A thyroglobulin antibody (TgAb) test looks for the presence of certain antibodies that attack the thyroid.

To conduct a TgAb test, a healthcare professional will take a blood sample and send it to a laboratory for evaluation. The results can inform a doctor if a person has an elevated level of thyroglobulin antibodies, which could indicate autoimmune diseases or cancer.

This article reviews the TgAb test, what to expect, what the results could mean, and more.

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The thyroid is a small gland located in the neck. It releases hormones that impact various bodily functions, including helping with metabolism. It creates proteins, such as thyroglobulin, that help to create thyroid hormones.

Autoimmune disorders can disrupt the production of thyroglobulin. Autoimmune disorders occur when the immune system attacks healthy cells with antibodies.

When the immune system attacks the thyroid, it typically targets thyroglobulin. In doing so, the immune system creates thyroglobulin antibodies.

A TgAb test checks the level of these antibodies in a person’s blood. A high level may suggest that a person has an autoimmune disorder that affects the thyroid.

However, a doctor may order other tests to check for autoimmune disorders. They may use a thyroglobulin test to help diagnose differentiated thyroid cancer.

Learn more about the thyroid gland.

The TgAb test checks for the presence of thyroglobulin antibodies. These antibodies can suggest the presence of an autoimmune disease that targets the thyroid, thyroid cancer, or other damage to the thyroid.

A doctor may order the test to check for the presence of Graves’ disease or Hashimoto’s thyroiditis. According to a 2019 study, TgAb levels may correspond to Hashimoto’s thyroiditis symptom severity. However, other tests can also help diagnose these conditions.

A 2018 study notes that TgAb tests are less effective than tests checking thyroid peroxidase antibodies in predicting thyroid dysfunction. However, they noted that doctors might use the test to check for thyroid cancers.

Learn about common thyroid disorders.

A TgAb requires a blood sample. A person will need to attend a doctor’s office, hospital, or another dedicated facility so a healthcare professional can draw some blood.

Before the test

A person may not need to do anything special to prepare for the test. However, they should check with a doctor about taking their medications, eating and drinking before the blood test. The doctor may recommend fasting or stopping certain medications.

During the test

A healthcare professional will clean an area of the arm with an alcohol swab. Once cleaned, they will insert the needle into a vein and draw a small amount of blood into a tube or vial.

The healthcare professional will likely apply a small amount of pressure to the injection site and check for bleeding. They will then use tape and cotton wool to cover the injection site before sending the sample to a laboratory for analysis.

After the test

The test results typically go to the doctor or hospital that ordered the test. A person should talk with a doctor about accessing their results.

The test results may take a few days. A person may need to contact their doctor’s office to access the results.

The results of a TgAb test will show if a person has elevated levels of thyroglobulin antibodies. While this may suggest an autoimmune disorder, it could indicate other conditions, such as thyroid cancer.

A person should review their test results with a doctor. The doctor can recommend the next steps and additional testing if needed.

Learn more about blood tests.

Blood tests are generally safe and noninvasive, but they carry a small risk of complications. A person may feel slight pain or discomfort when the needle penetrates the skin.

Other possible side effects could include:

  • bruising at the injection site
  • fainting or dizziness
  • infection at the injection site
  • development of a hematoma, which is a blood clot under the skin
  • bleeding

A positive test result means a person has elevated levels of TgAb, which can indicate the following issues:

  • damage to the thyroid
  • an autoimmune disorder, such as Hashimoto’s disease
  • thyroid cancer

A doctor may recommend additional testing to help diagnose certain conditions.

Below are some common thyroid issues. Treating the conditions can help improve a person’s quality of life and help prevent additional health issues.

Underactive thyroid

Also known as hypothyroidism, an underactive thyroid means the gland does not produce enough thyroid hormones to meet the body’s needs. Doctors often prescribe levothyroxine to replace the hormones that the thyroid typically produces.

Learn more about levothyroxine.

Overactive thyroid

Also known as hyperthyroidism, an overactive thyroid produces too many thyroid hormones. This can speed up several different functions in the body. Treatment may include medications or surgical procedures.

Treatment for hyperthyroidism varies based on a person’s age, other health conditions, surgeon access, and possible medication allergies.

Learn more about hyperthyroidism.

Chronic thyroiditis

Chronic thyroiditis is also known as Hashimoto’s thyroiditis. It is an autoimmune disorder that causes inflammation of the thyroid. Treatments can vary, but most people with the condition will need levothyroxine medication for the rest of their lives.

Learn about the best diets for Hashimoto’s thyroiditis.

Subacute thyroiditis

Subacute thyroiditis is an inflammatory condition that affects the thyroid, causing pain and swelling. In some cases, a person may not need treatment. Others may need over-the-counter or prescription-strength pain medications to help with inflammation.

The following sections provide answers to common questions about TgAb testing.

What does it mean if thyroglobulin antibody levels are high?

A high level of thyroglobulin antibodies can suggest:

  • damage to the thyroid
  • presence of an autoimmune condition that affects the thyroid
  • thyroid cancer

Does the presence of thyroglobulin antibodies mean cancer?

According to a 2018 study, high thyroglobulin antibody levels can indicate cancer and be useful in diagnosis. However, other conditions can also cause high levels, so a doctor will likely need to order additional testing to help rule out other causes.

A TgAb test checks for the presence of thyroglobulin antibodies. A person will need to provide a small blood sample for analysis in a laboratory.

If the results show elevated levels of thyroglobulin antibodies, it may indicate several conditions that affect the thyroid, including autoimmune conditions and thyroid cancer.

A person should talk with a doctor about their results. A doctor may recommend further testing and various treatment options.