with resistance to RAI. However, of sixteen patients without detectable TBI activity and who required two or more doses of RAI, ten patients were DR3 positive (62%) compared with 25% in a control population. Only one patient who was both TBI and DR3 negative required more than one dose of RAI. These data indicate that TBI may be an accurate predictor of the therapeutic response to RAI in patients with hyperthyroid Graves' disease. Investigation of HLA status alone was of limited value, although it appeared that the combination of TBI and DR3 may be of additional help in developing an overall strategy for the treatment of hyperthyroid Graves' disease.