BACK TOTOP Browse A-ZSearchBrowse A-ZABCDEFGHIJKLMNOPQRSTUVWXYZ0-9 E-mail FormEmail ResultsName:Email address:Recipients Name:Recipients address:Message: Print-FriendlyBookmarksbookmarks-menuThyroid peroxidase antibodyThyroid antimicrosomal antibody; Antimicrosomal antibody; Microsomal antibody; Antithyroid microsomal antibody; TPOAb; Anti-TPO antibodyThyroid peroxidase is a type of protein (called an enzyme) that cells in the thyroid gland use to make thyroid hormone. If these enzymes leak out into the bloodstream (as when thyroid cells are damaged) the immune system makes antibodies against these proteins. The thyroid peroxidase antibody test measures these antibodies in the blood.EnzymeEnzymes are complex proteins that cause a specific chemical change. For example, they can help break down the foods we eat so the body can use them....Read Article Now Book Mark Article AntibodiesAn antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. Examples of antigens include micr...ImageRead Article Now Book Mark Article How the Test is Performed A blood sample is needed. Blood sampleVenipuncture is the collection of blood from a vein. It is most often done for laboratory testing.ImageRead Article Now Book Mark Article How the Test will Feel When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away. Why the Test is Performed This test is done to confirm the cause of thyroid problems, including Hashimoto thyroiditis.Hashimoto thyroiditisChronic thyroiditis is caused by a reaction of the immune system against the thyroid gland. It often results in reduced thyroid function (hypothyroi...ImageRead Article Now Book Mark Article The test is also used to find out if an immune or autoimmune disorder is damaging the thyroid.Autoimmune disorderAn autoimmune disorder occurs when the body's immune system attacks and destroys healthy body tissue by mistake. There are more than 80 autoimmune d...ImageRead Article Now Book Mark Article Normal Results A negative test means the result is normal.Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your health care provider about the meaning of your specific test results. What Abnormal Results Mean A positive test may be due to:Granulomatous or subacute thyroiditis (an immune reaction of the thyroid gland that often follows an upper respiratory infection) Granulomatous or subacute thyroiditisSubacute thyroiditis is an immune reaction of the thyroid gland that often follows an upper respiratory infection. The thyroid gland is located in th...ImageRead Article Now Book Mark Article Hashimoto thyroiditis (a reaction of the immune system against the thyroid gland)High levels of these antibodies have also been linked with an increased risk of:Miscarriage Preeclampsia (high blood pressure and protein in the urine after the 20th week of pregnancy) PreeclampsiaPreeclampsia is high blood pressure and signs of liver or kidney damage that occur in women after the 20th week of pregnancy. While it is rare, pree...ImageRead Article Now Book Mark Article Premature birth In vitro fertilization failure In vitro fertilizationIn vitro fertilization (IVF) is the joining of a woman's egg and a man's sperm in a laboratory dish. In vitro means outside the body. Fertilization...Read Article Now Book Mark Article Important: A positive result does not always mean that you have a thyroid condition or that you need treatment for your thyroid. A positive result may mean that you have a higher chance of developing thyroid disease in the future. This is often associated with a family history of thyroid disease.Antithyroid microsomal antibodies may be seen in your blood if you have other autoimmune conditions, including:Autoimmune hemolytic anemia Autoimmune hemolytic anemiaAnemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to the body's tissues. Red bloo...ImageRead Article Now Book Mark Article Autoimmune hepatitis Autoimmune hepatitisAutoimmune hepatitis causes inflammation of the liver. It occurs when immune cells mistake the liver's normal cells for harmful invaders and attack ...ImageRead Article Now Book Mark Article Autoimmune adrenal disease Rheumatoid arthritis Rheumatoid arthritisRheumatoid arthritis (RA) is a disease that leads to inflammation of the joints and surrounding tissues. It is a long-term disease. It can also aff...ImageRead Article Now Book Mark Article Sjögren syndrome Sjögren syndromeSjögren syndrome is an autoimmune disorder in which the glands that produce tears and saliva are destroyed. This causes dry mouth and dry eyes. The...ImageRead Article Now Book Mark Article Systemic lupus erythematosusSystemic lupus erythematosusSystemic lupus erythematosus (SLE) is an autoimmune disease. In this disease, the immune system of the body mistakenly attacks healthy tissue. It c...ImageRead Article Now Book Mark Article Risks There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.Other risks associated with having blood drawn are slight, but may include:Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma (blood buildup under the skin) HematomaA bruise is an area of skin discoloration. A bruise occurs when small blood vessels break and leak their contents into the soft tissue beneath the s...ImageRead Article Now Book Mark Article Infection (a slight risk any time the skin is broken)Open ReferencesReferencesBrent GA, Weetman AP. Hypothyroidism and thyroiditis. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 13.Guber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Pearce EN, Hollenberg AN. Thyroid. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 207.Ramos-Levi AM, Marazuela M. Thyroiditis. In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 73.Smith JR, Wassner AJ. Thyroiditis. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 604.AllVideoImagesTogBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustrationBlood test - illustration Blood is drawn from a vein (venipuncture), usually from the inside of the elbow or the back of the hand. A needle is inserted into the vein, and the blood is collected in an air-tight vial or a syringe. Preparation may vary depending on the specific test.Blood testillustrationA Closer Look Hypothyroidism - InDepth(In-Depth) Tests for Thyroid peroxidase antibody Thyroid peroxidase antibodyRelated Information Antibody(Special Topic)Autoimmune disorders(Condition)Chronic thyroiditis (Hashimoto disease)(Condition)Subacute thyroiditis(Condition)Simple goiter(Condition)Rheumatoid arthritis(Condition)Sjogren syndrome(Condition)Systemic lupus erythematosus(Condition)Cancer(Condition)Autoimmune hepatitis(Condition)Rheumatoid arthritis - InDepth(In-Depth)Systemic lupus erythematosus - InDepth(In-Depth) Review Date: 2/28/2024 Reviewed By: Sandeep K. Dhaliwal, MD, board-certified in Diabetes, Endocrinology, and Metabolism, Springfield, VA. Also reviewed by David C. Dugdale, MD, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team. The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed medical professional should be consulted for diagnosis and treatment of any and all medical conditions. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. No warranty of any kind, either expressed or implied, is made as to the accuracy, reliability, timeliness, or correctness of any translations made by a third-party service of the information provided herein into any other language. © 1997- A.D.A.M., a business unit of Ebix, Inc. Any duplication or distribution of the information contained herein is strictly prohibited. © 1997- All rights reserved. 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Thyroid peroxidase antibodyThyroid antimicrosomal antibody; Antimicrosomal antibody; Microsomal antibody; Antithyroid microsomal antibody; TPOAb; Anti-TPO antibodyThyroid peroxidase is a type of protein (called an enzyme) that cells in the thyroid gland use to make thyroid hormone. If these enzymes leak out into the bloodstream (as when thyroid cells are damaged) the immune system makes antibodies against these proteins. The thyroid peroxidase antibody test measures these antibodies in the blood.EnzymeEnzymes are complex proteins that cause a specific chemical change. For example, they can help break down the foods we eat so the body can use them....Read Article Now Book Mark Article AntibodiesAn antibody is a protein produced by the body's immune system when it detects harmful substances, called antigens. Examples of antigens include micr...ImageRead Article Now Book Mark Article How the Test is Performed A blood sample is needed. Blood sampleVenipuncture is the collection of blood from a vein. It is most often done for laboratory testing.ImageRead Article Now Book Mark Article How the Test will Feel When the needle is inserted to draw blood, some people feel moderate pain. Others feel only a prick or stinging. Afterward, there may be some throbbing or a slight bruise. This soon goes away. Why the Test is Performed This test is done to confirm the cause of thyroid problems, including Hashimoto thyroiditis.Hashimoto thyroiditisChronic thyroiditis is caused by a reaction of the immune system against the thyroid gland. It often results in reduced thyroid function (hypothyroi...ImageRead Article Now Book Mark Article The test is also used to find out if an immune or autoimmune disorder is damaging the thyroid.Autoimmune disorderAn autoimmune disorder occurs when the body's immune system attacks and destroys healthy body tissue by mistake. There are more than 80 autoimmune d...ImageRead Article Now Book Mark Article Normal Results A negative test means the result is normal.Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or may test different specimens. Talk to your health care provider about the meaning of your specific test results. What Abnormal Results Mean A positive test may be due to:Granulomatous or subacute thyroiditis (an immune reaction of the thyroid gland that often follows an upper respiratory infection) Granulomatous or subacute thyroiditisSubacute thyroiditis is an immune reaction of the thyroid gland that often follows an upper respiratory infection. The thyroid gland is located in th...ImageRead Article Now Book Mark Article Hashimoto thyroiditis (a reaction of the immune system against the thyroid gland)High levels of these antibodies have also been linked with an increased risk of:Miscarriage Preeclampsia (high blood pressure and protein in the urine after the 20th week of pregnancy) PreeclampsiaPreeclampsia is high blood pressure and signs of liver or kidney damage that occur in women after the 20th week of pregnancy. While it is rare, pree...ImageRead Article Now Book Mark Article Premature birth In vitro fertilization failure In vitro fertilizationIn vitro fertilization (IVF) is the joining of a woman's egg and a man's sperm in a laboratory dish. In vitro means outside the body. Fertilization...Read Article Now Book Mark Article Important: A positive result does not always mean that you have a thyroid condition or that you need treatment for your thyroid. A positive result may mean that you have a higher chance of developing thyroid disease in the future. This is often associated with a family history of thyroid disease.Antithyroid microsomal antibodies may be seen in your blood if you have other autoimmune conditions, including:Autoimmune hemolytic anemia Autoimmune hemolytic anemiaAnemia is a condition in which the body does not have enough healthy red blood cells. Red blood cells provide oxygen to the body's tissues. Red bloo...ImageRead Article Now Book Mark Article Autoimmune hepatitis Autoimmune hepatitisAutoimmune hepatitis causes inflammation of the liver. It occurs when immune cells mistake the liver's normal cells for harmful invaders and attack ...ImageRead Article Now Book Mark Article Autoimmune adrenal disease Rheumatoid arthritis Rheumatoid arthritisRheumatoid arthritis (RA) is a disease that leads to inflammation of the joints and surrounding tissues. It is a long-term disease. It can also aff...ImageRead Article Now Book Mark Article Sjögren syndrome Sjögren syndromeSjögren syndrome is an autoimmune disorder in which the glands that produce tears and saliva are destroyed. This causes dry mouth and dry eyes. The...ImageRead Article Now Book Mark Article Systemic lupus erythematosusSystemic lupus erythematosusSystemic lupus erythematosus (SLE) is an autoimmune disease. In this disease, the immune system of the body mistakenly attacks healthy tissue. It c...ImageRead Article Now Book Mark Article Risks There is little risk involved with having your blood taken. Veins and arteries vary in size from one person to another and from one side of the body to the other. Obtaining a blood sample from some people may be more difficult than from others.Other risks associated with having blood drawn are slight, but may include:Excessive bleeding Fainting or feeling lightheaded Multiple punctures to locate veins Hematoma (blood buildup under the skin) HematomaA bruise is an area of skin discoloration. A bruise occurs when small blood vessels break and leak their contents into the soft tissue beneath the s...ImageRead Article Now Book Mark Article Infection (a slight risk any time the skin is broken)Open ReferencesReferencesBrent GA, Weetman AP. Hypothyroidism and thyroiditis. In: Melmed S, Auchus RJ, Goldfine AB, Koenig RJ, Rosen CJ, eds. Williams Textbook of Endocrinology. 14th ed. Philadelphia, PA: Elsevier; 2020:chap 13.Guber HA, Oprea M, Russell YX. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 24th ed. Philadelphia, PA: Elsevier; 2022:chap 25.Pearce EN, Hollenberg AN. Thyroid. In: Goldman L, Cooney KA, eds. Goldman-Cecil Medicine. 27th ed. Philadelphia, PA: Elsevier; 2024:chap 207.Ramos-Levi AM, Marazuela M. Thyroiditis. In: Robertson RP, ed. DeGroot's Endocrinology. 8th ed. Philadelphia, PA: Elsevier; 2023:chap 73.Smith JR, Wassner AJ. Thyroiditis. In: Kliegman RM, St. Geme JW, Blum NJ, et al, eds. Nelson Textbook of Pediatrics. 22nd ed. Philadelphia, PA: Elsevier; 2025:chap 604.