Serum levels of soluble Fas in patients with Graves' ophthalmopathy.

AIM To assess levels of soluble Fas (sFas) in the sera of patients with Graves' ophthalmopathy. METHODS The subjects in this study were 43 patients with Graves' ophthalmopathy and 11 normal subjects. Serum levels of sFas were determined by sandwich enzyme linked immunosorbent assay. In addition, serum levels of thyroid stimulating antibody (TSAB) were also measured in all the patients. RESULTS The mean serum level of sFas was 1.35 (SD 2.03) ng/ml in patients with Graves' ophthalmopathy, and 0.93 (0.32) ng/ml in normal subjects. Serum levels of sFas in the subgroup of 24 patients with diplopia (1.98 (2.56) ng/ml) were significantly higher than those in the subgroup of 19 patients without diplopia (0.56 (0.24) ng/ml) and normal subjects (p <0.001). Serum levels of sFas in the subgroup of 27 patients with extraocular muscle hypertrophy (1.81 (2. 46) ng/ml) were significantly higher than those in the subgroup of 16 patients without extraocular muscle hypertrophy (0.58 (0.26) ng/ml) among the patients with Graves' ophthalmopathy and normal subjects (p <0.001). Serum levels of sFas were not significantly different between the subgroup of 24 patients with proptosis (1.15 (0.98) ng/ml) and the subgroup of 19 patients without proptosis (1. 61 (2.88)). In contrast, the serum levels of TSAB in the subgroup of patients with proptosis (723% (1161%)) were significantly higher than those in the subgroup of patients without proptosis (194% (122%)) (p <0.05). CONCLUSIONS Elevated sFas levels were associated with extraocular muscle disorders but not with proptosis. On the other hand, elevated TSAB levels were associated with proptosis but not with extraocular muscle disorders, suggesting different immunological mechanisms for the extraocular muscle disorders and proptosis in Graves' ophthalmopathy. Determination of the serum levels of sFas and TSAB could provide useful markers for evaluation of the immunological processes involved in the development of Graves' ophthalmopathy.