The Prognostic Value of Thyroid Stimulating Immunoglobulin in the Management of Graves’ Disease

Abstract Background: The bioassay of thyroid-stimulating immunoglobulin (TSI) appears to be more sensitive than the commonly used TSH binding inhibition assay (TBII), also known as thyroid receptor antibody assay or TRAb.Methods: An observational study was conducted to evaluate the prognostic value of TSI in clinic. Patients with different etiologies of thyrotoxicosis were enrolled to verified the diagnostic value of TSI.Results: 77 Graves’ disease (GD) patients who were treated with anti-thyroid drug (ATD) were in a continuous follow-up until 1 year after ATD discontinuation. Commercial kits of TSI (Thyretain™) and M22-TBII were used and compared. TSI was all negative in healthy controls, Hashimoto thyroiditis, subacute thyroiditis. TSI value was highest in untreated GD patients (P < 0.001). Under ATD treatment, TSI value decreased gradually. 21 patients had positive TSI at the end of treatment. According to clinical fate of patients with GD after withdrawal ATD, TSI value and positivity in patients with relapse were significantly higher than that reported in patients with remission (P = 0.001, P < 0.001). After adjustment for age, gender, initial TRAb, initial TSI, and TRAb at the end of treatment, the odds ratio (OR) of positive TSI for the risk of relapse was 33.271 (95% confidence interval [CI]: 4.741-233.458, P < 0.001) and OR of quantitative TSI was 1.009 (95% CI: 1.002–1.015, P < 0.001).Conclusions: TSI is a good predictor of relapse in patients with GD subjected to ATD treatment. It might be safer to discontinue ATD when TSI and TRAb were both negative.