In plain words
A thyroid peroxidase antibody is a protein made by the immune system that can attack the thyroid. The blood test that checks for it looks for TPO antibodies. A positive result suggests an autoimmune process, most often Hashimoto's disease. Antibodies can be present for years before thyroid levels change. In pregnancy, a positive test is linked with a higher chance of thyroid problems and of pregnancy loss, though the size of that risk is debated. It is also linked with thyroid changes after birth, which is why testing may come up. A positive test does not on its own mean treatment is needed. Your provider reads it together with your thyroid levels.
The deeper version
Anti-thyroid peroxidase antibodies (anti-TPO) target thyroid peroxidase, the enzyme central to thyroid hormone synthesis, and are the marker of autoimmune thyroiditis. Positivity is more common in women and rises with age. In pregnancy, TPO positivity is associated with higher and preterm birth risk in meta-analyses, and with . Levothyroxine trials in antibody-positive, euthyroid women have produced mixed results, and guidance on routine testing differs between societies (ATA 2011 and 2017 guidelines).
Where it comes up
- Postpartum thyroid problemsPostpartum: Your Body
- Anemia and exhaustion after birthPostpartum: Your Body
What mothers here say about thyroid peroxidase antibody
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Sources
- Alexander EK et al. — Guidelines for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum, Thyroid 2017
- Stagnaro-Green A et al. — Guidelines of the American Thyroid Association for the diagnosis and management of thyroid disease during pregnancy and postpartum, Thyroid 2011