Thyroid peroxidase antibody test: What is it?

What is a thyroid peroxidase antibody test? Does it diagnose thyroid disease?

- Kelly / New York

Answer

If you've been diagnosed with thyroid disease, your doctor may recommend a thyroid peroxidase (TPO) antibody test — in addition to other thyroid tests — to help determine the cause. TPO, an enzyme normally found in the thyroid gland, plays an important role in the production of thyroid hormones. A thyroid peroxidase test detects antibodies against TPO in the blood.

The presence of thyroid peroxidase antibodies in your blood suggests that the cause of thyroid disease is due to an autoimmune disorder such as Hashimoto's disease or Graves' disease. In autoimmune disorders, your immune system makes antibodies that mistakenly attack normal tissue. Antibodies that attack the thyroid gland cause inflammation and impaired function of the thyroid.

Your doctor may also order a thyroid peroxidase test if you are pregnant and have a thyroid disease such as Hashimoto's disease or Graves' disease. In such cases, the thyroid peroxidase test can help determine whether your baby is at risk of thyroid disease.

Some people without thyroid disease may have TPO antibodies. However, the presence of thyroid peroxidase antibodies may increase the risk of future thyroid disorders. If you have normal thyroid function with TPO antibodies, your doctor may recommend periodic checkups to watch for future thyroid problems.

MORE ON THIS TOPIC

• Hashimoto's disease
• Graves' disease