Gestational diabetes mellitus (GDM) is defined as “glucose intolerance first detected in 24–28 weeks of gestation by oral glucose tolerance test (OGTT). In pregnancy, the activity of thyroid hormones is altered and not balanced in some of the pregnant women leading to thyroid dysfunction. GDM and thyroid dysfunctions may cause maternal and fetal complications which includes Preterm birth, macrosomia, cesarean-sections and future risk of type II diabetes mellitus. Aim of our study is to find the association of thyroid hormones status and insulin resistance (IR) in GDM and normal pregnant women. The cross sectional study was conducted between the period of October 2021 to September 2023 at Annapoorana Medical College and hospitals, Salem. Total numbers of samples are 160.OGTT (Oral Glucose Tolerance Test) performed during 24-28 weeks of gestation. Subjects were divided into two groups. Group I: 80 Gestational Diabetes Mellitus women were taken as cases. Group II: 80 normal pregnant women were taken as controls. We found 13.75 % subclinical hypothyroidism and 6.25% maternal hypothyroxinaemia in 80 GDM women. There was no significance of thyroglobulin antibodies (TG) between cases 73±29.74 and controls 69±18.21. This study suggests that women with GDM should be considered as high risk for hypothyroidism and their TSH levels should be monitored closely during pregnancy. This would help to introduce preventive therapies earlier in GDM and then to prevent maternal fetal complications. © 2025 Elsevier B.V., All rights reserved.