Insulin-like growth factor-1 (IGF-1) is a hormone that, along with growth hormone (GH), helps promote normal bone and tissue growth and development.
IGF-1 hormone is produced by the liver and skeletal muscle as well as many other tissues in response to GH stimulation. IGF-1 mediates many of the actions of GH, stimulating the growth of bones and other tissues. IGF-1 is a useful indicator of average GH levels. The IGF-1 test is therefore often used to help evaluate for GH deficiency or GH excess.
IGF-1 levels, like GH, are normally low in early childhood, increase gradually during childhood, peak during puberty, and then decline in adult life. Deficiencies in GH and IGF-1 may be caused by a dysfunctional pituitary gland with decreased pituitary hormones (hypopituitarism) or by the presence of a non-GH-producing pituitary tumor that damages hormone-producing cells. Deficiencies in IGF-1 also occur where there is a lack of responsiveness to GH.
How is the test performed?
The test is performed on a blood sample.
What are the signs and symptoms of growth hormone deficiency in children?
In children, the following may indicate GH or IGF-1 deficiency:
- Slowed growth rate in early childhood
- Shorter stature than others of the same chronological age
- Delayed puberty
- X-rays showing delayed bone development
What are the signs and symptoms of growth hormone deficiency in adults?
In adults, abnormally low levels of GH or IGF-1 may cause following symptoms such:
- Decreased bone density
- Fatigue
- Adverse lipid changes
- Reduced exercise tolerance
This test measures the amount of IGF-1 in the blood.
- Decreased IGF-1:
If the IGF-1 level is decreased, then it is likely that there is a growth hormone deficiency or an insensitivity to GH. If this is in a child, the GH deficiency may have already caused short stature and delayed development and may be treated with GH supplementation. Adults will have an age-related decrease in production, but lower than expected levels may reflect a GH deficiency or insensitivity.
- Increased IGF-1
Elevated levels of IGF-1 usually indicate increased production of GH. Increased levels of GH and IGF-1 are normal during puberty and pregnancy but otherwise are most frequently due to pituitary tumors (usually benign).
