What are Thyroid Peroxidase Antibodies?
Thyroid peroxidase (TPO) is an enzyme your thyroid uses to produce thyroid hormones. When the immune system mistakenly attacks this enzyme, it creates TPO antibodies against it.
Measuring TPO antibodies (TPO-Ab) on a blood test helps physicians diagnose a patient with Hashimoto’s thyroiditis, which means that thyroid dysfunction is autoimmune in nature. Elevated TPO antibodies can appear years before thyroid hormone levels (TSH, T4, or T3) become abnormal, making this test useful for early detection.
Why Does TPO Matter?
Measuring TPO antibodies in a blood test helps:
- Detect autoimmune thyroid activity early, before TSH or T4 become abnormal
- Helps determine the cause of hypothyroidism, as elevated TPO antibody levels often indicate autoimmune disease such as Hashimoto’s
- Protecting pregnancy and postpartum health, since higher levels are linked to pregnancy complications and postpartum thyroiditis
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How to Interpret TPO
(Ranges may vary slightly by lab)
Standard reference ranges represent the middle 95% of healthy individuals but don’t necessarily reflect levels associated with longevity. Optimal ranges are derived from clinical guidelines, peer-reviewed research, and real-world outcomes data, with an emphasis on levels associated with peak functioning and reduced disease risk.
Benefits of Optimizing TPO Antibodies
- Improved pregnancy outcomes
- Lower inflammation
- Better metabolic health
- Improved thyroid function
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Low TPO Antibody Levels
Low TPO antibody levels are a good sign, revealing a lack of thyroid autoimmune disease.
High TPO Antibody Levels
Elevated TPO antibodies are a marker of autoimmune thyroid disease, such as Hashimoto’s disease.
Symptoms:
- Persistent fatigue
- Cold sensitivity
- Increased sleepiness
- Dry skin
- Hair loss
- Unexpected weight gain
- Muscle weakness
- Constipation
Causes:
- Hypothyroidism
- Autoimmune disorder
Healthspan Impacts:
How Hone Treats Out of Range Thyroid Peroxidase Antibodies
Your Hone physician will evaluate thyroid peroxidase antibodies alongside a full thyroid function panel, which may include thyroid-stimulating hormone (TSH) and free thyroxine (Free T4) along with any symptoms, and overall health. From there, they can map out a thyroid treatment plan that may include medications, supplements, and lifestyle changes.
Khan, S.R., et al. (2022). Determinants and Clinical Implications of Thyroid Peroxidase Antibodies in Middle-Aged and Elderly Individuals: The Rotterdam Study. Thyroid.
↑Pathan, A., et al. (2025). Assessing thyroid peroxidase antibodies in Emirati medical students: A cross-sectional pilot study. Frontiers in Endocrinology.
↑Li, J., et al. (2024). Thyroid antibodies in Hashimoto’s thyroiditis patients are positively associated with inflammation and multiple symptoms. Scientific Reports.
↑Zuhair V, et al (2024). Role of Supplementation with Selenium and Myo-Inositol Versus Selenium Alone in Patients of Autoimmune Thyroiditis: A Systematic Review and Meta-Analysis. Clin Med Insights Endocrinol Diabetes.
↑Chaudhary, S., et al. (2016). Vitamin D supplementation reduces thyroid peroxidase antibody levels in patients with autoimmune thyroid disease: An open-labeled randomized controlled trial. Indian Journal of Endocrinology and Metabolism.
↑Piticchio T, et al. (2023). Effect of gluten-free diet on autoimmune thyroiditis progression in patients with no symptoms or histology of celiac disease: a meta-analysis. Front Endocrinol (Lausanne).
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Reviewed for Accuracy by Our Medical Review Board
This biomarker information has been reviewed by a member of Hone’s medical review board. As part of the medical review team, physicians fact-check this content against the latest research and their own experience treating their patients.
Ashley Winter, M.D., is a board-certified urogynecologist trained at Weill Cornell and Cleveland Clinic. She specializes in female and male sexual dysfunction, urinary issues, genital pain, and hormone therapy.
James Staheli, D.O., is the Medical Director for Broad Health, Hone Health’s affiliated medical practice and a family medicine doctor in Atlanta, Georgia.
