Thyroid-Stimulating Antibody is Related to Graves' Ophthalmopathy,But Thyrotropin-Binding Inhibitor Immunoglobulin is Related to Hyperthyroidism in Patients with Graves' Disease

We investigated the relationship between thyroid function or ophthalmopathy of Graves' disease and thyrotropin receptor antibodies (TRAb) in 155 untreated patients with Graves' hyperthyroidism. All patients were examined by ophthalmologists, and underwent computed tomography of the orbit and measurement of serum free triiodothyronine (FT₃), free thyroxine (FT₄), thyrotropin-binding inhibitor immunoglobulin (TBII), and thyroid stimulating antibodies (TSAb). Patients were divided into three groups according to the presence of orbital fat increase (OFI) and extraocular muscle enlargement (EME): 57 patients without OFI and EMO formed the no Graves' ophthalmopathy (NGO) group; 55 patients with OFI but without EMO formed the OF group; 43 patients with EME with or without OFI formed the EM group. The FT₃, FT₄, and thyroid weight increased in the order of the EME, NGO, and OFI groups. TSAb increased in the order of the NGO, OFI, and EME groups, and TSAb was significantly greater in the EME and OFI than in the NGO group. TBII was not significantly different among the three groups, but was lower in EME than NGO. There was a significant positive correlation between TBII and FT₃ or FT₄ in all patients combined as well as in all three groups, but correlation between TSAb and FT₃ or FT₄ was very weak in all groups, and that between TSAb and FT₃ was not significant in the EM group In the relationship between ophthalmopathy and TRAb, the sum of the scores of eyelid swelling, proptosis, and extraocular muscle enlargement was taken as a measure of the overall severity of the Graves' ophthalmopathy (GO). TSAb was significantly correlated with the GO score, but there was no correlation between TBII and GO scores. In conclusion, TSAb was correlated with ophthalmopathy but TBII was related to hyperthyroidism.