Juvenile Graves disease: usefulness and limitations of thyrotropin receptor antibody determinations

Thyrotropin receptor antibodies (TRAb) were measured in serum from 49 patients with active and inactive juvenile Graves disease, and the results were compared with values from control subjects and patients with Hashimoto disease. With a thyrotropin binding inhibition immunoglobulin (TBII) assay, TRAb were found in serum from 25 (93%) of 27 patients with untreated, active Graves disease. The TRAb values remained positive in 20 (72%) of 29 patients during the first 6 months of antithyroid therapy and in 13 (54%) of 24 patients during the second 6 months. After discontinuation of antithyroid therapy, 15 patients experienced 18 episodes of relapse of thyrotoxicosis; during relapse TRAb values were positive in all but one patient. Among 19 patients who remained clinically and biochemically euthyroid after cessation of antithyroid therapy, TRAb were not detected in 28 (78%) of 36 serum specimens. Of the eight positive values from six patients, no antiidiotypic antibodies were found, and thyroid stimulating immunoglobulins (TSI) were not detected in four specimens. The TRAb determination correctly predicted the subsequent clinical course in 26 (72%) of 36 patients. Furthermore, TRAb values and results of triiodothyronine suppression tests were in agreement in 27 of 36 patients, or 75% of the time. TSI were present in serum from only 19 (73%) of 26 patients with active disease; however, TSI were negative in all patients with inactive Graves disease. During the management of Graves disease, TRAb measurements by TBII determinations are valuable in the diagnosis of active disease, assist in the decision to discontinue antithyroid drug therapy, and are useful as the T3 suppression test to predict the clinical course of the disease. The TSI measurement is most useful to determine the activity of the disease when TRAb values are positive in a euthyroid patient.