Thyroid Peroxidase Antibodies

Thyroid marker

TPO Antibodies

Thyroid Peroxidase Antibodies

Category: Thyroid
Unit: kIU/L

Autoantibodies against thyroid peroxidase. Elevated levels are the hallmark of Hashimoto's thyroiditis (autoimmune hypothyroidism).

PED Notes

AAS reduce thyroxine-binding globulin (TBG), causing total T3/T4 to appear low while free hormones remain unchanged — this is not autoimmune. GH increases T4-to-T3 conversion and can unmask latent thyroid insufficiency if anti-TPO is borderline. Exogenous T3 (Cytomel) suppresses TSH, which can mask rising anti-TPO. If symptoms like fatigue, weight gain, or poor recovery persist post-cycle, check anti-TPO alongside TSH and Free T4 to rule out Hashimoto's.

When high

When elevated (>34 kIU/L):

Diagnostic workup:

  • Full thyroid panel: TSH, Free T4, Free T3, anti-thyroglobulin antibodies (TgAb)
  • Thyroid ultrasound if anti-TPO >100 kIU/L
  • If on T3: taper and recheck thyroid panel 6-8 weeks after discontinuation

Supplements (evidence-based for reducing TPO antibodies):

  • Selenium (Selenomethionine) -- 200mcg/day: Most well-studied supplement for reducing anti-TPO. Meta-analyses show significant reduction after 3-6 months. Do NOT exceed 400mcg/day
  • Myo-Inositol -- 600mg/day (with selenium 83mcg): Combination is superior to selenium alone, reducing both TPOAb and TgAb by up to 51%
  • Vitamin D3 -- 5000 IU/day if deficient: Deficiency is strongly associated with autoimmune thyroid disease. Aim for 75-150 nmol/L
  • Zinc (Picolinate) -- 30mg/day: Cofactor for thyroid hormone synthesis and immune modulation
  • Omega-3 (EPA/DHA) -- 2-3g/day: Anti-inflammatory, may help modulate the autoimmune response

Lifestyle:

  • Consider gluten assessment — autoimmune thyroiditis has a documented association with coeliac disease
  • Ensure adequate iodine (150-300mcg/day) but do NOT mega-dose (excess iodine worsens autoimmune thyroiditis)
  • Monitor progression: euthyroid patients with elevated anti-TPO progress to overt hypothyroidism at ~5% per year

History Chart

Reading History

Frequently Asked Questions

Reference Ranges

Standard Range

0 - 34 kIU/L

VitalMetrics Range

0 - 20 kIU/L

Statistics