What it measures.
TPO antibodies attack thyroid peroxidase, an enzyme essential for thyroid hormone production. Positive in over 90% of Hashimoto's thyroiditis cases, elevated TPO antibodies can predict future hypothyroidism even when TSH is currently normal.
The presence and concentration of autoantibodies targeting thyroid peroxidase enzyme. TPO is essential for iodine oxidation and thyroid hormone synthesis.
Why it matters.
Elevated TPO antibodies indicate autoimmune thyroid inflammation, even before hormone levels change. They correlate with symptoms like fatigue and brain fog independent of thyroid hormone status. High levels predict progression to overt hypothyroidism.
Physiology.
In autoimmune thyroiditis, the immune system mistakenly targets thyroid tissue. TPO antibodies mark this immune attack, causing gradual thyroid destruction. Women are affected 7-10x more often than men. Genetic susceptibility combines with environmental triggers (infections, stress, gut dysbiosis).
Testing & preparation.
How to prepare
- No special preparation needed
- Can be drawn anytime
- No fasting required
When to test
When investigating hypothyroidism cause, family history of autoimmune thyroid disease, other autoimmune conditions, or unexplained thyroid symptoms with normal TSH.
How often
At diagnosis, then every 6-12 months if elevated to monitor response to interventions.
Interpretation.
High tpo antibodies
Common causes:
- Hashimoto's thyroiditis (most common)
- Graves' disease
- Other autoimmune conditions (Type 1 diabetes, celiac, rheumatoid arthritis)
- Post-partum thyroiditis
- Family history of autoimmune thyroid disease
Implications:
- Active autoimmune attack on thyroid
- Increased risk of progression to hypothyroidism
- May explain symptoms despite normal TSH
- Higher miscarriage risk in pregnancy
- Should monitor TSH more frequently
Low tpo antibodies
Common causes:
- Normal finding
- Thyroid disease from non-autoimmune cause
Implications:
- Low likelihood of Hashimoto's
- If hypothyroid, consider other causes (iodine deficiency, medication, prior treatment)
Optimization.
Diet
- Consider gluten-free trial (21-49% antibody reduction in studies)
- Mediterranean diet for anti-inflammatory effects
- Selenium-rich foods (Brazil nuts, seafood)
- Avoid excess iodine if antibodies elevated
Lifestyle
- Stress management (stress triggers autoimmune flares)
- Quality sleep for immune regulation
- Regular moderate exercise
- Address gut health (gut-thyroid immune connection)
Supplements
- Selenium 200mcg (can reduce antibodies 40% in 3 months)
- Vitamin D if deficient
- Omega-3 fatty acids for inflammation
FAQs.
Can TPO antibodies be reduced?
Yes, research shows significant reductions are possible. Selenium 200mcg daily reduces TPO antibodies by ~40% within 3 months. Gluten-free diet shows 21-49% reduction in some studies. Combined interventions (selenium + gluten-free) show best results. Stress management and addressing gut health may also help. However, reducing antibodies doesn't always halt disease progression.
I have positive TPO antibodies but normal TSH—should I worry?
This is 'euthyroid Hashimoto's'—autoimmune attack without hormone changes yet. While your thyroid function is currently normal, there's increased risk of progression to hypothyroidism. Research suggests elevated antibodies alone can cause symptoms through inflammation. Monitor TSH every 6-12 months, implement lifestyle interventions, and work with your provider on preventive strategies.