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Thyroid-Stimulating Hormone (TSH) Test

Last updated Sept. 19, 2018

TSH in conjunction with T4 is the starting point for testing, in order to evaluate the thyroid gland function. Some of the other tests, which are performed along with TSH include test for T3 and for thyroid antibodies.


What are the other Names for this Test? (Equivalent Terms)

  • Thyrotropin Test
  • TSH (Thyroid-Stimulating Hormone) Test 

What is Thyroid-Stimulating Hormone (TSH) Test? (Background Information)

  • Thyroid-Stimulating Hormone (TSH) is a hormone that is made by the thyrotrope cells in the anterior pituitary gland
  • Thyrotropin-releasing hormone (TRH) is made by the hypothalamus in the brain. TRH, in-turn stimulates the anterior pituitary gland, to produce Thyroid-Stimulating Hormone
  • The purpose of TSH is to stimulate the thyroid gland to produce thyroxin (T4), which is then converted to triiodothyronine (T3), in the liver and thyroid gland. T3 is very critical in controlling the body cell metabolism
  • TSH in conjunction with T4 is the starting point for testing, in order to evaluate the thyroid gland function. Some of the other tests, which are performed along with TSH include test for T3 and for thyroid antibodies

What are the Clinical Indications for performing the Thyroid-Stimulating Hormone (TSH) Test?

Clinical indications for performing TSH Testing include:

  • Diagnosing signs and symptoms related to a hyperthyroid state, or a hypothyroid state
  • As part of thyroid screening in newborns, to determine thyroid gland functioning
  • It is routinely used to assess the effectiveness of thyroid replacement therapy in individuals:
    • Who are under treatment for hypothyroidism
    • Or on those, who are on thyroid replacement therapy after a partial or complete thyroid removal (individuals, who have undergone thyroid resection for thyroid cancer)
  • As part of menstrual problem work-up

How is the Specimen Collected for Thyroid-Stimulating Hormone (TSH) Test?

Sample required: Blood

Process: Insertion of a needle into a vein (arm).

Preparation required: None. However, certain medications can interfere with T3 testing. Hence, any medications one is currently taking, has to be disclosed to the healthcare provider. 

What is the Significance of the Thyroid-Stimulating Hormone (TSH) Test Result?

The significance of Thyroid-Stimulating Hormone Test is as follows:

TSH is increased:

  • Thyroid gland is underperforming (hypothyroidism), such as due to Hashimoto’s thyroiditis
  • Tumors of anterior pituitary gland that secrete TSH (pituitary adenomas)
  • Individuals, who have undergone partial or complete thyroid removal (like a thyroid resection for thyroid cancer) 

TSH is decreased:

  • When the thyroid gland is hyperactive (hyperthyroidism), such as with Graves’ disease
  • Tumors of thyroid secreting hormone, such as toxic nodule
  • Individuals on thyroid replacement therapy
  • Non-functioning of the anterior pituitary gland
  • During early pregnancy (first trimester)
  • Severe stress
  • With certain medications, such as lithium, steroids, and heparin 

It is important to note that interpretation of TSH should be performed in conjunction with other tests, such as T4 level test, T3 level test, and thyroid antibodies (which would be increased in autoimmune thyroid conditions, such as Hashimoto’s thyroiditis). 

The following is a guide to interpretation of thyroid function tests: 

  • In case of hypothalamus/pituitary pathology, such as benign tumor of the pituitary (adenoma), or thyroid hormone resistance:
    • TSH is high
    • Thyroid hormone level is high 
  • In case of hypothalamus/pituitary pathology, such as hypopituitarism:
    • TSH is low
    • Thyroid hormone level is low 
  • In case of thyroid pathology, such as hyperthyroidism, or Graves' disease:
    • TSH is low
    • Thyroid hormone level is high 
  • In case of thyroid pathology such as congenital hypothyroidism (cretinism), hypothyroidism, or Hashimoto's thyroiditis:
    • TSH is high
    • Thyroid hormone level is low 

Additional and Relevant Useful Information: 

  • Most of the states in the United States screen newborns, as part of thyroid wellness checkup (and to detect congenital hypothyroidism, if any)
  • Many healthcare institutions perform TSH Testing for pregnant and postpartum women
  • The American Thyroid Association recommends that TSH Testing should be performed every 5 years in all individuals, older than 35 years. However, the US Preventive Services Task Force does not recommend this frequency of screening, for thyroid disease. As to who should be screened for TSH levels, is currently controversial!
  • Medications, such as aspirin and thyroid-hormone replacement therapy, may cause erroneous levels of TSH. It is important to let your healthcare provider know, if you are taking such medications
  • Thyroid replacement therapy can take up to 2 months to have the desired effect. Hence, TSH Testing should be performed 8 weeks after initiating thyroid replacement therapy

References and Information Sources used for the Article:


Reviewed and Approved by a member of the DoveMed Editorial Board
First uploaded: Feb. 3, 2014
Last updated: Sept. 19, 2018