What it measures
Antibodies against thyroid peroxidase, an enzyme the thyroid uses to make its hormones. They are the antibodies most often found in autoimmune thyroid disease, such as Hashimoto's thyroiditis and Graves' disease.
Why people test it
- Checked when TSH is raised, to see whether an autoimmune cause is likely.
- Checked by people with thyroid symptoms or a family history of thyroid conditions.
- Part of many thyroid panels, alongside TSH, free T4 and thyroglobulin antibodies.
Typical range
Ranges vary by lab, method, age and sex, and your report shows the lab's own range. Labs use different methods and cut-offs, so results from two labs may not match.
Finger-prick or vein?
A finger-prick sample is usually fine for TPO antibodies, and many providers also offer a vein draw.
High-dose biotin, found in some hair and nail supplements, can upset some lab methods used for thyroid tests.