Comparison
IGF-1 LR3 vs. Sermorelin
Two peptides side-by-side — identity, evidence base, legal status and known adverse events.
Identity
Category
Growth
Growth
CAS no.
143045-27-6
86168-78-7
Molecular weight
9117.6 g/mol
3358 g/mol
Half-life
21 h
0.2 h
Sequence
MFPAMPLSSLFVNGPRTLCGAELVDALQFVCGDRGFYFNKPTGYGSSSRRAPQTGIVDECCFRSCDLRRLEMYCAPLKPAKSAYADAIFTNSYRKVLGQLSARKLLQDIMSRMechanism 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.
Sermorelin
Synthetic analogue of the first 29 amino acids of human growth-hormone-releasing hormone (GHRH). Stimulates pulsatile endogenous growth-hormone secretion from the pituitary via the GHRH receptor. Very short plasma half-life — pharmacodynamic effect lasts several hours nevertheless.
Evidence base
Highest evidence
Animal model
Human RCT
Studies
4
5
of which in humans
0
3
Effects recorded
4
3
Open conflicts
1
1
Documented adverse events
1
3
Legal status
Full entries
Frequently asked questions
- What is the difference between IGF-1 LR3 and Sermorelin?
- IGF-1 LR3 is classified as "Growth", while Sermorelin 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. Sermorelin: Synthetic analogue of the first 29 amino acids of human GHRH. Stimulates pulsatile growth-hormone secretion from the pituitary. Formerly FDA-approved as Geref Diagnostic, now withdrawn in many markets — compounding and research use dominate. 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 Sermorelin?
- The highest available evidence level is "Animal model" for IGF-1 LR3 and "Human RCT" for Sermorelin. 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 Sermorelin in Germany and the United States?
- Germany: IGF-1 LR3 — Unapproved, Sermorelin — Unapproved. United States: IGF-1 LR3 — Unapproved, Sermorelin — Research only. These are factual summaries with source and review date on the individual pages.