TPO Antibodies
Autoantibodies against thyroid peroxidase – primary marker for autoimmune thyroiditis
Also known as
Definition
TPO antibodies (anti-TPO, microsomal antibodies) are autoantibodies against thyroid peroxidase, a key enzyme in thyroid hormone synthesis. They are elevated in more than 90% of Hashimoto's thyroiditis cases and in ~70% of Graves' disease. Elevated TPO antibodies without clinical symptoms or TSH change are termed latent autoimmune thyroiditis. They are a predictor of future hypothyroidism development.
| Parameter | Value |
|---|---|
| Unit | IU/ml (U/ml) |
| Reference Range | < 35 IU/ml (lab-dependent; some labs: < 60 IU/ml) |
| Optimal Range (lab2go) | < 10 IU/ml (lab2go Optimum Zone — below the borderline with a safety margin) |
↓ What a low value means
Low or negative TPO antibodies (< 35 IU/ml) argue against active autoimmune thyroiditis. No pathological condition is known at very low values. A negative result does not fully exclude autoimmune thyroiditis (5–10% of Hashimoto's cases are seronegative).
↑ What a high value means
Elevated TPO antibodies (> 35 IU/ml) indicate autoimmune thyroiditis. Antibody titer height does not always correlate with disease severity. Together with TSH, fT3, and fT4, they determine whether hypo- or hyperthyroidism is already present. Elevated values increase the risk of future thyroid dysfunction, postpartum thyroiditis, and miscarriage.
✓ How to optimize this marker
Selenomethionine (200 µg/day) is the best-evidenced natural intervention for reducing TPO antibodies in Hashimoto's (several RCTs). Optimize vitamin D to > 40 ng/ml. Stress reduction, avoid alcohol, quit smoking. Reduce gluten with coexisting celiac disease or gluten sensitivity. Inositol (4 g/day) studied in trials.
When to test
With thyroid dysfunction (TSH change), suspected Hashimoto's or Graves' disease, infertility, recurrent miscarriages, postpartum depression, autoimmune disease, or family history of thyroid disease. With a positive initial finding: follow-up every 6–12 months.
Frequently asked questions
Can I live with elevated TPO antibodies and no symptoms? +
Yes, many people have elevated TPO antibodies without symptoms or with normal thyroid function (euthyroid autoimmune thyroiditis). Regular monitoring (TSH every 6–12 months) is advisable. The lifetime risk of developing overt hypothyroidism is ~50%. Early intervention (selenium, vitamin D) may slow progression.
Hashimoto's or Graves' — how do I distinguish them by antibodies? +
TPO antibodies (anti-TPO) are elevated in both conditions. More specific to Graves' disease are TRAK (TSH receptor antibodies / anti-TSHR), which stimulate the thyroid to overproduce. Anti-thyroglobulin (TG-AK) can occur in both. The combination of TSH + fT3 + fT4 + anti-TPO + TRAK enables differentiation.
Does a gluten-free diet really help with Hashimoto's? +
Only with coexisting celiac disease or confirmed non-celiac gluten sensitivity is there evidence of benefit (antibody normalization with a gluten-free diet). In Hashimoto's without celiac disease, the evidence for gluten-free eating is weak. An exclusion trial (12 weeks gluten-free) may be reasonable for individuals with unclear symptoms.
Does selenium really affect TPO antibodies? +
Multiple randomized controlled trials (including meta-analyses) show that selenomethionine 200 µg/day significantly lowers TPO antibody titers in Hashimoto's (~20–30%). The European Thyroid Association lists selenium as an adjunctive option. Prerequisites: check selenium status (selenium deficiency is common in Central Europe).
Sources
- Stassi G, De Maria R (2002) Autoimmune thyroid disease: new models of cell death in autoimmunity. Nat Rev Immunol.
- Toulis KA et al. (2010) Selenium supplementation in the treatment of Hashimoto's thyroiditis: a systematic review and meta-analysis. Thyroid.
- Kahaly GJ et al. (2017) European Thyroid Association Guideline for the Management of Graves' Hyperthyroidism. Eur Thyroid J.
Last Reviewed: May 28, 2026 · sina
This information is for orientation only and does not replace medical advice. Reference ranges can vary by laboratory, method and country.