Quick answer: TPO (thyroid peroxidase) antibodies are produced when the immune system targets an enzyme the thyroid uses to make hormone. Elevated TPO antibodies are the most common marker of Hashimoto’s thyroiditis, the leading cause of hypothyroidism, and can be present before thyroid function clearly changes. They are also seen in Graves’ disease and sometimes in people with normal thyroid function.
Key takeaways
TPO antibodies form when the immune system targets an enzyme the thyroid needs to make hormone.
Elevated levels are the most common marker of Hashimoto’s and can appear before thyroid function clearly changes.
They can also show up in Graves’ disease and occasionally in people whose thyroid works normally.
What is TPO Antibodies?
Thyroid peroxidase is an enzyme the thyroid uses to attach iodine and make hormones. TPO antibodies are autoantibodies against this enzyme.
Why TPO Antibodies matters
TPO antibodies identify autoimmune thyroid disease and help predict future hypothyroidism. They are also important before and during pregnancy.
Understanding your result
Reference ranges vary by lab, age and sex. Your provider interprets your result against the lab’s range and your overall picture, rather than chasing a single number. Functional labs are optional. They can be helpful in more complex cases.
What elevated TPO antibodies can mean
Elevated TPO antibodies can mean Hashimoto’s thyroiditis or Graves’ disease, or other autoimmune conditions. They can also appear after pregnancy (postpartum thyroiditis).
What affects TPO Antibodies
TPO antibodies are affected by genetics and family history, pregnancy, excess iodine in some people, and other autoimmune conditions.
Ways to support healthy levels
- Monitor TSH and free T4 over time with your provider
- Eat a nutrient-dense diet with selenium-rich foods
- Avoid high-dose iodine supplements
- Support gut health (see gut health and autoimmunity)
- Check thyroid closely if pregnant or planning pregnancy
What does the research show about TPO antibodies?
The NHANES III survey tested 17,353 Americans aged 12 and older and found TPO antibodies in 11.3% of people without known thyroid disease. Positive results were more common in women and with age, and TPO antibodies were linked with both underactive and overactive thyroid function. As a one-time survey, it cannot show who goes on to develop thyroid problems. (Hollowell et al., 2002)
The Whickham Survey followed a random sample of 2,779 British adults for 20 years. Women with positive thyroid antibodies alone at the start had about 8 times the odds of developing hypothyroidism, and women with both a raised TSH and positive antibodies had about 38 times the odds, compared with women who had neither. The antibody tests used in the 1970s were less sensitive than today’s assays. (Vanderpump et al., 1995)
In a placebo-controlled trial, 70 women with autoimmune thyroiditis took 200 micrograms of selenium a day or placebo for 3 months, while all continued thyroid hormone. TPO antibody levels fell to 63.6% of baseline in the selenium group compared with 88% in the placebo group, but TSH and thyroid hormone levels did not change. The trial was small and short, and it measured antibodies rather than symptoms or long-term thyroid function. (Gärtner et al., 2002)
Overall, the research shows that TPO antibodies raise the chance of future thyroid changes, which is why they are usually checked alongside TSH over time.
TPO Antibodies and healthy aging
Autoimmunity becomes more common with age as immune regulation shifts and inflammation rises. Spotting thyroid autoimmunity early allows timely monitoring.
Related thyroid tests: TSH, free T4, free T3, reverse T3, thyroglobulin antibodies.
When to see a naturopathic doctor
It may be time to see a naturopathic doctor if you have fatigue, weight change, feeling cold or hot, hair loss or constipation, or anxiety, palpitations or tremor. The same is true if you have irregular periods or trouble conceiving, a family history of thyroid disease, or abnormal thyroid results you want explained.
See a medical provider promptly for a racing or irregular heartbeat, severe confusion or drowsiness, a rapidly growing neck lump, or trouble swallowing or breathing.
TPO Antibodies at a glance
| Topic | What the article explains |
|---|---|
| Why it matters | Identifies autoimmune thyroid disease; helps predict future hypothyroidism; and important before and during pregnancy |
| What can affect it | Genetics and family history; pregnancy; excess iodine in some people; and other autoimmune conditions |
| Supportive habits discussed | Monitor TSH and free T4 over time with your provider; eat a nutrient-dense diet with selenium-rich foods; avoid high-dose iodine supplements; support gut health; and check thyroid closely if pregnant or planning pregnancy |
Questions to bring to your clinician
These questions can help you get the most out of your next visit.
If my TPO antibodies are elevated, how often should we recheck my thyroid function?
What might my TPO antibodies be telling us, given my health history and symptoms?
Which other labs would be worth pairing with my TPO antibodies to get a clearer picture?
When would it make sense to recheck my TPO antibodies, and what could I work on in the meantime?
Frequently asked questions
Do positive TPO antibodies mean I have Hashimoto’s?
Often, especially with symptoms or abnormal TSH, but some people with positive antibodies have normal thyroid function.
Can TPO antibodies go down?
They can fluctuate; the main goal is protecting thyroid function.
Should I test TPO if my TSH is normal?
It can be useful with symptoms, family history or pregnancy plans.
Does gluten affect Hashimoto’s?
People with Hashimoto’s should be screened for celiac disease; others can discuss a trial with their provider.
Have questions about whether this fits your situation? Dr. Kneessi offers a free 15-minute call to talk through your history and goals.
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Sources
- Gärtner R, et al. Selenium supplementation in patients with autoimmune thyroiditis decreases thyroid peroxidase antibodies concentrations. J Clin Endocrinol Metab 2002. PMID: 11932302. https://pubmed.ncbi.nlm.nih.gov/11932302/
- Hollowell JG, et al. Serum TSH, T(4), and thyroid antibodies in the United States population (1988 to 1994): National Health and Nutrition Examination Survey (NHANES III). J Clin Endocrinol Metab 2002. PMID: 11836274. https://pubmed.ncbi.nlm.nih.gov/11836274/
- Huber G, et al. Prospective study of the spontaneous course of subclinical hypothyroidism: prognostic value of thyrotropin, thyroid reserve, and thyroid antibodies. J Clin Endocrinol Metab 2002. PMID: 12107228. https://pubmed.ncbi.nlm.nih.gov/12107228/
- Leung AM, et al. Consequences of excess iodine. Nat Rev Endocrinol 2014. PMID: 24342882. https://pubmed.ncbi.nlm.nih.gov/24342882/
- Ralli M, et al. Hashimoto's thyroiditis: An update on pathogenic mechanisms, diagnostic protocols, therapeutic strategies, and potential malignant transformation. Autoimmun Rev 2020. PMID: 32805423. https://pubmed.ncbi.nlm.nih.gov/32805423/
- Vanderpump MP, et al. The incidence of thyroid disorders in the community: a twenty-year follow-up of the Whickham Survey. Clin Endocrinol (Oxf) 1995. PMID: 7641412. https://pubmed.ncbi.nlm.nih.gov/7641412/
- Ventura M, et al. Selenium and Thyroid Disease: From Pathophysiology to Treatment. Int J Endocrinol 2017. PMID: 28255299. https://pubmed.ncbi.nlm.nih.gov/28255299/
- MedlinePlus: Thyroid Antibodies
- NIDDK: Hashimoto’s Disease
This article is for educational purposes only and is not medical advice. It does not replace an individual evaluation. Talk with your healthcare provider before starting supplements or changing medications, especially if you are pregnant, nursing, or managing a health condition.
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