← Shelf·Modified IGF-1 analog (Long R3 variant)·XIX.
IGF-1 LR3.
An 83-amino-acid analog of insulin-like growth factor 1 with an N-terminal 13-residue extension (from methionyl-porcine growth hormone) and a single Arg-for-Glu substitution at position 3. The Long R3 modification substantially reduces binding to circulating IGF-binding proteins, extending plasma half-life relative to native IGF-1.
IGF-1 is a hormone your liver produces primarily in response to growth-hormone signaling, and it is the principal mediator of GH's anabolic effects. LR3 IGF-1 is a laboratory-manufactured analog engineered for a specific pharmacokinetic profile — not the native hormone your body makes.
Sold across the strength-training peptide community with confidence the primary literature does not share about the LR3 variant specifically. Native IGF-1 has decades of published biology; LR3 was originally developed as a cell-culture reagent, and much of its "in humans" narrative extrapolates from the parent hormone.
Straight talk
Straight talk: the LR3 variant was engineered as a research-grade reagent — its whole design point is longer receptor engagement in cell-culture and animal experiments. Human clinical data on injectable LR3 IGF-1 as sold is essentially absent. The parent IGF-1 (mecasermin) IS FDA-approved for one specific pediatric indication under a branded formulation — but the LR3 variant is not that molecule, and the two are not interchangeable.
What the research studies
The literature, not a summary of it.
Foundational IGF-1 biology: Rinderknecht, Humbel, LeRoith, Yakar, Rosen. LR3-specific work: Francis, Ballard, and the CSIRO cell-culture literature that produced the analog. Journals: Endocrinology, J Endocrinol, Growth Horm IGF Res. Read the research yourself:
Recommended vendor · Amino Club
≥ 99% by HPLC on the current lot — ILS Laboratories (ISO/IEC 17025).
$45.49 during Fall Sale (was $69.99)
35% off applied automatically at checkout when you land through this link.