Comparison
GHRP-2 vs. IGF-1 LR3
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
158861-67-7
143045-27-6
Molecular weight
817.93 g/mol
9117.6 g/mol
Half-life
0.5 h
21 h
Sequence
D-Ala-D-2-Naphthyl-Ala-Ala-Trp-D-Phe-Lys-NH2MFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSAMechanism of action
GHRP-2
GHRP-2 binds with high affinity to the GH secretagogue receptor (GHSR-1a) in the pituitary and hypothalamus. Activation leads to rapid release of pulsatile growth hormone. Unlike GHRH, GHRP-2 acts via a separate pathway and can be combined synergistically with GHRH to elicit maximal GH responses in provocation tests.
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.
Evidence base
Highest evidence
Human trial
Animal model
Studies
4
4
of which in humans
4
0
Effects recorded
3
4
Open conflicts
0
1
Documented adverse events
1
1
Legal status
Full entries
Frequently asked questions
- What is the difference between GHRP-2 and IGF-1 LR3?
- GHRP-2 is classified as "Growth", while IGF-1 LR3 is classified as "Growth". GHRP-2: Synthetic hexapeptide of the GH secretagogue family. Approved in Japan as GHRP Kaken as a diagnostic test for GH deficiency. Not available as a medicine outside Japan. 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. This page contrasts both neutrally and source-based — with no usage or dosing recommendation.
- Which peptide is better supported by science, GHRP-2 or IGF-1 LR3?
- The highest available evidence level is "Human trial" for GHRP-2 and "Animal model" for IGF-1 LR3. 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 GHRP-2 and IGF-1 LR3 in Germany and the United States?
- Germany: GHRP-2 — Unapproved, IGF-1 LR3 — Unapproved. United States: GHRP-2 — Unapproved, IGF-1 LR3 — Unapproved. These are factual summaries with source and review date on the individual pages.