AbstractObjectiveGraves’ disease (GD) is an organ-specific autoimmune disease. The production of anti-thyrotropin receptor antibodies (TRAb) is associated with a loss of immune tolerance. Dipeptidyl peptidase-4 (DPP-4) is expressed on multiple immune cells. This study aimed to investigate the relationship between serum concentration/activity of DPP4 and the severity of hyperthyroidism in GD patients.MethodsA total of 82 newly diagnosed drug-naive patients with GD hyperthyroidism, 20 patients with non-autoimmune thyrotoxicosis and 122 age- and sex- matched healthy controls were enrolled. The clinical parameters and serum concentration and activity of DPP4 were measured.ResultsThe GD group had increased serum concentration and activity of DPP4 than the healthy controls and patients with non-autoimmune thyrotoxicosis, while no significant difference was observed in the latter two groups. Multivariate linear regression indicated that the serum concentration/activity of DPP4 were positively associated with FT3, FT4 and TRAb levels in the GD patients. And the positive association between serum concentration/activity of DPP4 and TRAb was remained even after adjustment for confounding factors (allp< 0.05).ConclusionsThe GD patients had significantly increased serum concentration/activity of DPP4. And the serum concentration/activity of DPP4 was positively associated with the severity of hyperthyroidism in GD patients.Key messagesThe activity and concentration of DPP4 in patients with Graves’ disease were higher than those in healthy controls.There was a significant positive correlation between serum DPP4 concentration and TRAb levels in patients with Graves’ disease.In patients with Graves ‘disease, serum DPP4 activity was positively correlated with TRAb levels.