Skip to content

Thyroid Peroxidase Antibodies (TPO-Ab)

Published: July 27, 2026Updated: August 25, 2026

Thyroid Peroxidase Antibodies (TPO-Ab) measure the level of antibodies targeting the thyroid peroxidase enzyme, which is crucial for thyroid hormone production.

Quick summary

TPO-Ab levels help diagnose autoimmune thyroid disorders like Hashimoto's thyroiditis and Graves' disease.

Medically reviewed by WellAlly Editorial TeamLast reviewed August 25, 2026Editorial policy

Key facts at a glance

Units
IU/mL
Clinical utility
diagnostic
Result kind
quantitative
FDA-cleared
Roche Anti-TPO, Abbott Anti-TPO, Siemens Anti-TPO, ImmunoSource TPO
interpretation: {"text":"0–34 IU/mL: No indication of autoimmune thyroid disease.","label":"Normal"}; {"text":">34 IU/mL: Possible autoimmune thyroid disorder, further evaluation recommended.","label":"Elevated"}

Thyroid Peroxidase Antibodies (TPO-Ab) are antibodies that target the thyroid peroxidase enzyme, which is essential for the production of thyroid hormones. Elevated levels of TPO-Ab are often indicative of autoimmune thyroid diseases, such as Hashimoto's thyroiditis and Graves' disease.

The measurement of TPO-Ab is a key diagnostic tool for identifying autoimmune thyroid conditions. It helps clinicians differentiate between different types of thyroid disorders and guides treatment strategies.

Normal TPO-Ab levels are typically below 34 IU/mL. Levels above this range may suggest an autoimmune thyroid disorder, prompting further evaluation and management.

Frequently asked questions

What does a high TPO-Ab level mean?
A high TPO-Ab level indicates the presence of antibodies attacking the thyroid, suggesting an autoimmune thyroid disorder such as Hashimoto's thyroiditis or Graves' disease.
Can TPO-Ab levels change over time?
Yes, TPO-Ab levels can fluctuate with disease activity and treatment. Regular monitoring may be necessary to assess disease progression and treatment effectiveness.
  1. 1
    American Thyroid AssociationSource
  2. 2
    Mayo ClinicSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 25, 2026. · Read our editorial policy