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PeptideMostly animalNot FDA approved

MGF

Mechano growth factor

Last reviewed October 27, 2026 · 14 sources · Written for general readers · Compare with another compound →

The bottom line

MGF is a form of the IGF-1 gene product that muscle makes after strain or injury, and its biology is still debated. The synthetic peptides sold as MGF and PEG-MGF have never been tested in human trials, and FDA says it has no human exposure data for PEG-MGF. Both are unapproved, PEG-MGF faces an FDA advisory committee review by early 2027, and both are banned in sport.

Where the evidence stands

What it is

Mechano growth factor (MGF) is a form of the IGF-1 gene product that muscle makes after stretch, load or injury. It comes from alternative splicing, a way cells cut and join the message from one gene in different ways.[1][2]

Most lab studies use a synthetic peptide of 24 amino acids based on the unique tail of this form. Researchers note that no matching natural peptide has been isolated from cells or animal tissue, so it is unclear whether the body makes it as a separate signal.[1]

PEG-MGF is the same peptide with a chemical chain called PEG attached. FDA says it has found no human exposure data for PEG-MGF by any route.[3]

Name
MGF (Mechano growth factor)
Other names
IGF-1Ec, IGF-IEb, PEG-MGF (pegylated MGF)
Type
Peptide

How it works

MGF message levels in muscle rise early after injury, and the peptide is linked to satellite cells, the stem cells that repair muscle.[1]

  • In lab and animal work, MGF is tied to satellite cell activation and the growth of myoblasts (young muscle cells).[1][4]
  • Mechanical stretch, especially combined with electrical stimulation, increases MGF in muscle.[5]
  • It is also studied in bone, tendon, heart, brain and cartilage, but its role in cartilage is still debated and the mechanism is unclear.[4][6]

Even the basic biology is unsettled, so the effects of an injected peptide are speculative.

What the research shows

We keep animal and human evidence apart. A result in animals is a reason to study something in people, not proof that it works in people.

Animal and lab studies

Mixed lab results and a few animal signals

  • The synthetic peptide promotes the growth and survival of muscle cells in lab studies.[1]
  • In experimental animals, MGF rises in muscle, bone and tendon after damage and in brain and heart after loss of blood flow.[4]
  • It has been tested in animal models of muscular dystrophy and of brain injury from low oxygen.[4]
  • In sheep with a lab induced heart attack, the MGF tail peptide preserved heart pumping and left about 35 percent less damaged heart tissue after 8 days.[9]
  • In mice with an ALS like disease, delivering the MGF gene into hindlimb muscles improved muscle strength and kept more motor nerve cells alive than delivering the regular IGF-1 gene.[10]
  • A 2014 study by two drug companies found the synthetic MGF peptide did not boost growth of mouse or human muscle cells or muscle stem cells, and did not switch on key growth signals in heart cells. The authors questioned whether MGF has any real role in the body.[7]

Limit: These studies are early and mixed, and none show that injecting MGF or PEG-MGF is safe.

Human studies

No clinical trials of MGF or PEG-MGF

  • We found no published study that gave MGF or PEG-MGF to people, so there are no human data on effects people noticed or side effects. FDA says it has no human exposure data for PEG-MGF by any route. Human research has only measured the body's own MGF activity in muscle, for example after hard exercise in young and older men or growth hormone treatment in older adults.[3][8][2]

Limit: Nothing is known about the benefit or safety of these peptides in people.

Claims check

The most common claims about this compound, and what studies actually found. Verdicts rate the evidence, not whether you should use it.

Builds muscle

Only in animals

Some lab studies reported that the synthetic peptide helps young muscle cells grow and survive.[1] But when scientists at two drug companies tried to repeat this in 2014, the peptide did not make mouse or human muscle cells multiply, and did not change muscle stem cells, while normal IGF-1 did.[7] No study has tested muscle gain in people.

Speeds muscle repair and recovery

Only in animals

MGF messages rise in animal muscle, bone and tendon after damage, and the peptide has been tested in animal models of muscular dystrophy.[4] The 2014 lab study that found no effect on muscle stem cells casts doubt on this idea.[7] No human trial has tested recovery from training or injury.

Fights age related muscle loss

Not tested

In 8 young men and 7 men aged 70 to 82, a hard leg workout raised MGF messages in the young men's thigh muscle but not in the older men's.[8] That only measured the body's own MGF. We found no study that gave MGF or PEG-MGF to older people to see whether it slows muscle loss.[3]

Protects the heart

Only in animals

In sheep given a heart attack in the lab, the MGF tail peptide given at the time preserved heart pumping and left about 35 percent less damaged heart tissue after 8 days.[9] No human study exists.

Protects nerves and the brain

Only in animals

In mice with an ALS like disease, delivering the MGF gene into leg muscles improved strength and kept more motor nerve cells alive.[10] It has also been studied in animal brain injury from low oxygen.[4] This was gene delivery, not the injected peptide, and no human study exists.

Heals joints and cartilage

Only in animals

Lab and animal studies have explored MGF for cartilage cells and cartilage defects, but a 2023 review said its role is still debated and the mechanism unclear.[6] No human study exists.

Known risks and side effects

  • Unknown human safety. FDA says it has no human exposure data for PEG-MGF and lacks the information to judge whether it would cause harm.[3] Even its basic action is in doubt, since a careful lab study found no effect on muscle cells.[7]
  • Immune reactions and impurities. FDA warns PEG-MGF may trigger significant immune reactions for certain routes, and that peptide impurities and its complex structure make it hard to check.[3]
  • Unregulated products. Falsified peptide and protein drugs can contain the wrong ingredient, the wrong amount, nothing active, or toxic contaminants.[11]
  • Banned in sport. WADA lists mechano growth factors as prohibited growth factors.[12]

Regulatory status

Today: MGF and PEG-MGF are not approved drugs. FDA's 503A nomination list puts MGF in Category 3, meaning it was nominated without enough support.[13] FDA lists PEG-MGF among withdrawn nominations, no longer in Category 2, and plans to ask its Pharmacy Compounding Advisory Committee about it at a meeting before the end of February 2027.[3][14] WADA bans MGFs.[12]

  1. The 2026 WADA Prohibited List took effect and bans mechano growth factors.[12]
  2. FDA listed PEG-MGF among withdrawn nominations no longer in Category 2, while keeping its safety concerns on its safety page.[3] FDA also named PEG-MGF for a future advisory committee meeting.[14]
  3. FDA's updated 503A nomination list shows MGF in Category 3.[13]
  4. FDA plans a Pharmacy Compounding Advisory Committee meeting that will cover PEG-MGF, along with LL-37, GHK-Cu, dihexa and melanotan II.[14]

Sources

  1. Matheny RW Jr, Nindl BC, Adamo ML, et al. 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
  2. Goldspink G, Harridge SDR. Growth factors and muscle ageing. Exp Gerontol. 2004;39(10):1433-1438. PMID 15501012
  3. U.S. Food and Drug Administration. Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks. Content current as of April 22, 2026. FDA
  4. Dai Z, Wu F, Yeung EW, et al. IGF-IEc expression, regulation and biological function in different tissues. Growth Horm IGF Res. 2010;20(4):275-281. PMID 20494600
  5. Goldspink G, Yang SY. Effects of activity on growth factor expression. Int J Sport Nutr Exerc Metab. 2001;11 Suppl:S21-S27. PMID 11915923
  6. Liu Y, Duan M, Zhang D, et al. The role of mechano growth factor in chondrocytes and cartilage defects: a concise review. Acta Biochim Biophys Sin (Shanghai). 2023;55(5):701-712. PMID 37171185
  7. Fornaro M, Hinken AC, Needle S, Hu E, Trendelenburg AU, Mayer A, 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. Am J Physiol Endocrinol Metab. 2014;306(2):E150-E156. PMID 24253050
  8. 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. J Physiol. 2003;547(Pt 1):247-254. PMID 12562960
  9. Carpenter V, Matthews K, Devlin G, Stuart S, Jensen J, Conaglen J, et al. Mechano-growth factor reduces loss of cardiac function in acute myocardial infarction. Heart Lung Circ. 2008;17(1):33-39. PMID 17581790
  10. Riddoch-Contreras J, Yang SY, Dick JRT, Goldspink G, Orrell RW, Greensmith L. Mechano-growth factor, an IGF-I splice variant, rescues motoneurons and improves muscle function in SOD1(G93A) mice. Exp Neurol. 2009;215(2):281-289. PMID 19038252
  11. Janvier S, De Spiegeleer B, Vanhee C, et al. Falsification of biotechnology drugs: current dangers and/or future disasters? J Pharm Biomed Anal. 2018;161:175-191. PMID 30165334
  12. World Anti-Doping Agency. World Anti-Doping Code: 2026 Prohibited List, section S2 (peptide hormones, growth factors, related substances and mimetics). In effect January 1, 2026. WADA 2026
  13. U.S. Food and Drug Administration. Bulk Drug Substances Nominated for Use in Compounding Under Section 503A of the Federal Food, Drug, and Cosmetic Act. Updated May 14, 2026. FDA 503A categories
  14. U.S. Food and Drug Administration. Meeting of the Pharmacy Compounding Advisory Committee (meeting planned before the end of February 2027). Content current as of April 15, 2026. FDA PCAC
Medical disclaimer

This page is educational information only. It is not medical advice and does not replace care from a licensed medical provider. Do not use this page to decide whether to take any substance. Talk to a licensed medical provider first.

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