What is IGF-1?
IGF-1 is a polypeptide hormone about the same size as insulin, or 70 amino acids. It´s a highly anabolic hormone released primarily in the liver (but also in peripheral tissues) and stimulates the production of growth hormone. It is responsible for much of the anabolic activity of growth hormone, including nitrogen retention and protein synthesis as well as muscle cell hyperplasia (increase in number of muscle cells), as well as mitogenesis (the growth of new muscle fibers).
IGF-1 is necessary as well as sufficient in muscle growth (anabolic) and has been shown to also be highly anti-catabolic agent as well. As with all anabolic substances, IGF-1´s anabolic effects are still limited only by the protein supply within muscle cells. Thus IGF works much better when enough protein is supplied to the muscle.
For athletes and bodybuilders who are rehabilitating an injury IGF is vital to the proper production of connective tissue, and studies have shown that exogenous IGF administration may improve collagen formation and aid in the repair of cartilage and would greatly decrease recovery time as well as increase the strength of the recovered area.
A study examined the injection of insulin-like growth factor I (IGF-I) in different muscle fibers. The researchers concluded that IGF-I promotes an average increase of 15% in muscle mass and a 14% increase in strength in muscle tissue. The researchers have speculated that these effects are primarily due to stimulation of muscle regeneration via the activation of satellite cells by IGF-I.
A 15% increase in muscle mass, and a 14% increase in strength are no small increases. If we could realistically expect 7% gains in muscle mass and strength (half of the gains experienced in the study), then this would be able to help through plateaus or injuries.
What is IGF-1 Lr3?
IGF-1 Lr3 (Insulin-like Growth Factor-I Long R3) is an 83 amino acid analog of human IGF-I comprising the complete human IGF-I sequence with the substitution of an Arg for the Glu at position 3 (hence R3), as well as a 13 amino acid extension peptide at the N-terminus. IGF-I Lr3 is significantly more potent (2-3x) than IGF-I in studies, because it has a lower affinity to be rendered inactive by IGF binding proteins.