TPO antibodies elevated — Hashimoto research
Anti-thyroid peroxidase (anti-TPO) antibodies above ~35 IU/mL indicate active autoimmune attack on thyroid tissue — most commonly Hashimoto thyroiditis (the leading cause of hypothyroidism in iodine-replete populations). Anti-TPO antibodies are present in ~10% of euthyroid adults (no symptoms, normal TSH) but predict significantly higher risk of progression to overt hypothyroidism — about 4% per year for antibody-positive individuals vs <1% for antibody-negative. The number itself doesn't tightly correlate with severity; presence vs absence is the key signal. Selenium supplementation has the most-cited research support for reducing anti-TPO titres over months.
Reference ranges
| Negative | < 35 IU/mL |
| Borderline | 35 – 100 IU/mL |
| Positive | 100 – 500 IU/mL |
| Strongly positive | > 500 IU/mL |
What this marker measures
Thyroid peroxidase (TPO) is the enzyme that catalyses iodide oxidation and tyrosine iodination during thyroid hormone synthesis. Anti-TPO antibodies bind and inhibit TPO and are also markers of cytotoxic T-cell-mediated thyroid destruction. Their presence essentially defines autoimmune thyroid disease. The two major patterns: Hashimoto thyroiditis (high anti-TPO, often anti-thyroglobulin too, progresses to hypothyroidism) and Graves' disease (anti-TPO present in ~70% but TSH-receptor antibody is the primary driver of hyperthyroidism).
Why might it be elevated?
- ·Hashimoto thyroiditis (most common)
- ·Graves disease (~70% of cases)
- ·Postpartum thyroiditis
- ·Type 1 diabetes (~25% co-occurrence)
- ·Coeliac disease (autoimmune cluster)
- ·Other autoimmune disease (RA, lupus, vitiligo)
- ·Family history of autoimmune thyroid disease
- ·Iodine excess (paradoxically — large iodine doses can trigger autoimmunity)
Why might it be low?
- ·No clinical significance to a "low" reading — the question is positive vs negative
FAQ
What does selenium do for anti-TPO?+
Multiple trials (Gärtner 2002 onwards) show 200 mcg/day selenium (selenomethionine) reduces anti-TPO titres ~30-50% over 3-12 months in Hashimoto patients. The proposed mechanism is enhanced glutathione peroxidase activity reducing oxidative damage to thyroid tissue. Effect on clinical thyroid function (TSH, free T4) is more variable than the antibody effect.
Does this mean I have Hashimoto?+
Positive anti-TPO + symptoms or thyroid dysfunction (TSH out of range, abnormal T4/T3) confirms Hashimoto. Positive anti-TPO with normal thyroid function is 'Hashimoto in evolution' or 'silent Hashimoto' — present but not yet causing overt dysfunction. Annual TSH monitoring is the standard next step.
This page describes biomarker research and reference ranges for self-tracking and research-context discussion only. It is not medical advice, not a diagnosis, and not a substitute for a qualified physician. Take any concerns about your health to a clinician.
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