Correlation between serum anti-TSH receptor autoantibodies (TRAbs) and the clinical feature of Graves' orbitopathy

Background Graves' orbitopathy (GO) is the most common extrathyroidal manifestation of Graves' disease (GD). Several studies support the involvement of TSH receptor autoantibodies (TRAbs) in the pathogenesis of GO, and a correlation between GO features and TRAbs has been reported, but not confirmed by all studies. Thus, we conducted a cross-sectional investigation to determine whether there is a correlation between TRAbs and the clinical features of GO in an initial phase of the eye disease. Methods Ninety consecutive patients with untreated GO (67 women and 23 men, age 48.9 +/- 12.6 years) were included. Patients who had received treatments other than anti-thyroid drugs for hyperthyroidism or lubricants for GO were excluded. All patients underwent an endocrinological and ophthalmological evaluation, the latter including exophthalmometry, measurement of eyelid width, clinical activity score (CAS), visual acuity, assessment of diplopia, and NOSPECS score. TRAb levels were measured by a third-generation competitive immunoassay. Results There was a statistically significant, direct correlation between serum TRAb levels and CAS by linear regression analysis (R = 0.278,P = 0.007). The correlation was confirmed by a multiple regression analysis (R = 0.285;P = 0.006) including age and FT3 levels, which also correlated with CAS. There were no relationships between TRAbs and exophthalmometry, eyelid aperture, degree of diplopia, visual acuity, and NOSPECS score. Conclusions The levels of TRAb in subjects with a recent-onset, untreated GO are directly correlated with the clinical activity of the disease, confirming a possible role of these antibodies in the pathogenesis of GO.