Abstract: Objective To study the clinical significance of the serum thyroid peroxidase antibody (TPOAb) for the diagnosis of Graves disease (GD) and Graves with combined Hashimoto thyroiditis (GH). Methods Fifty-eight in-patients who were diagnosed as GD and underwent thyroidectomy in the Department of General Surgery at Tianjin Medical University General Hospital between January 2008 and December 2014 were enrolled in this study. Patients were divided into GD group (n=39) and GH group (n=19) according to the postoperative pathological results of the thyroid gland. The serum TPOAb titer and the degree of thyroid lymphocytic infiltration were compared between two groups. Results The preoperative serum TPOAb titer was obviously lower in GD group than that in GH group [60.0 (15.0， 317.0) IU/mL vs. 800.0 (231.6, 1000.0) IU/mL, P＜0.01]. The degree of thyroid lymphocytic infiltration was obviously lower in GD group than that of GH group (Z=4.334, P＜0.01). Conclusion The serum TPOAb titer and the degree of thyroid lymphocytic infiltration are higher in GH patients than those in patients with GD alone.

Key words: iodide peroxidase, antibodies, Graves disease, Hashimoto disease, lymphocytes