MGF

Mechano Growth Factor (IGF-1Ec)

MGF (Mechano Growth Factor (IGF-1Ec)) is a gh & growth research compound. Locally-produced IGF-1 splice variant that activates muscle satellite cells after mechanical stress — the non-pegylated, ultra-short-acting form.

How MGF works

Locally-produced IGF-1 splice variant that activates muscle satellite cells after mechanical stress — the non-pegylated, ultra-short-acting form.

Proposed benefits

Researched for lean-mass support, recovery, sleep depth, connective-tissue repair and improved body composition via the GH/IGF-1 axis.

Where to get MGF

The evidence for MGF

Graded by what exists behind each claim.

Human clinical evidence

• No human trials: development stopped at preclinical, so the ceiling on any claim here is a rodent model — and these transfer poorly.

📊 Correlative data

• No human series. Reported use is local injection alongside training, on the reasoning that MGF is what muscle produces after mechanical damage.
• Beyond that the record is self-reported: community dosing logs are real information about tolerability and almost none about efficacy.

🧪 How the mechanism reads

• Mechano-Growth Factor is a splice variant of IGF-1 produced by muscle in response to mechanical loading. It activates satellite cells — the resident stem cells that fuse into damaged fibers — which is a genuinely distinct action from IGF-1's general anabolic signaling.
• The mechanism predicts the practical limit that the anecdotal record ignores: unmodified MGF has a half-life measured in minutes in serum, so systemic dosing is largely wasted and local injection is the only thing the biology supports.

Why an empty tier is not a verdict → · What community dosing logs are worth →

How to read these tiers: they say how much human evidence exists, not how well something works — and ✗ flags harm, never a disappointing trial. How the evidence tiers work →

What MGF actually does

MGF is sold as a growth factor. It is more accurately described as the last 24 residues of a pro-protein, and whether those 24 residues exist on their own inside a living animal is the only question on this page that matters. Everything else follows from the answer.

Where the name came from. The IGF-1 gene is transcribed into more than one message. Every version encodes the same 70-residue mature IGF-1 protein; what differs is the C-terminal extension called the E-domain, produced by alternative splicing across exons 4, 5 and 6. The splice variant that rises after mechanical loading was named IGF-IEb in rodent and IGF-1Ec in human, and the mRNA itself was nicknamed mechano-growth factor Matheny 2010. Somebody then synthesized a peptide matching the 24 most C-terminal residues of that pro-protein and moved the name from the message to the peptide. That single transfer is the entire commercial history of this compound, and the 2010 Endocrinology review states the consequence in one line: no analogous peptide product of the Igf1 gene has been identified in, or isolated from, cultured cells, their conditioned medium, or in vivo animal tissues or biological fluids Matheny 2010.

Read that carefully, because it is not the same as saying MGF does nothing. The splice event is real. The mRNA is real, measurable by quantitative RT-PCR, and it genuinely responds to loading Hameed 2003. What has never been recovered from a cell, a medium, a tissue or a body fluid is the free 24-residue peptide. The molecule in the vial is a chemist's construct built from a sequence read off a gene.

The receptor problem, which is the mechanistic core. A receptor-activation study using kinase-specific receptor activation assays put four things side by side: recombinant human IGF-1, full-length MGF (that is, the entire unprocessed pro-IGF-1Ec), the synthetic 24-residue human MGF peptide, and a stabilized analog Janssen 2016. The full-length pro-protein activated the IGF-1 receptor with an EC50 of 7.83 nmol/L against 0.86 nmol/L for IGF-1, reaching a similar ceiling, 89-fold against 77-fold. The 24-residue peptide and its stabilized analog produced no IGF-1 receptor activation at all. Not weak activation. None.

That result has a structural reason behind it. The part of the pro-protein that binds the IGF-1 receptor is the mature IGF-1 domain, and the peptide people inject contains none of it. The E-domain is the tail that gets cleaved off. So the compound in the vial is not a weak IGF-1 analog; it is a molecule with no identified receptor of any kind, which is a different and much less comfortable position for a product marketed as an IGF-1 variant.

One more number from the same study, because it matters for safety rather than for efficacy. Full-length MGF also activated both insulin receptor isoforms, with an EC50 of 73.11 nmol/L at IR-A and 35.10 nmol/L at IR-B, and its maximal IR-B response, 292-fold, exceeded insulin's own 98-fold Janssen 2016. Nothing sold as MGF is the full-length pro-protein, but that is an assumption about a vial, not a certified fact about one.

Cell, rodent, human — and where it stops

Step one, in humans, and this is the strongest link in the whole chain. Eight young subjects aged 25 to 36 years and seven elderly subjects aged 70 to 82 years performed 10 sets of 6 repetitions of single-legged knee extension at 80% of one repetition maximum, with biopsies taken from the quadriceps of both the exercised and the control leg 2.5 hours afterwards Hameed 2003. Resting MGF mRNA sat roughly 100-fold below IGF-IEa mRNA in both groups. High-resistance exercise raised MGF mRNA significantly in the young and not at all in the elderly, while IGF-IEa mRNA did not move in either group.

Two things about that experiment are usually skipped. It measured messenger RNA in a biopsy, not a peptide in plasma, so it says the gene responds to load and says nothing about a circulating molecule. And nobody was injected with anything: this is a study of what a squat does to a gene, being used to sell a vial.

Step two, in cells, and this is where the compound was actually tested. Two pharmaceutical companies attempted to reproduce the claimed effects of the MGF peptide Fornaro 2014. Concentrations up to 500 ng/mL failed to increase proliferation of C2C12 myoblasts or of primary human skeletal muscle myoblasts. The same peptide failed to inhibit myoblast fusion into myotubes. Primary mouse skeletal muscle stem cells, run to check whether the immortalized lines had lost the response, showed no significant effect either. A separate documented action, activation of p-ERK but not p-Akt in cardiac myocytes, was tested with both the native and a stabilized peptide and produced no activating response, while IGF-1 in the same wells gave a robust one. Mature IGF-1 and full-length IGF-1Eb worked in every cell type tested. The peptide did not work in any of them.

The contradicting paper, stated rather than buried. A 2018 C2C12 study reports the opposite in part: it found that the N-terminal portion of IGF1Ec, the region homologous to IGF-1, promotes proliferation, while the C-terminal sequence identical to the MGF E peptide promotes differentiation and migration, and it concludes that MGF E cannot completely replace the functions of the intact IGF1Ec Yi 2018. So the literature is genuinely split. What it is not split about is which experiments were better controlled: one side is a single-laboratory C2C12 result, the other is a multi-site industrial replication attempt across three cell systems with positive controls that responded Fornaro 2014, plus a receptor assay in which the peptide moved nothing Janssen 2016.

Step three, in humans given the drug: zero. There is no randomized trial, no controlled trial and no published case series of the MGF peptide administered to a person by any route. The evidence ceiling on this compound is a cell culture dish, and in the largest attempt to reach that ceiling the dish stayed empty.

The obstacles, named one at a time. (1) The entity itself is unconfirmed — the free E-peptide has never been isolated from any tissue or fluid Matheny 2010, so the pharmacology is being reasoned from a molecule whose natural existence is a hypothesis. (2) There is no receptor, and the one receptor it was supposed to use was tested and gave nothing Janssen 2016. (3) The human data is transcript abundance in a needle biopsy, and transcript abundance does not establish that a peptide is produced, released, or stable. (4) There is no published assay for MGF peptide in human plasma, so even a willing self-experimenter cannot check whether a dose arrived. (5) The one human result points the wrong way for the buyer: the subjects who did not raise MGF at all were the 70-to-82-year-olds Hameed 2003, which is the group most often sold on this compound.

MGF pharmacokinetics — how much of it actually gets in

The catalog says ‘minutes, very labile’. That is almost certainly right, it has never been measured, and the arithmetic behind it is more interesting than the phrase.

What degrades it. This is an unmodified 24-residue peptide with a free N-terminus. Aminopeptidase N on vascular endothelium chews residues off that end; dipeptidyl peptidases take them in pairs; serum endopeptidases cut internally. There is no D-amino acid, no N-acetyl cap, no C-terminal amide and no ring anywhere in it to slow any of that down. The commercial existence of PEG-MGF is itself the admission: somebody attached polyethylene glycol precisely because the unmodified peptide does not last, and the site sells both as though they were two strengths of the same idea rather than two different exposure profiles.

The number, and the honest form of it. There are 0 published pharmacokinetic measurements of MGF in any species, human or animal. So the only defensible statement is a bound rather than a value: an unprotected linear peptide of this size in plasma is a minutes-scale molecule, and even a generous 20 minutes of meaningful plasma residence has to be set against the biology it is supposed to drive. Satellite-cell activation and proliferation after a damaging training bout run over days. A post-workout injection whose material is gone inside an hour cannot be present for the process it is sold to influence, unless it triggers something that then persists without it — and no such trigger has been identified, because no receptor has been identified Janssen 2016.

The oral barrier, which is why nobody sells a capsule. Swallowed, this peptide meets gastric acid, then pancreatic proteases, then brush-border peptidases, and anything surviving faces hepatic first-pass extraction. No oral bioavailability figure has ever been published for it, and the practical answer is that the oral route for a 24-mer with no transporter is not a route.

The injectable comparator. Subcutaneous or intramuscular injection removes the gut and the first-pass liver, which is a real advantage and the reason every vendor sells it that way. It does not remove plasma peptidases, and it does not answer the question the page actually turns on, which is whether an intramuscular depot produces a local tissue concentration high enough to matter at a receptor nobody has found.

What would have to be true, and how you would know it was not

Three predictions, and the first two say the compound should do nothing measurable. That is what the mechanism implies, and a page predicting only good news would be an advertisement.

1. IGF-1 should not move, and if it does, something else in the stack moved it. Draw IGF-1 (Insulin-like Growth Factor 1) before you start and again at 6 to 8 weeks. The prediction is no change, because the injected peptide does not activate the IGF-1 receptor Janssen 2016 and is not the ligand that circulating IGF-1 assays detect. Most people running MGF also run a growth hormone secretagogue, and IGF-1 rising in that setting is the secretagogue working, not this. Anyone reporting an IGF-1 rise on MGF alone has either found something the receptor assay missed or has a vial containing something other than the 24-mer, and both are worth knowing.

2. The falsification a single person can run in 4 weeks: inject one side only. This compound's whole rationale is local action at the trained muscle. So use the unilateral design the human splice-variant study already used Hameed 2003: train both limbs identically, inject one, and measure the same thing on both sides — circumference at a marked point, and grip strength or a limb-specific one-repetition maximum. A local anabolic agent must produce asymmetry. The prediction is that it will not, and a within-subject comparison is the one design that removes diet, sleep, training and expectation in a single stroke.

3. Fasting insulin and HbA1c should be flat. The full-length pro-protein activates both insulin receptor isoforms in vitro, at 73.11 and 35.10 nmol/L Janssen 2016; the 24-residue peptide should not touch them. Check fasting insulin and HbA1c at baseline and at 8 weeks. Movement there is not a benefit signal — it is a signal that the vial contains a larger molecule than the label claims, and it is the single cheapest identity check available to a buyer.

What nobody has tested yet

Four experiments, and the first one costs less than a month of the compound.

1. Nobody has ever run a mass spectrum on a vendor vial of MGF. Every published result, positive or negative, used peptide the authors synthesized to a known sequence. Nothing published tells you what is in a research-market vial: whether it is the 24-mer, whether it is the right 24 residues, whether it is truncated, or whether it is full-length pro-IGF-1Ec, which has a completely different pharmacology Janssen 2016. Three lots from three vendors, one tandem mass spectrometry run, and this market would have its first compositional data.

2. Nobody has measured MGF in a human after injecting it. There is no published assay and therefore no time-course, no maximum concentration and no half-life in any person. A single plasma series over 4 hours after one dose would produce the first pharmacokinetic number this compound has ever had, and it would settle the minutes-versus-hours argument that every dosing protocol assumes an answer to.

3. Nobody has looked for the receptor. The IGF-1 receptor was tested and gave nothing Janssen 2016. No published work has run a labeled-peptide pull-down or a membrane-binding screen on myoblasts to ask whether the E-peptide binds anything. That experiment has two informative outcomes: it finds an orphan receptor, which would be a genuinely new result, or it finds nothing, which would close the question.

4. Nobody has adjudicated the disagreement. One group reports the E-peptide driving differentiation and migration in C2C12 cells Yi 2018; two industrial groups report no effect in C2C12 cells, primary human myoblasts and primary mouse muscle stem cells Fornaro 2014. Nobody has run both protocols in one laboratory with one peptide lot. That is a small, cheap, decisive study and it has not been done in the 8 years since the papers landed.

MGF — its own safety story, not its class's

The class block on this page is the growth hormone and IGF-1 safety story: insulin resistance, fluid retention, carpal tunnel, the acromegaly literature. Almost none of it is this compound's risk profile, because the injected peptide has never been shown to activate the IGF-1 receptor Janssen 2016 and there is no evidence it raises circulating IGF-1 at all. Borrowing the acromegaly warnings here is not caution; it is the wrong mechanism attached to the wrong molecule, and it obscures the three risks that are actually specific.

1. Identity risk is the dominant risk, and it is unusually large here. With no receptor assay a buyer can run, no plasma assay, no pharmacokinetics and no clinical trial, there is no observable at all that would tell you whether the vial contains the intended peptide. For most compounds on this site an ineffective batch is detectable because the effect is absent. Here the expected effect is already indistinguishable from nothing, so a mislabelled or contaminated vial produces exactly the same experience as a correct one.

2. The one pharmacological hazard worth naming runs through the insulin receptor, not the IGF-1 receptor. Full-length pro-IGF-1Ec activates IR-A and IR-B in vitro, and its maximal IR-B response exceeded insulin's Janssen 2016. If a preparation sold as MGF actually contains the full-length pro-protein, the plausible adverse event is hypoglycemia, which is fast, symptomatic and occasionally dangerous. That is a specific, testable, mechanism-derived concern, and it is the reason fasting insulin belongs on the panel above.

3. The repeated local injection is a real harm and it is not about the molecule. The usage pattern for this compound is intramuscular injection into the same trained muscle after training, often several times a week for 4 to 8 weeks. Repeated intramuscular dosing into one site carries infection, sterile abscess and local fibrosis risk regardless of what is in the syringe, and here that risk is being taken for a molecule whose benefit has failed to appear in every controlled system it has been tested in.

What zero means. There are 0 published adverse events for MGF, and 0 human studies of it, so no setting has ever existed in which an adverse event could have been recorded. That is not a safety record.

Sources read for this page

• Matheny RW Jr, Nindl BC, Adamo ML. Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration. Endocrinology 2010 · PMID 20130113
• Fornaro M, et al. Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells. American Journal of Physiology: Endocrinology and Metabolism 2014 · PMID 24253050
• Janssen JA, et al. Potency of Full-Length MGF to Induce Maximal Activation of the IGF-I R Is Similar to Recombinant Human IGF-I at High Equimolar Concentrations. PLoS One 2016 · PMID 26991004
• Hameed M, Orrell RW, Cobbold M, Goldspink G, Harridge SDR. Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise. Journal of Physiology 2003 · PMID 12562960
• Yi Q, et al. The structure-function relationships of insulin-like growth factor 1 Ec in C2C12 cells. Cell Adhesion and Migration 2018 · PMID 28471324

MGF — safety, predicted from mechanism

MGF — interference & stacking

Bloodwork to run alongside MGF

Baseline first, then again at 8–12 weeks.

The Athletic Performance & Recovery panel covers these in one order — 12 markers, $207.90 with the discount applied.

Check results you already have → · All 103 markers A–Z

MGF — frequently asked questions

What MGF is used for

MGF appears under 1 goal in the goal router.

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