Lr3IGF-1 (Long R3 Insulin-like Growth Factor-I or Long R3IGF-I) is an 83 amino acid analog of human IGF-I actually comprising the complete human IGF-1 sequence but with the substitution of an Arg for the Glu at position 3, as well as a 13 amino acid extension peptide at the N-terminus. This makes Long R3IGF-I significantly more potent (2-3x) than IGF-I in studies, because it has a lower affinity to be rendered inactive by IGF binding proteins, and consequently more potential activity in the body. IGF-1 consists of 70 amino acids in a single chain with three intramolecular disulfide bridges.
IGF-1 is a peptide roughly the same structure and size as insulin, or about 70 amino acids long. It belongs to the peptide family of substances identified as growth factors. It is a highly anabolic hormone released in the liver as well as in peripheral tissues such as skeletal muscle. In the body, IGF-1 is released in response to the presence of Human Growth Hormone (HGH). After intense resistance training, the body experiences a surge in GH and IGF, and this is one way that new muscle is built. Although GH is considered to be highly anabolic, in actuality, IGF-1 is suspected to be responsible for the primary anabolic activities of GH.
IGF-1 builds new muscle tissue by promoting nitrogen retention and protein synthesis. This causes the growth of muscles through both hyperplasia (which is an increase in number of muscle cells) and mitogenesis (which is the actual growth of new muscle fibres) IGF-1s effects are not limited to building new muscle, however. It has a potent effect on lipid (fat) metabolism, and helps the body burn fat at a significantly elevated rate. In addition, IGF-1 is both a neuroprotector and neuropromotor, which improves mental functions such as reflexes, memory, and learning ability. IGF is also important for production of connective tissue and insuring proper bone density.