Antithyroid peroxidase: what é and why can it be high

Anti-thyroid peroxidase (anti-TPO) is an antibody produced by the immune system that attacks the thyroid gland, resulting in a change in the levels of hormones produced by the thyroid. Anti-TPO values vary from laboratory to laboratory, with increased values usually indicative of autoimmune diseases.

However, the amount of this thyroid autoantibody can increase in several situations, so it is important that the diagnosis is made taking into account the results of other thyroid-related tests, such as other thyroid autoantibodies and TSH, T3 dosage and T4. Know the tests that are indicated to evaluate the thyroid.

High Antithyroid Peroxidase

Increased levels of antithyroid peroxidase (anti-TPO) are usually indicative of autoimmune thyroid diseases, such as Hashimoto's Thyroiditis and Graves' Disease, for example, however it may be increased in other situations, such as pregnancy and hypothyroidism. The main causes of increased thyroid antiperoxidase are:

1. Hashimoto's Thyroiditis

Hashimoto's thyroiditis is an autoimmune disease in which the immune system attacks the thyroid, dysregulating the production of thyroid hormones and resulting in symptoms of hypothyroidism, such as excessive tiredness, weight gain, muscle pain and thinning of the hair and nails.

Hashimoto's thyroiditis is one of the main causes of increased thyroid antiperoxidase, however further tests are needed to complete the diagnosis. Understand what Hashimoto's thyroiditis is, symptoms and how to treat it.

2. Graves' Disease

Graves disease is one of the main situations in which thyroid antiperoxidase is high and it happens because this autoantibody acts directly on the thyroid and stimulates the production of hormones, resulting in characteristic symptoms of the disease, such as headache, eyes eyes, weight loss, sweating, muscle weakness and swelling in the throat, for example.

It is important that Graves' disease is identified and treated correctly to relieve symptoms, and the treatment is indicated by the doctor according to the severity of the disease, and the use of medication, iodine therapy or thyroid surgery may be recommended. Learn more about Graves' disease and how it is treated.

3. Pregnancy

Due to hormonal changes common in pregnancy, it is possible that there are also alterations related to the thyroid gland, including increased levels of thyroid antiperoxidase in the blood.

Nevertheless, pregnant women do not necessarily have thyroid changes. Therefore, it is important to measure anti-TPO in early pregnancy so that the doctor can monitor the levels during pregnancy and check the risk of developing thyroiditis after childbirth, for example.

4. Subclinical hypothyroidism

Subclinical hypothyroidism is characterized by a decrease in thyroid gland activity that does not generate symptoms and is only noticed through blood tests, in which normal T4 levels and an increase in TSH are verified.

Although anti-TPO measurement is not normally indicated for the diagnosis of subclinical hypothyroidism, the doctor may order this test to assess the progression of hypothyroidism and verify that the person is responding well to treatment. This is possible because this antibody acts directly on the enzyme that regulates the production of thyroid hormones. Thus, when measuring thyroid antiperoxidase in subclinical hypothyroidism, it is possible to verify whether the decrease in the amount of anti-TPO accompanies the regularization of TSH levels in the blood.

Learn how to recognize and treat hypothyroidism.

5. Family history

People who have relatives with autoimmune thyroid diseases may have altered levels of antithyroid peroxidase antibody, which is not indicative that they also have the disease. Therefore, it is important that the value of anti-TPO is evaluated together with the other tests requested by the doctor.