IGF-1 LR3 vs MGF
IGF-1 LR3 is a modified IGF-1 with an arginine substitution and a 13-residue extension that reduces binding to IGF-binding proteins and prolongs its action. MGF (mechano growth factor) refers to the E-domain peptide of an IGF-1 splice variant expressed after muscle loading; its independent activity is debated.
IGF-1 LR3
A recombinant analogue of insulin-like growth factor-1 with an Arg3 substitution and N-terminal extension that sharply reduces binding to IGF-binding proteins.
BEST STUDIED FOR
GH secretagogues
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MGF
A splice variant of the IGF-1 gene (IGF-IEc) produced in response to mechanical load, with a distinct E-domain peptide studied in tissue repair.
BEST STUDIED FOR
GH secretagogues
Read the cited profile →
SIDE BY SIDE
| IGF-1 LR3 | MGF | |
|---|---|---|
| The key difference | Long-acting IGF-1 analogue, weak IGFBP binding | IGF-1Ec splice-variant E-peptide |
| Class | GH secretagogues | GH secretagogues |
| Mechanism | Most circulating IGF-1 is held by IGF-binding proteins. | Alternative splicing of IGF-1 exons yields the IGF-IEc isoform, up-regulated by mechanical stress in muscle, bone, tendon and cartilage. |
| Status | A laboratory and animal-research reagent; not an approved medicine. Found in black-market "performance" products. | Cell and animal research only; synthetic "MGF" peptides sold online are E-domain fragments with no clinical development. |
| Reported safety signals | In pigs it suppressed endogenous GH, IGFBP-3 and IGF-1; IGF-1 signalling carries hypoglycaemia risk; black-market products are frequently mislabelled. | No human safety data. Increased IGF-IEc expression has been linked to smooth-muscle hypertrophy in fibrostenotic Crohn’s disease tissue. |
| A key study | Identified a His-tagged LR3-IGF-I in a black-market product, illustrating mislabelled performance products. (Growth Horm IGF Res 2010, PMID 20675162) | Reviews how mechanical stress regulates IGF-I splice isoforms and the evidence for an MGF role in repair. (Endocrinology 2010, PMID 20130113) |
WHEN TO RESEARCH WHICH
IGF-1 LR3 is the tool for sustained IGF-1 receptor activation in cell culture; MGF for questions about the splice variant’s local role after mechanical load. Both are discussed here strictly as research compounds; nothing on this page is medical advice or a dosing guide.
REFERENCES (PUBMED)
- [IGF-1 LR3] Detection of His-tagged Long-R³-IGF-I in a black market product — Growth Horm IGF Res 2010. PMID 20675162
- [IGF-1 LR3] Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs — J Endocrinol 1997. PMID 9488001
- [IGF-1 LR3] Effect of recombinant porcine IGFBP-3 on IGF-I and long-R3-IGF-I-stimulated proliferation and differentiation of L6 myogenic cells — J Cell Physiol 2004. PMID 15254966
- [MGF] Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration — Endocrinology 2010. PMID 20130113
- [MGF] The role of mechano growth factor in chondrocytes and cartilage defects: a concise review — Acta Biochim Biophys Sin (Shanghai) 2023. PMID 37171185
- [MGF] Mechano Growth Factor Accelerates ACL Repair and Improves Cell Mobility of Mechanically Injured Human ACL Fibroblasts by Targeting Rac1-PAK1/2 and RhoA-ROCK1 Pathways — Int J Mol Sci 2022. PMID 35457148
FREQUENTLY ASKED
What is the difference between IGF-1 LR3 and MGF?
IGF-1 LR3 is a modified IGF-1 with an arginine substitution and a 13-residue extension that reduces binding to IGF-binding proteins and prolongs its action. MGF (mechano growth factor) refers to the E-domain peptide of an IGF-1 splice variant expressed after muscle loading; its independent activity is debated.
What is the regulatory status of IGF-1 LR3 and MGF?
IGF-1 LR3: A laboratory and animal-research reagent; not an approved medicine. Found in black-market "performance" products. MGF: Cell and animal research only; synthetic "MGF" peptides sold online are E-domain fragments with no clinical development.
What safety signals have been reported?
IGF-1 LR3: In pigs it suppressed endogenous GH, IGFBP-3 and IGF-1; IGF-1 signalling carries hypoglycaemia risk; black-market products are frequently mislabelled. MGF: No human safety data. Increased IGF-IEc expression has been linked to smooth-muscle hypertrophy in fibrostenotic Crohn’s disease tissue.
Which studies is this comparison based on?
For IGF-1 LR3: “Detection of His-tagged Long-R³-IGF-I in a black market product” (PMID 20675162); “Long [R3] insulin-like growth factor-I reduces growth, plasma growth hormone, IGF binding protein-3 and endogenous IGF-I concentrations in pigs” (PMID 9488001); “Effect of recombinant porcine IGFBP-3 on IGF-I and long-R3-IGF-I-stimulated proliferation and differentiation of L6 myogenic cells” (PMID 15254966). For MGF: “Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration” (PMID 20130113); “The role of mechano growth factor in chondrocytes and cartilage defects: a concise review” (PMID 37171185); “Mechano Growth Factor Accelerates ACL Repair and Improves Cell Mobility of Mechanically Injured Human ACL Fibroblasts by Targeting Rac1-PAK1/2 and RhoA-ROCK1 Pathways” (PMID 35457148).
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