A TPO (Thyroid Peroxidase) Antibody test measures the level of antibodies that target the thyroid peroxidase enzyme, which plays an essential role in thyroid hormone production. High TPO antibody levels indicate that the immune system is attacking the thyroid gland, commonly seen in autoimmune thyroid disorders such as Hashimoto’s thyroiditis and Graves’ disease. Doctors usually recommend this test when symptoms like fatigue, weight changes, hair loss, swelling in the neck, or irregular thyroid levels are present.

For the TPO test, a small blood sample is collected from a vein, and no fasting or special preparation is required. Elevated TPO antibodies do not always mean active disease but can indicate a higher risk of developing thyroid problems in the future. The test is often performed along with TSH, T3, and T4 tests to provide a complete assessment of thyroid health.