TPO Antibodies (Anti-Thyroid Peroxidase)
Antibodies that attack the thyroid gland. Elevated levels indicate autoimmune thyroid disease like Hashimoto's or Graves' disease.
What are TPO Antibodies?
TPO antibodies (anti-thyroid peroxidase antibodies) are immune proteins that mistakenly attack thyroid peroxidase — an enzyme essential for thyroid hormone production.
Their presence indicates autoimmune thyroid disease, where your immune system attacks your own thyroid gland.
Normal Ranges
| TPO Antibodies | Interpretation |
|---|---|
| Below 35 IU/mL | Negative (normal) |
| Above 35 IU/mL | Positive (autoimmune activity) |
Ranges vary by lab. Even low-positive levels are significant.
Why It Matters
Hashimoto's Thyroiditis
TPO antibodies are found in 90%+ of Hashimoto's patients. They confirm autoimmune cause when TSH is elevated and suggest increased risk of progression.
Graves' Disease
About 75% of Graves' disease patients also have TPO antibodies, though TSI (thyroid-stimulating immunoglobulin) is more specific.
Predicting Thyroid Problems
Positive TPO antibodies in someone with normal thyroid function predict higher risk of developing hypothyroidism over time.
Pregnancy Considerations
TPO-positive women have higher risk of:
- Postpartum thyroiditis
- Pregnancy loss
- Thyroid dysfunction during pregnancy
TPO Antibodies vs. Other Thyroid Antibodies
- TPO Antibodies — Most common in Hashimoto's
- Thyroglobulin Antibodies — Also common in autoimmune thyroiditis
- TSI — Specific for Graves' disease
Related Biomarkers
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