Comparison
IGF-1 LR3 vs. Ipamorelin
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
143045-27-6
170851-70-4
Molecular weight
9117.6 g/mol
711.86 g/mol
Half-life
21 h
2 h
Sequence
MFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSAAib-His-D-2-Nal-D-Phe-Lys-NH2Mechanism of action
IGF-1 LR3
IGF-1 LR3 is a recombinantly produced variant of human IGF-1. Two changes define its properties: (1) at position 3, glutamic acid is replaced by arginine; (2) a 13-amino-acid sequence is added at the N-terminus ('Long'). Both modifications drastically reduce affinity for the six IGF-binding proteins (IGFBP-1 to -6) that normally bind native IGF-1 in the blood and regulate its availability at the receptor. As a result, a larger fraction of the molecule is freely available to bind the type-1 IGF receptor (IGF-1R) — the same receptor as native IGF-1. In preclinical models and cell culture, LR3 IGF-1 therefore acts as a more potent agonist than unmodified IGF-1. The downstream signalling pathway (PI3K/Akt and MAPK) is identical to that of IGF-1; the modification changes bioavailability, not the receptor target.
Ipamorelin
Ipamorelin is a selective agonist at the GH secretagogue receptor (GHSR-1a). Compared to GHRP-2 and GHRP-6 its selectivity for the growth-hormone axis is higher; ACTH, cortisol and prolactin are not significantly stimulated in clinical studies. This selectivity was the main reason for its development over older GHRPs.
Evidence base
Highest evidence
Animal model
Human RCT
Studies
4
4
of which in humans
0
3
Effects recorded
4
3
Open conflicts
1
1
Documented adverse events
1
1
Legal status
Full entries
Frequently asked questions
- What is the difference between IGF-1 LR3 and Ipamorelin?
- IGF-1 LR3 is classified as "Growth", while Ipamorelin is classified as "Growth". IGF-1 LR3: Synthetic analogue of insulin-like growth factor 1 (IGF-1) carrying an arginine substitution at position 3 and a 13-amino-acid N-terminal extension. These modifications lower binding to IGF-binding proteins and extend its duration of action relative to native IGF-1. LR3 IGF-1 is primarily an established cell-culture reagent (serum-free media, bioprocessing); it is NOT an approved human medicine. Use in the bodybuilding grey market is described; as an IGF-1 analogue, LR3 IGF-1 falls under the WADA anti-doping prohibition. Ipamorelin: Synthetic pentapeptide and selective growth-hormone secretagogue. Developed at Novo Nordisk in the 1990s as a pentapeptide GHRP successor; clinical development was discontinued after phase 2 (post-operative ileus). This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
- Which peptide is better supported by science, IGF-1 LR3 or Ipamorelin?
- The highest available evidence level is "Animal model" for IGF-1 LR3 and "Human RCT" for Ipamorelin. A higher evidence level means more robust data, but says nothing about suitability for an individual. The full body of evidence is on each peptide's own page.
- What is the legal status of IGF-1 LR3 and Ipamorelin in Germany and the United States?
- Germany: IGF-1 LR3 — Unapproved, Ipamorelin — Unapproved. United States: IGF-1 LR3 — Unapproved, Ipamorelin — Unapproved. These are factual summaries with source and review date on the individual pages.