T cell‐derived leptin contributes to increased frequency of T helper type 17 cells in female patients with H ashimoto's thyroiditis

Summary Leptin modulates T cell function and plays an important role in autoimmune diseases. Our study aimed to explore the role of leptin and T helper type 17 ( T h17) cells in H ashimoto's thyroiditis patients. Twenty‐seven patients with Hashimoto's thyroiditis ( HT ) and 20 healthy controls were enrolled into the current study. A modest increase of plasma leptin in HT patients and the CD4 + T cell‐derived leptin from HT patients was stronger than that from healthy controls. In HT patients, there are no statistically significant correlations between plasma leptin concentrations and the percentage of T h17 cells or the level of retinoic acid‐related orphan receptor γt ( RORγt ), but strong positive correlations were observed between CD4 + T cell‐derived leptin and the percentage of Th17 cells or the level of RORγt mRNA , and additionally significantly up‐regulated leptin, interleukin ( IL )17 and RORγt mRNA levels in the thyroid tissue. Furthermore, neutralization of leptin decreases the frequency of T h17 cells in vitro . Current study has revealed an increased leptin involvment in H ashimoto's thyroiditis associated with an increased number of T h17 cells.