Thyroid Peroxidase (TPO) Antibody test detects autoantibodies directed against thyroid peroxidase, an enzyme essential for thyroid hormone production. These antibodies are present in 70-90% of patients with autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves' disease. Elevated TPO antibody levels indicate an autoimmune attack on the thyroid gland, which can lead to hypothyroidism, hyperthyroidism, or thyroid inflammation. The presence of TPO antibodies helps distinguish autoimmune thyroid disorders from other causes of thyroid dysfunction. This test is particularly useful for evaluating patients with unexplained thyroid symptoms, monitoring autoimmune thyroid disease progression, and assessing the risk of developing thyroid problems in individuals with a family history of autoimmune thyroid disease. TPO antibodies can also be present in other autoimmune conditions and may occasionally be found in healthy individuals.