Hashimoto's thyroiditis, but not treatment of hypothyroidism, is associated with altered TGF-beta1 levels.

Background. Although the role of cytokines in the development of Hashimoto's thyroiditis has already been established, its pathogenesis has not yet been clearly elucidated. The aim of our study was to investigate serum transforming growth factor-beta 1 (TGF-beta 1) levels in patients with Hashimoto's thyroiditis as well as the effect of achieving euthyroidism by levothyroxine replacement on TGF-beta 1 levels