IGF-1 (Insulin-Like Growth Factor 1) Testing Fact Sheet
Overview of the Test
AN IGF-1 test is an indirect way of measuring how much growth hormone is being produced in the body.
Growth hormone (GH) is able to trigger production and secretion of IGF-1 and other insulin-like growth factors. IGF-1 (insulin-like growth factor 1) or somatomedin C is a specialized protein. IGF-1 simulates growth in almost every cell of the body. This means that a reduction in either IGF-1 or growth hormone in children causes a slower growth rate, later puberty and delayed bone development. In adults, a deficiency in IGF-1 can cause lower muscle mass, altered fat (lipid) levels and low bone density.
The IGF-1 test is frequently used in children with a short stature to assess what has caused their altered growth. It can also help evaluate pituitary function and testing is common after the removal of certain types of pituitary tumors – to check whether removal is successful.
In adults and children, an IGF-1 test may be done alongside a GH stimulation test, or even a GH suppression test. If GH is suppressed, then an IGF-1 test may detect a pituitary tumor.
Evidence and Science behind the Test
IGF-1 levels gradually increase through early childhood, peaking during puberty. They then decline during adult life. A deficiency in IGF-1 can occur when if IGF-1 is unable to respond properly to stimulation by GH – which can arise through disease or malnutrition. IGF-1 deficiency can also occur through conditions such as hypopituitarism.
Excessive levels of IGF-1 can lead to abnormal growth, such as that seen in acromegaly and gigantism. Not only are do these conditions display obvious physical characteristics, but they also lead to a number of serious health problems and reduced lifespan.
However, IGF-1 is linked to increased lifespan in bacteria, rodents, nematodes and insects and therefore may be important in human longevity. IGF-1 is also involved in the regulation of natural killer (NK) cells in the body. These cells play a key role in the immune response, killing viruses and bacteria. They also play a part in inducing tumor cell death.
How is it done?
A small blood sample is taken from the arm and then sent to a laboratory for analysis. A fast may be required before the sample is taken.
Who Does It?
Doctors, nurses and other qualified professionals.
When and How Often?
AN IGF-1 test is only recommended for adults and children that are displaying signs of an IGF-1 and/or growth hormone deficiency.
Cost
AN IGF-1 test is available from some clinics for under $200. Some IGF-1 testing may be available under insurance or Medicare.
Issues
A growth hormone test is usually necessary alongside IGF-1 to provide as much information as possible. If the IGF-1 test is for adult growth hormone deficiency, caution is required with the test results. Normal IGF-1 results do not always mean that there is no growth hormone deficiency – there are overlaps in results ranges for adults with GH deficiencies and adults without.
References
- IGF-1: http://www.labtestsonline.org.uk/understanding/analytes/igf1/tab/glance
- Ni F, Sun R, Fu B, Wang F, Guo C, Tian Z, Wei H. (2013). IGF-1 promotes the development and cytotoxic activity of human NK cells. Nat Commun. Feb 12;4:1479. doi: 10.1038/ncomms2484.
- Anisimov VN, Bartke A. (2013) The key role of growth hormone-insulin-IGF-1 signaling in aging and cancer. Crit Rev Oncol Hematol. Feb 21. pii: S1040-8428(13)00031-0. doi: 10.1016/j.critrevonc.2013.01.005. [Epub ahead of print]
- Piero Anversa (2005). The IGF-1 Enigma. Circulation Research. 97: 411-414
- A Mukherjee and S M Shalet. (2009). The value of IGF1 estimation in adults with GH deficiency. European Journal of Endocrinology. 161 S33–S39
Last reviewed 26/Feb/2014
