Abstract: Objective To investigate the effect of thyroid peroxidase antibody (TPO-Ab) on vascular disease of lower extremities in patients with type 2 diabetes mellitus (T2DM). 
Methods The clinical data of 500 patients with T2DM who were admitted to Cangzhou Central Hospital were retrospectively collected. According to the level of TPO-Ab, the patients were divided into the positive group (TPO-Ab≥34 U/mL, n=73) and negative group (TPO-Ab＜34 U/mL, n=427), and the incidence of vascular disease of lower extremities in two groups was recorded. According to presence or absence of vascular disease of lower extremities in patients with T2DM, they were divided into the occurrence group (n=186) and the non-occurrence group (n=314), and the correlation between TPO-Ab and vascular disease of lower extremities in patients with T2DM was analyzed. 
Results The incidence of vascular disease of lower extremities was 56.16% (41/73) in the positive group, which was higher than that ［33.96% (145/427)］ in the negative group (χ2=13.160, P＜0.01). Univariate analysis was performed, and further Logistic regression analysis showed that coronary heart disease (OR=10.345), history of cerebral infarction (OR=26.942), duration of T2DM (OR=1.921), TPO-Ab (OR=2.080), triglycerides (OR=1.531), low density lipoprotein cholesterol (OR=1.559), glycosylated hemoglobin (OR=1.703), 2h postprandial blood glucose (OR=1.519) were the influencing factors of vascular disease of lower extremities in patients with T2DM. 
Conclusion The incidence of vascular disease of lower extremities in T2DM patients with TPO-Ab≥34 U/mL is higher than that of T2DM patients with TPO-Ab ＜34 U/mL. Clinicians should strengthen the screening of TPO-Ab, as well as evaluation and control of the above influencing indicators in T2DM patients, so as to prevent or slow down the progression of vascular disease of lower extremities in T2DM patients.

Key words: diabetes mellitus, type 2, iodide peroxidase, vascular disease of lower extremities