MGF Research

MGF is sold as a research peptide associated with muscle repair, and the record behind that association is unusually thin.

What MGF is

"Mechano growth factor" is a splice variant name, not a product name. It denotes IGF-1Ec, one of four annotated isoforms of the human IGF1 gene product ^[3].

The founding work cloned an IGF-1 messenger RNA isoform, IGF-1Eb, from stretched rabbit muscle undergoing hypertrophy (animal) ^[1]. A 52 base-pair insert in the E domain shifts the reading frame and yields a different precursor protein ^[1]. The term "mechano growth factor" was applied to that variant in later work, not in the original paper ^[2].

What is sold as MGF is only the C-terminal E-domain peptide of that variant, roughly 24 residues: YQPPSTNKNTKSQRRKG, shared with IGF-1Eb, followed by the Ec-specific tail STFEERK ^[3]. It contains no part of the 70-residue mature IGF-1 chain, unlike IGF-1 DES and IGF-1 LR3 ^[3].

The human and rodent E-domain peptides are different sequences, so rodent results do not transfer cleanly ^[6].

Receptor

MGF is often grouped with the IGF-1 receptor agonists, and two independent in vitro studies place it outside that group. In the first, an antibody blocking the IGF-1 receptor showed that the E domain acts through a different receptor ^[3]. In the second, its proliferative effect on C2C12 cells survived an anti-IGF-1-receptor neutralizing antibody, and Akt was not phosphorylated ^[4].

Both are negative findings, and the receptor the E peptide acts through has not been identified. Assigning a receptor also presumes a reproducible effect to assign, and the replication attempt below found none ^[5].

The laboratory record is contested

Scientists at two pharmaceutical companies tried to reproduce the claimed effects of the MGF E-domain peptide and failed in every model (in vitro) ^[5]. Concentrations up to 500 ng/mL did not increase proliferation of C2C12 cells or primary human myoblasts, and did not activate p-ERK in cardiac myocytes ^[5]. Mature IGF-1 and full-length IGF-1Eb responded robustly in the same experiments, so the assays were working ^[5]. The authors concluded that their results call into question whether MGF has a physiological role at all ^[5]. The commercial incentive of those laboratories ran toward finding an effect, which strengthens the null. The honest counter-argument is that synthetic peptide quality and the exact sequence used could explain the discrepancy.

In human satellite cells, by contrast, the peptide increased proliferative lifespan and delayed senescence, but only in cells from neonatal and young adult donors (in vitro) ^[6]. A separate hypertrophy and fusion effect was reported at every age tested, and the authors' overall conclusion was positive ^[6]. That study and the replication failure used overlapping cell types and reached opposite conclusions. A third in vitro study found an opposite-direction effect in bone, inhibiting osteoblast differentiation and mineralization ^[7].

No analogous peptide product of the IGF1 gene has been identified in or isolated from cultured cells, conditioned medium, animal tissues or biological fluids ^[2]. Absence of isolation is not proof of non-existence. But the natural counterpart of this synthetic peptide has never been shown to exist.

Human evidence

There are no registered interventional trials of MGF, and a registry query returns 105 studies, none with an MGF intervention ^[8]. Every human MGF study retrievable from PubMed instead measures endogenous IGF-1Ec messenger RNA in muscle biopsies, and none administers an MGF peptide to anyone ^[8].

That distinction carries the subject: humans do upregulate the IGF-1Ec splice variant in response to mechanical loading, and the observation is real and replicated ^[8]. It is not evidence that injecting a synthetic 24-residue peptide does anything in a person.

Pegylated MGF was nominated as a compounding bulk substance and withdrawn ^[9]. FDA states it has not identified any human exposure data on drug products containing PEG-MGF administered by any route ^[9]. PEG-MGF has no primary literature at all ^[8]. There is therefore no human pharmacokinetic data for either form ^[9][10]. Every half-life or "active window" figure circulating for it is extrapolated from animal or in vitro work, or invented ^[9][10]. Mechano growth factors are named in Section S2 of the 2026 WADA Prohibited List ^[11].

What tesamorelin's approval does not transfer

Tesamorelin is the one molecule in this family holding a marketing authorization. FDA approved it on 10 November 2010 for reduction of excess abdominal fat in adults with HIV-associated lipodystrophy ^[12]. That approval remains in force ^[12]. It never obtained a European authorization, because the applicant withdrew the application while it was under CHMP review ^[13].

The approval belongs to the molecule tesamorelin and to one indication. It is not a family credential and must never be written as one.

On mechanism, tesamorelin acts at the pituitary GHRH receptor, while MGF acts neither there nor at the IGF-1 receptor, so no shared receptor connects them ^[3][4].

On duration, a shared receptor says nothing about exposure even within the GHRH limb. Tesamorelin's mean elimination half-life is formulation-specific at 8 and 11 minutes, and it is given daily ^[14]. CJC-1295 with DAC has an estimated half-life of 5.8 to 8.1 days ^[15], with trough growth hormone raised 7.5-fold after a single dose ^[16]. Same receptor, exposures orders of magnitude apart. "GHRH analogue" names a receptor target, not a duration of action.

On approval count, GHRP-2 carries a reported Japanese approval as a diagnostic agent for growth hormone deficiency testing ^[17]. That report is unverified against any primary regulatory database, and a diagnostic provocative-test approval is not a therapeutic one. Its source is a 2004 trade profile that recorded approval as then pending ^[17]. It is not comparable to tesamorelin's.

What the record supports

The honest contrast is not that tesamorelin works and the others might too. It is that tesamorelin is the only one of the nine that has been through the process that would let anyone know.

The epidemiology linking circulating IGF-1 to cancer risk derives from ranked categories of lifelong endogenous IGF-1 in cohort studies. It is not applied to MGF, which has never been shown to raise IGF-1 in a person because no study administering it to one is retrievable ^[8].

MGF is supplied for laboratory research use only. Not for human consumption.

Frequently Asked Questions

Has MGF been given to humans in a study? No study administering an MGF peptide to a person is retrievable, and there are no registered interventional trials ^[8]. Every human MGF paper measures endogenous IGF-1Ec messenger RNA in muscle biopsies instead, and upregulating that transcript after loading is a different event from injecting a peptide ^[8]. FDA has identified no human exposure data for PEG-MGF by any route ^[9].

Is MGF a form of IGF-1? Not in the way IGF-1 DES and IGF-1 LR3 are, because what is sold contains no part of the mature IGF-1 chain ^[3]. Two independent in vitro studies also found that its action is not blocked by an anti-IGF-1-receptor antibody, so it is not an IGF-1 receptor agonist ^[3][4].

What is MGF's half-life? No human pharmacokinetic data exist for MGF or PEG-MGF ^[9][10]. Every half-life and "active window" figure circulating for it is extrapolated from animal or in vitro work, or invented ^[9][10].

References

1. 1

   Yang S, et al. Cloning and characterization of an IGF-1 isoform expressed in skeletal muscle subjected to stretch. J Muscle Res Cell Motil. 1996. PMID 8884603. (Animal, rabbit. Cloning content only; this paper does not use the term "mechano growth factor".)
2. 2

   Matheny RW Jr, et al. Minireview: Mechano-growth factor: a putative product of IGF-I gene expression involved in tissue repair and regeneration. Endocrinology. 2010. PMID 20130113.; DOI: 10.1210/en.2009-1217. (Review. Source of the naming attribution and of the never-isolated statement.)
3. 3

   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. PMID 12095637.; DOI: 10.1016/s0014-5793(02)02918-6. Sequence and isoform detail from UniProt P05019 (IGF1_HUMAN), retrieved 2026-08-27. (In vitro.)
4. 4

   Philippou A, et al. Expression of IGF-1 isoforms after exercise-induced muscle damage in humans: characterization of the MGF E peptide actions in vitro. In Vivo. 2009. PMID 19567392. (no DOI in the PubMed record). (In vitro for the receptor finding; the human component is expression profiling, not administration.)
5. 5

   Fornaro M, 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. PMID 24253050.; DOI: 10.1152/ajpendo.00408.2013. (In vitro. Conducted at two pharmaceutical companies.)
6. 6

   Kandalla PK, et al. Mechano growth factor E peptide (MGF-E), derived from an isoform of IGF-1, activates human muscle progenitor cells and induces an increase in their fusion potential at different ages. Mech Ageing Dev. 2011. PMID 21354439.; DOI: 10.1016/j.mad.2011.02.007. (In vitro.)
7. 7

   Xin C, et al. Mechano-growth factor E peptide inhibits the differentiation and mineralization of osteoblasts. Arch Oral Biol. 2012. PMID 22186070.; DOI: 10.1016/j.archoralbio.2011.11.016. (In vitro, mouse cell line.)
8. 8

   Database absence result. ClinicalTrials.gov API v2 and PubMed E-utilities, run 2026-08-27. Registry query on "mechano growth factor" returns 105 studies, none carrying an MGF intervention. Example endogenous-expression studies: Hameed M, et al. J Physiol. 2004. PMID 14565994.; Bickel CS, et al. J Appl Physiol. 2005. PMID 15465884.; Delgado-Diaz DC, et al. Am J Sports Med. 2011. PMID 21785002.
9. 9

   US FDA, Human Drug Compounding programme. "Certain Bulk Drug Substances for Use in Compounding that May Present Significant Safety Risks", nominated-but-withdrawn table, entry "Mechano growth factor pegylated (PEG-MGF)". Page content current as of 22 April 2026.
10. 10

    Dominikowski A, et al. 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. PMID 42395176.; DOI: 10.3389/fendo.2026.1822475. (Review. Attribute each claim to the specific compound named in it.)
11. 11

    World Anti-Doping Agency. The 2026 Prohibited List, World Anti-Doping Code, Section S2. In force 1 January 2026.
12. 12

    US FDA, Drugs@FDA / openFDA. Tesamorelin, application 022505; approval letter 10 November 2010 (Reference ID 2863003); Structured Product Label effective 29 July 2026.
13. 13

    European Medicines Agency / CHMP. Tesamorelin, EMEA/H/C/002427, withdrawn application. Questions-and-answers document EMA/CHMP/475021/2012; withdrawal notified by the applicant, Ferrer Internacional S.A., on 21 June 2012 and announced 26 June 2012.
14. 14

    US FDA approved product labeling, application 022505, section 12.3. Mean elimination half-life 8 minutes for the 2 mg/vial formulation and 11 minutes for the 11.6 mg/vial formulation, in healthy subjects after a single subcutaneous dose.
15. 15

    Teichman SL, et al. Prolonged stimulation of growth hormone (GH) and insulin-like growth factor I secretion by CJC-1295, a long-acting analog of GH-releasing hormone, in healthy adults. J Clin Endocrinol Metab. 2006. PMID 16352683.; DOI: 10.1210/jc.2005-1536. (Human.)
16. 16

    Ionescu M, Frohman LA. Pulsatile secretion of growth hormone (GH) persists during continuous stimulation by CJC-1295, a long-acting GH-releasing hormone analog. J Clin Endocrinol Metab. 2006. PMID 17018654.; DOI: 10.1210/jc.2006-1702. (Human.)
17. 17

    Pralmorelin: GHRP 2, GPA 748, growth hormone-releasing peptide 2, KP-102 D, KP-102 LN, KP-102D, KP-102LN. Drugs R D. 2004. PMID 15230633.; DOI: 10.2165/00126839-200405040-00011. Supporting validation study: Chihara K, et al. Eur J Endocrinol. 2007. PMID 17609397.; DOI: 10.1530/EJE-07-0066. (Trade-intelligence profile, not primary regulatory documentation.)