High circulating IL-6 level in Graves' ophthalmopathy.

IL-6 is a paracrine and autocrine cytokine, which acts in the regulation of immunological and inflammatory processes. Its production can be observed in different cell types, as well as thyrocytes. The purpose of the study was to examine the serum IL-6 levels between the patients with Graves' disease (N = 47) and without (N = 29) ophthalmopathy in respect of the presence of inflammatory eye signs and thyroiditis, thyroid function and radioiodine or medical treatments. The serum IL-6 levels were greater (P < 0.025) in the patients with ophthalmopathy (440 +/- 32.4 pg/ml) than in those without eye disease (81.6 +/- 25.2 pg/ml). An elevated serum IL-6 levels could be detected in 22 out of 47 patients with ophthalmopathy with longer manifestation of thyroid disease than one year in comparison with those who had shorter (694 +/- 35.3 pg/ml vs 215.8 +/- 27.9 pg/ml, P < 0.05). The increase showed a strong association with the inflammatory signs of eye disease in the patients with Graves' hyperthyroidism compared with those without ophthalmopathy (513.3 +/- 33.7 pg/ml vs 96.9 +/- 12.1 pg/ml, P < 0.025). Euthyroid function and the presence of thyroiditis did not influence the serum IL-6 levels. Radioiodine and medical treatments did not lead to a remarkable decrease in the serum IL-6 levels. The results supported that IL-6 cytokine may be an important factor in the inflammatory events of Graves' ophthalmopathy.