Anti-thyroid Peroxidase (TPO)
Anti-thyroid Peroxidase (TPO)Thyroid

Anti-thyroid Peroxidase (TPO)

February 24, 2021


What is anti-TPO?

Anti-TPO is a type of autoantibody. Autoantibodies are produced by the immune system, and are similar to antibodies which are produced against viruses and bacteria, but instead of outside invaders, autoantibodies attack the body itself. In this instance anti-TPO attacks thyroid peroxidase (TPO) - an enzyme found in the thyroid gland, needed for the production of thyroid hormones. Attacks on the TPO enzyme block its activity, which in turn affects the production of thyroid hormones.

Why is this analysis important?

The anti-TPO antibody test is used for detection of autoimmune thyroid disease such as Hashimoto’s thyroiditis and Grave’s disease. There are a number of thyroid antibodies which cause thyroid disease, with anti-TPO being the most common. Checking for anti-TPO helps differentiate autoimmune thyroid disorders from non-autoimmune ones, which can affect the choice of treatment. Anti-TPO antibodies are present in the blood of 90% of the patients with Hashitomoto’s thyroiditis and 60-80% of patients with Grave’s disease.

Hashitomoto’s thyroiditis is the most common cause for hypothyroidism. It is caused by attacks on the thyroid gland by our own immune system. The exact causes for this is unknown, but genetic factors are believed to play at least some role. It is about 7 times more likely to happen in women than men.

Grave’s disease, also known as toxic diffuse goiter, is the most common cause for hyperthyroidism. Similar to Hashitomoto’s thyroiditis, Grave’s disease is also caused by attacks on the thyroid gland by our own immune system, but the result is increased production of thyroid hormones instead of decreased production as in Hashitomoto’s thyroiditis. Grave’s disease is also considerably more common in women than men.

In people with normal thyroid hormone levels, having high levels of anti-TPO antibodies in the blood can be a sign of increased risk of developing thyroid problems in the future.

In short, it is useful to analyse anti-TPO antibody levels in the blood to:

  • Detect Hashitomoto’s thyroiditis

  • Detect Grave’s disease

  • Determine the cause of thyroid problems

  • Assessing the risk of developing thyroid problems


The level of anti-TPO antibodies in the blood that is considered to be “positive” can be different depending on the laboratory and technique used. Doctors usually also take into account a number of factors when evaluating anti-TPO antibody values.

The anti-TPO antibody test offered by Melio gives you two types of results; a qualitative (positive/negative) anti-TPO Antibody Status, and a quantitative one (the exact level of antibodies). 

A negative anti-TPO antibody test is considered normal. You may still have some anti-TPO antibodies present in the blood even with a negative result, but the level is so low that it is unlikely to be associated with any disease conditions.

A positive anti-TPO antibody test may be associated with:

  • Hashitomoto’s thyroiditis and under active thyroid (hypothyroidism)

  • Grave’s disease and overactive thyroid (hyperthyroidism)

  • Higher risk of developing thyroid problems

Other Considerations

Not everyone with thyroid disease has a high level of anti-TPO antibodies, and many people with increased levels of anti-TPO antibodies do not have thyroid disease. It is therefore important to also take into account the levels of thyroid hormones and clinical symptoms in the evaluation.

Taking high levels of biotin (vitamin B7) supplement can affect the readings from your TPO test, giving you a falsely high value.

Tests that include this marker


Laboratory assessment of thyroid function. Douglas S Ross, MD. UpToDate Nov 07, 2017

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