PEG-MGF
A pegylated fragment of a proposed muscle-specific IGF-1 splice variant — the underlying "MGF" biology remains scientifically contested, and PEG-MGF itself has no human clinical data.
A pegylated synthetic peptide corresponding to the 24-amino-acid E-domain of the IGF-1Ec splice variant (named "mechano-growth factor" by Goldspink based on its upregulation after mechanical loading of rodent muscle), with PEGylation intended to extend the very short plasma half-life of the unconjugated peptide.
Mechanism of action
Proposed mechanism: the MGF E-peptide acts on a receptor distinct from IGF-1R (unidentified) to drive satellite cell activation, myoblast proliferation, and local muscle hypertrophy after mechanical loading. Rodent overexpression and injection studies have shown effects on muscle fiber regeneration. Human validation of a distinct MGF receptor is lacking, and some groups argue the observed effects are artifacts of the IGF-1 mature domain rather than a genuine E-peptide activity.
Primary uses
- Muscle biology research (contested)
- Community bodybuilding use (unapproved, mechanism disputed)
Typical dosing
No human clinical dosing. Community protocols range widely and have no evidence base.
Regulatory status
Not approved for any indication. The underlying "mechano-growth factor" concept, popularized by Geoffrey Goldspink's group in the 1990s–2000s, remains disputed — multiple independent labs have questioned whether IGF-1Ec produces a biologically active standalone E-peptide in humans at all.
Status as of this entry's last review, October 4, 2026. Approvals, compounding rules and sport rules change; the regulatory tracker is checked more often.
What we checked
PEG-MGF has no study of its own indexed on PubMed; a 2026 review names it among performance-enhancing peptides. It rests on the contested biology of mechano growth factor. This section records what can be checked.
Identity, computed
| Sequence | E-domain peptide, before PEGylation (YQPPSTNKNTKSQRRKGSTFEERK) |
| Formula | C121H199N41O40 |
| Average mass | 2868.17 g/mol |
| Monoisotopic mass | 2866.4798 Da |
| Isoelectric point | 11.23 (net charge +4.98 at pH 7) |
The calculator gives the mass of the peptide portion only. The polyethylene glycol chain attached to it varies in length between products and is not specified by sellers, so no formula or mass for the finished product can be given.
Regulatory status, read October 5, 2026
Drugs@FDA: 0 records for “mechano growth factor”. EMA medicines list: 0 records for “mechano growth factor”. Run for semaglutide, the same queries return 6 and 5 records (and the registry search 84 trials), so a zero here is an absence, not a broken search. WADA 2026: section S2.3; WADA 2027: section S2.3.
What the maker or sellers claim
Claim, from research-chemical sellers: PEG-MGF builds muscle and speeds repair after training. No study of the PEGylated product in animals or people was found.
About MGF, not the PEGylated product
Mechano growth factor was proposed by Goldspink as a splice variant of IGF-1 made by muscle in response to loading, with its own E-domain peptide signalling repair (Goldspink, 2005). A 2010 review called it a putative product and set out why the evidence for a distinct MGF peptide acting on its own receptor remained unsettled (Matheny et al., 2010).
A 2026 review of performance-enhancing peptides acting on the growth-hormone and IGF-1 axis lists PEG-MGF among IGF-1 analogues in circulation and summarises adverse effects reported across the class, such as fluid retention, joint and muscle pain and blood-sugar changes, without data specific to PEG-MGF.
What we looked for and did not find
No study of PEG-MGF itself in cells, animals or people, no registry record, no pharmacokinetic data and no dose from any controlled study. The other matches for the PEGylated search are PEGylated IGF-1 and PEGylated growth hormone, different molecules.
| Source | Query | Results, October 5, 2026 | What it was |
|---|---|---|---|
| PubMed | PEG-MGF | 1 | the 2026 performance-peptide review |
| PubMed | pegylated mechano growth factor | 5 | the same review plus PEGylated IGF-1 and GH papers |
| PubMed | mechano growth factor | 2393 | broad match: mostly other growth factors; the MGF hypothesis papers and review are among them |
| ClinicalTrials.gov | mechano growth factor | 0 | |
| Drugs@FDA (openFDA) | mechano growth factor | 0 | |
| EMA medicines list | mechano growth factor | 0 |
References
- [pubmed] Goldspink G. "Mechanical signals, IGF-I gene splicing, and muscle adaptation." Physiology (Bethesda), 2005;20:232-238. PMID: 16024511.
- [pubmed] Matheny RW Jr, Nindl BC, Adamo ML. "Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration." Endocrinology, 2010;151:865-875. PMID: 20130113.
- [pubmed] Dominikowski A, et al. "The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration." Front Endocrinol (Lausanne), 2026;17:1822475. PMID: 42395176.
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Guides & tools
This entry is for educational purposes only and does not constitute medical advice. Dosing information reflects published regulatory or research data and is not a recommendation. Many compounds described here are not approved for human use in the United States. Consult a licensed medical professional before considering any peptide therapy.