A TSH test is a lab test that measures the amount of thyroid stimulating hormone (TSH) in your blood. TSH is produced by the pituitary gland. It tells the thyroid gland to make and release thyroid hormones into the blood.
A blood sample is needed. For information on how this is done, see: Venipuncture
Other tests that may be done at the same time include:
There is no preparation needed for this test. Ask your health care provider about any medicines you are taking that may affect the test results. Do not stop taking any medicines without first asking your health care provider.
Medicines you may need to stop taking include:
When the needle is inserted to draw blood, some people feel moderate pain, while others feel only a prick or stinging sensation. Afterward, there may be some throbbing.
Your doctor will order this test if you have symptoms or signs of an overactive or underactive thyroid gland. It is also used to monitor treatment of these conditions.
Normal values can range from 0.4 - 4.0 mIU/L (milli-international units per liter), depending on:
Even without signs or symptoms of an underactive thyroid (hypothyroidism), you will need to be followed closely by your doctor if your TSH level is over 3.5 mIU/L but your T4 test is normal (called subclinical hypothyroidism).
If you are being treated for a thyroid disorder, your TSH level should be between 0.5 and 2.0 mIU/L.
The examples above are common measurements for results of these tests. Normal value ranges may vary slightly among different laboratories. Some labs use different measurements or test different samples.Talk to your doctor about the meaning of your specific test results.
Higher-than-normal TSH levels are most often due to an underactive thyroid gland (hypothyroidism). There are many causes of this problem.
Lower-than-normal levels may be due to an overactive thyroid gland, which can be caused by:
Veins and arteries vary in size from one patient 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:
Thyrotropin; Thyroid stimulating hormone
Kim M, Ladenson P. Thyroid. In: Goldman L, Schafer AI, eds. Cecil Medicine. 24th ed. Philadelphia, Pa: Saunders Elsevier; 2011:chap 233.
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: Saunders Elsevier; 2011:chap 11.
Updated by: Shehzad Topiwala, MD, Chief Consultant Endocrinologist, Premier Medical Associates, The Villages, FL. Review provided by VeriMed Healthcare Network. Also reviewed by David Zieve, MD, MHA, Medical Director, A.D.A.M. Health Solutions, Ebix, Inc.
A.D.A.M., Inc. is accredited by URAC, also known as the American Accreditation HealthCare Commission (www.urac.org). URAC's accreditation program is an independent audit to verify that A.D.A.M. follows rigorous standards of quality and accountability. A.D.A.M. is among the first to achieve this important distinction for online health information and services. Learn more about A.D.A.M.'s editorial policy, editorial process and privacy policy. A.D.A.M. is also a founding member of Hi-Ethics and subscribes to the principles of the Health on the Net Foundation (www.hon.ch).
The information provided herein should not be used during any medical emergency or for the diagnosis or treatment of any medical condition. A licensed physician should be consulted for diagnosis and treatment of any and all medical conditions. Call 911 for all medical emergencies. Links to other sites are provided for information only -- they do not constitute endorsements of those other sites. Copyright 1997-2012, A.D.A.M., Inc. Duplication for commercial use must be authorized in writing by ADAM Health Solutions.