Thyroglobulin, thyrotropin and thyrotropin binding inhibiting immunoglobulins assayed at the withdrawal of antithyroid drug therapy as predictors of relapse of Graves' disease within one year.

"Sensitive" thyrotropin (TSH), thyroglobulin (TG) and even thyrotropin binding inhibiting immunoglobulins (TBII) assays are now widely available. The objective of the present study was to determine the most accurate of these three parameters to predict the relapse of Graves' disease during the year following treatment discontinuation and to evaluate whether the assay of three markers is able to improve the prediction. TSH, TG and TBII were measured in the sera of 67 Graves' disease patients after at least 12 months of medical treatment. In 52 patients, TBII had also been determined before the beginning of the medical treatment. Under treatment, all the patients were clinically and biologically euthyroid, but in 9 goitrous patients it was impossible to lower the doses of carbimazole without an immediate relapse. The TSH levels of these 9 patients were still low in all cases but one; TG and TBII levels were abnormal in all. In the other 58 patients, the treatment was discontinued; 22 relapsed within one year, more frequently when a goiter was present. The most reliable parameter for the prediction of relapse was found to be TBII, as its specificity was high (94.5%), although its sensitivity was poor (45%); TG was more sensitive (64%) but far less specific (57%); TSH and "initial" TBII appeared to be of a little interest. When TBII was elevated prior to the withdrawal of treatment, the determination of TG was useful: abnormal values of both TBII and TG were always associated with a relapse. When TBII testing was negative, the relapse risk fell to 0.26, and to 0.08 when three criteria were matched: no goiter, negative TBII, normal TG.