Muscle & Performance
MGF / PEG-MGF (Mechano Growth Factor)
aka MGF · mgf · mechano growth factor · mechano-growth factor · mechanogrowth factor · PEG-MGF · peg mgf · peg-mgf · pegmgf · pegylated mgf · pegylated mechano growth factor · IGF-1Ec · IGF-1 Ec · IGF-IEc · IGF-1Eb · MGF E peptide · MGF-E · MGF 24aa
Grade
A lab-made peptide based on a muscle-repair signal discovered in stretched animal muscle, sold (usually as PEG-MGF) for muscle growth and recovery, though it has never been tested in people and even the lab results are disputed.
- Class
- Synthetic 24-amino-acid peptide copying the tail end (E domain) of IGF-1Ec, a splice variant of the insulin-like growth factor 1 gene. PEG-MGF is the same peptide with polyethylene glycol (PEG) chains attached to slow its breakdown. It does not contain mature IGF-1
- Evidence
- Grade D · Animal data only
- Sport / WADA
- Prohibited at all times (in and out of competition). The 2026 WADA Prohibited List names 'Mechano growth factors (MGFs)' under S2.3 (Growth factors and growth factor modulators).
- Last reviewed
- 2026-10
Grade D · Animal data only
Why this grade
No human trial of MGF or PEG-MGF has ever been registered or published, and a 2026 clinical review (Dominikowski et al.) places PEG-MGF in its lowest tier: no peer-reviewed human studies. The only human work concerns the body's own MGF gene activity, for example that it rises in muscle after heavy exercise in younger adults. That tells us nothing about injecting a man-made peptide. The lab evidence is also contested: some cell and animal studies found muscle, heart and brain-protective effects, while a careful 2014 study from two pharmaceutical companies could not reproduce the claimed effects on muscle cells at all. PEG-MGF, the version mostly sold, has no published research of its own.
What is it?
Why people buy it
Gym-goers and bodybuilders buy it to grow muscle and recover faster after training. It is often sold as a longer-lasting form called PEG-MGF.
What we actually know
- •Muscle makes a natural repair signal after hard exercise. MGF is a small man-made copy of one part of it.
- •In younger adults, heavy exercise raised this natural signal in muscle. In older adults it did not.
- •Some lab dish and animal studies found helpful effects. A careful 2014 study found no effect on muscle cells.
- •It has never been tested in people. It is not a licensed medicine in the UK.
What might happen
- •Nobody knows if it builds muscle in people. There are no studies in people at all.
- •The longer-lasting PEG-MGF form has no published research of its own.
- •Nobody knows what a safe amount is, or what it does over months.
- •The natural signal is found at higher levels in some cancers. This does not prove it causes cancer.
- •It is sold online as 'not for human use'. Nobody checks what is really in the bottle.
- •It is banned in sport at all times. Tested athletes can fail a drugs test.
Bottom line
An interesting muscle-repair idea with mixed lab results. In people, it is completely untested.
Know someone taking this?
Send on WhatsAppIt is like hearing a factory's alarm bell ring every time a machine breaks, then selling recordings of the bell as a repair kit. The bell is real and it does ring after damage. Whether playing it fixes anything has never been tested on a person.
How is it meant to work?
Unclear and disputed. The peptide copies the unique tail (E domain) of IGF-1Ec, the version of IGF-1 that muscle switches on after stretch or damage. Supporters propose it activates muscle stem cells (satellite cells) so they multiply before fusing into muscle fibres, and that it protects stressed heart and brain cells, possibly through a route that does not involve the IGF-1 receptor. Because it lacks the mature IGF-1 part, it should not act like IGF-1 itself. Independent attempts to reproduce its effects on muscle cells have failed. PEG-MGF adds polyethylene glycol chains, intended to slow breakdown and extend how long it lasts, but this has not been characterised in published research.
What's it studied for?
Research contexts. Not proven uses, and not recommendations.
Does the human evidence stack up?
None for the peptide sold as MGF or PEG-MGF. No trial is registered on ClinicalTrials.gov and none has been published. Human research covers only the body's own MGF: muscle biopsy studies showing its gene activity rises after heavy resistance exercise in younger but not older adults, detection of the Ec peptide in human tissue, and higher IGF-1Ec levels in some cancer tissue. None of that involves giving the peptide to anyone. A 2026 clinical review found no peer-reviewed human studies of PEG-MGF.
What could go wrong?
- !No human safety or efficacy data of any kind, for MGF or PEG-MGF.
- !Lab evidence is contested: a two-company replication effort found no effect on muscle cells.
- !PEG-MGF has no published pharmacology; how long it lasts, where it goes and what PEGylation changes are unknown.
- !Theoretical cancer concern: IGF-1Ec is found at higher levels in colorectal and prostate cancer tissue; this is an association, not proof of harm.
- !Grey-market purity and identity are unverified; vials may be mislabelled, degraded or non-sterile.
- !Banned at all times in sport; named on the WADA Prohibited List.
Is it legal in the UK?
MGF and PEG-MGF are not licensed medicines in the UK, and the MHRA has authorised no product containing them for any use. They are not controlled drugs under the Misuse of Drugs Act 1971 (the Class C hormone list covers somatropin and related growth hormones, not MGF). They are sold online as unlicensed 'research chemicals, not for human consumption'; supplying or marketing them for human use would breach the Human Medicines Regulations 2012. There is no lawful route to obtain them as a medicine.
Sources
- 01Cloning and characterization of an IGF-1 isoform expressed in skeletal muscle subjected to stretch — Yang S, Alnaqeeb M, Simpson H, Goldspink G, Journal of Muscle Research and Cell Motility (1996)
Original description of the stretch-induced IGF-1 isoform (rabbit IGF-1Eb; human Ec) later called MGF.
- 02Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells — Fornaro M, Hinken AC, Needle S, et al., American Journal of Physiology - Endocrinology and Metabolism (2014)
Two pharmaceutical companies could not reproduce claimed effects of the MGF peptide on human or mouse muscle cells or cardiomyocytes.
- 03Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration — Matheny RW Jr, Nindl BC, Adamo ML, Endocrinology (2010)
Explains the synthetic 24-residue MGF peptide versus the natural gene product, and that no free natural peptide had then been isolated.
- 04Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise — Hameed M, Orrell RW, Cobbold M, Goldspink G, Harridge SD, Journal of Physiology (2003)
Human biopsy study of the body's own MGF mRNA after exercise (rose in young, not elderly, subjects). No peptide was given.
- 05Mechano Growth Factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages — Kandalla PK, Goldspink G, Butler-Browne G, Mouly V, Mechanisms of Ageing and Development (2011)
Positive lab-dish result in human muscle cells; also explains human Ec (49 bp insert) versus rodent Eb (52 bp).
- 06Identification of the IGF-1 processing product human Ec/rodent Eb peptide in various tissues: evidence for its differential regulation after exercise-induced muscle damage in humans — Vassilakos G, Philippou A, Koutsilieris M, Growth Hormone & IGF Research (2017)
Reports the natural Ec peptide is produced in human and rodent tissues. Observational; no peptide given.
- 07A strong neuroprotective effect of the autonomous C-terminal peptide of IGF-1 Ec (MGF) in brain ischemia — Dluzniewska J, Sarnowska A, Beresewicz M, et al., FASEB Journal (2005)
Gerbil and brain-slice study; effect reported as independent of the IGF-1 receptor. Not human.
- 08The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration — Dominikowski A, Rękoś Z, Olejarz M, et al., Frontiers in Endocrinology (2026)
Clinical review: PEG-MGF has no peer-reviewed human studies (lowest evidence tier); PEGylation means native E-peptide data cannot be assumed to apply.
- 09Increased expression of IGF-1Ec with increasing colonic polyp dysplasia and colorectal cancer — Alagaratnam S, Loizidou M, Yang SY, Fuller B, Ramesh B, Journal of Cancer Research and Clinical Oncology (2020)
Higher IGF-1Ec in colorectal cancer and high-grade polyps than normal colon; notes overexpression in prostate cancer. Association only.
- 10World Anti-Doping Code International Standard: Prohibited List 2026 (official reproduction, Austrian Federal Law Gazette BGBl. III Nr. 219/2025), World Anti-Doping Agency (2025)
S2.3 names 'Mechano growth factors (MGFs)'. Gazette reproduction of the WADA list; the wada-ama.org page is https://www.wada-ama.org/en/prohibited-list.
Related
Before you trust a vial
Peptides are freeze-dried for a reason. If you have seen MGF / PEG-MGF (Mechano Growth Factor) sold pre-mixed in a ready-to-use pen or syringe, here is why that is a red flag for potency, sterility and dosing.
Storage & stability →Stay posted
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