Thyroid stimulating hormone receptor antibody (TRAb) plays an important role in Graves' disease (GD). A second-generation measurement system has been developed and we have gotten a benefit by the system clinically. In this study, we determined 4 kinds of TRAb in 42 GD patients using the current and second-generation measurement systems to investigate the differences between them. The secondgeneration
measurement system exhibited higher positive rates and inhibition rates of thyroid stimulating hormone (TSH) binding than those of the current system. Furthermore, 42 patients with GD were classified into 4 groups by GD activity. The actual values of all TRAbs and positive rates exhibited a tendency to increase significantly with GD activity. Of significance, 2 TRAbs in the second-generation measurement system exhibited high positive rates. However, all actual values of patients did not necessarily agree with these tendencies. The values of TRAb-human detecting anti-human TSH receptors at an approximate cut-off value reflected GD activity more accurately than those of TRAb-CT detecting anti-porcine TSH receptor. This suggests the possibility of specific differences between TSH receptors and
further studies are required to further examine these effects.