Introduction: Hypothyroidism is a common endocrine disorder characterized by decreased levels of thyroid hormones. Anti–thyroperoxidase antibody is produced in autoimmune thyroiditis which inhibits the synthesis of thyroid hormones.

Aims & Objectives: The study was planned to explore the significance of anti–TPO antibody in hypothyroid patients.

Materials and Methods: 150 newly diagnosed patients, age 20–60 years were enrolled for the study.  Patients were divided on the basis of anti–TPO levels as anti–TPO positive (n= ) and anti–TPO negative (n= ).Thyroid hormones viz. serum triiodothyronine (T3), thyroxine (T4), free T3 (FT3), free T4 (FT4) and thyroid stimulating hormone (TSH) levels were compared between the two groups.

Results: Mean serum TSH level was significantly higher in anti–TPO positive group. Mean serum T3 & T4 levels were comparable (P= NS) among the two groups whereas FT3 (P= 0.014) and FT4 (P= 0.003) were significantly lower in the anti–TPO positive group.

Conclusion: Serum FT3 & FT4 represent the biologically active proportion of thyroid hormones. The present study suggests that lower FT3 & FT4 levels can better correlate with anti–TPO activity in patients of hypothyroidism.