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.