Background: Gestational diabetes mellitus (GDM) is defined as glucose intolerance due to insulin resistance during pregnancy. This metabolic disorder includes 8.3% of pregnancies worldwide. Thyroid gland autoantibodies can induce insulin resistance probably because of inflammatory cytokines production. However, a distinct mechanism of this phenomenon has not well understood. Objectives: Regarding the high prevalence of GDM which concerns the mother and fetus health, this study aimed to compare the therapeutic methods frequency in GDM patients with or without anti-thyroperoxidase (TPO) autoantibodies. Methods: One hundred and two GDM patients aged between 20-30 years, with (n=52) or without (n=50) anti-TPO antibodies were enrolled in this experimental study. Overt hypothyroidism or hyperthyroidism, creatinine>1.4 mg/dl, Congestive Heart Failure, liver diseases, and diabetes history were considered as exclusion criteria. Insulin administration was performed in patients with fasting blood glucose (FBS)>105 mg/dl. Other patients regarding the blood glucose level were treated by metformin or diet. All patients were followed up for one week. Results: Patients were divided into anti-TPO (+) and anti-TPO (-) groups with the average age of 25.52±3.35 and 26.28±3.53, respectively. Significant differences were observed in FBS, 1hour BS and 2 hour BS levels between groups (p=0.003, p=0.041 and p=0.007 for FBS, 1 hour BS and 2 hour BS, respectively). Based on therapeutic methods, significant differences were observed in insulin (p=0.026) and diet (p=0.03) therapy. Conclusion: Our data showed that the presence of anti-TPO antibody is correlated with GDM severity, indicating the importance of thyroid gland function on feto-maternal health status.