Immunological findings and thyroid function of untreated Graves' disease patients with undetectable TSH‐binding inhibitor immunoglobulin

Abstract

TSH-binding inhibitory immunoglobulin (TBII) is undetectable in about 10% of untreated Graves' disease patients, but the clinical characteristics and immunological significance of this finding are unknown. In this study we evaluated the clinical characteristics of TBII negative Graves' disease. We examined TBII in 1048 untreated patients at Kuma hospital from 1986 to 1990 and found 69 TBII undetectable patients (12 men and 57 women, mean age +/- SEM 35 +/- 2 years, group A). We compared the clinical characteristics and immunological findings of group A with 57 untreated TBII detectable Graves' patients who were selected randomly (11 men and 46 women, mean age +/- SEM 40 +/- 2 years, group B). T4, TSH, FT4, FT3, 123I thyroid uptake, TBII, thyroid stimulating antibodies (TSAb) and the volume of the thyroid using ultrasonography were measured at the first visit. Serum T4, FT4 and FT3 levels in group A were significantly lower than those in group B (P < 0.001). The values of TSAb in group A were significantly lower than those in group B (593 +/- 67 (mean +/- SE) vs 2143 +/- 280%, respectively, P < 0.001). The 123I thyroid uptake in group A was significantly lower than that in group B (53.1 +/- 1.1 vs 61.4 +/- 1.4%, respectively, P < 0.01). The thyroid volume in group A was significantly smaller than that in group B (39.1 +/- 3.0 vs 51.3 +/- 3.3 ml, respectively, P < 0.01). TSAb was undetectable in about 10% (6) of the TBII negative untreated Graves' patients at their first visit. In the present study, untreated TBII negative patients with Graves' disease were characterized by mild elevation of thyroid hormones, mildly elevated 123I uptake, weak TSAb activities and small goitres. The finding of both TBII and TSAb negative titres in untreated Graves' disease patients was also confirmed.