Clinical features of thyroid-associated ophthalmopathy in clinically euthyroid Korean patients

Abstract

Aim: To compare clinical characteristics and thyroid-stimulating hormone receptor antibodies (TRAbs) in thyroid-associated ophthalmopathy (TAO) in euthyroid Korean patients with those in hyperthyroid patients.

Methods: Clinical activity scores (CASs), modified NOSPECS scores, exophthalmometry values, prevalence of optic neuropathy, restrictive myopathy and lid retraction, and the positivity and levels of TRAb (thyrotropin-binding inhibitor immunoglobulin (TBII) and thyroid-stimulating immunoglobulin (TSI)) were compared in 24 euthyroid (group A) and 139 clinical/subclinical hyperthyroid TAO patients (group B).

Results: Group A presented more clinically unilateral involvement than group B (79.2% vs 27.3%, P<0.001), less active (CAS 1.50 vs 2.26, P=0.014) and less severe clinical course (NOSPECS 3.38 vs 4.13, P=0.037). Lid retraction was more prevalent in group A than group B (91.7% vs 66.2%, P=0.014). Prevalence of optic neuropathy and restrictive myopathy, and the mean value of exophthalmometry were not different. Mean TBII levels were lower (7.20 IU/l) in group A than in group B (44.58 IU/l, P<0.001). A similar difference was found in the TSI bioassay (201.40% vs 425.19%, P=0.001). The positive rate of TBII in group A (34.8%) was significantly lower than in group B (90.8%, P<0.001). The positive rate of TSI was high in both group A (83.3%) and B (91.7%), with no significant difference (P=0.337).

Conclusions: Patients with euthyroid TAO showed a less active and severe clinical course, more unilateral involvement, and lower levels of TRAb than those in patients with hyperthyroid TAO. These distinct clinical and biochemical characteristics might be useful in assessment of euthyroid TAO, and the TSI might be more sensitive for diagnosing these patients.

Figure 1

Thyrotropin-TBII and TSI assays. The percentage of positive results using the TBII assay in group A (34.8%, 8/23) was significantly lower than that in group B (90.8%, 113/119, P<0.001); however, the percentage of positive results of the TSI assay was high in both group A (83.3%, 15/18) and B (91.7%, 55/60), with no statistically significant difference (P=0.337).