Recent studies have demonstrated that T-helper 17 lymphocytes (Th17), which produce mostly IL-17, play a major role in several autoimmune diseases commonly thought to be Th1-related, including Hashimoto's thyroiditis (HT). IL-23, a member of the IL-12 cytokine family, is known to guide T cells toward the Th17 phenotype and its serum levels are increased in several autoimmune disease. Few data a...