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Immunology & Autoimmune
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Currently under review
Pending specialist review and validation.
This blood test measures antibodies your immune system may make against thyroid peroxidase, an enzyme in the thyroid that helps produce thyroid hormones. These are called anti-thyroid peroxidase antibodies, or TPO antibodies.
Clinicians use this test to look for signs of autoimmune thyroid disease. It is often ordered together with thyroid function tests to help explain symptoms, changes in thyroid levels, or an enlarged thyroid, and to better understand conditions such as Hashimoto thyroiditis or Graves disease.
TPO antibodies point to immune activity directed at the thyroid. Their presence can support a diagnosis of autoimmune thyroid disease and helps estimate the likelihood of future thyroid underactivity even when thyroid hormone levels are currently within the expected range. In people with a goiter, nodules, or symptoms of thyroid problems, the result helps identify an autoimmune cause and guides follow-up and treatment planning.
During pregnancy and after delivery, TPO antibodies are linked with a higher chance of thyroid dysfunction and postpartum thyroiditis. Your clinician may order this test when evaluating infertility or pregnancy loss, when planning conception, or if you have other autoimmune conditions. Results can influence how closely your thyroid function is monitored and whether preventive or earlier interventions are considered.
If the test is positive, it means the immune system is recognizing thyroid tissue, which increases the likelihood of autoimmune thyroid disease. Some people without symptoms can have antibodies, and not everyone with antibodies will develop thyroid problems. A negative test makes autoimmune thyroid disease less likely, but early disease can still be present, so your clinician will consider the whole clinical picture.
Your result is interpreted alongside symptoms, exam findings, and other labs such as thyroid-stimulating hormone and thyroid hormone levels. If antibodies are present, your clinician may recommend periodic monitoring to watch for changes over time. Shifts in antibody levels do not always mean your thyroid function has changed immediately, so treatment decisions are based mostly on thyroid hormone levels and how you feel.
Reference intervals vary by laboratory, analyzer, methodology, population, and units. The ranges shown here are for education only. Always interpret your results against the reference interval printed on your own lab report.
High-dose biotin and some over-the-counter supplements can interfere with certain immunoassays, potentially causing misleading results. Tell your clinician about all supplements and follow advice on holding biotin before testing.
Drugs such as interferon, immune checkpoint inhibitors, amiodarone, and lithium can trigger or unmask thyroid autoimmunity. If you take these, your clinician may interpret results with extra caution and monitor more closely.
Immune changes in pregnancy and the months after delivery can reveal or worsen autoimmune thyroid disease. Testing may be used to assess risk and to plan monitoring during prenatal and postpartum care.
People with autoimmune diseases like type 1 diabetes or celiac disease, or with a family history of thyroid disease, are more likely to have TPO antibodies. Let your clinician know about personal or family autoimmune history.
Different laboratories use different methods and calibrations, so results may not be interchangeable. When monitoring over time, try to use the same lab to make trend comparisons more reliable.
Episodes of thyroiditis or significant illness can be associated with changes in antibody patterns. Your clinician may consider timing of symptoms or illness when interpreting the result.
References