BiomarkersAnti-TPO antibodies
Thyroid
Anti-TPO antibodies
Antibodies that signal autoimmune thyroid disease
On your report it may say: Anti-thyroid peroxidase, TPO Ab
Anti-TPO antibodies show whether the immune system is targeting the thyroid. A positive result is the hallmark of Hashimoto's thyroiditis, the most common cause of an underactive thyroid.
Typical ranges · IU/mL
kIU/L is the same number
Cut-offs vary between labs (often 9–35 IU/mL).
Ranges vary by lab, age and sex. The range printed on your report applies.
If it's low
A negative result makes autoimmune thyroid disease less likely.
Common causes
- Normal result
If it's high
Your immune system is reacting to the thyroid; thyroid function should be monitored.
Common causes
- Hashimoto's thyroiditis
- Graves' disease
- After pregnancy
What you might notice
- May have none until thyroid function changes
Testing
- Who should test
- People with a raised TSH, a family history of thyroid disease, or planning pregnancy with thyroid concerns.
- How to prepare
- No fasting needed.
- When to retest
- Not usually repeated; TSH is monitored instead.
What can help
Some studies use selenium with positive antibodies, but SYNC doesn't recommend it from this result alone. Ask your doctor.
See a doctor if positive, especially if pregnant or planning pregnancy.
Common questions
Does a positive result mean I need medicine?
Not always; it depends on your TSH and T4.
Can diet lower antibodies?
Evidence is limited; follow your doctor's advice.
Explore further
Sources
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Build My Nutrition PlanFor general education only, not medical advice. Ranges shown are typical for adults; the range printed on your lab report applies. Talk to a qualified doctor about your results.