IGF-1 LR3 and DES(1-3) IGF-1 are two laboratory versions of IGF-1, altered so that they escape the proteins that normally keep IGF-1 in check. They do it differently and end up at opposite ends of the time scale. IGF-1 LR3 has an extended and altered start to the chain, barely binds the binding proteins and acts for about 20 to 30 hours. DES(1-3) IGF-1 has its first three amino acids removed, also bypasses those proteins, but disappears in about 20 to 30 minutes, acting fast and locally. Neither is an approved medicine, both are research substances and both are banned in sport.
Why is IGF-1 modified at all?
Natural IGF-1 is a protein of 70 amino acids that circulates in the blood almost entirely bound. More than 90 per cent of circulating IGF-1 is held by binding proteins, mainly IGFBP-3. That bound pool does not act on the receptor straight away; it works as a store and a buffer. Modifications that weaken binding to IGFBP leave more free peptide and give a stronger and faster signal at the IGF-1 receptor. That is the idea behind both analogues described here. The context of the whole IGF-1 axis in muscle is set out in the article on muscle peptides.
What is IGF-1 LR3?
IGF-1 LR3 is an IGF-1 analogue of 83 amino acids. It carries two changes against the parent molecule: arginine in place of glutamic acid at position three, and a thirteen amino acid extension attached at the N-terminus. The result is very weak binding to the IGF binding proteins, potency about three times that of IGF-1, and a half-life on the order of 20 to 30 hours against 12 to 15 hours for IGF-1. It has no authorisation for use in humans. Its real application is as a supplement to cell culture media in biotechnology, not the role of a medicine. In the shop it appears as IGF-1 LR3, a lyophilisate for research.
What is DES(1-3) IGF-1?
DES(1-3) IGF-1 is a shortened variant of IGF-1 with 67 amino acids. It is produced by removing the first three amino acids of the chain, that is, glycine, proline and glutamic acid. This fragment occurs naturally: it was first isolated from bovine colostrum and later found in brain tissue. It binds the IGF binding proteins far more weakly than IGF-1, by a factor of 10 to 70 depending on the protein and the method. In an environment rich in those proteins it is sometimes described as about ten times more potent than IGF-1. Its half-life is about 20 to 30 minutes, so the peptide is cleared quickly and acts briefly and locally, near the site of administration. In the shop it appears as DES(1-3) IGF-1, also as a research reagent.
IGF-1 LR3 and DES(1-3) IGF-1: table of differences
| Feature | IGF-1 LR3 | DES(1-3) IGF-1 |
|---|---|---|
| Number of amino acids | 83 | 67 |
| Modification | arginine at position 3 plus a 13 amino acid N-terminal extension | removal of the first 3 amino acids (Gly-Pro-Glu) |
| Binding to IGFBP | very weak | weakened 10 to 70 fold |
| Potency against IGF-1 | about 3 times | about 10 times (in an IGFBP-rich environment) |
| Half-life | about 20 to 30 hours | about 20 to 30 minutes |
| Character of action | long, systemic | short, local |
| Status | no authorisation, research substance | no authorisation, research substance |
Which one is better?
Neither is better, because they are tools built on different assumptions, none of them confirmed in humans. The long half-life of IGF-1 LR3 means steady exposure of the whole body, and therefore steady risk: falls in blood glucose and an effect on every tissue sensitive to IGF. The short window of DES(1-3) IGF-1 is an idea about a local impulse, but that is a hypothesis, not a demonstrated advantage. There are no studies in humans of either analogue for building muscle, no safe dose has been established, and the pillar article explains why the story about muscle peptides runs ahead of the data.
What is the legal and sporting status of these analogues?
Neither IGF-1 LR3 nor DES(1-3) IGF-1 is an approved medicine anywhere. Both are sold as substances for laboratory research. The whole family of IGF-1 analogues appears on the WADA prohibited list as growth factors, in group S2, with a ban that applies all year. More on the legal categories is in the article on the legal status of peptides and on the legal warning page.
Frequently asked questions
What is the difference between IGF-1 LR3 and DES(1-3) IGF-1?
Both bypass the IGF binding proteins, but they differ in how long they act. IGF-1 LR3 acts for about 20 to 30 hours and systemically, DES(1-3) IGF-1 for about 20 to 30 minutes and locally. LR3 has an extended N-terminus, DES has its first three amino acids removed.
Which is more potent?
Per molecule, DES(1-3) IGF-1 is sometimes described as about ten times more potent than IGF-1 in an environment rich in binding proteins, and IGF-1 LR3 about three times. Those figures come from cell systems, not from studies in humans.
Are there human studies on muscle building?
There are none. Neither analogue has efficacy or safety data in humans for that use. The findings come from cell culture and animal models.
Can they be used in sport?
No. IGF-1 analogues are on the WADA prohibited list as growth factors in group S2 and are banned all year, in and out of competition.
Where this information comes from
The 83 amino acid structure of IGF-1 LR3, the arginine substitution at position three, the thirteen amino acid extension, the roughly threefold potency and the half-life of 20 to 30 hours come from the published characterisation of that analogue. The 67 amino acid structure of DES(1-3) IGF-1, its isolation from bovine colostrum, the 10 to 70 fold weaker binding to IGFBP and the half-life of 20 to 30 minutes come from the literature on that fragment. The share of circulating IGF-1 bound to binding proteins comes from endocrinology reference material. The group S2 listing comes from the WADA prohibited list. These sources were checked on 6 September 2026.