# Mechano growth factor (MGF / PEG-MGF)

IGF-1 splice-variant peptide (plain or PEGylated) for muscle repair; disputed biology, cancer-cell signal.

- Page: https://peprank.xyz/peptides/mechano-growth-factor
- Category: Recovery, joints & healing (Research peptide)
- Also known as: MGF: synthetic 24-amino-acid E-domain peptide of the IGF-1Ec splice variant (IGF-1Eb in rodents); PEG-MGF: the same peptide attached to polyethylene glycol to make it last longer; pegylated mechano growth factor; '3x blend MGF' (vendor blends)
- Routes: Injection / Nasal
- Safety tier: Strict: Avoid · Balanced: Avoid · Evidence only: Caution
- Risk axes (0 none to 3 severe): Seen harm 0, Mechanism 2, Data gap 3, Silent harm 3, Product 3
- Positive: 53% of 5 graded reports glowing or positive, shrunk toward the 49% all-report average by 8 reports' weight
- Rank: #29 of 61 research peptides
- Graded reports: 5 (Positive 3, Mixed 1, Nothing 1)
- Evidence: Animal only — No human has been given MGF or PEG-MGF in any published study. The human evidence is about the body's own MGF: muscle biopsies show its mRNA rises after resistance exercise in young but not older men. The rest is cell and mouse work, and its key claim (muscle stem-cell activation) failed independent replication in 2014.
- Access: Grey market
- Onset: Users report less soreness from the first sessions; injury reports talk of weeks.
- Lasts: Plain MGF is described as lasting minutes, so it is injected straight after training; PEG-MGF is dosed every 2-3 days.
- Cost per month: ≈ €27–110 (researchers' estimate)
- Updated: 2026-10-30

**Why Avoid under the strict bar:** An unapproved growth-factor fragment with no human dosing data at all. The peptide drove prostate-cancer cell growth and metastasis in mice by a route that bypasses the IGF-1 receptor, and the pegylated form people buy has never been characterised.

## What users report

Very few first-hand reports exist; most threads are people asking whether anyone has tried it. The two positive reports are about recovery, not growth: one used plain MGF in the biceps after training and could train arms to failure daily without soreness, the other ran PEG-MGF with BPC-157 and TB-500 for a sports injury. Others got nothing but a painful injection. Bodybuilders say it has circulated for over a decade without catching on, and the YouTuber Vigorous Steve is cited as calling the products junk. One intranasal user felt warm and sweaty after the first dose and never reported back. Felt nothing: Too few reports to judge. Of the handful of users, one felt nothing but a painful injection; long-time bodybuilders say most people get nothing from it..

**Effects:** faster recovery and less soreness after training (anecdotal); faster injury healing, usually alongside BPC-157/TB-500

**Downsides:** painful intramuscular injections; no felt effect for many; plain MGF has to be injected right after each session; PEG-MGF 2-3 times a week

**Risks:** Growth-factor-like signalling: the MGF E peptide drove prostate-cancer cell growth in vitro and tumour growth and metastasis in mice, independently of the IGF-1 receptor; theoretical promotion of existing cancers; PEG-MGF is an uncharacterised pegylated conjugate: its exposure, clearance and immunogenicity in people are unknown; Disputed biology: a two-company replication found the peptide inactive on muscle stem cells, so a vial may be inert or contain something else; No human data; grey-market injectable

**Caveat:** MGF and PEG-MGF differ mainly in how long they last. Plain MGF is the short synthetic E-domain peptide, injected into the trained muscle within about 30 minutes of a session. PEG-MGF carries a polyethylene glycol chain meant to extend that to days, and is injected subQ or IM a few times a week. Neither has human pharmacokinetic data, and the 2014 failed replication means it is unclear whether either does anything; reported benefits may be placebo or the other compounds they are stacked with.

**Typical use:** No clinical dose exists. Plain MGF: about 100-200 mcg per muscle straight after training. PEG-MGF: 200-400 mcg 2-3 times a week.

**Getting it:** Research-peptide vials only. MGF was nominated for US 503A compounding but is not on the list. Both forms are banned in sport by WADA (S2, 'mechano growth factors').

**Stacked with:** BPC-157 and TB-500 (Used together for injuries; the one positive PEG-MGF injury report is for this trio, so MGF's share cannot be told apart.); IGF-1 LR3 or IGF-1 DES (Old forum protocols alternate LR3 weeks with PEG-MGF weeks, or pair MGF with DES on the same day, on the theory that LR3 blunts MGF; none of this has been tested.); HGH or CJC-1295/ipamorelin (Users ask whether raised IGF-1 from GH cancels MGF; nobody knows.)

## Risk profile

- **Seen harm 0/3:** No case report, trial or regulator warning involves MGF or PEG-MGF, and the few first-hand Reddit reports describe only injection pain and, in one intranasal user, sweating. The zero reflects almost no documented human exposure, not reassurance; the gap is carried by dataGap.
- **Mechanism 2/3:** The MGF E peptide behaves as a growth factor. It stimulated prostate-cancer cells by a route independent of the IGF-1 receptor, and in mice the endogenously overexpressed peptide drove tumour growth and metastasis. That is growth-factor signalling shown in animals (2). It falls short of 3 because no study injected the peptide at user doses, and a two-company replication found synthetic MGF inactive on muscle cells. PEG-MGF is scored the same, since it is the same peptide made to last longer.
- **Data gap 3/3:** No human has been given MGF or PEG-MGF in any published study. The only human data measure the body's own MGF mRNA after exercise (n=15) and say nothing about an injected peptide. The pegylated conjugate sold has never been characterised for exposure, clearance or immunogenicity.
- **Silent harm 3/3:** The feared harm is promotion of an existing tumour (the prostate-cancer signal), which would be silent and delayed and which testimonials cannot reveal.
- **Product 3/3:** Bought only as grey-market vials (plain MGF or PEG-MGF, sometimes '3x blends') and injected IM or subQ, occasionally made into a home nasal spray. Since the pure peptide showed no bioactivity in an independent replication, users cannot tell a working vial from an inert or mislabelled one.
- **Never if:** Active or past cancer, especially prostate cancer, or a known predisposition to cancer; Pregnancy or breastfeeding (no human reproductive data); Children and teenagers; Known allergy to polyethylene glycol (PEG-MGF)

## Top reports

- Positive, recovery: “I did a cycle of PEG-MGF with BPC + TB 10mg from a sports injured. Was inspired by the "research" and presentation from Hunter Williams making some solids arguments about the synergies with all 3 compounds. It's all of course subjective and anecdotal but I felt I got over my injury faster then expected.” — [r/BodyHackGuide](https://www.reddit.com/r/BodyHackGuide/comments/1ntcbc3/experience_with_pegmgf/ngtltoq/)
- Positive, recovery, 200 mcg plain (non-PEG) MGF into each bicep after training: “Noticed much faster healing on non peg mgf 200mcg bilaterally in each bicep, the healing also helped surrounding muscles.” — [r/BodyHackGuide](https://www.reddit.com/r/BodyHackGuide/comments/1ntcbc3/experience_with_pegmgf/ngsqb8f/)
- Positive, recovery: “I tried a bottle of each last time i was doing an lgd-4033 and mk677 stack.” — [r/moreplatesmoredates](https://www.reddit.com/r/moreplatesmoredates/comments/1346n75/any_bruhs_dabble_with_either_pegmgf_or_igfdes/)
- Mixed, recovery: “Just got it, so will report back after the first week. All I can say is the first nasal spray dose made me warm and sweaty lol.” — [r/moreplatesmoredates](https://www.reddit.com/r/moreplatesmoredates/comments/1346n75/any_bruhs_dabble_with_either_pegmgf_or_igfdes/k4m6wlr/)
- Nothing, recovery: “The injection hurts like hell. I didn't get any benefit but I may not have been running enough.” — [r/BodyHackGuide](https://www.reddit.com/r/BodyHackGuide/comments/1ntcbc3/experience_with_pegmgf/ngsp0ju/)

## Studies

- [Hameed et al. 2003: expression of IGF-I splice variants in young and old human skeletal muscle after high resistance exercise](https://pubmed.ncbi.nlm.nih.gov/12562960/) (observational, n=15, 2003): One bout of heavy leg exercise raised MGF mRNA in eight young men but not in seven men aged 70-82; nobody was given MGF.
- [Yang & Goldspink 2002: different roles of the IGF-I Ec peptide (MGF) and mature IGF-I in myoblast proliferation and differentiation](https://pubmed.ncbi.nlm.nih.gov/12095637/) (in-vitro, 2002): The MGF E-domain peptide increased myoblast proliferation and delayed differentiation through a receptor other than the IGF-1 receptor; this is the founding claim.
- [Kandalla et al. 2011: MGF-E peptide activates human muscle progenitor cells and increases their fusion potential at different ages](https://pubmed.ncbi.nlm.nih.gov/21354439/) (in-vitro, 2011): The 24-amino-acid peptide extended the proliferative life of satellite cells from neonatal and young-adult donors, but not from old-adult donors.
- [Mills et al. 2007: pro-migratory activity on human myogenic precursor cells for a synthetic peptide within the E domain of MGF](https://pubmed.ncbi.nlm.nih.gov/17156777/) (in-vitro, 2007): A synthetic E-domain peptide increased the migration of human muscle precursor cells in culture.
- [Fornaro et al. 2014: MGF peptide has no apparent effect on myoblasts or primary muscle stem cells](https://pubmed.ncbi.nlm.nih.gov/24253050/) (in-vitro, 2014): Scientists at two pharmaceutical companies, Novartis among them, could not reproduce any effect of native or stabilised MGF peptide on human or mouse myoblasts, muscle stem cells or cardiac myocytes, while mature IGF-1 worked in every assay.
- [Armakolas et al. 2010: preferential expression of IGF-1Ec (MGF) in prostate cancer and autonomous growth-factor activity of the MGF E peptide](https://pubmed.ncbi.nlm.nih.gov/20564425/) (in-vitro, 2010): Synthetic MGF E peptide stimulated prostate-cancer cell growth and ERK1/2 signalling even with the IGF-1 and insulin receptors silenced; MGF expression was higher in cancerous than normal prostate tissue.
- [Armakolas et al. 2015: oncogenic role of the Ec peptide of the IGF-1Ec isoform in prostate cancer](https://pubmed.ncbi.nlm.nih.gov/25569803/) (animal, 2015): The Ec peptide drove prostate-cancer cell proliferation in vitro and in mice, and normal prostate cells overexpressing it metastasised more often in SCID mice.

## Sources

- [Fornaro et al. 2014: MGF peptide has no apparent effect on myoblasts or muscle stem cells (two-company replication)](https://pubmed.ncbi.nlm.nih.gov/24253050/)
- [Armakolas et al. 2015: oncogenic role of the Ec peptide in prostate cancer (Mol Med)](https://pubmed.ncbi.nlm.nih.gov/25569803/)
- [Dominikowski et al. 2026: GH-IGF-1 axis performance peptides, PEG-MGF in the no-human-data tier (review)](https://pubmed.ncbi.nlm.nih.gov/42395176/)
- [FDA: bulk drug substances nominated for 503A compounding (lists mechano growth factor)](https://www.fda.gov/media/94155/download?attachment=)
- [WADA Prohibited List 2026 (S2.3: mechano growth factors)](https://www.wada-ama.org/sites/default/files/2025-09/2026list_en_final_clean_september_2025.pdf)
- [Peptigrity: PEG-MGF price per mg across 16 shops (Oct 2026)](https://peptigrity.com/prices/peg-mgf)