IGF-1 LR3, or Insulin-like Growth Factor-1 Long R3, is a synthetic peptide that is a modified version of the naturally occurring IGF-1 hormone. It has been altered to include an additional 13 amino acids at the N-terminal end and a substitution of Arginine for Glutamic Acid at the third position
In sports, particularly bodybuilding and athletics, IGF-1 LR3 is popular for its ability to enhance muscle growth, recovery, and performance.