Thyroid Peroxidase Antibodies (Anti-TPO Ab)

Metabolic Health

A healthy result should fall into the range 0 - 34 IU/ml.

Thyroid peroxidase (TPO) is an enzyme that is critical for to thyroid hormone synthesis in the thyroid gland. Thyroid peroxidase (TPO) antibodies bind to and block the action of TPO, resulting in decreases in thyroid hormone levels. The presence of TPO antibodies in the blood is abnormal and usually indicates thyroid disease. The thyroid peroxidase (TPO) antibodies test is usually ordered after thyroid abnormalities have been detected with some other type of testing, such as TSH and free T4. It is usually ordered with thyroglobulin antibody testing.

Normal range for Thyroid Peroxidase Antibodies:

<35 IU/mL

Thyroid Peroxidase Antibodies (Anti-TPO Ab) result calculator

insert the value from you Thyroid Peroxidase Antibodies (Anti-TPO Ab) test result.

What does it mean if your Thyroid Peroxidase Antibodies (Anti-TPO Ab) result is too low?

The thyroglobulin antibody level cannot be too low. 

What does it mean if your Thyroid Peroxidase Antibodies (Anti-TPO Ab) result is too high?

Thyroid peroxidase (TPO) antibodies are autoantibodies, which means the body mistakenly produces these antibodies that act against a normal protein, TPO. As such, thyroglobulin antibodies usually indicate an autoimmune disease. TPO antibodies are present in roughly 90% of people with Hashimoto's thyroiditis and in half to three-quarters of people with Graves' disease. Thyroglobulin antibodies may be detectable in people without symptoms of thyroid hormone imbalance (subclinical hypothyroidism). When hypothyroidism causes symptoms, it may cause weakness and fatigue, cold intolerance, shortness of breath, weight gain, constipation, cognitive problems, dry skin, hoarseness, and swelling (edema). In about 10% of cases, TPO antibodies will be detectable in non-autoimmune thyroid disease such as pernicious anemia and type 1 diabetes mellitus.

Some specific causes of thyroid peroxidase (TPO) antibodies are:

  • Hashimoto's thyroiditis/chronic autoimmune hypothyroidism
  • Goitrous autoimmune thyroiditis 
  • Atrophic autoimmune thyroiditis
  • Grave’s disease
  • Differentiated thyroid carcinoma
  • Subclinical hypothyroidism
  • Pregnancy (abnormal)
  • Neonatal period (transient)
  • Postpartum thyroiditis
  • Painless (silent) thyroiditis


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