Growth Factor-I (IGF-I)

Human Insulin-like Growth Factor-I (IGF-I) is a single chain, 70 amino acid polypeptide. Human LONG™R³ Insulin-like Growth Factor-I (IGF-I) is an 83 amino acid analog of human IGF-I comprising the complete human IGF-I sequence with the substitution of an Arg for the Glu at position 3 (hence R³), and a 13 amino acid extension peptide at the N-terminus.

The main difference between the two forms is half-life. The hIGF-1 has a half-life of less than one hour, most estimates between 13 mins – 48 mins via cell culture studies. In-human studies are not available at this time but the only difference should be peak blood levels, not half-life. The half life of Long IGF-1 has been estimated to be around 17 hours; therefore less frequent injections are necessary.

Because of the incredibly short half-life, regular hIGF-1 is all but useless to bodybuilders. The only form currently being used is the Long R3 form. LR3 has been shown to be 3 times more potent in tissue growth than IGF-1 in lab cultures. LR3 is also more resistant to the binding proteins that deactivate the effects of IGF-1.