Test library
Thyroid Peroxidase Antibody Test
The TPO antibody test measures autoantibodies against thyroid peroxidase, an enzyme involved in thyroid hormone production. It is used to help evaluate autoimmune thyroid conditions such as Hashimoto thyroiditis and thyroiditis.
Order TPO Test (Thyroid Peroxidase Antibody)
Order online and visit a local collection site, or choose an at-home kit where available. No referral and no insurance required.
Order TPO Test (Thyroid Peroxidase Antibody)- Typical turnaround
- 1-3 business days
- Starting price
- From $158
- Results
- Confidential, online
Quick answer
The TPO antibody test measures autoantibodies that target thyroid peroxidase, an enzyme the thyroid uses to make hormones. Their presence points to an autoimmune process affecting the thyroid. The test is usually ordered with other thyroid tests and is interpreted by a qualified healthcare provider.
What this test measures
Thyroid peroxidase is an enzyme in the thyroid gland that plays a key role in producing thyroid hormones. In autoimmune thyroid disease, the immune system produces antibodies against this enzyme and other thyroid proteins. Detecting these antibodies can support the evaluation of conditions such as Hashimoto thyroiditis and other forms of thyroid inflammation.
The test needs a blood sample, drawn from a vein. The laboratory measures thyroid peroxidase antibodies with an immunoassay and reports a level against a reference range. Because these antibodies can appear alongside thyroglobulin antibodies, TPO testing is often combined with other thyroid markers such as TSH and free T4.
A positive result indicates autoimmune activity against the thyroid, but it does not by itself confirm a specific diagnosis or predict how symptoms will progress. Some people with antibodies have normal thyroid function. A qualified healthcare provider interprets the result with hormone levels and clinical findings.
- Thyroid peroxidase antibodies (TPOAb)
- Thyroglobulin antibodies (TgAb) when paired
- Thyroid-stimulating hormone (TSH)
- Free thyroxine (free T4)
- Free triiodothyronine (free T3)
- Antibody titer level
Why people order this test
- Support evaluation of autoimmune thyroid disease
- Investigate an underactive thyroid with a provider
- Check for autoimmune thyroid activity with normal hormone levels
- Follow up on goiter or thyroid swelling
- Complete a thyroid antibody panel
How to prepare
No fasting is usually needed for this blood test. A sample is collected from a vein, usually at the arm. Follow any instructions provided by the laboratory, particularly if other thyroid tests are included.
Understanding your results
Results are typically available within one to three business days. The report shows the thyroid peroxidase antibody level and its reference range. A positive result suggests autoimmune thyroid activity, and a qualified healthcare provider interprets it with other thyroid tests.
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Frequently Asked Questions
What is thyroid peroxidase?
It is an enzyme in the thyroid gland that helps produce thyroid hormones. Antibodies against it are a marker of autoimmune thyroid activity.
What does a positive TPO antibody test mean?
It indicates the immune system is producing antibodies against the thyroid. This supports evaluation of autoimmune thyroid conditions but does not confirm one by itself.
Can I have normal thyroid function with positive TPO antibodies?
Yes. Some people with these antibodies have normal hormone levels. A provider monitors function over time if needed.
Why are other thyroid tests ordered too?
TPO antibodies are usually reviewed with TSH and free T4 to show how the thyroid is functioning alongside the autoimmune finding.
Do I need to fast?
Fasting is not usually required unless the test is combined with other panels that call for it.
Ready to get tested?
Order online and visit a collection site near you, or choose a mail-in kit. No referral and no insurance required.
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