Thyroid-Stimulating Hormone (TSH)
The normal values listed here—called a reference range—are just a guide. These ranges vary from lab to lab, and your lab may have a different range for what's normal. Your lab report should contain the range your lab uses. Also, your doctor will evaluate your results based on your health and other factors. This means that a value that falls outside the normal values listed here may still be normal for you or your lab.
Results are usually available in 2 to 3 days.
0.4–4.2 microunits per milliliter (mcU/mL) or 0.4–4.2 Reference milliunits per liter (mU/L) Opens New Window
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
High TSH levels may be caused by:
- An underactive thyroid (Reference hypothyroidism Opens New Window). Reference Hashimoto's thyroiditis Opens New Window 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 TSH levels may be caused by:
- An overactive thyroid gland (Reference hyperthyroidism Opens New Window). Causes of hyperthyroidism include Reference Graves' disease Opens New Window, a type of Reference goiter Opens New Window (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 Reference trimester Opens New Window.
|By:||Reference Healthwise Staff||Last Revised: Reference April 5, 2012|
|Medical Review:||Reference E. Gregory Thompson, MD - Internal Medicine
Reference Matthew I. Kim, MD - Endocrinology