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Comparison

IGF-1 LR3 vs MGF

Both are IGF & growth factors, so the meaningful differences are in kinetics, evidence and regulatory status.

IGF-1 LR3 MGF
Class IGF & growth factors IGF & growth factors
Evidence Animal models only Animal models only
Human trials None published ~1
Half-life ~20-30 hours ~5-7 minutes
Reported range 20-50 mcg 100-200 mcg
Frequency Once daily Post-training, localised
Routes Subcutaneous, Intramuscular Subcutaneous, Intramuscular
FDA approved No No
Research use only Yes Yes
Banned in sport Yes Yes
Studied for Muscle hypertrophy research, Cell-culture growth supplement, Recovery Satellite cell activation research, Muscle repair studies
Reported side effects Hypoglycaemia, Injection-site swelling, Headache, Jaw pain Injection-site reactions, Transient fatigue

IGF-1 LR3

IGF-1 LR3 substitutes arginine for glutamic acid at position 3 and adds a 13-residue N-terminal extension. The position-3 substitution sharply reduces affinity for IGF binding proteins, so a much larger fraction remains free and active in circulation, extending the functional half-life from minutes to more than a day. It activates the IGF-1 receptor to drive protein synthesis, satellite-cell proliferation and hyperplasia, and it also has appreciable affinity for the insulin receptor, which accounts for its hypoglycaemic effect.

MGF

Mechano growth factor is the IGF-1Ec splice variant, produced locally in skeletal muscle after mechanical overload or injury. Its distinct C-terminal E-domain peptide acts independently of the IGF-1 receptor to activate satellite cells and promote myoblast proliferation, positioning it upstream of the differentiation signalling that mature IGF-1 drives. Its extremely short half-life in circulation is the central practical problem and the reason the pegylated form was developed.

IGF-1 LR3 vs MGF: common questions

What is the difference between IGF-1 LR3 and MGF?

Both are IGF & growth factors. IGF-1 LR3: An IGF-1 analog modified to evade binding proteins, giving it far longer activity than native IGF-1. MGF: A splice variant of IGF-1 expressed by muscle in response to mechanical loading and damage.

Which has stronger evidence, IGF-1 LR3 or MGF?

They sit at the same evidence level: animal models only. IGF-1 LR3 has about 0 human studies and MGF about 1.

Are IGF-1 LR3 and MGF FDA approved?

Neither is FDA approved for any indication.

References

Regulatory and primary sources

  1. WADA Prohibited List ↗ · current year
  2. FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
  3. CAS Registry Number 946870-92-4 ↗ · chemical identity

Published literature

  1. Lu Z, Liu N, Huang H, et al.. Recombinant expression of IGF-1 and LR3 IGF-1 fused with xylanase in Pichia pastoris.Appl Microbiol Biotechnol 2023.PubMed 37261455 · doi:10.1007/s00253-023-12606-0
  2. von der Thüsen JH, Borensztajn KS, Moimas S, et al.. IGF-1 has plaque-stabilizing effects in atherosclerosis by altering vascular smooth muscle cell phenotype.Am J Pathol 2011.PubMed 21281823 · doi:10.1016/j.ajpath.2010.10.007
  3. McTavish H, Griffin RJ, Terai K, et al.. Novel insulin-like growth factor-methotrexate covalent conjugate inhibits tumor growth in vivo at lower dosage than methotrexate alone.Transl Res 2009.PubMed 19446281 · doi:10.1016/j.trsl.2009.02.005
  4. Engel MG, Narayan S, Cui MH, et al.. Intranasal long R3 insulin-like growth factor-1 treatment promotes amyloid plaque remodeling in cerebral cortex but fails to preserve cognitive function in male 5XFAD mice.J Alzheimers Dis 2025.PubMed 39610283 · doi:10.1177/13872877241299056
  5. Dominikowski A, Rękoś Z, Olejarz M, 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.PubMed 42395176 · doi:10.3389/fendo.2026.1822475
  6. Long E, Huynh HT, Zhao X. Involvement of insulin-like growth factor-1 and its binding proteins in proliferation and differentiation of murine bone marrow-derived macrophage precursors.Endocrine 1998.PubMed 9867252 · doi:10.1385/ENDO:9:2:185
  7. Goldspink G, Harridge SD. Growth factors and muscle ageing.Exp Gerontol 2004.PubMed 15501012 · doi:10.1016/j.exger.2004.08.010
  8. Goldspink G, Wessner B, Bachl N. Growth factors, muscle function and doping.Curr Opin Pharmacol 2008.PubMed 18353722 · doi:10.1016/j.coph.2008.02.002
  9. Harridge SD. Ageing and local growth factors in muscle.Scand J Med Sci Sports 2003.PubMed 12535315 · doi:10.1034/j.1600-0838.2003.20235.x
  10. Dai Z, Wu F, Yeung EW, et al.. IGF-IEc expression, regulation and biological function in different tissues.Growth Horm IGF Res 2010.PubMed 20494600 · doi:10.1016/j.ghir.2010.03.005
  11. Janssen JA. Impact of Physical Exercise on Endocrine Aging.Front Horm Res 2016.PubMed 27348867 · doi:10.1159/000445158
  12. Goldspink G. Gene expression in skeletal muscle.Biochem Soc Trans 2002.PubMed 12023866
  13. Goldspink G. Age-related loss of skeletal muscle function; impairment of gene expression.J Musculoskelet Neuronal Interact 2004.PubMed 15615114
  14. Heilig CW, Deb DK, Abdul A, et al.. GLUT1 regulation of the pro-sclerotic mediators of diabetic nephropathy.Am J Nephrol 2013.PubMed 23817135 · doi:10.1159/000351989

Literature retrieved from PubMed on October 16, 2026, favouring human studies and reviews. Numbered markers in the text show which paper supports which statement; uncited entries are background reading.

Read this first This page compares published reference data. It is not medical advice and not a recommendation to use either compound. Several compounds documented on this site are not approved for human use.