Circulating Th17 cytokine levels are altered in Hashimoto’s thyroiditis

•Hashimoto thyroiditis patients have higher IL-17 and IL-23 levels compared with non-thyroiditis controls.•IL-17 and IL-23 levels in hypothyroid thyroiditis patients are comparable to non-thyroiditis controls.•IL-17 and IL-23 levels are negatively correlated with TSH and positively with FT4.•Th17 cytokines are altered in Hashimoto thyroiditis.•The course of thyroiditis might be associated with differences in cytokine patterns. The disrupted autoimmune response in Hashimoto’s thyroiditis (HT) has long been considered to be dominantly T helper type 1 (Th1) mediated. Recent advances in the field of immunology have introduced a new class of effector T cells, named ‘Th17’, which plays important roles in autoimmune disorders once thought to be merely Th1 mediated. We aimed to examine the levels of major Th17 cytokines in patients with HT in this study. We studied serum interleukin 17 (IL-17) and interleukin 23 (IL-23) levels in 46 newly diagnosed, untreated patients with HT (40 women and 6 men, aged 40.0±11.8years) divided into euthyroid (n=22) and hypothyroid (n=24) groups and compared them with age and sex matched 26 healthy euthyroid controls without HT (21 women and 5 men; aged 36.0±12.9years). Serum IL-17 and IL-23 levels were significantly different among euthyroid and hypothyroid HT patients and controls, with highest levels obtained in the euthyroid HT group (p=0.041 for IL-17 and p