What is thyroid peroxidase?
Thyroid peroxidase (TPO) is an enzyme made in the thyroid gland that is important in the production of thyroid hormone. TPO is found in thyroid follicle cells where it converts the thyroid hormone T4 to T3.
The thyroid gland is located in the lower part of the neck, below the Adam's apple, wrapped around the trachea (windpipe).
What is the thyroid peroxidase test?
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.
What does a positive thyroid peroxidase test mean?
- Most people with chronic thyroiditis 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:
- Sjogren's syndrome,
- lupus,
- rheumatoid arthritis, and
- pernicious anemia.
- About 3% of people with a positive TPOAb test show no evidence of disease.
- The chance of having a positive TPOAb test is greater in females and increases with age.
What are other names for thyroid peroxidase test?
This test goes by a confusing number of names, including:
- thyroid peroxidase (TPO) antibody (TPOAb) test,
- thyroid peroxidase autoantibody test,
- antimicrosomal antibody test, and
- antithyroid microsomal antibody test.
Previous contributing author: Frederick Hecht, MD, FAAP
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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.
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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.
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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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Rheumatoid arthritis (RA) is an autoimmune disease that causes chronic inflammation of the joints, the tissue around the joints, as well as other organs in the body. Because it can affect multiple other organs of the body, rheumatoid arthritis is referred to as a systemic illness and is sometimes called rheumatoid disease. The 16 characteristic early RA signs and symptoms include the following.- Anemia
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Systemic lupus erythematosus 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 only the skin is involved, the condition is called discoid lupus. When internal organs are involved, the condition is called systemic lupus erythematosus (SLE).
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