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Mechano Growth Factor (IGF-1Ec splice variant)
A grey-market injectable 'research peptide' with NO human efficacy trials — the muscle-growth marketing is extrapolated from cell-culture and animal work. MGF (mechano growth factor) is not a separate hormone but an alternatively spliced variant of the IGF-1 gene — the IGF-1Ec isoform — that muscle produces transiently after mechanical loading or damage. Its distinctive C-terminal 'E peptide' is thought to help activate satellite (muscle stem) cells and kick off repair before the mature IGF-1 portion takes over. That biology made it interesting to muscle physiologists; grey-market vendors then turned the synthetic E-peptide (often as 'PEG-MGF', a PEGylated longer-lasting version) into an injectable for bodybuilders. There has never been a published human trial of injected MGF for muscle, strength, or recovery. The real evidence is preclinical: in animals, MGF injection into injured muscle reduced fibrosis and inflammation but did NOT improve fiber regeneration; in cells, MGF E-peptide promotes proliferation and shows neuroprotective effects. It is not an approved drug or a regulated supplement; it is an unregulated grey-market injectable. Because MGF is part of the IGF-1 system, activating that axis carries the same theoretical cancer-promotion concerns, and an unsterile injectable adds infection risk. This entry exists to inform, not to recommend.
Research peptide — not a dietary supplement
MGF is a research compound, not a regulated dietary supplement. It is typically administered by injection and sold “for research use only.” The evidence below is largely preclinical (animal and in-vitro) or early-stage, so no evidence score is assigned. This page is provided for transparency and education — it is not a recommendation to use. Consult a qualified healthcare provider, and be aware that purity, dosing, and legal status vary by jurisdiction.
What the evidence says
Most MGF studies are mechanism or observational rather than RCTs that measure a clinical effect — keep findings provisional.
Most evidence is from mixed-quality studies published 2018–2024.
Based on 7 studies
Confidence
Low confidenceBy outcome
Scored very low because there is not a single human trial of injected MGF; all evidence is preclinical cell and animal work, and the strongest in-vivo effect was anti-fibrotic, not the marketed muscle growth.
13 trials ongoing or recruiting · 67 completed on ClinicalTrials.gov
23 of the completed trials have posted results
Registered trials show research momentum for MGF, not proof of effect — a registration is a plan, and posted results are sponsor-reported, not peer-reviewed. They are never counted toward the evidence rating above.
Browse these trials on ClinicalTrials.govClinicalTrials.gov · as of Aug 2026
MGF ('mechano growth factor') is the bodybuilding name for a naturally occurring product of the human IGF-1 gene.
IGF-1 is alternatively spliced into several isoforms; one of them — IGF-1Ec in humans (the rodent ortholog is often called IGF-1Eb) — carries a distinctive C-terminal 'Ec/E peptide' and is rapidly and transiently upregulated in skeletal muscle in response to mechanical loading and damage, which is why it was named 'mechano growth factor' (Kasprzak & Szaflarski, 2020).
The prevailing physiological model is that this E peptide acts early after exercise or injury to activate satellite cells (the muscle stem cells) and prime regeneration, with the mature IGF-1 domain driving the subsequent protein-synthesis and differentiation phase.
Grey-market vendors took the synthetic E-peptide and sell it as an injectable 'research peptide' — frequently as 'PEG-MGF', a PEGylated form engineered to resist rapid clearance and last longer in circulation — marketed for muscle growth and recovery.
The honest evidence picture: there has never been a published human trial of injected (exogenous) MGF for muscle, strength, recovery, or anything else. What exists is preclinical and, importantly, mixed.
In the most directly relevant in-vivo administration study, injecting MGF into contused mouse muscle after macrophage depletion did NOT rescue muscle-fiber regeneration, though it did reduce fibrosis and dampen inflammatory cytokines, chemokines, oxidative-stress markers, and matrix metalloproteinases (Liu et al., 2019) — i.e., an anti-fibrotic/anti-inflammatory effect rather than the muscle-building effect implied by the marketing.
In cells, MGF and KCl-driven endogenous MGF/IGF-1 expression promote myoblast proliferation (Kravchenko et al., 2019), and an MGF E-peptide promoted osteoblast proliferation/mineralization and bone-defect healing in a rabbit model (Wei et al., 2020).
A second, genuinely interesting line of preclinical work is neuroprotection: exogenous MGF increased proliferation of hypoxic neural stem cells (Aydıntuğ-Gürbüz et al., 2024) and protected dorsal-root-ganglion neurons from cisplatin chemotherapy toxicity by binding nucleolin (Podratz et al., 2020); MGF also protects growth-plate chondrocytes from mechanical-overload damage via RhoA/YAP signaling (Jing et al., 2018).
Read carefully, the strongest demonstrated exogenous-MGF effects are anti-fibrotic, anti-inflammatory, and neuroprotective in cells and animals — not a proven anabolic/hypertrophy effect, and certainly not in humans.
The caveats are the same as for any IGF-1-system grey-market injectable: because MGF is part of the IGF-1 family and IGF-1-receptor signaling is implicated in tumor biology (Kasprzak & Szaflarski, 2020), chronically dosing it carries a theoretical cancer-promotion concern; it is an unapproved, unregulated injectable with no guarantee of identity, purity, dose, or sterility (non-sterile injection adds infection risk); and its human side-effect and long-term-safety profile is entirely unknown because no human has been studied.
The evidence here is scored well below 3 and flagged Emerging: a real and scientifically interesting preclinical signal (mostly regenerative/anti-fibrotic and neuroprotective rather than directly hypertrophic), with zero human efficacy or safety data and real theoretical risks — sandboxed out of all goal- and stack-based recommendations.
MGF is not a distinct hormone but the IGF-1Ec splice variant of the IGF-1 gene, carrying a unique C-terminal E peptide. It is transiently upregulated in skeletal muscle after mechanical loading and damage (Kasprzak & Szaflarski, 2020) — hence 'mechano growth factor'. Established as endogenous muscle biology; the injected synthetic version (often PEGylated 'PEG-MGF') has never been tested in humans.
The E peptide is proposed to activate satellite cells (muscle stem cells) and prime regeneration before the mature IGF-1 domain drives differentiation. In cell culture, MGF/IGF-1 expression promotes myoblast proliferation (Kravchenko et al., 2019). A cell-level proliferative signal — not a demonstrated human hypertrophy effect.
Injected into contused mouse muscle, MGF reduced fibrosis and lowered inflammatory cytokines, chemokines, oxidative-stress markers, and matrix metalloproteinases — but did NOT improve muscle-fiber regeneration (Liu et al., 2019). The strongest demonstrated in-vivo effect is anti-fibrotic/anti-inflammatory, not hypertrophic. Animal data.
Exogenous MGF protected dorsal-root-ganglion neurons from chemotherapy (cisplatin) toxicity by binding nucleolin (Podratz et al., 2020) and increased proliferation of hypoxic neural stem cells (Aydıntuğ-Gürbüz et al., 2024). A genuine preclinical neuroprotective signal — in cells and animals only.
How MGF works — from molecular targets to health outcomes. Click an edge to see supporting research.This visualization is in beta — pathways are being refined and expanded.
Avoid — there are no human trials, no approved use, and no quality-controlled product. Preclinical cell/animal signals (largely anti-fibrotic and neuroprotective, not proven hypertrophy) do not justify human self-injection.
Avoid — as an IGF-1-axis peptide, MGF carries a theoretical tumor-promotion risk.
Avoid entirely — a growth-factor-family peptide, completely unstudied in human pregnancy.
Stacking MGF with growth hormone, IGF-1 analogs, or other growth-promoting agents would further amplify IGF-1-axis signaling and the associated cancer-promotion and tissue-overgrowth concerns. Never studied in humans.
There are no human drug-interaction data for exogenous MGF of any kind; interactions cannot be reliably predicted.
Tip: MGF is an IGF-1 splice variant, and IGF-1-system signaling is implicated in tumor biology; chronically dosing it is a recognized theoretical cancer-promotion concern. Never quantified in human MGF users.
Tip: Grey-market injectable material has no identity/purity/sterility guarantees; reconstituting and injecting it carries contamination and infection risk independent of the molecule.
Tip: No human has ever been studied on exogenous MGF — the side-effect profile in people is genuinely unknown. This is itself the warning.
The current evidence for MGF is insufficient to assign an evidence score, based on 7 indexed studies. A grey-market injectable 'research peptide' with NO human efficacy trials — the muscle-growth marketing is extrapolated from cell-culture and animal work. MGF (mechano growth factor) is not a separate hormone but an alternatively spliced variant of the IGF-1 gene — the IGF-1Ec isoform — that muscle produces transiently after mechanical loading or damage. Its distinctive C-terminal 'E peptide' is thought to help activate satellite (muscle stem) cells and kick off repair before the mature IGF-1 portion takes over. That biology made it interesting to muscle physiologists; grey-market vendors then turned the synthetic E-peptide (often as 'PEG-MGF', a PEGylated longer-lasting version) into an injectable for bodybuilders. There has never been a published human trial of injected MGF for muscle, strength, or recovery. The real evidence is preclinical: in animals, MGF injection into injured muscle reduced fibrosis and inflammation but did NOT improve fiber regeneration; in cells, MGF E-peptide promotes proliferation and shows neuroprotective effects. It is not an approved drug or a regulated supplement; it is an unregulated grey-market injectable. Because MGF is part of the IGF-1 system, activating that axis carries the same theoretical cancer-promotion concerns, and an unsterile injectable adds infection risk. This entry exists to inform, not to recommend. Representative study: PMID 31164836.
The commonly studied dose of MGF is No legitimate or recommended dose — MGF is an unapproved grey-market research chemical with no human dosing data and no quality control. We do NOT provide a dosing protocol. There has never been a human trial to establish a safe or effective dose; published dosing is only in cell and animal models and does not translate to a human regimen.. Individual needs vary — start at the lower end of the range and adjust based on how you respond.
Timing is flexible for MGF — consistent daily use matters more than the time of day. There is no validated human dosing schedule because MGF has never been tested in humans.
MGF should be used with caution — talk to a healthcare provider before taking it. The most commonly reported side effects are theoretical promotion of tumor growth (IGF-1 axis), injection-site infection / harm from non-sterile, impure product, unknown human side-effect profile. Use caution if any of these apply to you: Not an approved medicine and not a regulated dietary supplement — unapproved grey-market injectable research chemical; do not self-source; No human safety data of exogenous MGF exists — every safety conclusion would be an extrapolation from cells or animals; Any personal or family history of cancer — MGF is part of the IGF-1 axis, which carries a theoretical tumor-promotion risk.
Mecasermin (IGF-1)
Mostly mechanism / observationalThe pharmaceutical-grade version of IGF-1 — an FDA/EMA-approved prescription injectable, but approved ONLY for a rare childhood growth disorder (severe primary IGF-1 deficiency / Laron syndrome), where it genuinely raises height velocity in clinical trials. It is the regulated counterpart to the grey-market igf-1-lr3 peptide bodybuilders inject, and shares the same core risks. Crucially, there is NO trial supporting its off-label use for muscle, performance, or anti-aging in healthy adults — and IGF-1's documented harms (hypoglycemia, intracranial hypertension, lymphoid/tonsillar hypertrophy, and a theoretical cancer concern because IGF-1 is mitogenic) are real. Not a dietary supplement, not a longevity drug.
Insulin (bodybuilding use)
Mostly mechanism / observationalInsulin is a life-saving prescription hormone for diabetes — and, used illicitly by bodybuilders as an off-label 'anabolic,' one of the most dangerous performance drugs in existence. The theory is nutrient partitioning: insulin drives glucose and amino acids into muscle and suppresses muscle-protein breakdown. But there is NO controlled evidence that insulin builds muscle or improves performance in healthy, non-diabetic athletes — and a non-diabetic who injects it risks profound, sometimes FATAL hypoglycemia (coma, seizures, brain injury, death), plus fat gain. This is a harm-reduction reference documenting a popular, deadly misuse, NOT a recommendation and NOT a dietary supplement.
ACE-031
Mostly mechanism / observationalAn investigational myostatin/activin 'trap' whose only human trial in patients was STOPPED for safety. ACE-031 is a fusion protein of the activin receptor type IIB (ActRIIB) extracellular domain and an IgG1-Fc, engineered by Acceleron Pharma to soak up myostatin and related ligands and thereby release the brake on muscle growth. It has real human data — a single-dose study in healthy postmenopausal women showed a genuine ~3% gain in lean mass — but its phase 2 trial in boys with Duchenne muscular dystrophy was HALTED after the second dosing regimen because of bleeding-related safety signals (nosebleeds/epistaxis and telangiectasias, dilated surface blood vessels). It is NOT an approved drug, development was discontinued, and anything sold grey-market under this name is unregulated. This entry exists to inform, not to recommend.
CJC-1295
Mostly mechanism / observationalA synthetic long-acting analog of growth-hormone-releasing hormone (GHRH), promoted online to raise GH and IGF-1 for muscle, fat loss and 'anti-aging'. Honest appraisal: the only real human data are two small early-phase pharmacokinetic / safety studies from ~2006 that showed it raises GH and IGF-1 for days — they were never followed by efficacy trials in muscle, body composition or aging. There are NO human outcome RCTs. It is not a dietary supplement: it is sold 'for research use only', is injectable, and is banned by WADA. The original DAC version's clinical development was abandoned.
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Reviewed by Dr. Baher Al Hakim · Last reviewed June 2026 · evidence from 7 studies · how we score · editorial policy
This information is for educational purposes only. It is not a substitute for professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any supplement or medication.
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