VALUE OF THYROID-STIMULATING ANTIBODY IN THE DIAGNOSIS OF THYROID-ASSOCIATED OPHTHALMOPATHY OF EUTHYROID PATIENTS

Aims/background-Thyroid associated ophthalmopathy (TAO) of euthyroid p atients is difficult to diagnose because clinical findings overlap wit h other conditions, and no confirmatory diagnostic tests are available . Recently, it was reported that TSH binding inhibitor immunoglobulin (TBII) and thyroid stimulating antibody (TSAb) are sensitive markers o f TAO. The sensitivity of these antibodies in the detection of TAO wer e therefore studied to determine if they could be a useful criterion i n the diagnosis of TAO of euthyroid patients. Methods-Serum values of TBII and TSAb of 35 patients with euthyroid TAO (group A) were compare d with those of 27 patients with Graves' disease and TAO (group B). Th e relation between the serum value of TSAb and the eye symptoms of pat ients with euthyroid TAO were also examined by multiple linear regress ion analysis. Results-In group A, TBII was positive in 10 cases (28.6% ) and TSAb was positive in 29 cases (82.9%). In group B, both TBII and TSAb were positive in all cases (100%). The titre of serum TBII in gr oup A (15.6% (SD 18.0%)) was significantly lower (p<0.0001) than in gr oup B (57.9% (21.5%)). The titre of serum TSAb in group A (1400.9% (21 63.9%)) was significantly lower (p=0.0026) than in group B (2243.9% (1 472.8%)). Among the eye findings of patients with euthyroid TAO, kerat opathy was significantly (p=0.034) related to the value of TSAb. Concl usion-These results suggest that the activity of TSAb is a more sensit ive marker of euthyroid TAO than is TBII, and could be a useful criter ion in the diagnosis of TAO of euthyroid patients.