TPO Antibodies

Thyroid peroxidase (TPO) antibodies are a type of thyroid antibody. Thyroid antibodies can form in autoimmune thyroid disease. The body wrongly identifies thyroid cells and tissues as non-self. This means that our body sees our own cells and tissues as foreign, and attacks them.

The two main autoimmune thyroid diseases are Grave’s disease and Hashimoto’s thyroiditis. 1 Thyroid peroxidase antibodies are also called anti-TPO antibodies or TPO antibodies. You can read more about thyroid peroxidase antibodies in this article and find more general information about the thyroid in Ada's thyroid guide.

Thyroid peroxidase (TPO) antibodies are a type of thyroid antibody. Thyroid peroxidase is an enzyme which helps to make thyroid hormones (T3, T4 and TSH). 2 The body’s immune system makes antibodies in response to non-self proteins. These non-self proteins are called antigens. Making antibodies is important to protect us from diseases. However, sometimes the immune system identifies our own proteins as non-self, making autoantibodies. 3

The immune system then attacks our own body proteins in error. This is known as an autoimmune disease. Thyroid antibodies develop when the immune system identifies our own thyroid cells and tissues as non-self. This can cause inflammation and affect thyroid function. 1

Thyroglobulin antibodies (Tg Ab) are another type of thyroid antibody. Thyroglobulin is a protein made by thyroid cells. It helps to make thyroid hormones. Thyroglobulin antibodies (Tg Ab) are made when the body attacks its own thyroglobulin. Thyroglobulin antibodies can be raised in Hashimoto’s thyroiditis. They are also raised in 10-15% of the general population. 1

Normal TPO antibodies range is less than 30 international units per millimeter (IU/ml). 4 Thyroid peroxidase antibodies are considered high if above this. Note that the normal range used can differ in different laboratories. It is not possible for the thyroid peroxidase antibodies to be too low. 5

Autoimmune thyroid disorders cause high thyroid peroxidase antibodies. 2 The two main autoimmune thyroid disorders are Grave’s disease and Hashimoto’s thyroiditis.

Anti-TPO antibodies are present in:

• 80-95% of cases of Hashimoto’s thyroiditis
• 65-80% of cases of Grave’s disease
• 10-20% of cases of thyroid cancer. 1 2 4

10-15% of people with no thyroid disorder can have raised TPO antibodies. 1 4 High TPO antibodies may increase the risk of developing a thyroid disorder in the future. 2

Thyroid peroxidase and thyroglobulin antibodies are two different types of thyroid antibodies. The body needs thyroglobulin and thyroid peroxidase to make thyroid hormones. Both types of thyroid antibodies are often raised in autoimmune thyroid disorders. Raised thyroid peroxidase antibodies are found in a higher percentage of people with autoimmune thyroid diseases. 1

High TPO antibodies do not necessarily mean cancer. TPO antibodies are raised in 1-20% of people who have thyroid cancer and they can be raised in healthy people. 4 The main symptom of thyroid cancer is a painless neck lump. 6 It is important to speak to your doctor if you think you have thyroid cancer or any other thyroid disease.

You can read more about the symptoms of thyroiditis and hyperthyroidism on Ada's website.

At a population level, having a raised TPO antibody level alone doesn’t increase your risk of developing thyroid cancer. 6 A raised TPO antibody level should be considered together with other blood tests and clinical assessments. The meaning of a raised TPO antibody test in isolation is difficult to interpret and additional investigations may be needed.

There is some limited evidence that selenium supplementation can reduce anti-TPO antibodies. 2 More research in this area is needed. 7 The role of vitamin D supplementation in reducing TPO antibodies is being considered. Currently, there is not enough evidence to support this claim. 8 9 10