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

 

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Whilst wielding a couple of dumbbells in a gym class in 2003, Kate experienced an epiphany around the lack of accepted best practice guidelines when it came to staying well and avoiding disease. Kate realized that she had no chance of slowing her own aging process unless she became better educated about her options.
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