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Not medical advice. The Atlas is not a substitute for a clinician who can examine you.

MGF

Mechano Growth Factor

Evidence grade 1 of 5, Untested. Read how the Atlas grades evidence.

MGF is IGF-1Ec, a locally expressed splice variant of IGF-1 characterized by the Goldspink laboratory at University College London and the Royal Free Hospital from 1996 onward. The muscle-repair and satellite-cell-activation biology rests on animal and in vitro work (for example the 2013 PLoS ONE growth-plate study and Hill and Goldspink's 2003 satellite-cell paper); there are no human randomized controlled trials of the synthetic MGF or PEG-MGF peptide for hypertrophy or repair, so the marketed muscle-building use is animal-only and correctly graded 1.

FDA
Not FDA-approved and not evaluated by the FDA for human use; marketed only as a research chemical
WADA
Prohibited at all times under WADA S2 (growth factors) since 2005

Reference only. Not medical advice.

What can go wrong

WADA-prohibited; no human RCT; potent anabolic agent.

Talk to a clinician before taking this, particularly if you have any history of cancer. The Atlas can tell you what has been studied about MGF. It cannot tell you how it would interact with your body, your history, or anything else you are taking, and nothing on this page is a reason to start.

An IGF-1 splice variant produced locally in damaged muscle in response to mechanical stress, activating satellite cells for repair. Strong animal data for hypertrophy.

What people take it for

These are the reasons people give for taking it. They are not effects it has been shown to have.

  • Muscle repair after injury
  • Hypertrophy

How it is supposed to work

MGF (Mechano Growth Factor) is a natural splice variant of IGF-1, called IGF-1Ec, that muscle produces locally when it is overloaded or damaged by exercise. Its job is to kick-start repair: it activates satellite cells, the muscle’s resident stem cells, prompting them to multiply and fuse into damaged fibers, which is the basis for its use as an anabolic, muscle-building peptide. It acts locally and briefly, a short pulse that, in the body, is normally followed by other IGF-1 forms that finish the repair.

MGF is IGF-1Ec, an alternatively-spliced variant of the IGF-1 gene carrying a unique C-terminal E-peptide, a 24-amino-acid extension created by a reading-frame shift, that gives it activity independent of the mature IGF-1 portion. It is the muscle-derived, mechano-sensitive isoform, distinct from the liver-derived systemic IGF-1Ea. Natural MGF has an extremely short half-life of minutes, which is why the pegylated, longer-acting PEG-MGF exists.

Type
IGF-1 splice variant (IGF-1Ec)
Action
Activates satellite cells
Half-life
Minutes (PEG-MGF longer)
Human trials
None
WADA
Prohibited (S2)
Approved
No

Well-Mapped Biology, Sold Without Human Data

MGF is unusual in this library because its underlying biology is genuinely well-characterized. Geoffrey Goldspink’s group at University College London identified it in the 1990s as the IGF-1 splice variant that muscle makes in response to mechanical load, and careful work showed its distinctive E-peptide acts on its own, upstream of mature IGF-1, to activate satellite cells and start repair. That is real, interesting science. The problem is the gap between that biology and the gray-market product. There are no human clinical trials of injected MGF or PEG-MGF; the muscle-building claims and the dosing protocols come from bodybuilding community experience, not evidence. It is also unclear whether injecting a synthetic E-peptide reproduces what the body’s finely-timed, locally-produced signal actually does. And because it belongs to the IGF-1 family, it carries that family’s proliferation and cancer concerns, with the MGF E-peptide even implicated in prostate cancer cell growth. It is banned in sport and unapproved.

Safety in detail

MGF is an unapproved research chemical with no human trial safety data; as a growth-factor anabolic it carries theoretical concerns around unregulated cell proliferation, and it is WADA-prohibited for athletes.

  • No human safety or efficacy trials exist; effects are from cell and animal studies.
  • As a member of the IGF-1 growth-factor family, it carries a theoretical cancer-promotion concern.
  • Synthetic MGF degrades within minutes and unregulated product is prone to impurities, degradation and inaccurate dosing.
  • Prohibited at all times in sport under WADA category S2, banned by name since 2005.
  • Not approved anywhere; sold only as a gray-market research chemical.

Children and teenagers

MGF is an IGF-family growth factor with proliferation and cancer concerns and no human trials, which makes it inappropriate for minors, especially given IGF-1 signaling in developing tissues and its expression in growth-plate cartilage. Any genuine pediatric growth disorder belongs with pediatric endocrinology, using approved IGF-1 therapy rather than gray-market MGF. There is no appropriate pediatric use.

What people get wrong

Nothing recorded here yet. There is almost certainly something people get wrong about this one, and the blank space means we have not written it down, not that the record is clean.

Who profits, and who pushes back

Nobody is named here yet, because we have not done that work on this entry. Read that as unfinished. Somebody almost certainly sells this, and somebody almost certainly disputes it. Assume both until we have checked.

MGF’s money runs through gray-market bodybuilding-peptide vendors selling MGF and PEG-MGF for muscle growth, recovery and localized site growth, repackaging a real piece of splice-variant biology as an injectable product. There is no approved version. Demand is driven by bodybuilding community lore rather than human evidence, with the science used as marketing for protocols that have never been tested in people.

How we got here

The name traces to Geoffrey Goldspink's laboratory at University College London and the Royal Free Hospital, which from 1996 onward identified an IGF-1 messenger RNA isoform expressed transiently in skeletal muscle after mechanical stretch or damage and named it Mechano Growth Factor. It was later mapped to the human IGF-1Ec splice variant (IGF-1Eb in rodents), which carries a distinct C-terminal E-domain. Academic interest centered on the E-peptide as a candidate for muscle wasting, aging and cardiac repair, all of which stayed preclinical, while the performance-enhancement potential led WADA to prohibit MGF from 2005. The peptide and its PEGylated PEG-MGF form are now sold by research-chemical vendors labeled not for human consumption.

Geoffrey Goldspink and colleagues at UCL identified Mechano Growth Factor in the mid-1990s as the IGF-1 splice variant muscle expresses under mechanical load, and a 1999 mechanical-loading study and the 2002 demonstration of its E-peptide’s autonomous, satellite-cell-activating activity established its biology. Preclinical work extended its reported effects to muscle, heart and nerve. The bodybuilding gray-market then adopted synthetic MGF, and because the natural peptide lasts only minutes, the pegylated PEG-MGF was created for practical use, all without any human trials.

  1. 1990sGoldspink identifies MGF as the mechano-responsive IGF-1 splice variant.
  2. 1999A mechanical-loading study shows the splice variant spikes with muscle load.
  3. 2002The MGF E-peptide is shown to activate satellite cells independently of mature IGF-1.
  4. 2000s-2010sPreclinical work reports muscle, cardiac and neural effects; gray-market use begins.
  5. ongoingPEG-MGF becomes the practical gray-market form; no human trials are conducted.

The numbers behind the grade

Type
IGF-1 splice variant (IGF-1Ec)
Size
~24-25 aa E-peptide
Effect
Satellite-cell activation
Half-life
Minutes
WADA
Prohibited (S2)
Approved
No

The people taking it

A long-standing bodybuilding peptide built on a real piece of muscle-repair biology, popular for its anabolic promise despite the absence of human evidence.

MGF’s users are predominantly bodybuilders and strength athletes seeking muscle growth, recovery and localized site growth, along with the broader muscle-building gray-market crowd and IGF- or GH-stack users. It tends to attract advanced, recovery-focused lifters comfortable with research-grade peptides.

Used illicitly in bodybuilding and performance settings for muscle repair and growth, almost entirely gray-market. Banned in sport; not an approved therapy.

Set against the alternatives

The key comparison is to systemic IGF-1 and its gray-market analog IGF-1 LR3: that compound is a long-acting mature-IGF-1 analog that drives growth through the IGF-1 receptor and carries clear cancer, acromegaly and hypoglycemia risks, while MGF is the splice variant whose distinct E-peptide acts upstream on satellite-cell proliferation, a different mechanism that still shares the IGF cancer concern. Together they show the two anabolic faces of the IGF-1 gene, systemic versus local repair. Against its own pegylated sibling PEG-MGF, standard MGF is the same molecule with a half-life too short to be practical, which is the entire reason PEG-MGF exists. And against the GH secretagogues, which raise IGF-1 indirectly and physiologically, MGF acts directly and bypasses feedback, which is riskier. Its strength is well-mapped biology; its weakness is an unproven product.

What we do not know

  • Whether synthetic MGF does anything useful in humans given its near-instant breakdown.
  • Whether mistimed dosing interferes with the natural repair sequence.
  • Whether the theoretical cancer concern from IGF-1-family activity is real at used doses.

What could change

Human trialsThe key open question is whether injected MGF does anything in people.Synthetic versus endogenousWhether the injected peptide matches the natural signal stays unresolved.Cancer riskThe IGF-family and prostate-cancer links need clarification.Doping controlsMass-spectrometry methods to detect biotech MGF continue to develop.

The market for this

What follows describes how this is bought and sold. It is not a buying guide and it is not an endorsement of any seller.

Available only as research-use-only material from peptide vendors, which is not for human use and is banned in competitive sport. Given the near-instant degradation and unregulated quality, it is a poor and risky choice; any use should at least involve third-party-tested product.

Gray-market MGF and PEG-MGF are moderately priced research peptides, with PEG-MGF the more practical form because of its longer half-life. The cost buys an untested product rather than a validated therapy.

Synthesized overseas, predominantly in China, and sold as research material with significant impurity and concentration variability; an independent certificate of analysis is the only check.

China and research vendorsThe source of gray-market MGF and PEG-MGF, sold as research-use-only material.Pegylation stepPEG-MGF adds a polyethylene glycol chain to extend the short half-life into a usable range.No approved supplyThere is no approved product and no clinical supply chain.

What this entry does not yet cover

What follows is unfinished work on our side, not a finding about MGF.

Nothing outstanding on this one.

Sources

The studies that matter

  • Goldspink and colleagues1990s-2000s

    Identified MGF as the exercise- and damage-induced IGF-1 splice variant and characterized its role in muscle repair, the foundational work.

  • Satellite-cell and muscle studies2000s-2010s

    The MGF E-peptide activated human muscle progenitor cells and produced hypertrophy in animal models, mostly in younger tissue.

  • Human efficacy trialsnone

    There are no completed human efficacy trials of synthetic MGF; the evidence is cell and animal work.