Insulin-like growth factor 1 (IGF-1) is an anabolic hormone produced in the liver through the stimulation of growth hormone release. Most scientists agree that nearly all of the anabolic effects linked to growth hormone (GH) are produced by IGF-1. IGF-1 has attained mythical status among bodybuilders and athletes because of its reputed significant anabolic effects in muscle. While you always have to be wary when considering 'Bro Science claims, there is some scientific justification of the anabolic effects of IGF-1, mainly in animals and in humans shown to be deficient in the hormone. At present, the only medical indications for prescribing IGF-1 are to treat a form of dwarfism and also to treat patients who have become refractory to GH therapy; that is, GH no longer works for them. Some patients produce antibodies that neutralize GH, and providing pharmaceutical forms of IGF-1 overcomes the problem. In the bodybuilding world, IGF-1 is considered more potent than GH and is thought to provide a number of substantial benefits. These include increased energy and endurance; increased tissue repair, especially connective tissue such as joints and tendons; muscle growth;anti-aging effects; fat-loss; skin anti-aging effects; improved mood and mental function.
But as is the case with most other hormones, IGF-1 is also controversial. Animal studies show that those animals either born with or through genetic manipulation have resistance to IGF-1 appear to live longer than animals with normal IGF-1 physiology. The mechanism behind this is that IGF-1 appears to stimulate the activity of genes that are associated with both death and disease, at least in animals. In addition, some animals, such as rodents, which are the primary animals used in lab studies, are far more prone to cancer than are humans. The significance here is that while there is no evidence that IGF-1 causes cancer (as does estrogen), there is some evidence that it may aid both the continuing existence of, and the spread of tumors. In humans, IGF-1 has been implicated in breast and colon cancers. But scientists still argue over whether the circulating IGF-1 in the body stimulates tumors, or whether tumors themselves produce IGF-1 to aid in their survival and spread. Among other functions, IGF-1 promotes a process called apoptosis, which refers to cellular self-destruction. Normal cells undergo apoptosis when something abnormal is detected in the cell. Since tumor cells are abnormal, they would also undergo apoptosis, but the IGF-1 they may produce blocks this process and thus allows them to survive. Some new cancer therapies involve blocking IGF-1 activity in tumors, and early results show that it appears to work, at least in animals.
But what happens in animals in relation to IGF-1 may vary in humans. While some people who live to 100 or older show an IGF-1 receptor resistance, in . . .