MGF

Dosing from the Literature

Published for muscle: animal doses only. Not published: any human dose; no trial has given MGF to people.

No trial or label gives a human dose of MGF. The MGF rows below are what forum protocols describe; the PEG-MGF row is what online protocols describe, as collected in a 2026 review (Dominikowski et al., 2026). None has been tested.

What It Is

MGF — Mechano Growth Factor — is a splice variant of the insulin-like growth factor 1 (IGF-1) gene that muscle makes more of after mechanical loading or damage: in rats after stretch or injury (Hill & Goldspink, 2003), and in some studies of young men after heavy resistance exercise (Hameed et al., 2003; Kim et al., 2005). It carries a 49-base insert from exon 5 in humans, where it is called IGF-1Ec, and a 52-base insert in rodents, where it is called IGF-1Eb (Hill & Goldspink, 2003). What studies and sellers call MGF is a synthetic peptide matching the last 24 amino acids of the variant's E domain; no such peptide has been found in the body (Matheny et al., 2010).

The distinction between IGF-1Ec (MGF-producing) and IGF-1Ea (the systemic liver-produced isoform responsible for most circulating IGF-1) was established by Geoffrey Goldspink, Shi-Yu Yang, and Michael Hill at the Royal Free Hospital, University College London in a series of landmark papers between 1996 and 2005. In rat muscle damaged by stretching under electrical stimulation, or by an injected local anaesthetic, they found an early, brief burst of MGF expression, ahead of the main IGF-1 form, and proposed that this pulse activates satellite cells — the quiescent, basal-lamina-associated stem cells in muscle that donate their nuclei to damaged fibers during repair and hypertrophy (Hill and Goldspink, J Physiol 2003); in culture, MGF's E domain acted differently from mature IGF-1 on myoblasts (Yang and Goldspink, FEBS Lett 2002).

Satellite cells are the rate-limiting input to skeletal muscle regeneration. Quiescent satellite cells sit beneath the basal lamina of each muscle fiber; upon mechanical damage or growth stimulus, they activate, proliferate as myoblasts, and either fuse with existing fibers (adding myonuclei) or fuse with each other (forming new fibers). The biological sequence that Goldspink's work implied — mechanical damage → MGF (E-peptide) release → satellite cell (muscle stem cell) activation → mature IGF-1Ea release → protein synthesis in activated tissue — is the integrative model that positions MGF as the "initiating signal" and the mature IGF-1 as the "amplification signal." This two-phase model is the central reason MGF remains a compound of interest despite the paucity of human data.

Commercial synthetic MGF is the 24-amino-acid E-peptide fragment (not the full IGF-1Ec pre-pro-peptide), synthesized chemically and supplied as lyophilized powder. Its short plasma half-life (approximately 5–7 minutes) reflects the biological role as a local, transient mechanical signal — it was never evolutionarily selected to circulate systemically. PEG-MGF is the synthetic E-peptide covalently coupled to a polyethylene glycol moiety, promoted commercially as a way to add stability and prolong exposure; its half-life has not been reported (Dominikowski et al., 2026).

MGF is not FDA-approved, has never been formally advanced into human clinical trials, and is classified as a banned substance by the World Anti-Doping Agency (WADA) under section S2 (peptide hormones, growth factors, related substances, and mimetics), which names mechano growth factors. The compound exists entirely in research-peptide channels for human use.

Mechanism of Action

MGF comes from the same gene as IGF-1, but in culture MGF's E domain acted differently from mature IGF-1: it increased myoblast proliferation while holding back their final differentiation, and blocking the IGF-1 receptor (IGF-1R) with an antibody did not stop it (Yang & Goldspink, 2002). No separate MGF receptor has been identified, and one lab proposes that the E peptides work with IGF-1 on IGF-1R instead (Brisson & Barton, 2013).

• Satellite cell activation (proposed) — Satellite cells stay quiescent until activated, when they multiply and fuse with muscle fibers to donate nuclei, a process needed for growth, hypertrophy and repair (Hill & Goldspink, 2003). In damaged rat muscle, MGF expression rose before a marker of satellite cell activation, which the authors took to mean that the early MGF pulse activates these cells (Hill et al., 2003). A 2010 review finds a direct role unproven, and work from another lab suggests the MGF isoform may not activate them (Matheny et al., 2010).
• Independence from IGF-1R (unresolved) — In rat heart-derived H9C2 cells, an antibody that blocks IGF-1R stopped mature IGF-1's effect on proliferation but not the synthetic MGF E peptide's (Stavropoulou et al., 2009), and the synthetic MGF-Ct24E peptide raised human muscle-precursor proliferation by a mechanism other than binding IGF-1R (Mills et al., 2007). A specific MGF receptor has not been identified (Matheny et al., 2010).
• Signaling and cell survival — In two cell studies, the synthetic MGF peptide activated ERK but not Akt, the pathway mature IGF-1 uses for differentiation and growth (Matheny et al., 2010). In sheep hearts after an induced infarct, staining for cleaved caspase 3, a marker of cell death, was absent with MGF's E domain (Carpenter et al., 2008); in human muscle precursor cells, the peptide had no effect on survival (Mills et al., 2007).
• Downstream IGF-1Ea coordination — In damaged rat muscle, MGF mRNA rose quickly and declined within a few days, while IGF-1Ea mRNA rose more slowly; the authors propose that IGF-1Ea then supplies the mature IGF-1 for the protein synthesis that completes repair (Hill & Goldspink, 2003). A 2010 review calls this two-phase sequence the MGF hypothesis (Matheny et al., 2010).
• Neuroprotection — In gerbils, transient brain ischemia raised MGF expression in the hippocampal neurons that resisted it, and a synthetic C-terminal MGF peptide strongly protected vulnerable neurons; in hippocampal slice cultures its effect outlasted IGF-1's and did not depend on the IGF-1 receptor (Dluzniewska et al., 2005).
• Cardiac injury response — In rats, MGF expression in the heart rose four to eight weeks after an induced infarct (Stavropoulou et al., 2009). In sheep with induced infarcts, MGF's E domain preserved cardiac function and left 35% less compromised heart muscle than in controls (Carpenter et al., 2008).
• Age-related decline — After a bout of heavy resistance exercise, MGF mRNA rose in young men but not in men aged 70–82 (Hameed et al., 2003); rat studies disagree on whether the response fades with age (Matheny et al., 2010). Goldspink links loss of muscle mass in old age to an impaired ability to express MGF (Goldspink, 2005).
• Local action (proposed) — The Goldspink group describes MGF as a mechanosensitive, autocrine (locally acting) growth factor (Hill et al., 2003). In mice, though, the synthetic peptide also worked when given systemically (Mills et al., 2007).
• PEGylation (PEG-MGF) — PEGylation is promoted commercially to add stability and prolong exposure, but PEG-MGF's half-life has not been reported, and effects seen with unmodified MGF peptides cannot be assumed to apply to it (Dominikowski et al., 2026).

What the Research Shows

Cell and animal studies, plus human studies that measured the body's own MGF after exercise (Hameed et al., 2003; Kim et al., 2005). None of those human studies gave MGF to anyone, and ClinicalTrials.gov lists no trial of it.

• Mechanistic foundation (Yang and Goldspink, FEBS Lett 2002; PMID 12095637) — "Different roles of the IGF-1 Ec peptide (MGF) and mature IGF-1 in myoblast proliferation and differentiation." In a cell model, MGF's E domain increased myoblast proliferation and inhibited their final differentiation, unlike mature IGF-1, and an antibody blocking the IGF-1 receptor did not stop it.
• Satellite cell activation (Hill and Goldspink, J Physiol 2003; PMID 12692175) — Expression and splicing of the IGF-I gene in rodent muscle is associated with muscle satellite cell activation following local tissue damage. The authors read the timing as suggesting that the early MGF pulse activates satellite cells; a 2010 review calls a direct role unproven (Matheny et al., 2010).
• MGF review (Goldspink, Physiology 2005; PMID 16024511) — Comprehensive review: "Mechanical signals, IGF-I gene splicing, and muscle adaptation." Integrates the two-decade mechanistic literature from the Goldspink lab.
• Neuroprotection (Dluzniewska et al., FASEB J 2005; PMID 16144956) — In a gerbil model of transient brain ischemia, the synthetic C-terminal peptide of IGF-1 Ec (MGF) gave very significant protection to the vulnerable neurons; in organotypic hippocampal culture it was as potent as full-length IGF-1 and lasted longer, and its action was independent of the IGF-1 receptor.
• Cardiac infarction (Carpenter et al., Heart Lung Circ 2008; PMID 17581790) — In sheep given infarcts by microsphere injection, the MGF E domain preserved cardiac function on echocardiography and left 35% less compromised heart muscle than controls, with no cleaved caspase 3 staining in the treated hearts.
• Exercise-induced MGF expression (Kim et al., Am J Physiol Endocrinol Metab 2005; PMID 15644458) — In 38 younger and older men and women, MGF mRNA in the thigh muscle was 49% higher 24 hours after a bout of resistance exercise; within groups the rise was significant only in young men. It measures the body's own response and does not address MGF given as a drug.
• Age-related MGF response (Hameed et al., J Physiol 2003) — After one bout of heavy knee-extension exercise, MGF mRNA rose in eight young men but not in seven men aged 70–82.
• Tendon and bone progenitor activation (multiple preclinical) — MGF upregulated in injured tendon and bone tissue; exogenous MGF accelerated progenitor recruitment in rat models.
• E-peptides and IGF-1 (Pfeffer et al., Mol Biol Cell 2009; PMID 19605562) — In mouse C2C12 muscle cells, the rodent E-peptides did not change IGF-1 secretion but increased its entry into cells. No E-peptide receptor has been found, and a later review from the same lab proposes that there is none: the E-peptides would instead modulate IGF-1R activity together with IGF-1 (Brisson & Barton, 2013).
• Muscle precursor cells (Mills et al., Am J Transplant 2007; PMID 17845560) — The synthetic MGF-Ct24E peptide raised the proliferation of human muscle precursor cells by a mechanism other than binding the IGF-1 receptor, and delayed their differentiation; given into the muscle or systemically, it improved engraftment of these cells transplanted into mice.

Human Data

Human MGF data is limited to observational studies of endogenous MGF expression following exercise or injury; no interventional trials of exogenous MGF or PEG-MGF have been published.

• Exercise-induced endogenous MGF expression — Thigh-muscle biopsies found MGF mRNA raised 2.5 hours after heavy resistance exercise in young men (Hameed et al., 2003) and 24 hours after it, significantly in young men only (Kim et al., 2005); a 2010 review calls the human evidence conflicting (Matheny et al., 2010).
• Age-related blunting — In older men, MGF mRNA did not rise after a single bout of heavy exercise (Hameed et al., 2003) but did after weeks of resistance training or growth hormone (Matheny et al., 2010).
• Cardiac MGF following MI — Human myocardial samples post-infarction show increased IGF-1Ec expression in the infarct border zone, paralleling the rodent model.
• Rehabilitation-associated expression — Physical-therapy and post-surgical rehabilitation studies show measurable IGF-1Ec induction during recovery phases; associative, not interventional.
• No Phase 1 / 2 / 3 RCT — No pharmaceutical-industry or academic-consortium-funded human trial of exogenous MGF or PEG-MGF administration has been published. Community use is entirely extrapolation.
• Community-practice case reports — Anecdotal reports of improved injury recovery and hypertrophy on MGF + training protocols; no standardized outcome measures, no control.
• WADA detection — WADA and anti-doping science groups have published method development for MGF and PEG-MGF urinary / plasma detection; these are the most rigorous "human exposure" datasets available, though they are forensic rather than clinical.

The evidence gap between preclinical mechanism and human clinical validation is one of the largest in the peptide space. For MGF even the mechanism is unsettled: a 2010 review finds inadequate evidence that MGF is made in the body, or that it plays a role in repair that full-length IGF-1 does not fill (Matheny et al., 2010).

Reconstitution & Storage

Seller listings describe MGF as lyophilized powder in 2 mg vials, and PEG-MGF in 2 mg or 5 mg vials.

• Reconstitution — Reconstitution guides describe adding the bacteriostatic water down the vial wall and swirling gently rather than shaking.
• MGF storage (dry powder) — Some seller listings give −20°C for vials kept beyond 30 days.
• MGF storage (mixed) — Forum protocols describe mixing only what will be used the same day.
• PEG-MGF storage (mixed) — A seller guide lists refrigeration after mixing and use within 7–10 days.
• Timing — Forum protocols describe injecting MGF within minutes of training; online protocols for PEG-MGF describe 30–60 minutes after training, two or three times a week (Dominikowski et al., 2026).

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Side Effects & Risks

The human studies cited here only measured the body's own MGF, so there are no human safety data; the lines below are theoretical or carried over from related compounds.

• Injection-site reactions — Reported for the GH–IGF-1 axis peptides used off-label (Dominikowski et al., 2026); not documented for MGF itself.
• Hypoglycemia (theoretical) — A 2026 review rates low blood sugar a theoretical risk of the IGF-1 analogues it covers, PEG-MGF among them (Dominikowski et al., 2026); there are no human data for either form.
• Cancer risk (theoretical) — In culture, MGF's E domain made myoblasts multiply (Yang & Goldspink, 2002), and a 2026 review rates a cell-growth concern for PEG-MGF as theoretical, based on preclinical work on MGF in cancer biology (Dominikowski et al., 2026).
• PEG-MGF — Its PEG-specific risks, such as antibodies against PEG, are covered on the PEG-MGF page.
• Unknown long-term effects — No study has followed people taking MGF, so its long-term effects are unknown.
• Product purity variability — Peptides of this kind are sold through unregulated supply chains, where product composition and dose are uncertain (Dominikowski et al., 2026).
• WADA banned — Explicitly prohibited under S2 (growth factors: the 2026 List names mechano growth factors) in and out of competition. Modern anti-doping laboratories have validated detection methods for both MGF and PEG-MGF.
• Pregnancy and lactation — No data.
• Drug interactions — None studied.

Bloodwork & Monitoring

No trial, label or guideline sets monitoring for MGF, and no trial has given it to people. A 2026 review written for clinicians lists fasting glucose or HbA1c as worth obtaining in users of any GH–IGF-1 axis peptide; for the IGF-1 analogues it covers, PEG-MGF among them, it rates low blood sugar a theoretical risk (Dominikowski et al., 2026).

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Related Compounds

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References

1. Yang SY, Goldspink G. Different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation. FEBS Lett. 2002;522(1-3):156-160. PMID: 12095637. DOI: 10.1016/s0014-5793(02)02918-6.
2. Hill M, Goldspink G. Expression and splicing of the insulin-like growth factor gene in rodent muscle is associated with muscle satellite (stem) cell activation following local tissue damage. J Physiol. 2003;549(Pt 2):409-418. PMID: 12692175. DOI: 10.1113/jphysiol.2002.035832.
3. Goldspink G. Mechanical signals, IGF-I gene splicing, and muscle adaptation. Physiology (Bethesda). 2005;20:232-238. PMID: 16024511. DOI: 10.1152/physiol.00004.2005.
4. Dluzniewska J, Sarnowska A, Beresewicz M, Johnson I, Srai SK, Ramesh B, Goldspink G, Górecki DC, Zabłocka B. A strong neuroprotective effect of the autonomous C-terminal peptide of IGF-1 Ec (MGF) in brain ischemia. FASEB J. 2005;19(13):1896-1898. PMID: 16144956. DOI: 10.1096/fj.05-3786fje.
5. Carpenter V, Matthews K, Devlin G, Stuart S, Jensen J, Conaglen J, Jeanplong F, Goldspink P, Yang SY, Goldspink G, Bass J, McMahon C. Mechano-growth factor reduces loss of cardiac function in acute myocardial infarction. Heart Lung Circ. 2008;17(1):33-39. PMID: 17581790. DOI: 10.1016/j.hlc.2007.04.013.
6. Hameed M, Orrell RW, Cobbold M, Goldspink G, Harridge SD. Expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise. J Physiol. 2003;547(Pt 1):247-254. PMID: 12562960.
7. Hill M, Wernig A, Goldspink G. Muscle satellite (stem) cell activation during local tissue injury and repair. J Anat. 2003;203(1):89-99. PMID: 12892408.
8. Mills P, Dominique JC, Lafrenière JF, Bouchentouf M, Tremblay JP. A synthetic mechano growth factor E peptide enhances myogenic precursor cell transplantation success. Am J Transplant. 2007;7(10):2247-2259. PMID: 17845560.
9. Kim JS, Cross JM, Bamman MM. Impact of resistance loading on myostatin expression and cell cycle regulation in young and older men and women. Am J Physiol Endocrinol Metab. 2005;288(6):E1110-E1119. PMID: 15644458. (Human muscle MGF expression in training response.)
10. 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;151(3):865-875. PMID: 20130113.
11. Pfeffer LA, Brisson BK, Lei H, Barton ER. The insulin-like growth factor (IGF)-I E-peptides modulate cell entry of the mature IGF-I protein. Mol Biol Cell. 2009;20(17):3810-3817. PMID: 19605562.
12. Brisson BK, Barton ER. New modulators for IGF-I activity within IGF-I processing products. Front Endocrinol (Lausanne). 2013;4:42. PMID: 23543904.
13. Stavropoulou A, Halapas A, Sourla A, Philippou A, Papageorgiou E, Papalois A, Koutsilieris M. IGF-1 expression in infarcted myocardium and MGF E peptide actions in rat cardiomyocytes in vitro. Mol Med. 2009;15(5-6):127-135. PMID: 19295919.
14. WADA. World Anti-Doping Code: The 2026 Prohibited List. Section S2.3 — Growth factors and growth factor modulators (“Mechano growth factors (MGFs)”). World Anti-Doping Agency.
15. Thomas A, Höppner S, Geyer H, Schänzer W, Petrou M, Kwiatkowska D, Pokrywka A, Thevis M. Determination of growth hormone-releasing peptides and peptide hormones in doping control samples by liquid chromatography/(tandem) mass spectrometry. Anal Bioanal Chem. 2011;401(2):507-516.
16. Philippou A, Maridaki M, Halapas A, Koutsilieris M. The role of the insulin-like growth factor 1 (IGF-1) in skeletal muscle physiology. In Vivo. 2007;21(1):45-54. PMID: 17354613.
17. Philippou A, Halapas A, Maridaki M, Koutsilieris M. Type I insulin-like growth factor receptor signaling in skeletal muscle regeneration and hypertrophy. J Musculoskelet Neuronal Interact. 2007;7(3):208-218. PMID: 17947802.
18. FDA. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the FD&C Act (503A categories list), versions updated April 15, April 22 and May 14, 2026. fda.gov/media/94155/download. Read October 3, 2026. (Notice that 12 peptides would leave Category 2 because their nominations were withdrawn; their removal; GHK-Cu, except injectable, back in Category 1.)
19. Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, Domin R, Ruchała M. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. PMID: 42395176. DOI: 10.3389/fendo.2026.1822475. (Online PEG-MGF dosing protocols; no peer-reviewed human study of PEG-MGF; half-life not reported.)

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