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Thyroid-Stimulating Hormone (TSH)

Results continued...

Results are usually available in 2 to 3 days.

Thyroid-stimulating hormone (TSH) 1
Adults:

0.4–4.2 microunits per milliliter (mcU/mL) or 0.4–4.2 milliunits per liter (mU/L)

Children:

0.7–6.4 mcU/mL or 0.7–6.4 mU/L

Newborns ( 1-4 days):

1–39 mcU/mL or 1–39 mU/L

A slightly high TSH value may not require treatment. The doctor will consider any symptoms you might have along with other test results to determine if treatment is needed.

High values

High TSH levels may be caused by:

  • An underactive thyroid (hypothyroidism). Hashimoto's thyroiditis is the most common cause of primary hypothyroidism.
  • A pituitary gland tumor that is making too much TSH. This is uncommon.
  • Not taking enough thyroid hormone medicine for treatment of an underactive thyroid gland.

Low values

Low TSH levels may be caused by:

  • An overactive thyroid gland (hyperthyroidism). Causes of hyperthyroidism include Graves' disease, a type of goiter (toxic multinodular goiter), or a noncancerous (benign) tumor called a toxic nodule.
  • Damage to the pituitary gland that prevents it from making TSH (a condition called secondary hypothyroidism).
  • Taking too much thyroid medicine for treatment of an underactive thyroid gland.
  • Pregnancy during the first trimester.

What Affects the Test

Reasons you may not be able to have the test or why the results may not be helpful include:

  • Taking medicine, such as corticosteroids, levodopa, heparin, dopamine, or lithium (such as Lithobid).
  • Having had a recent X-ray with iodine dye or test using radioactive materials.
  • Having severe stress or a long-term (chronic) illness.

What To Think About

  • The thyroid-stimulating hormone (TSH) test is the best screening test for conditions that can affect the thyroid gland.
  • The results of a TSH test should be considered along with the results of thyroid hormone tests, especially thyroxine (T4) results. To learn more about T3 and T4 testing, see the topic Thyroid Hormone Tests.

Citations

  1. Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

Other Works Consulted

  • Fischbach FT, Dunning MB III, eds. (2009). Manual of Laboratory and Diagnostic Tests, 8th ed. Philadelphia: Lippincott Williams and Wilkins.

  • Pagana KD, Pagana TJ (2010). Mosby’s Manual of Diagnostic and Laboratory Tests, 4th ed. St. Louis: Mosby Elsevier.

WebMD Medical Reference from Healthwise

Last Updated: April 05, 2012
This information is not intended to replace the advice of a doctor. Healthwise disclaims any liability for the decisions you make based on this information.

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