Thyroid peroxidase (TPO) is an enzyme made in the thyroid gland that is important in the production of thyroid hormones. TPO is found in thyroid follicle cells, where it converts the thyroid hormone T4 to the thyroid hormone T3.
TPO also facilitates the binding of iodine to proteins within the thyroid gland, a process essential for synthesizing thyroid hormones T4 and T3.
The thyroid gland is located in the lower part of the neck, below the Adam's apple, wrapped around the trachea (windpipe).
In autoimmune thyroid diseases such as Hashimoto's thyroiditis and Graves' disease, the body produces antibodies against thyroid peroxidase (TPOAb). These antibodies can interfere with the normal activity of TPO, resulting in disrupted thyroid hormone production and thyroid dysfunction.
The thyroid peroxidase test is a test that measures the level of an antibody that is directed against thyroid peroxidase (TPO).
Autoantibodies to thyroid peroxidase (TPOAb) are produced within the body. The presence of TPOAb in the blood reflects a prior attack on the thyroid tissue by the body's immune system.
A TPO test can help evaluate the functionality of the thyroid gland and detect disorders related to the thyroid gland or thyroid hormones. Thyroid hormones play a vital role in various bodily processes such as metabolism, development, growth, and fertility .
The presence of TPOAb indicates the presence of autoimmune thyroid diseases, including:
Both hypothyroidism and hyperthyroidism can disrupt bodily functions and result in fatigue, weight changes, mood swings and affect fertility and pregnancy. It is advised to undergo TPO tests before or during pregnancy to detect thyroid diseases that can negatively affect both the mother and the unborn child. A TPO test can also help monitor the progression of the condition.
Most people with chronic thyroiditis (Hashimoto’s disease or Graves’ disease) display a positive TPO test. The test is also positive in lesser numbers of people with other thyroid diseases.
Other autoimmune disorders that may cause a positive TPOAb test include:
About 3% of people with elevated TPO antibodies show no evidence of disease. The chance of having a positive TPOAb test is greater in females and increases with age.
When thyroid peroxidase antibodies (TPOAb) are high, it typically indicates that your immune system is mistakenly attacking your thyroid gland, which can lead to thyroid issues. This is common in conditions such as Hashimoto's thyroiditis, in which the thyroid becomes underactive, and Graves' disease, in which it becomes overactive.
High TPOAb levels assist clinicians in diagnosing and monitoring the progression of various autoimmune thyroid diseases. It can also signify other autoimmune illnesses and possible thyroid difficulties during pregnancy. Elevated TPOAb levels indicate that more testing and monitoring may be required to successfully manage thyroid function.
The typical range for thyroid peroxidase antibodies (TPOAb) is less than 34 international units per milliliter (IU/mL). A TPOAb level below this threshold is considered normal, indicating no significant autoimmune activity against your thyroid.
If the level is higher than 34 IU/mL, it suggests the existence of these antibodies, which may indicate an autoimmune thyroid illness such as Hashimoto's thyroiditis or Graves' disease. Elevated TPOAb levels indicate that your immune system is attacking your thyroid gland, which may affect its function.
Having TPOAb levels within the normal range, typically less than 34 IU/mL, is considered optimal and is often not associated with autoimmune thyroid disease.
Low or undetectable TPOAb levels are typically not a cause for concern, indicating minimal autoimmune activity against the thyroid gland and suggesting a lower risk of autoimmune thyroid disorders.
A positive TPO result indicates that your blood test has detected high amounts of thyroid peroxidase antibodies. This means that your immune system is attacking your thyroid gland, which is said to be an autoimmune thyroid condition. A positive TPO result is commonly associated with Hashimoto's thyroiditis (which can lead to an underactive thyroid) and Graves' disease (which can cause an overactive thyroid).
A positive result helps doctors diagnose these conditions and determine the appropriate treatment plan for managing your thyroid health.
This test goes by a confusing number of names, including:
"Laboratory assessment of thyroid function"
Thyroid Peroxidase. Science Direct. Accessed July 22, 2024. https://www.sciencedirect.com/topics/medicine-and-dentistry/thyroid-peroxidase
Thyroid Antibodies. Medline Plus. Accessed July 22, 2024. https://medlineplus.gov/lab-tests/thyroid-antibodies/
Thyroid Disease and Pregnancy. American Thyroid Association. Accessed July 22, 2024. https://www.thyroid.org/patient-thyroid-information/ct-for-patients/october-2019/vol-12-issue-10-p-12-13/
Alhubaish ES, Alibrahim NT, Mansour AA. The Clinical Implications of Anti-thyroid Peroxidase Antibodies in Graves' Disease in Basrah. National Library of Medicine. Accessed July 22, 2024. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10133893/
Hyperthyroidism is an excess of thyroid hormone due to an overactive thyroid gland. Symptoms can include increased heart rate, weight loss, heart palpitations, frequent bowel movements, depression, fatigue, fine or brittle hair, sleep problems, thinning skin, and irregular vaginal bleeding. Graves' disease is the most common cause of hyperthyroidism. Many other health problems or taking excess thyroid hormone medication can cause an overactive thyroid gland. Treatment for the condition is with medication, radioactive iodine, thyroid surgery (rarely), or reducing the dose of thyroid hormone. No diet has been shown to treat hyperthyroidism or its symptoms and signs.
What are the symptoms of hyperthyroidism? What causes hyperthyroidism? What happens when you take thyroid medication? Hyperthyroidism occurs when an overactive thyroid gland produces an excessive amount of thyroid hormone. Learn hyperthyroidism causes, symptoms, and treatment.
Hypothyroidism is any state in which thyroid hormone production is below normal. Normally, the rate of thyroid hormone production is controlled by the brain by the pituitary gland. Hypothyroidism is a very common condition and the symptoms of hypothyroidism are often subtle but may include constipation, memory loss, hair loss, and depression. There are a variety of causes of hypothyroidism, and treatment depends on the cause.
Pernicious anemia is a blood disorder in which the body does not make enough red blood cells due to a lack of vitamin B12 in the blood. Pernicious anemia can develop from a lack of a protein that helps the body absorb vitamin B12, not getting enough B12 in the diet, and certain intestinal conditions that interfere with the absorption of vitamin B12 such as Crohn's disease, celiac sprue, or ulcerative colitis. There is no cure for pernicious anemia, thus treatment is life-long.
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Lupus is a condition characterized by chronic inflammation of body tissues caused by autoimmune disease. Lupus can cause disease of the skin, heart, lungs, kidneys, joints, and nervous system. When internal organs are involved, the condition is called systemic lupus erythematosus (SLE). When only the skin is involved, the condition is called discoid lupus.
Thyroid blood tests determine the adequacy of the levels of thyroid hormones in in a patient. The blood tests can determine if the thyroid gland's hormone production is normal, overactive, or underactive. The level of thyroid hormones may help to diagnose hypothyroidism or hyperthyroidism. The test may also point to other diseases of conditions of the thyroid gland.
There are four major types of thyroid cancer: papillary, follicular, medullary, and anaplastic thyroid cancer. Tumors on the thyroid are referred to as thyroid nodules. Symptoms of thyroid cancer include swollen lymph nodes, pain in the throat, difficulty swallowing, hoarseness, and a lump near the Adam's apple. Treatment usually involves chemotherapy, surgery, radioactive iodine, hormone treatment or external radiation and depends upon the type of thyroid cancer, the patient's age, the tumor size, and whether the cancer has metastasized.
Thyroid diseases and disorders are caused because the body either makes too much or too little thyroid hormones, which are necessary for vital functions of the body. Thyroid disease and disorder symptoms and signs depend on the type of thyroid problem. Examples include heat or cold intolerance, sweating, weight loss or gain, palpitations, fatigue, dry skin, constipation, brittle hair, joint aches and pains, heart palpitations, edema, feeling bloated, puffiness in the face, reduced menstrual flow, changes in the frequency of bowel movements and habits, high cholesterol, hoarseness, brittle hair, difficulty swallowing, shortness of breath, a visible lump or swelling in the neck, tremors, memory problems, depression, nervousness, agitation, irritability, or poor concentration. Thyroid problems are more common in women.
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