Thyroid-Stimulating Hormone (TSH)

Thyrotropin, TSH (Thyroid-Stimulating Hormone)

Results

A thyroid-stimulating hormone (TSH) blood test is used to check for thyroid gland problems.

The normal ranges for the results of this test may vary from laboratory to laboratory. Results are usually available within 2 to 3 days.

Thyroid-stimulating hormone (TSH)

Adults:	0.4–4.5 mIU/L or 0.4–4.5 mU/L (SI units)
Babies:	3–18 mIU/L or 3–18 mU/L (SI units)

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.

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Author:	Bets Davis, MFA	Last Updated: June 11, 2008
Medical Review:	Caroline S. Rhoads, MD - Internal Medicine Matthew I. Kim, MD - Endocrinology & Metabolism
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