THYROID-STIMULATING ANTIBODY AND TSH-BINDING INHIBITOR IMMUNOGLOBULININ 277 GRAVES PATIENTS AND IN 686 NORMAL SUBJECTS

TSH receptor antibodies (TRAb) are believed to cause hyperthyroidism o f Graves' disease. Thyroid-stimulating antibody (TSAb) and TSH-binding inhibitor immunoglobulin (TBII) have been measured as TRAb to diagnos e Graves' disease and to follow Graves' patients. We intended to evalu ate the clinical value of TRAb (TSAb and TBII) assay in establishing t he diagnosis of Graves' disease and in predicting its clinical course. TSAb and TBII were studied in 686 normal subjects and in 277 Graves' patients before antithyroid drug therapy. We followed serial changes o f TSAb and TBII in 30 Graves' patients before, during and after antith yroid drug therapy over 3.5-9 yr. We measured TSAb as a stimulator ass ay and TBII as a receptor assay. Both TSAb and TBII were distributed n ormally in 686 normal subjects. ROC curves demonstrated that both TSAb and TBII had high sensitivity and specificity for the diagnosis of Gr aves' disease, and were equally sensitive and specific; 150% was chose n as cut-off value for TSAb and 10% for TBII. Of the 277 untreated Gra ves' patients, 254 (92%) had positive TSAb and positive TBII. All of t he 277 untreated Graves' patients had positive TRAb (TSAb and/or TBII) . We followed the serial changes of TSAb and TBII in 30 Graves' patien ts over 3.5-9 yr. During antithyroid drug therapy, TSAb and TBII activ ities decreased and disappeared in 27 patients (Group A), but continue d to be high in the other 3 (Group B). The former 27 Group A patients achieved remission, but the latter 3 Group B patients continued to hav e hyperthyroidism. Of the 27 Group A patients, 16 (59%) had parallel d ecreases of TSAb and TBII activities; in 6, the changes were predomina ntly observed in either TSAb or TBII, and in 4, complex changes in TSA b and TBII activities were observed. Disappearance of TSAb and appeara nce of TSBAb was seen in one. The other 3 Group B patients continued t o have high TSAb and TBII activities and to have hyperthyroidism. In c onclusion, TSAb and TBII are of clinical value in establishing the dia gnosis of Graves' disease and in predicting its clinical course. We cl early demonstrated its diagnostic usefulness. Both TSAb and TBII have high sensitivity and specificity. All of the 277 untreated Graves' pat ients had TRAb (TSAb and/or TBII). Serial changes of TSAb and TBII dur ing therapy differ from one patient to another, and can be classified into several groups. Changes in TSAb and TBII activities reflect the c linical courses of Graves' patients. The simultaneous measurement of b oth TSAb and TBII is clinically useful, since TSAb and TBII reflect tw o different aspects of TRAb. TSAb and TBII are different. (C) 1997, Ed itrice Kurtis.