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URL of this page: https://medlineplus.gov/lab-tests/tsh-thyroid-stimulating-hormone-test/

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. TSH levels that are too high or too low may be a sign of a thyroid problem.

The thyroid is a small, butterfly-shaped gland in the front of your neck. Your thyroid makes hormones that control how your body uses energy. Thyroid hormones affect nearly every organ in your body, including your heart. They help control your weight, body temperature, muscle strength, and even your mood. If you don't have enough thyroid hormones in your blood, many of your body functions slow down. If you have too much, many body functions speed up.

Your thyroid is controlled by a gland in your brain, called the pituitary gland. The pituitary gland makes thyroid stimulating hormone (TSH). TSH tells your thyroid how much thyroid hormone it needs to make.

If the thyroid hormone levels in your blood are too low, your pituitary gland makes larger amounts of TSH to tell your thyroid to work harder. If your thyroid hormone levels are too high, the pituitary gland makes little or no TSH. By measuring TSH levels in your blood, you can find out if your thyroid is making the right level of hormones.

Other names: thyrotropin test

What is it used for?

A TSH test is used to find out how well your thyroid is working. It can tell if you have hyperthyroidism (too much thyroid hormone) or hypothyroidism (too little thyroid hormone) in your blood. But a TSH test can't show what is causing a thyroid problem.

If you take prescription thyroid hormone medicine because of hypothyroidism or because you had your thyroid removed, you'll have regular TSH tests to check your thyroid hormone levels. TSH tests are also used to monitor your thyroid hormone levels after treatment for hyperthyroidism.

Why do I need a TSH test?

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

Hyperthyroidism (too much thyroid hormone) is also called overactive thyroid. Having more thyroid hormones than you need speeds up your body functions and causes symptoms that include:

Hypothyroidism (too little thyroid hormone) is also called underactive thyroid. Not having enough thyroid hormone slows down your body functions and causes symptoms that include:

You may also have a TSH test, along with other tests, to help diagnose unusual bumps or lumps on your thyroid that may be thyroid cancer or thyroid nodules (growths on your thyroid that aren't cancer).

What happens during a TSH test?

A health care professional will take a blood sample from a vein in your arm, using a small needle. After the needle is inserted, a small amount of blood will be collected into a test tube or vial. You may feel a little sting when the needle goes in or out. This usually takes less than five minutes.

Will I need to do anything to prepare for the test?

You don't need any special preparations for a TSH blood test. If your health care provider has ordered other blood tests, you may need to fast (not eat or drink) for several hours before the test. Your provider will let you know if there are any special instructions to follow.

Are there any risks to the test?

There is very little risk to having a blood test. You may have slight pain or bruising at the spot where the needle was put in, but most symptoms go away quickly.

What do the results mean?

Your TSH test results can tell you if your thyroid is making too much or too little thyroid. But the test can't explain why your TSH levels may be too high or too low.

If your test results aren't normal, your provider will probably order other thyroid blood tests to find out what's causing your thyroid problem. These blood tests may include:

In certain cases, an abnormal TSH result may be a sign of a pituitary gland problem, but this doesn't happen often.

Learn more about laboratory tests, reference ranges, and understanding results.

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

TSH levels may be high or low even when your thyroid gland is healthy. Serious illnesses not related to your thyroid may cause lower TSH levels for a short time. And TSH levels may be higher in people over age 80, even though they don't have any thyroid problems.

Pregnancy also affects TSH levels. They are often a little low during the first three months. But sometimes, thyroid disease develops during pregnancy. If you develop thyroid disease during pregnancy, your provider will monitor your condition through your pregnancy and after your baby is born. That's because hyperthyroidism, and less often, hypothyroidism, can continue after you give birth. If you have a history of thyroid disease, be sure to talk with your provider if you are pregnant or are thinking of becoming pregnant.

Newborn babies are routinely screened with a TSH test to see if they were born with hypothyroidism (congenital hypothyroidism).

References

  1. American Thyroid Association [Internet]. Falls Church (VA): American Thyroid Association; c2022. Thyroid Disease and Pregnancy; [cited 2022 Feb 21]; [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. Merck Manual Consumer Version [Internet]. Kenilworth (NJ): Merck & Co Inc.; c2022. Overview of the Thyroid Gland; [modified 2020 Sep; cited 2022 Feb 21]; [about 4 screens]. Available from: https://www.merckmanuals.com/home/hormonal-and-metabolic-disorders/thyroid-gland-disorders/overview-of-the-thyroid-gland
  4. Merck Manual Professional Version [Internet]. Kenilworth (NJ): Merck & Co. Inc.; c2022. Overview of Thyroid Function; [modified 2020 Sep;; cited 2022 Feb 21]; [about 11 screens]. Available from: https://www.merckmanuals.com/professional/endocrine-and-metabolic-disorders/thyroid-disorders/overview-of-thyroid-function
  5. National Heart, Lung, and Blood Institute [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Blood Tests; [updated 2022 Mar 24; cited 2022 Feb 21]; [about 5 screens]. Available from: https://www.nhlbi.nih.gov/health/blood-tests
  6. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Graves' Disease; [last reviewed 2021 Nov; cited 2022 Feb 21]; [about 13 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/graves-disease#what
  7. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hashimoto's Disease; [last reviewed 2021 June; cited 2022 Feb 21]; [about 9 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hashimotos-disease#what
  8. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hyperthyroidism (Overactive Thyroid); [last reviewed 2021 Aug; cited 2022 Feb 21]; [about 13 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hyperthyroidism#symptoms
  9. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human Services; Hypothyroidism (Underactive Thyroid); [last reviewed 2021 Mar; cited 2022 Feb 21]; [about 10 screens]. Available from: https://www.niddk.nih.gov/health-information/endocrine-diseases/hypothyroidism#diagnosis
  10. National Institute of Diabetes and Digestive and Kidney Diseases [Internet]. Bethesda (MD): U.S. Department of Health and Human ServicesThyroid Disease & Pregnancy; [last reviewed 2017 Dec; cited 2022 Feb 21]; [about 12 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; [last reviewed 2017 May; cited 2022 Feb 21]; [about 6 screens]. Available from: https://www.niddk.nih.gov/health-information/diagnostic-tests/thyroid
  12. Testing.com [Internet]. Seattle (WA): OneCare Media; c2022. Thyroid-stimulating Hormone (TSH); [modified 2021 Nov 21; cited 2022 Feb 21]; [about 14 screens]. Available from: https://www.testing.com/tests/thyroid-stimulating-hormone-tsh/
  13. University of Rochester Medical Center [Internet]. Rochester (NY): University of Rochester Medical Center; c2022. Health Encyclopedia: Thyroid Stimulating Hormone; [cited 2022 Feb 21]; [about 5 screens]. Available from: https://www.urmc.rochester.edu/encyclopedia/content.aspx?contenttypeid=167&contentid=thyroid_stimulating_hormone

The information on this site should not be used as a substitute for professional medical care or advice. Contact a health care provider if you have questions about your health.