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 LR3 was also modified from the base peptide by replacing the glutamic acid at position 3 with arginine (R) – hence the R3.
The L stands for long, as an additional 13 amino acids were added, again reducing binding, while improving metabolic stability. This increases the half-life to 20-30 hours, and also increasing the potency 3fold