PeptidePeptideGrowth factorIGF-1 splice variant

MGF (Mechano Growth Factor)

Also known as Mechano Growth Factor · IGF-1Ec · IGF-1 E domain peptide

Written by enwyReviewed 15 Jul 20261 sources0 comments

MGF is the C-terminal peptide of IGF-1Ec, a splice variant of IGF-1 expressed transiently in mechanically loaded or damaged muscle. It is marketed to bodybuilders for local muscle repair. The biology is real in animal models, but the injectable research-chemical peptide has no human trials and an extremely short half-life.

01 Overview

In response to mechanical overload or injury, muscle expresses IGF-1Ec, whose distinct C-terminal E-domain peptide (MGF) is thought to kick-start satellite cell activation ahead of the mature IGF-1 systemic signal. This makes it a plausible early actor in the repair cascade, and it has been studied in rodents and in vitro.

The unmodified MGF peptide is cleared within minutes, which undermines the rationale for systemic injection and is why vendors also sell a pegylated form. No human efficacy or safety trials of injected MGF exist. Claims of muscle growth in users are anecdotal and confounded by concurrent training, diet, and other compounds.

02 Mechanism

The MGF E-domain peptide activates muscle satellite cells and promotes their proliferation independent of the IGF-1 receptor's mature-peptide binding, priming repair after mechanical damage.

03 Dosing

Tier	Dose	Route	Notes
Anecdotal	200–400 mcg	SubQ	Forum protocols only, often injected locally post-workout due to the very short half-life. No validated dosing.

04 Effects

Effect	Magnitude	Evidence
Satellite cell proliferationDemonstrated in rodent and cell-culture models of muscle repair.	Not quantified in humans	Preclinical
Claimed local muscle repairReported by users but unsupported by human data.	Unquantified	Anecdotal

05 Side effects

Effect	Severity	Frequency	Evidence	Countermeasures
Injection-site reactionsLocal redness, irritation or swelling.	Mild	Common with subcutaneous peptides	Anecdotal
Theoretical IGF-1 pathway risksUnstudied long-term consequences of repeatedly activating an IGF-1-related growth signal.	Moderate	Uncharacterised	Unconfirmed

06 Legal status

United States

Not FDA-approved; research chemical

Not approved for human use; WADA-prohibited in sport. · as of Jan 2026

07 References

The mechano-growth factor E domain peptide activates muscle satellite cellsJournal of Cell Biology / FEBS (preclinical)

08 Discussion0 comments

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This page is reference information, not medical advice. Doses and protocols are documented as they appear in the clinical literature and in practice — describing them is not a recommendation to use them. Countermeasures listed here are not a substitute for a physician. Legal status varies by jurisdiction and changes.