Serum levels of cytokines in children and adolescents with Graves' disease and non-toxic nodular goiter.

It has been shown that human thyrocytes can synthesize cytokines which activate T and B lymphocytes. These immune cells play important roles in the initiation and continuation of thyroid autoimmunity. The aim of this study was to estimate serum concentrations of soluble interleukin-6 receptor (sIL-6R), interleukin-6 (IL-6) and interleukin-8 (IL-8) in patients with Graves' disease (GD) (n=44, mean age 14.8 years), in patients with nontoxic nodular goiter (NTNG) (n=36, mean age 15.6 years) and in a group of healthy controls (n=20, mean age 14.5 years). ELISA was used to determine the concentration of cytokines, antithyroglobulin and antithyroid peroxidase antibodies in patients with thyroid disease. Radio receptor assay (RRA) was performed to detect anti-TSH receptor autoantibodies (TRAb). Serum levels of IL-6, sIL-6R and IL-8 were markedly elevated in patients with GD before treatment with methimazole (p<0.0001 for IL-6, p<0.006 for sIL-6R, p<0.004 for IL-8) and after 8 weeks of therapy (p<0.011 for IL-6, p<0.04 for IL-8). However, following 24 months of treatment, normal serum concentrations of these cytokines were restored. Furthermore, patients with NTNG showed a slightly elevated concentration of cytokines (IL-6, IL-8). Serum levels of tri-iodothyronine in patients with GD positively correlated with serum concentrations of IL-6 (r = 0.35, p<0.025) and sIL-6R (r = 0.31, p<0.047), while no correlation was found between thyroxine and cytokines. Moreover, we observed a positive correlation between serum levels of TPO-Abs, TRAb and IL-6 (r = 0.43, p<0.008; r = 0.5, p<0.003) and between TPO-Abs and IL-8 (r = 0.67, p<0.0001). However, in patients with NTNG no correlation was observed between serum levels of antithyroid antibodies or thyroid hormones and serum levels of cytokines. We conclude that the cytokines (IL-6, sIL-6R, IL-8) could play an important role in the development of Graves' disease and that their levels are modulated by thyreostatic treatment.