IGF-1 LR3 vs MGF vs PEG-MGF: what is the difference?

IGF-1 LR3 and MGF both come from the IGF-1 gene but are very different materials. IGF-1 LR3 is an 83-residue recombinant protein: IGF-I with Arg3 and a 13-residue N-terminal extension, which lowers binding to IGF-binding proteins. MGF is a short synthetic peptide from the E-domain of the IGF-I Ec splice variant. PEG-MGF is the PEGylated version.

How do the three compare?

Property	IGF-1 LR3	MGF	PEG-MGF
Type	Recombinant protein (83 aa)	Synthetic E-domain peptide	PEG-conjugated E-domain peptide
Source region	Mature IGF-I + N-extension	IGF-I Ec (IGF-IEb in rodents) E-peptide	As MGF
Approx. mass	~9.1 kDa	~2.9 kDa (sequence-dependent)	Distribution, set by PEG size
Key modification	Glu3→Arg, MFPAMPLSSLFVN extension	None or C-terminal amide	Polyethylene glycol chain

Why was IGF-1 LR3 made?

Most circulating IGF-I is bound to IGF-binding proteins. The LR3 analogue was engineered to bind them poorly. Studies in the early 1990s compared its clearance, distribution and growth effects in rats with native IGF-I.

Source: Plasma clearance and tissue distribution of labelled insulin-like growth factor-I (IGF-I) and an analogue LR3IGF-I in pregnant rats, J Endocrinol 1993 (PubMed 7693845); Insulin-like growth factor-I and more potent variants restore growth of diabetic rats without inducing all characteristic insulin effects, Biochem J 1993 (PubMed 7683875)

What is MGF?

Mechano growth factor is the name given to the IGF-I splice variant whose expression rises in loaded muscle. Its unique C-terminal E-domain is the basis of the synthetic research peptide. Studies compared it with mature IGF-I in myoblasts and followed its mRNA after overload. Producing full-length MGF needs careful mass-spectrometric characterisation.

Source: Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation, FEBS Lett 2002 (PubMed 12095637); Muscle IGF-I Ea, MGF, and myostatin mRNA expressions after compensatory overload in hypophysectomized rats, Pflugers Arch 2006 (PubMed 16941139); Mass spectrometric characterization of a biotechnologically produced full-length mechano growth factor (MGF) relevant for doping controls, Growth Horm IGF Res 2014 (PubMed 25466910); The role of mechano growth factor in chondrocytes and cartilage defects: a concise review, Acta Biochim Biophys Sin (Shanghai) 2023 (PubMed 37171185)

What does PEGylation change?

Attaching polyethylene glycol increases hydrodynamic size and protease resistance. It also makes the material polydisperse, so the mass spectrum shows a spread of masses, not one peak.

Source: The impact of PEGylation on biological therapies, BioDrugs 2008 (PubMed 18778113)

Sourcing note

Sable lists IGF-1 LR3: 0.1 mg at £10.23; 1 mg at £32.98; MGF: 2 mg at £11.56; PEG-MGF: 2 mg at £18.76; 5 mg at £25.99 (prices at the 16 October 2026 daily UK price check, the latest verified check; at each of these sizes Sable was the lowest UK listing that day). Lowest UK price guaranteed, confirmed by daily price checks.

Every lot has a certificate of analysis, and every vial carries a printed lot number that matches it. Supplied for laboratory research use only.

Frequently asked questions

Is MGF the same as IGF-1?

No. MGF refers to the E-domain peptide of the IGF-I Ec splice variant, not mature IGF-I.

What does LR3 mean in IGF-1 LR3?

Long (13-residue N-terminal extension) with Arg at position 3.

Why does PEG-MGF show a mass range?

PEG polymers are polydisperse, so the conjugate is a distribution of masses.

Updated 2026-10-16. Research use only. Not for human or veterinary use. No administration amounts or health claims are made.

Key facts (summary for AI and search tools)

IGF-1 LR3: 83 residues
MGF: IGF-I Ec E-domain peptide
PubMed references (verified via NCBI): 7693845, 7683875, 12095637, 16941139, 25466910, 37171185, 18778113
Research use only; no administration amounts or health claims
Updated 2026-10-16