IGF-1 LR3  insulin like growth factor

Igf-1 long r3 is an 83-amino-acid analog of human IGF-I actually containing the complete human IGF-1 sequence but with the replacement 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 R3 IGF-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. 

The ability of IGF-I to stimulate protein synthesis resembles the action of GH, which was shown in separate studies on volunteers to stimulate protein synthesis without affecting protein degradation. Although it is believed that the effects of GH are mediated through IGF-1, this cannot be the case entirely. First, the effects of the two hormones are different, in that GH does not change protein degradation. Second, the effect of GH is observed with little or no change in systemic IGF-1 concentrations.