Serum interleukin-22 (IL-22) is increased in the early stage of Hashimoto's thyroiditis compared to non-autoimmune thyroid disease and healthy controls.

Hashimoto's thyroiditis (HT) is considered to be a Th1-related autoimmune disease (AID). Recent studies revealed that Th17 lymphocytes (producing mostly IL-17, IL-21 and IL-22) play a major role in numerous AIDs commonly thought to be Th1 diseases. More recently, another subset of Th cells, which produce IL-22 and thus so-called Th-22, have been identified. Few data are available in the literature on the role of IL-22, the main soluble mediator of both Th17 and Th22 cells, in HT. Using IL-22 Quantikine ELISA Kit (lower limit of detection 0.7 pg/ml), we assayed serum levels of IL-22 in three groups of subjects: newly diagnosed HT patients (n=55, 5 males and 50 females, age 38±17 years), non-HT patients with nodular goiter (n=30, 4 males and 26 females, age 43±14 years) and an age- and sex-matched group of healthy individuals. HT patients were euthyroid and were not receiving any treatment. HT patients showed significantly higher levels of serum IL-22 (group A, 42±34 pg/ml) as compared to non-HT-goitrous patients (18±15 pg/ml; P<0.001) and healthy controls (20±13 pg/ml; P=0.014). Serum IL-22 levels did not differ between non-HT-goitrous patients and healthy controls (p=0.496). No significant correlation was found between serum levels of IL-22 and Tg-Ab, TPO-Ab or TSH in the HT patients. Serum IL-22 is increased in newly diagnosed, untreated HT patients, as compared to thyroid autoimmune disease-free individuals. Our data suggest that IL-22 could play some role in the development of HT.