What is MGF?

What sources report

Where the name comes from

The human IGF-1 gene is read into several precursor forms, IGF-1Ea, IGF-1Eb and IGF-1Ec. Each is cut into mature IGF-1, the part that acts on the IGF-1 receptor, plus a leftover tail called the E-peptide.¹³ MGF is the IGF-1Ec form: a 49-base insert gives it a unique E-domain, and the rodent equivalent is called IGF-1Eb.¹

Goldspink and colleagues reported the mRNA of this form in 1996, made in response to mechanical stress.²⁰ In a 1999 rabbit study, stretching a muscle in a cast raised both muscle forms of IGF-1 mRNA within 4 days, and the authors described MGF as a form for local action inside the muscle.²⁶

The research peptide called MGF is a synthetic copy of the last 24 amino acids of the E-domain, a sequence that matches the end of the E-peptide in one human IGF-1 isoform.⁴²⁷ A 2010 review noted that no matching peptide had been identified in or isolated from cells, animal tissues or body fluids, so whether the body makes a free MGF peptide was unproven.⁴ The MGF for sale listing on this site is a 2 mg research vial sold under this name.

MGF and exercise in people

Human data cover the body's own MGF, measured as mRNA (and in one study as protein) in muscle biopsies:

• After 10 sets of 6 knee extensions at 80% of one-repetition maximum, MGF mRNA rose 2.5 hours later in 8 young adults aged 25 to 36, but not in 7 adults aged 70 to 82.²
• After 60 minutes of eccentric (reverse pedal) cycling, mean MGF mRNA rose in both 9 young and 8 older adults.¹⁷
• Across 21 weeks of resistance training in 7 men aged 20 to 34 and 10 aged 51 to 71, MGF mRNA and protein did not change systematically; MGF mRNA rose after a single bout only in the older men, before training began.¹⁸

An animal finding fits the age pattern: older rat muscles that failed to adapt to overload expressed considerably less MGF.²⁸

Cell studies: a disputed signal

A 2002 cell study reported that the MGF E-domain raised the number of dividing muscle precursor cells while blocking their final maturation, unlike mature IGF-1.²⁹ Blocking the IGF-1 receptor suggested MGF acted through a different receptor.²⁹ A 2007 study found the E peptide increased progenitor cell numbers in muscle cell cultures from healthy people and from muscular dystrophy and ALS patients.³⁰

Other labs disagree. A 2012 study of rodent E-peptides in mouse muscle cells found their effects depended on the IGF-1 receptor after all.³¹ In 2014, scientists at two pharmaceutical companies tested MGF peptide at up to 500 ng/ml on mouse cells, human muscle cells and mouse muscle stem cells, saw no effect, and questioned whether MGF has a physiological role.¹² In a 2016 receptor assay, the short human MGF peptide and a stabilized version did not activate the IGF-1 receptor. A larger "full-length MGF" protein did, but needed about 9 times the concentration of IGF-1 for half its maximal effect.¹⁴

Animal studies

These are animal results; they do not show effects in people. Goal pages on muscle growth, healing and recovery and cognitive health place MGF next to the other compounds searched for each goal.

Side effects

Side effects of MGF in people have not been described: published studies of the synthetic peptide are preclinical.²⁰⁶ For PEG-MGF, FDA says it has not identified any human exposure data and lacks information on whether it would cause harm in humans, and that compounded PEG-MGF may pose a significant risk of immune reactions for certain routes.²³ For unregulated peptides acting on the growth hormone and IGF-1 axis as a group, a 2026 review lists hormone and blood sugar changes, fluid retention, muscle and joint pain and injection-site reactions; these are class-level reports, not MGF data.²¹

There is also a theoretical cancer concern. MGF (IGF-1Ec) is overexpressed in prostate cancer and pre-cancerous prostate tissue, and the synthetic E peptide made prostate cancer cells grow in the lab.³⁹ In tumor samples from 83 prostate cancer patients, higher IGF-1Ec levels went with more advanced stage and higher Gleason score.⁴⁰ A 2026 review lists a theoretical proliferative concern for PEG-MGF on the same basis.¹⁵

Dosage information

No human dose of MGF has been established: published studies of the synthetic peptide are preclinical, a 2026 review found no peer-reviewed human studies of PEG-MGF, and FDA has not identified any human exposure data for it.²⁰⁶²³ The same review labels the dosing patterns that circulate online as self-reported, not clinical recommendations.⁶ The published doses reviewed here come from animal and cell work:

• Rabbits with a bone defect: MGF-Ct24E at 28.5 or 57 micrograms per kg of body weight, injected for 5 consecutive days after surgery; only the higher dose differed from no treatment.⁷
• Rats with an injured Achilles tendon: an E peptide (MGF-C25E) at 1,000 ng/ml used to treat the tendon; the abstract does not give the route or volume.³⁷
• Sheep after a heart attack: the MGF E domain at 200 nM; the abstract does not give the route or total dose.³⁴
• Cells: MGF peptide up to 500 ng/ml had no effect on muscle cells in a replication study.¹²

These animal and cell figures are not guidance for people.

Reconstitution and storage

No approved MGF product exists, so there is no official label with mixing or storage directions.⁵ Researchers built stabilized versions of the peptide, such as Goldspink-MGF, and PEG-MGF is marketed to increase stability, but how long the plain peptide lasts in a vial is not documented in the sources reviewed.¹⁴¹⁵ Handling therefore follows general rules for injectable diluents and dissolved peptides:

• Diluent choice: bacteriostatic water contains 0.9% or 1.1% benzyl alcohol and comes in multiple-dose vials, while sterile water for injection has no preservative and comes only in single-dose containers.⁴¹⁴²
• Opened vials: CDC guidance says a multiple-dose vial that has been needle-punctured should be dated and discarded within 28 days, unless its maker gives another date.⁴³
• Mixing: the labels of two approved freeze-dried tesamorelin products say to roll or swirl the vial gently and not to shake it.⁴⁴⁴⁵
• Checking: the same labels say to use a mixed solution only if it is clear and colorless, with no particles.⁴⁴⁴⁵

For the bench steps, see the reconstitution guide; for dilution arithmetic, the reconstitution calculator; and for freezer and refrigerator choices, how to store peptides.

Regulatory status

MGF is not approved for therapeutic use. A 2012 doping-lab paper described it as readily available on the black market even so.⁵ On FDA's list of bulk substances nominated for 503A compounding (updated May 14, 2026), MGF is in Category 3, nominated without adequate support; Category 2, for substances that raise significant safety risks, held six entries, none of them MGF.⁹

PEG-MGF has a separate history. It sat in FDA's Category 2 until its nominators withdrew it.²³ FDA's advisory committee is set to discuss it, with LL-37, GHK-Cu, dihexa acetate and melanotan II, at a meeting FDA says it will hold before the end of February 2027; no date was posted as of October 25, 2026.²⁴ The committee's July 2026 meeting covered seven other peptides (BPC-157, KPV, TB-500, MOTS-c, DSIP, semax and epitalon), and its advice is non-binding: FDA generally follows it but is not legally bound to.⁴⁶ In a 2020 warning letter, FDA said drugs a pharmacy compounded from PEG-MGF did not qualify for the 503A exemptions, because the substance has no USP or NF monograph, is not a component of an FDA-approved drug and is not on the 503A bulks list.²⁵

In sport, mechano growth factors are prohibited at all times under WADA class S2.3, on the 2026 list and on the 2027 list, which WADA published on September 21, 2026 and which takes effect on January 1, 2027.¹⁰¹¹⁴⁷ Doping labs have identified MGF products from the black market and from confiscated vials.⁵¹⁹