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Growth hormone axis

PEG-MGF

A muscle-repair peptide with a compelling mechanism story and no robust human outcome evidence.

L2Animal / lab studiesNot approved for this usePreclinical
How settled this rating is:
very-low confidence in the current evidence rating
Routes studied:
Not established · Subcutaneous injection, Intramuscular (marketed but never approved)
Also known as:
pegylated mechano-growth factor, MGF, IGF-1Ec peptide
Last reviewed:
2026-09-06
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Evidence passport

Last reviewed 2026-09-06

A one-screen summary of what is known about this compound. Every field describes the evidence and legal status — not how safe or effective it is, and not a recommendation. The 0-100 figures are evidence-strength ratings, not percentages.

Evidence level (type of study, not a quality rating)
L2Animal / lab studies
How settled this rating is
Very low confidence in rating
Human efficacy evidence
6 of 100 evidence strength
Human safety evidence
6 of 100 evidence strength
Regulatory status
Not approved for this use
Development
Preclinical
Routes
SC injection· unapprovedIM· unapproved
Evidence base
Mostly animal and lab studies
Furthest stage
Preclinical
Source curation
Sources fully curated
How far human research has progressed
No robust human trial evidence identified in our curated record

Most of this evidence comes from animals and cells

The supporting research for PEG-MGF is predominantly preclinical (Level 1–2). That is a legitimate starting point for science and a poor basis for personal decisions. Human results are not simply a scaled-up version of mouse results.

Overview

Human efficacy evidence strength6 of 100 evidence strength

Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.

Preclinical (animal / lab) evidence strength42 of 100 evidence strength

Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.

Human safety evidence strength6 of 100 evidence strength

Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number.

How to read these scores

Every number here rates the evidence, not the compound. They are editorial 0-100 strength ratings, not percentages, and not a rating out of five stars.

  • Human efficacy evidence strength — Higher = more and better-quality human evidence. It does not mean the effect is bigger or that the compound works for you.
  • Preclinical evidence strength — Higher = more animal, tissue or cell research. Preclinical results are a starting point, not proof of a human benefit.
  • Human safety evidence strength — Higher = more mature, better-documented human safety data. It does not mean the compound is safer than one with a lower number. A score of 80 does not mean “80% safe”.
  • Evidence level (L0-L5) — the strongest type of study behind the compound, from anecdote (L0) to large replicated human trials (L5). It is a description of the study evidence, not a quality, safety or recommendation rating.
  • Confidence — how likely we think it is that this rating changes as new research lands. Low confidence means the picture is unsettled, not that the compound is bad.

None of these ratings is medical advice, a safety guarantee, or a recommendation to use anything. How we grade evidence.

How far human research has progressed: No robust human trial evidence identified in our curated record

Routes & formulations

Marketed / research routes — never approved

SC injection· unapprovedIM· unapproved

Marketed for injection, including localised injection near trained muscle. No approved formulation exists and the localised-effect claim is not established in humans.

Route availability is not evidence of efficacy, and evidence from one route does not transfer to another. The Registry never provides dosing or sourcing information.

Peptide lifecycle

  1. Discovery

  2. Preclinical

    Furthest established stage

  3. Phase I

  4. Phase II

  5. Phase III

  6. Approved

Preclinical

There is no pharmaceutical development programme in our record. Mechano-growth factor biology is a legitimate research field; PEG-MGF as a marketed injectable product is not a clinical programme.

What it is

A pegylated synthetic peptide based on a splice variant of IGF-1 expressed after mechanical loading of muscle. Pegylation is intended to extend how long it survives in circulation.

What people claim

  • Activates muscle stem cells for faster growth
  • Speeds recovery from training and injury
  • Localised muscle growth where injected

What the evidence actually says

Mechano-growth factor is real biology: muscle does express an IGF-1 splice variant after loading, and satellite-cell activation follows. What does not follow is that injecting a synthetic pegylated peptide reproduces that signal usefully in trained humans. We could not identify robust primary human outcome data for PEG-MGF, so the honest rating stays low — mechanism and cell-culture findings are not muscle growth.

Related evidence

Useful next reads based on this compound — not recommendations.

Human evidence

  • No robust primary human trial establishing muscle growth, strength or recovery benefit was identified in our curated record.
  • A 2026 peer-reviewed review documents PEG-MGF among substances self-administered in unregulated settings — evidence of use, not of effect.

Preclinical evidence

  • Cell and animal work on IGF-1 splice variant signalling and satellite-cell activation after mechanical loading.

Animal and cell findings are Level 1–2 evidence.

Mechanism and pathways

  • Proposed satellite-cell activation and myoblast proliferation via IGF-1 splice variant signalling.
  • Pegylation extends circulating half-life, which changes exposure but does not create an established clinical effect.

Safety and unknowns

  • No human safety dataset exists.
  • Growth-factor signalling raises theoretical concerns about unwanted tissue growth that no human study has resolved.
  • Unregulated supply adds purity, sterility and identity risks independent of the molecule.

Cancer relevance

This section covers questions raised by how the compound works in the body, plus anything regulators and trial teams keep an eye on. It is not a statement that this compound causes cancer — for most compounds here, no human data exist in either direction.

Theoretical / mechanistic concern only

IGF-1 pathway signalling is mechanistically linked to cell proliferation, so a theoretical concern exists. No human data establish or exclude a risk for this peptide.

Regulatory status

Not an approved medicine anywhere. Sold as a research chemical, widely discussed in performance and bodybuilding communities, and prohibited in sport. A 2026 peer-reviewed review documents it among substances being self-administered outside medical supervision.

Evidence grade

L2Animal / lab studiesVery low confidence in rating

Studies in animals or tissue, with no dependable human results yet. Mice are not tiny humans; promising animal data often fails in people.

What would change our rating?

  • A controlled human trial with strength, hypertrophy or recovery endpoints.
  • Any human pharmacokinetic and safety dataset.

References and sources

Sources fully curated

Source hierarchy: regulatory documents and trial registries first, peer-reviewed work next, sponsor material flagged as non-independent. We never use supplier or clinic marketing as evidence, and where a verified source has not yet been curated we say so rather than inventing one.

Evidence change history

These entries record changes to our assessment of the published evidence — not changes to the compound itself.

No recorded changes yet. Baseline position set on 2026-09-06.