Dissociation between serum interleukin-6 rise and other parameters of disease activity in subacute thyroiditis during treatment with corticosteroid.

Increased serum interleukin-6 (IL-6) concentrations have recently been reported in patients with subacute thyroiditis, possibly because of cytokine release from damaged thyroid cells. To investigate the changes in serum IL-6 concentrations in subacute thyroiditis during treatment with corticosteroid, serum IL-6 concentrations were determined by an enzyme-linked immunosorbent assay method in five patients with subacute thyroiditis. Serum IL-6 concentrations were increased moderately, and simultaneously, serum levels of T4, thyroglobulin, and C-reactive protein and erythrocyte sedimentation rate were increased markedly. The treatment with prednisolone rapidly and progressively decreased serum levels of thyroglobulin, T4, and C-reactive protein and the erythrocyte sedimentation rate. In contrast, serum IL-6 concentrations increased markedly 7 days after the treatment with prednisolone in all five patients and two of five patients showed further increases in serum IL-6 concentration on the 17th day. The rise in serum IL-6 levels in untreated patients with subacute thyroiditis in this study is compatible with previous reports. The rise in serum IL-6 levels after treatment with corticosteroid in subacute thyroiditis may reflect the dissociation between the persistent release of IL-6 from the damaged thyroid cells, immediate inhibition of secondary inflammatory reactions by corticosteroid, and the release of thyroglobulin and T4 from performed colloid stores in follicular lumen destroyed by subacute thyroiditis.