Thyroid Function Tests

Thyroid function tests

Thyroid function tests are used to check whether your thyroid is working normally.

The most common thyroid function tests are:

  1. Total T4 (the free hormone and the hormone bound to carrier proteins)
  2. Free T4 (the main thyroid hormone in your blood -- a precursor for T3)
  3. TSH (the hormone from the pituitary gland that stimulates the thyroid to produce T4)
  4. T3 (the active form of the hormone -- T4 is converted to T3)
  5. Free T3

Other thyroid tests include:

  1. Thyroid peroxidase antibodies (aTPO)
  2. Thyroglobulin antibodies (aTG)

The vitamin biotin (B7) can affect the results of many thyroid hormone tests. If you take biotin, talk to your provider before you have any thyroid function tests.

Guber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 24.

Salvatore D, Davies TF, Schlumberger MJ, Hay ID, Larsen PR. Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 13th ed. Philadelphia, PA: Elsevier; 2016:chap 11.

Weiss RE, Refetoff S. Thyroid function testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 78.

Review Date 2/22/2018

Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

Thyroxine (T4) Test

What is a thyroxine (T4) test?

A thyroxine test helps diagnose disorders of the thyroid. The thyroid is a small, butterfly-shaped gland located near the throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. Thyroxine, also known as T4, is a type of thyroid hormone. This test measures the level of T4 in your blood. Too much or too little T4 can indicate thyroid disease.

The T4 hormone comes in two forms:

  •  Free T4, which enters the body tissues where it's needed
  •  Bound T4, which attaches to proteins, preventing it from entering body tissues

A test that measures both free and bound T4 is called a total T4 test. Other tests measure just free T4. A free T4 test is considered more accurate than a total T4 test for checking thyroid function.

Other names: free thyroxine, free T4, total T4 concentration, thyroxine screen, free T4 concentration

What is it used for?

A T4 test is used to evaluate thyroid function and diagnose thyroid disease.

Why do I need a thyroxine test?

Thyroid disease is much more common in women and most often occurs under the age of 40. It also tend to run in families. You may need a thyroxine test if a family member has ever had thyroid disease or if you have symptoms of having too much thyroid hormone in your blood, a condition called hyperthyroidism, or symptoms of having too little thyroid hormone, a condition called hypothyroidism.

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

  1. Anxiety
  2. Weight loss
  3. Tremors in the hands
  4. Increased heart rate
  5. Puffiness
  6. Bulging of the eyes
  7. Trouble sleeping

Symptoms of hypothyroidism, also known as underactive thyroid, include:

  1. Weight gain
  2. Fatigue
  3. Hair loss
  4. Low tolerance for cold temperatures
  5. Irregular menstrual periods
  6. Constipation

What do the results mean?

Your results may come in the form of total T4, free T4, or a free T4 index.

  • The free T4 index includes a formula that compares free and bound T4.
  • High levels of any of these tests (total T4, free T4, or free T4 index) may indicate an overactive thyroid, also known as hyperthyroidism.
  • Low levels of any of these tests (total T4, free T4, or free T4 index) may indicate an underactive thyroid, also known as hypothyroidism.

If your T4 test results are not normal, your health care provider will likely order more thyroid tests to help make a diagnosis. These may include:

  • T3 thyroid hormone tests. T3 is another hormone made by the thyroid.
  • A TSH (thyroid stimulating hormone) test. TSH is a hormone made by the pituitary gland. It stimulates the thyroid to produce T4 and T3 hormones.
  • Tests to diagnose Graves' disease, an autoimmune disease that causes hyperthyroidism
  • Tests to diagnose Hashimoto's thyroiditis, an autoimmune disease that causes hypothyroidism

Is there anything else I need to know about a thyroxine test?

Thyroid changes can happen during pregnancy. These changes are usually not significant, but some women can develop thyroid disease during pregnancy. Hyperthyroidism happens in about one in every 500 pregnancies, while hypothyroidism happens in approximately one in every 250 pregnancies. Hyperthyroidism, and less often, hypothyroidism, may remain after pregnancy. If you develop a thyroid condition during pregnancy, your health care provider will monitor your condition after your baby is born. Also, if you have a history of thyroid disease, be sure to talk with your health care provider if you are pregnant or are thinking of becoming pregnant.

  1. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2017. Thyroid Disease and Pregnancy [cited 2017 May 22]; [about 2 screens]. Available from: http://www.thyroid.org/thyroid-disease-pregnancy
  2. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2017. Thyroid Function Tests [cited 2017 May 22]; [about 2 screens]. Available from: https://www.thyroid.org/thyroid-function-tests
  3. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Thyroxine, Serum 485 p.
  4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Free T4: The Test [updated 2014 Oct 16; cited 2017 May 22]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/t4/tab/test
  5. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. Free T4: The Test Sample [updated 2014 Oct 16; cited 2017 May 22]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/t4/tab/sample
  6. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. TSH: The Test Sample [updated 2014 Oct 15; cited 2017 May 22]; [about 3 screens]. Available from: https://labtestsonline.org/understanding/analytes/tsh/tab/sample
  7. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2017. Overview of the Thyroid Gland [cited 2017 May 22]; [about 2 screens]. Available from: https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/thyroid-gland-disorders/overview-of-the-thyroid-gland
  8. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Graves' Disease; 2012 Aug [cited 2017 May 22]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/graves-disease
  9. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hashimoto's Disease; 2014 May [cited 2017 May 22]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hashimotos-disease
  10. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Thyroid Tests; 2014 May [cited 2017 May 22]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
  11. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests? [updated 2012 Jan 6; cited 2017 May 22]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests#Risk-Factors
  12. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests [updated 2012 Jan 6; cited 2017 May 22]; [about 4 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
  13. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Free and Bound T4 [cited 2017 May 22]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=t4_free_and_bound_blood
  14. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Free T4 [cited 2017 May 22]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=free_t4_thyroxine

Free T4 test

T4 (thyroxine) is the main hormone produced by the thyroid gland. A laboratory test can be done to measure the amount of free T4 in your blood.

How the Test is Performed

A blood sample is needed.

Why the Test is Performed

Your provider may recommend this test if you have signs of a thyroid disorder, including:

  1. Abnormal findings of other thyroid blood tests, such as TSH or T3
  2. Symptoms of an overactive thyroid
  3. Symptoms of an underactive thyroid
  4. Hypopituitarism (the pituitary gland does not produce enough of its hormones)
  5. Lump or nodule in the thyroid
  6. Enlarged or irregular thyroid gland
  7. Problems becoming pregnant
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This test is also used to monitor people who are being treated for thyroid problems.

Normal Results
A typical normal range is 0.9 to 2.3 nanograms per deciliter (ng/dL).

Normal value ranges may vary slightly among different laboratories. Some laboratories use different measurements or may test different specimens. Talk to your provider about the meaning of your specific test results.

What Abnormal Results Mean

To fully understand results of the free T4 test, results of other thyroid blood tests, such as TSH or T3, may be needed.

Test results may also be affected by pregnancy, estrogen level, liver problems, more severe body-wide illnesses, and inherited changes in a protein that binds T4.

A higher than normal level of T4 may be due to conditions that involve an overactive thyroid, including:

  1. Graves disease
  2. Taking too much thyroid hormone medicine
  3. Thyroiditis
  4. Toxic goiter or toxic thyroid nodules
  5. Some tumors of the testes or ovaries (rare)
  6. Getting medical imaging tests with contrast dye that contains iodine (rare, and only if there is a problem with the thyroid)
  7. Eating a lot of foods that contain iodine (very rare, and only if there is a problem with the thyroid)

A lower than normal level of T4 may be due to:

  1. Hypothyroidism (including Hashimoto disease and other disorders involving an underactive thyroid)
  2. Severe acute illness
  3. Malnutrition or fasting
  4. Use of certain medicines

Guber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 24.

Salvatore D, Davies TF, Schlumberger MJ, Hay ID, Larsen PR. Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 11.

Weiss RE, Refetoff S. Thyroid function testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 78.

Review Date 2/22/2018

Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

T3 Test

Triiodothyronine (T3) is a thyroid hormone. It plays an important role in the body's control of metabolism (the many processes that control the rate of activity in cells and tissues).

A laboratory test can be done to measure the amount of T3 in your blood.

How the Test is Performed

A blood sample is needed.

How to Prepare for the Test

Your health care provider will tell you if you need to stop taking any medicines before the test that may affect your test result. DO NOT stop taking any medicine without first talking to your provider.

Drugs that can increase T3 measurements include:

  • Birth control pills
  • Clofibrate
  • Estrogens
  • Methadone
  • Certain herbal remedies

Drugs that can decrease T3 measurements include:

  • Amiodarone
  • Anabolic steroids
  • Androgens
  • Antithyroid drugs (for example, propylthiouracil and methimazole)
  • Lithium
  • Phenytoin
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Why the Test is Performed

This test is done to check your thyroid function. Thyroid function depends on the action of T3 and other hormones, including thyroid-stimulating hormone (TSH) and T4.

Sometimes it can be useful to measure both T3 and T4 when evaluating thyroid function.

The total T3 test measures the T3 that is both attached to proteins and floating free in the blood.

The free T3 test measures the T3 that is floating free in the blood. The tests for free T3 are generally less accurate than for total T3.

Your provider may recommend this test if you have signs of a thyroid disorder, including:

  • The pituitary gland does not produce normal amounts of some or all of its hormone (hypopituitarism)
  • Overactive thyroid gland (hyperthyroidism)
  • Underactive thyroid gland (hypothyroidism)
  • Taking medicines for hypothyroidism

Normal Results

The range for normal values are:

  • Total T3 -- 60 to 180 nanograms per deciliter (ng/dL), or 0.92 to 2.76 nanomoles per liter (nmol/L)
  • Free T3 -- 130 to 450 picgrams per deciliter (pg/dL), or 2.0 to 7.0 picomoles per liter (pmol/L)

Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different specimens. Talk to your provider about the meaning of your specific test results.

Normal values are age specific for people less than age 20. Check with your provider about your specific results.

What Abnormal Results Mean

A higher-than-normal level of T3 may be a sign of:

  • Overactive thyroid gland (for example, Graves disease)
  • T3 thyrotoxicosis (rare)
  • Toxic nodular goiter
  • Taking thyroid medicines or certain supplements (common)
  • Liver disease

A high level of T3 may occur in pregnancy (especially with morning sickness at the end of the first trimester) or with the use of birth control pills or estrogen.

A lower-than-normal level may be due to:

  1. Severe short-term or some long-term illnesses
  2. Thyroiditis (swelling or inflammation of the thyroid gland -- Hashimoto disease is the most common type)
  3. Starvation
  4. Underactive thyroid gland

Guber HA, Farag AF. Evaluation of endocrine function. In: McPherson RA, Pincus MR, eds. Henry's Clinical Diagnosis and Management by Laboratory Methods. 23rd ed. St Louis, MO: Elsevier; 2017:chap 24.

Salvatore D, Davies TF, Schlumberger MJ, Hay ID, Larsen PR. Thyroid physiology and diagnostic evaluation of patients with thyroid disorders. In: Melmed S, Polonsky KS, Larsen PR, Kronenberg HM, eds. Williams Textbook of Endocrinology. 12th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 11.

Weiss RE, Refetoff S. Thyroid function testing. In: Jameson JL, De Groot LJ, de Kretser DM, et al, eds. Endocrinology: Adult and Pediatric. 7th ed. Philadelphia, PA: Elsevier Saunders; 2016:chap 78.

Review Date 2/22/2018

Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

TSH (Thyroid-stimulating hormone) Test

What is a TSH test?

TSH stands for thyroid stimulating hormone. A TSH test is a blood test that measures this hormone. The thyroid is a small, butterfly-shaped gland located near your throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood. TSH is made in a gland in the brain called the pituitary. When thyroid levels in your body are low, the pituitary gland makes more TSH. When thyroid levels are high, the pituitary gland makes less TSH. TSH levels that are too high or too low can indicate your thyroid isn't working correctly.

What is it used for?

A TSH test is used to find out how well the thyroid is working.

Why do I need a TSH test?

You may need a TSH test if you have symptoms of too much thyroid hormone in your blood (hyperthyroidism), or too little thyroid hormone (hypothyroidism).

Symptoms of hyperthyroidism, also known as overactive thyroid, include:

  1. Anxiety
  2. Weight loss
  3. Tremors in the hands
  4. Increased heart rate
  5. Puffiness
  6. Bulging of the eyes
  7. Difficulty sleeping

Symptoms of hypothyroidism, also known as underactive thyroid, include:

  • Weight gain
  • Tiredness
  • Hair loss
  • Low tolerance for cold temperatures
  • Irregular menstrual periods
  • Constipation

What do the results mean?

High TSH levels can mean your thyroid is not making enough thyroid hormones, a condition called hypothyroidism. Low TSH levels can mean your thyroid is making too much of the hormones, a condition called hyperthyroidism. A TSH test does not explain why TSH levels are too high or too low. If your test results are abnormal, your health care provider will probably order additional tests to determine the cause of your thyroid problem. These tests may include:

  • T4 thyroid hormone tests
  • T3 thyroid hormone tests
  • Tests to diagnose Graves' disease, an autoimmune disease that causes hyperthyroidism
  • Tests to diagnose Hashimoto's thyroiditis, an autoimmune disease that causes hypothyroidism

Is there anything else I need to know about a TSH test?

Thyroid changes can happen during pregnancy. These changes are usually not significant, but some women can develop thyroid disease during pregnancy. Hyperthyroidism occurs in about one in every 500 pregnancies, while hypothyroidism occurs in approximately one in every 250 pregnancies. Hyperthyroidism, and less often, hypothyroidism, may remain after pregnancy. If you develop a thyroid condition during pregnancy, your health care provider will monitor your condition after your baby is born. If you have a history of thyroid disease, be sure to talk with your health care provider if you are pregnant or are thinking of becoming pregnant.

  1. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2017. Thyroid Disease and Pregnancy; [cited 2017 Mar 15]; [about 2 screens]. Available from: http://www.thyroid.org/thyroid-disease-pregnancy
  2. Hinkle J, Cheever K. Brunner & Suddarth's Handbook of Laboratory and Diagnostic Tests. 2nd Ed, Kindle. Philadelphia: Wolters Kluwer Health, Lippincott Williams & Wilkins; c2014. Thyroid-Stimulating Hormone, Serum; p. 484.
  3. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2017. TSH: The Test; [updated 2014 Oct 15; cited 2017 Mar 15]; [about 4 screens]. Available from: https://labtestsonline.org/understanding/analytes/tsh/tab/test
  4. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co Inc.; c2017. Overview of the Thyroid Gland; [cited 2017 Mar 15]; [about 2 screens]. Available from: https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/thyroid-gland-disorders/overview-of-the-thyroid-gland
  5. Merck Manual Professional Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2017. Overview of Thyroid Gall Function; [updated 2016 Jul; cited 2017 Mar 15]; [about 3 screens]. Available from: https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/thyroid-disorders/overview-of-thyroid-function
  6. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What Are the Risks of Blood Tests?; [updated 2012 Jan 6; cited 2017 Mar 15]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/risks
  7. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; What To Expect with Blood Tests; [updated 2012 Jan 6; cited 2017 Mar 15]; [about 4 screens]. Available from: https://www.nhlbi.nih.gov/health/health-topics/topics/bdt/with
  8. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Graves' Disease; 2012 Aug [cited 2017 Mar 15]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/graves-disease#what
  9. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hashimoto's Disease; 2014 May [cited 2017 Mar 15]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hashimotos-disease#what
  10. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Pregnancy & Thyroid Disease; 2012 Mar [cited 2017 Mar 15]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/pregnancy-thyroid-disease
  11. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Thyroid Tests; 2014 May [cited 2017 Mar 15]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
  12. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2017. Health Encyclopedia: Thyroid Stimulating Hormone; [cited 2017 Mar 15]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid;=thyroid_stimulating_hormone

Thyroid Antibodies

What is a thyroid antibodies test?

This test measures the level of thyroid antibodies in your blood. The thyroid is a small, butterfly-shaped gland located near the throat. Your thyroid makes hormones that regulate the way your body uses energy. It also plays an important role in regulating your weight, body temperature, muscle strength, and even your mood.

Antibodies are proteins made by the immune system to fight foreign substances like viruses and bacteria. But sometimes antibodies attack the body's own cells, tissues, and organs by mistake. This is known as an autoimmune response. When thyroid antibodies attack healthy thyroid cells, it can lead to an autoimmune disorder of the thyroid. These disorders can cause serious health problems if not treated.

There are different types of thyroid antibodies. Some antibodies destroy thyroid tissue. Others cause the thyroid to make too much of certain thyroid hormones. A thyroid antibodies test usually measures one or more of the following types of antibodies:

Thyroid peroxidase antibodies (TPO).  These antibodies can be a sign of:

  • Hashimoto disease, also known as Hashimoto thyroiditis. This is an autoimmune disease and the most common cause of hypothyroidism. Hypothyroidism is a condition in which the thyroid doesn't make enough thyroid hormones.
  • Graves' disease. This is also an autoimmune disease and the most common cause of hyperthyroidism. Hyperthyroidism is a condition in which the thyroid makes too much of certain thyroid hormones.
  • Thyroglobulin antibodies (Tg). These antibodies can also be a sign of Hashimoto disease. Most people with Hashimoto disease have high levels of both Tg and TPO antibodies.
  • Thyroid-stimulating hormone (TSH) receptor. These antibodies can be a sign of Grave's disease.

Other names: thyroid autoantibodies, thyroid peroxidase antibody, TPO, Anti-TPO, thyroid- stimulating immunoglobulin, TSI

What is it used for?

A thyroid antibodies test is used to help diagnose autoimmune disorders of the thyroid.

Why do I need a thyroid antibodies test?

You may need this test if you have symptoms of a thyroid problem and your provider thinks they may be caused by Hashimoto disease or Grave's disease.

Symptoms of Hashimoto disease include:

  • Weight gain
  • Fatigue
  • Hair loss
  • Low tolerance for cold temperatures
  • Irregular menstrual periods
  • Constipation
  • Depression
  • Joint pain

Symptoms of Grave's disease include:

  1. Weight loss
  2. Bulging of the eyes
  3. Tremors in the hand
  4. Low tolerance for heat
  5. Trouble sleeping
  6. Anxiety
  7. Increased heart rate
  8. Swollen thyroid, known as goiter

You may also need this test if other thyroid tests show that your thyroid hormone levels are too low or too high. These tests include measurements of hormones known as T3, T4, and TSH (thyroid-stimulating hormone).

What do the results mean?

Your results may show one of the following:

  • Negative: no thyroid antibodies were found. This means your thyroid symptoms are probably not caused by an autoimmune disease.
  • Positive: antibodies to TPO and/or Tg were found. This may mean you have Hashimoto disease. Most people with Hashimoto disease have high levels of one or both of these types of antibodies.
  • Positive: antibodies to TPO and/or TSH receptor were found. This may mean you have Grave's disease.

The more thyroid antibodies you have, the more likely it is that you have an autoimmune disorder of the thyroid. If you are diagnosed with Hashimoto disease or Grave's disease, there are medicines you can take to manage your condition.

Is there anything else I need to know about a thyroid antibodies test?

Thyroid disease can get worse during pregnancy. This can harm both the mother and her unborn baby. If you have ever had thyroid disease and are pregnant, you may be tested for thyroid antibodies along with tests that measure thyroid hormones. Medicines to treat thyroid disease are safe to take during pregnancy.

  1. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2019. Pregnancy and Thyroid Disease [cited 2019 Jan 2]; [about 2 screens]. Available from: http://www.thyroid.org/thyroid-disease-pregnancy
  2. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2019. Thyroid Function Tests [cited 2019 Jan 2]; [about 2 screens]. Available from: https://www.thyroid.org/thyroid-function-tests
  3. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2019. Hashimoto Thyroiditis [updated 2017 Nov 27; cited 2019 Jan 2]; [about 2 screens]. Available from: https://labtestsonline.org/conditions/hashimoto-thyroiditis
  4. Lab Tests Online [Internet]. Washington D.C.: American Association for Clinical Chemistry; c2001–2019. Thyroid Antibodies [updated 2018 Dec 19; cited 2019 Jan 2]; [about 2 screens]. Available from: https://labtestsonline.org/tests/thyroid-antibodies
  5. Mayo Clinic [Internet]. Mayo Foundation for Medical Education and Research; c1998–2019. Thyroid peroxidase antibody test: What is it?; 2018 May 8 [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.mayoclinic.org/thyroid-disease/expert-answers/faq-20058114
  6. Mayo Clinic: Mayo Medical Laboratories [Internet]. Mayo Foundation for Medical Education and Research; c1995–2019. Test ID: TPO: Thyroperoxidase (TPO) Antibodies, Serum: Clinical and Interpretative [cited 2019 Jan 2]; [about 4 screens]. Available from: https://www.mayocliniclabs.com/test-catalog/Clinical+and+Interpretive/81765
  7. Mayo Clinic: Mayo Medical Laboratories [Internet]. Mayo Foundation for Medical Education and Research; c1995–2019. Test ID: TPO: Thyroperoxidase (TPO) Antibodies, Serum: Overview [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.mayocliniclabs.com/test-catalog/Overview/81765
  8. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.nhlbi.nih.gov/health-topics/blood-tests
  9. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hashimoto's Disease; 2017 Sep [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hashimotos-disease
  10. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hyperthyroidism (Overactive Thyroid); 2016 Aug [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hyperthyroidism
  11. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hypothyroidism (Underactive Thyroid); 2016 Aug [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism
  12. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Thyroid Tests; 2017 May [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
  13. Physician's Weekly [Internet]. Physician's Weekly; c2018. Managing Thyroid Disease During Pregnancy; 2012 Jan 24 [cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.physiciansweekly.com/thyroid-disease-during-pregnancy
  14. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2019. Health Encyclopedia: Thyroid Antibody [cited 2019 Jan 2]; [about 2 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=thyroid_antibody
  15. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2019. Antithyroid Antibody Tests: Results [updated 2018 Mar 15; cited 2019 Jan 2]; [about 8 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/antithyroid-antibody-tests/abq5900.html#abq5907
  16. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2019. Antithyroid Antibody Tests: Test Overview [updated 2018 Mar 15; cited 2019 Jan 2]; [about 2 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/antithyroid-antibody-tests/abq5900.html
  17. UW Health [Internet]. Madison (WI): University of Wisconsin Hospitals and Clinics Authority; c2019. Antithyroid Antibody Tests: Why It is Done [updated 2018 Mar 15; cited 2019 Jan 2]; [about 3 screens]. Available from: https://www.uwhealth.org/health/topic/medicaltest/antithyroid-antibody-tests/abq5900.html#abq5902

Hemoglobin A1C Tests hbA1C

is a lab test that shows the average level of blood sugar (glucose) over the previous 3 months. It shows how well you are
controlling your diabetes.

Why the Test is Performed

Your provider may order this test if you have diabetes. It shows how well you are controlling your diabetes. The test may also be used to screen for diabetes. Ask your provider how often you should have your A1C level tested.
Usually, testing every 3 or 6 months is recommended.

Normal Results
The following are the results when A1C is being used to diagnose diabetes:

  • Normal (no diabetes): Less than 5.7%
  • Pre-diabetes: 5.7% to 6.4%
  • Diabetes: 6.5% or higher

If you have diabetes, you and your provider will discuss the correct range for you. For many people, the goal is to keep the level below 7%. The test result may be incorrect in people with anemia, kidney disease, or certain blood disorders (thalassemia). Talk to your provider if you have any of these conditions. Certain medicines can also result in a false A1C level. The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Talk to your provider about the meaning of your specific test results. What Abnormal Results Mean An abnormal result means that you have had a high blood sugar level over a period of weeks to months. If your A1C is above 6.5% and you do not already have diabetes, you may be diagnosed with diabetes. If your level is above 7% and you have diabetes, it often means that your blood sugar is not well controlled. You and your provider should determine your target A1C. The higher your A1C, the higher the risk that you will develop problems such as:

  • Eye disease
  • Heart disease
  • Kidney disease
  • Nerve damage
  • Stroke

If your A1C stays high, talk to your provider about how to best manage your blood sugar.

American Diabetes Association. 6. Glycemic targets: standards of medical care in diabetes – 2018. Diabetes Care. 2018;41(Suppl 1):S55-S64. PMID: 29222377 www.ncbi.nlm.nih.gov/pubmed/29222377. Chernecky CC, Berger BJ. Glycosylated hemoglobin (GHb, glycohemoglobin, glycated hemoglobin, HbA1a, HbA1b, HbA1c) - blood. In: Chernecky CC, Berger BJ, eds. Laboratory Tests and Diagnostic Procedures. 6th ed. St Louis, MO: Elsevier; 2013:596-597. Review Date 5/17/2018 Updated by: Brent Wisse, MD, Associate Professor of Medicine, Division of Metabolism, Endocrinology & Nutrition, University of Washington School of Medicine, Seattle, WA. Also reviewed by David Zieve, MD, MHA, Medical Director, Brenda Conaway, Editorial Director, and the A.D.A.M. Editorial team.

The medical information provided is for informational purposes only and is not to be used as a substitute for professional medical advice, diagnosis or treatment. Please contact your health care provider with questions you may have regarding medical conditions or the interpretation of test results.