IGF-1 LR3 (Long R3 IGF-1) is a lab-engineered analogue of insulin-like growth factor 1, first described by Australian researchers in 1992.
Researchers in Adelaide built it by adding an N-terminal extension taken from porcine growth hormone to IGF-1 and replacing the glutamic acid at position 3 with arginine (Francis et al., Journal of Molecular Endocrinology). Those changes cut its binding to IGF-binding proteins, which normally hold IGF-1 in reserve, so it was more potent than native IGF-1 in rat muscle cell cultures. The authors presented it as a research reagent for studying IGF-1 action, and in liver cells it also acted through the insulin receptor.
There are no peer-reviewed human studies of IGF-1 LR3, according to a 2026 review in Frontiers in Endocrinology that places it in its lowest evidence tier. Animal work exists: in guinea pigs, a 7-day infusion increased the relative weight of the adrenals, gut, kidneys and spleen without increasing overall growth (Conlon et al., 1995). The review flags a theoretical mitogenic concern based on IGF-1 receptor biology, not a demonstrated cancer signal in people.
IGF-1 LR3 is not FDA-approved, and WADA bans IGF-1 and its analogues at all times under class S2.3, growth factors.
The FDA-approved form of IGF-1 is mecasermin, sold as Increlex since August 30, 2005, for growth failure in children with severe primary IGF-1 deficiency. Its label warns that severe hypoglycemia, including hypoglycemic seizures, has occurred because IGF-1 has insulin-like effects. IGF-1 LR3 has no human safety data at all. The 2026 WADA Prohibited List names “insulin-like growth factor 1 (IGF-1, mecasermin) and its analogues” in section S2.3, prohibited in and out of competition.
IGF-1 LR3 is a recombinant protein made in bacteria, not a short synthetic peptide, and the 1992 method needed a refolding step to produce active material. A purity percentage does not show whether a batch is the right protein. A useful result confirms identity by mass and reports the amount found.
Before trusting a label, check that batch’s published result on our latest tests page or in Janoshik’s public results database. No results are published for IGF-1 LR3 in our index yet. When the first published result arrives, a vendor leaderboard appears above.