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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:
- 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
Medically reviewed by John A. Seibel, MD; Board Certified Internal Medicine with a subspecialty in Endocrinology & Metabolism
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Hashimoto's ThyroiditisHashimoto's thyroiditis is the most common cause of hypothyroidism in the US. This conditions is caused by inflammation of the thyroid gland. Symptoms may include:
- weight gain,
- cold intolerance,
- excessive sleepiness,
- dry or coarse hair,
- difficulty swallowing,
- a lump in the front of the throat, and
- many more.
Hyperthyroidism is an excess of thyroid hormone resulting from an overactive thyroid gland. Symptoms can include
- increased heart rate,
- weight loss,
- frequent bowel movements,
- depression, and
- cognitive slowing.
Treatment is by medication, the use of radioactive iodine, thyroid surgery, or reducing the dose of thyroid hormone.
Hyperthyroidism SlidesWhat is hyperthyroidism? Hyperthyroidism occurs when an overactive thyroid gland produces an excessive amount of thyroid hormones. 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
- memory loss,
- hair loss, and
There are a variety of causes of hypothyroidism, and treatment depends on the cause.
Rheumatoid ArthritisRheumatoid 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.
Sjogren's SyndromeSjögren's syndrome is an autoimmune disease involving the abnormal production of extra antibodies that attack the glands and connective tissue. Sjögren's syndrome with gland inflammation (resulting dry eyes and mouth, etc.) that is not associated with another connective tissue disease is referred to as primary Sjögren's syndrome. Sjögren's syndrome that is also associated with a connective tissue disease, such as rheumatoid arthritis, systemic lupus erythematosus, or scleroderma, is referred to as secondary Sjögren's syndrome. Though there is no cure for Sjögren's syndrome, the symptoms may be treated by using lubricating eye ointments, drinking plenty of water, humidifying the air, and using glycerin swabs. Medications are also available to treat dry eye and dry mouth.
Systemic LupusSystemic 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).
Thyroid Blood TestsThyroid 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.
Thyroid DisordersThere are several types of thyroid disorders including hypothyroidism, hyperthyroidism, goiters, thyroid nodules, and thyroid cancer. Symptoms vary by condition. Diagnosis is made with blood tests, scans, ultrasound, or biopsy. Treatments depend on the disorder and can include medication or surgery.
Thyroid NodulesThyroid nodules are the most common endocrine problem in the United States. The term "thyroid nodule" refers to any abnormal growth that forms a lump in the thyroid gland. The vast majority of thyroid nodules are benign.
Illustrations of ThyroidThe thyroid is a butterfly-shaped gland located in the front of the neck just below the Adams apple. See a picture of the Thyroid and learn more about the health topic.
Thyroid SlideshowLearn about thyroid problems such as hyperthyroidism, hypothyroidism, thyroid cancer, and more. Discover symptoms and treatments for various thyroid problems.
Thyroid ScanThyroid scanning is used to determine how active the thyroid is in manufacturing thyroid hormone. This can determine whether inflammation of the thyroid gland (thyroiditis) is present. It can also detect the presence and degree of overactivity of the gland (hyperthyroidism) or, conversely, it can determine the presence and degree of underactivity of the gland (hypothyroidism).