PEG-MGF

also known as: Pegylated MGF, PEGylated mechano-growth factor, PEG Mechano Growth Factor

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

research-only varies (subcutaneous or intramuscular (community))

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.

References

[pubmed] Goldspink G. "Mechanical signals, IGF-I gene splicing, and muscle adaptation." Physiology (Bethesda), 2005;20:232-238.
[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.

Related peptides

MGF

The native, non-pegylated splice variant of IGF-1 produced by skeletal muscle in response to mechanical overload — extremely short-lived in vivo and therefore superseded by PEG-MGF in research-chemical markets.

IGF-1 LR3

A 13-amino-acid N-terminal extension plus Arg3 substitution gives IGF-1 LR3 roughly 2–3× the potency of native IGF-1 in bioassays — a research-reagent favorite that became a bodybuilding staple despite no human approval.

IGF-1 DES(1-3)

Deleting the first three amino acids of IGF-1 cripples IGFBP binding while preserving receptor activity — giving DES(1-3) roughly 10× the in vitro potency of native IGF-1 at promoting cell growth in IGFBP-rich environments.

Follistatin-344

The longer of the two principal follistatin splice variants — binds tissues less avidly than FS-315 and therefore has broader systemic distribution, making it the form used in most gene-therapy and myostatin-inhibition research.

Disclaimer

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.