PEG-MGF

DNot approved; research reagentGrowth hormone, IGF-1 and growth factors →mechano growth factorMGFIGF-1Ec
In one paragraphMechano growth factor is a splice variant of IGF-1 that muscle makes briefly after loading or damage; its distinctive tail is thought to signal muscle stem cells to divide. PEG-MGF is a synthetic version of that tail with polyethylene glycol attached to make it last longer, sold for muscle repair and growth. No human study has ever administered it: the entire human literature measures how much MGF muscle expresses after exercise, growth hormone or ultrasound. It is not approved anywhere and is named on the Prohibited List.
Schematic 3D structure of PEG-MGF
24 residues · IGF-1Ec E-domain peptide, pegylated · schematic
Overall gradeD No human evidence
Human trials0 — every human study measures the body's own MGF
Outcomes graded3
Last reviewed10 September 2026
EvidenceWhat it isHow it worksUnknownsMolecule & PKRegulationQuestionsReferences

What the human research shows

A clean D. The biology behind it is real and studied in people — as something muscle makes — and the product built on it has never been tested in anyone.

MetabolicCardioMuscleHealingNeuroImmuneSexualSkinAgeing

Evidence profile0–5

  • Metabolic & weight—0.0
  • Cardiovascular—0.0
  • Muscle & growth—0.0
  • Healing & repairD0.0
  • Neuro & sleep—0.0
  • Immune & inflammation—0.0
  • Sexual & hormonal—0.0
  • Skin & appearance—0.0
  • Ageing & longevity—0.0
No benefit outcome for PEG-MGF has both human evidence and a measurable effect, so the profile is empty. That is the finding, not a gap in the chart.
OutcomeGradeEffect sizeHuman studiesWhere the evidence comes from
Muscle growth or repair (injected)DNo human evidenceNot measurable0 controlledNo human study of any design has given MGF or PEG-MGF. Claims rest on rodent injections and on human studies that only measured natural MGF expression.12
MGF expression after exercise (the body's own)DNo human evidenceNot measurableSeveral small physiology studiesHuman muscle raises MGF messenger RNA after resistance exercise and growth hormone, more in young than old. Real and interesting; it says nothing about injecting a synthetic fragment.1
Safety in humansadverseDNo human evidenceNot measurableNoneUnknown. A long-acting IGF-1-derived peptide would be expected to share IGF-1's concerns, including effects on glucose and on cell proliferation, and none of that has been measured.
AMultiple good human trials, consistentBSome human trials, mostly consistentCFew or weak human studiesDAnimal or anecdotal onlyeffect size · red = adverse

Literature searched to 10 September 2026. Human studies only; animal and cell work informs the mechanism section and nothing else.

What it is

IGF-1 is spliced differently by different tissues. The muscle variant, IGF-1Ec, carries a 24-amino-acid tail — the 'E domain' — that appears within hours of loading and is thought to prime satellite cells before the standard IGF-1 takes over to build fibres. Researchers named it mechano growth factor in the 1990s.

PEG-MGF is the E-domain peptide alone, pegylated so it survives in blood for hours rather than minutes. It exists as a research reagent and a grey-market product. No company has developed it as a drug.

How it is thought to work

In cell and rodent work the E-domain peptide increases satellite cell proliferation and, injected into rodent muscle, increases size. Whether a pegylated fragment in the bloodstream reaches muscle and does the same in people is the untested question. The 2026 review of performance peptides places MGF among those with no clinical evidence at all.

What is still unknown

  • Whether the E-domain peptide has any effect separate from full IGF-1 in humans — debated even in the physiology literature.
  • Safety, which has never been characterised for any dose.
  • What is in the vials.

The molecule and how long it lasts

Identity

A pegylated peptide with no single defined structure in public databases

Pharmacokinetics
Route
Injected as sold; no human study
Half-life
No human pharmacokinetic data

No pharmacokinetic study in people.

Regulatory status

European Union
Unauthorised medicinal product

No marketing authorisation anywhere. Supplying it for human use is an offence under national medicines law.

United States
Not approved

Research reagent 'not for human use'; no clinical programme.

United Kingdom
Unlicensed medicine

No MHRA licence.

Australia
Prescription-only / unapproved

Not on the ARTG; imports are seized.

Canada
Not authorised

No Drug Identification Number.

Sport (WADA)
Prohibited at all times

Mechano growth factors are named on the Prohibited List under growth factors (S2), in and out of competition.

Questions people actually ask

Does PEG-MGF build muscle?
Nobody knows. It has never been given to a human in any study. The rodent injections that drive the claim used the peptide in muscle directly, not a pegylated version in the blood.
Is MGF real?
Yes — as something muscle makes after loading. Human studies have measured it for twenty years. That is a fact about physiology, not about a product.
Is it legal?
It is not an approved medicine anywhere, and it is explicitly named on the WADA list. Selling it for human use is an offence in the EU and UK.

One page per claimed effect

References

  1. 1
  2. 2
    Searches of PubMed and trial registries for administered mechano growth factor or PEG-MGF in humans.LYO literature search, September 2026No human administration study identified.
  3. 3

Change log

  • 2026-09-10Initial publication. Grade D: no human administration study exists.