Association of TSH receptor antibody, thyroid stimulating antibody, and thyroid blocking antibody with clinical activity score and degree of severity of Graves ophthalmopathy.

Aim: to evaluate the association between TSH receptor antibody (TRAb), thyroid stimulating antibody (TSAb), and thyroid stimulation blocking antibody (TBAb) and TSAb/TBAb ratio with clinical activity score (CAS) and degree of severity of GO.

Methods: this was a cross sectional study involving 75 consecutive Graves' disease patients admitted at Cipto Mangunkusumo hospital between December 2009 until January 2011. Bartley criteria were used as clinical criteria for GO. In addition to clinical criteria, orbital CT scan and measurement of extraocular muscle thickness and increment of retroorbital fat volume were carried out. Furthermore, TSH, FT4, FT3 and TRAb were measured using ELISA method, TSAb and TBAb using RIA method. Clinical activity of GO was measured using clinical activity score (CAS). Degree of severity of GO was measured using Eckstein modified NOSPECS system.

Results: subjects consisted of various different ethnic groups in Indonesia, with the range of age between 20-63 years old. There were 28 (37%) and 61 (83.6%) GO subjects with clinical-based and CT scan-based respectively. Among all GD subjects, the proportion of TSAb were 70 (93.3%) and TBAb were 13 (17.3%). There was no correlation between TRAb and CAS nor the severity of GO, either clinical-based and CT scan-based GO. There was also no correlation between TSAb and CAS. No correlation between TSAb and severity of CT scan-based GO, but significant correlation between TSAb and severity of clinical-based GO (r=0.274; p=0.009) was noted. There was no correlation between TBAb and severity of GO. We also found no correlation between TBAb and CAS of clinical-based GO, but we found strong negative correlation with CAS CT scan-based GO (r=-0.565; p=0.035). The TSAb/TBAb ratio was also strongly correlated with all parameters evaluated, CAS of clinical-based GO (r=0.730; p=0.031), CAS of CT scan-based GO (r=0.607; p=0.024), degree of severity of clinical-based GO (r=0.563; p=0.023), and degree of severity of CT scan-based GO (r=0.762; p=0.001).

Conclusion: TRAb was not correlated with CAS and degree of severity of clinical-based and CT scan-based GO, while TSAb was correlated with degree of severity of GO. There was negative correlation between TBAb and CAS of clinical-based GO, whereas TSAb/TBAb ratio was correlated with CAS and degree of severity of both clinical-based and CT scan-based GO.