Insulin-like growth factor 1 (IGF-1) is a protein consisting of 70 amino acids that is encoded in the IGF1 gene. It is an important factor in childhood growth, and in anabolic processes in adults.
In the past it was believed that a deficiency of IGF-1 was an indicator of a lack of growth hormone, and so very short children were treated with recombinant human growth hormone replacement therapy. However, testing that measures the presence of growth hormone and IGF-1 of very short children reveals that abnormally low levels of IGF-1 can occur in the presence of normal or elevated growth hormone levels. So IGF-1 deficiency is better understood as its own distinct diagnostic category.
A recent study (Sub-study 6 of the National Cooperative Growth Study) suggests that IGF-1 deficiency is approximately equally common as growth hormone deficiency. (Not all height differences in children are attributable to either of course. Children can be of short or very short stature for any number of other reasons, for example poor nutrition, family history, or kidney, lung, heart, or gastrointestinal disease.)
Which is not to say that the more IGF-1 the better, as elevated levels of IGF-1 are associated with an increased risk of cancer.
A diagnosis of Primary Insulin-like Growth Factor Deficiency (IGFD) is made when IGF-1 levels are measured to be significantly below those typical of children of the same age, and when other causes for short stature such as low amount of growth hormone or an underlying disease can be ruled out.
The treatment for IGFD is mecasermin (sold under the brand name Increlex) or mecasermin rinfabate (sold under the brand name iPlex). These are manmade hormones usually taken by injection. These treatments have proven effective for some children who did not respond to standard growth hormone treatment.
Because IGF-1 also has anabolic effects in adults, some researchers believe synthetic IGF-1 could be beneficial in certain ways for adults. It is one of many substances that bodybuilders and athletes have experimented with to increase muscle mass and/or decrease body fat. In some such circles it has surpassed synthetic human growth hormone in popularity. It also has its proponents as a possible anti-aging wonder drug.
Needless to say, until more is known about IGF-1 and the effects of synthetic IGF-1, it is risky to self-medicate with such a substance, especially given its connection with cancer.
University of California
The Magic Foundation