# Thyroid antibodies (anti-TPO, anti-TgAb)

Anti-TPO and anti-thyroglobulin (TgAb) are antibodies. Your immune system makes them against your own thyroid enzymes. They are the main blood markers of autoimmune thyroid disease. Labs measure them by immunoassay. The cutoffs depend on the test. Common ones are anti-TPO under 34 IU/mL and TgAb under 115 IU/mL. So always read them against the lab's own range. Anti-TPO is positive in about 90% of Hashimoto's thyroiditis. It is positive in roughly 75% of Graves' disease. TgAb is less specific. But it helps when monitoring thyroid cancer, since it can interfere with the thyroglobulin test. The 2017 ATA pregnancy guidelines flag another risk. Being anti-TPO positive raises the odds of miscarriage, preterm birth, and postpartum thyroiditis. It also lowers the threshold for treating mild (subclinical) hypothyroidism. Watch the confounders, too. Tests vary. A passing viral infection can raise titers. And other autoimmune conditions (type 1 diabetes, vitiligo) can raise them without any thyroid trouble.

## Sources

- Alexander EK, Pearce EN, Brent GA, et al.. (2017). 2017 Guidelines of the American Thyroid Association for the Diagnosis and Management of Thyroid Disease During Pregnancy and the Postpartum. Thyroid. https://doi.org/10.1089/thy.2016.0457
- Caturegli P, De Remigis A, Rose NR. (2014). Hashimoto thyroiditis: clinical and diagnostic criteria. Autoimmunity Reviews. https://doi.org/10.1016/j.autrev.2014.01.007

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