Prediction of remission or relapse for Graves' hyperthyroidism by the combined determination of stimulating, blocking and binding TSH-receptor antibodies after the withdrawal of antithyroid drug treatment

The most likely reasons for the low predictive value of TSH-receptor antibodies (TRAbs) determinations in previous investigations are the biological heterogeneity of TRAbs and changes of the different stimulating (TSAb) or blocking (TSBAb) antibody bioactivities of TRAbs during the course of Graves' disease (GD), which have not been taken into account in most previous studies. Furthermore, in a recent study it has been demonstrated that the decline of TRAb values detected with highly sensitive hTBII or TSAB assays is not useful in evaluating remission or relapse of GD at the end of antithyroid drug treatment (ATDT). In order to make a thorough investigation of the predictive values of all different TRAb qualities for the recurrence for GD after the withdrawal, we investigated hTBII, TSAbs and TSBAbs in 54 consecutive patients with GD at the end of ATDT and 12-13.5 months after stopping ATDT. Using the TRAb values at the time of reinvestigation in a model, recurrence for GD was better predicted compared to the determination at the time of withdrawal of ATDT. Furthermore, using this model, the combined determination of hTBII, TSAbs, and TSBAbs revealed the highest level of significance for the prediction of remission or relapse of GD (OR = 15; p < 0.0001) compared to the detection of hTBII, TSAbs and TSBAbs alone. Therefore, significant changes of TSAbs after the end of ATDT and the biological heterogeneity of TRAb define the conditions for predicting remission or relapse of GD after ATDT by TRAb determinations. Consequently, our results suggest that the prediction of the individual course of GD can only be improved by combined determinations of all TRAb qualities (hTBII, TSAbs and TSBAbs) after the end of ATDT.