The Anti-Thyroid Peroxidase (Anti-TPO) test is a blood test that measures the levels of antibodies against thyroid peroxidase in the blood. Thyroid peroxidase is an enzyme produced by the thyroid gland, which plays a crucial role in the production of thyroid hormones. The test is used to diagnose autoimmune thyroid diseases such as Hashimoto’s thyroiditis and Graves’ disease, as well as to monitor the effectiveness of treatment for these conditions. In people with autoimmune thyroid diseases, the immune system mistakenly attacks the thyroid gland, leading to inflammation and damage. This can cause the thyroid gland to produce too little or too much thyroid hormone. Elevated levels of anti-thyroid peroxidase antibodies in the blood are a marker of autoimmune thyroid diseases. The Anti-Thyroid Peroxidase (Anti-TPO) test is usually performed alongside other thyroid function tests, such as thyroid hormone levels, to provide a comprehensive evaluation of thyroid function. The test involves taking a small sample of blood, which is then analyzed in a laboratory to determine the levels of anti-thyroid peroxidase antibodies.