Comparison
HGH Fragment 176-191 vs IGF-1 LR3
Both are IGF & growth factors, so the meaningful differences are in kinetics, evidence and regulatory status.
On published evidence alone, HGH Fragment 176-191 is the better documented of the two (preliminary human). That is a statement about the state of the literature, not a recommendation.
| HGH Fragment 176-191 | IGF-1 LR3 | |
|---|---|---|
| Class | IGF & growth factors | IGF & growth factors |
| Evidence | Preliminary human | Animal models only |
| Human trials | ~3 | None published |
| Half-life | ~30 minutes | ~20-30 hours |
| Reported range | 250-500 mcg | 20-50 mcg |
| Frequency | 1-2x daily, fasted | Once daily |
| Routes | Subcutaneous | Subcutaneous, Intramuscular |
| FDA approved | No | No |
| Research use only | Yes | Yes |
| Banned in sport | Yes | Yes |
| Studied for | Fat loss research, Body composition | Muscle hypertrophy research, Cell-culture growth supplement, Recovery |
| Reported side effects | Injection-site reactions, Headache, Transient fatigue | Hypoglycaemia, Injection-site swelling, Headache, Jaw pain |
HGH Fragment 176-191
This 16-residue fragment corresponds to the C-terminus of human growth hormone and reproduces the lipolytic and anti-lipogenic activity of the full molecule. Because it lacks the regions responsible for receptor-mediated growth signalling, it does not raise IGF-1 or produce the glucose intolerance associated with exogenous hGH. Human data for the fragment itself is thin, and the best-studied derivative is AOD-9604, which failed to separate from placebo on weight loss in its phase IIb trial.
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.
HGH Fragment 176-191 vs IGF-1 LR3: common questions
What is the difference between HGH Fragment 176-191 and IGF-1 LR3?
Both are IGF & growth factors. HGH Fragment 176-191: The C-terminal fragment of human growth hormone that carries its fat-metabolising activity without the growth-promoting portion. IGF-1 LR3: An IGF-1 analog modified to evade binding proteins, giving it far longer activity than native IGF-1.
Which has stronger evidence, HGH Fragment 176-191 or IGF-1 LR3?
HGH Fragment 176-191 has the stronger evidence base (preliminary human, about 3 human studies) compared with IGF-1 LR3 (animal models only).
Are HGH Fragment 176-191 and IGF-1 LR3 FDA approved?
Neither is FDA approved for any indication.
References
Regulatory and primary sources
- PubChem compound record (CID 172966176) ↗ · structure, identifiers, synonyms
- WADA Prohibited List ↗ · current year
- FDA: Unapproved drugs and "research use only" products ↗ · regulatory status of non-approved products
- CAS Registry Number 66004-57-7 ↗ · chemical identity
- CAS Registry Number 946870-92-4 ↗ · chemical identity
Published literature
- Therapeutic Peptides in Orthopaedics: Applications, Challenges, and Future Directions.J Am Acad Orthop Surg Glob Res Rev 2026.PubMed 41490200 · doi:10.5435/JAAOSGlobal-D-25-00236
- AOD-9604 Metabolic.Curr Opin Investig Drugs 2004.PubMed 15134286
- Safety and Efficacy of Approved and Unapproved Peptide Therapies for Musculoskeletal Injuries and Athletic Performance.Sports Med 2026.PubMed 41966639 · doi:10.1007/s40279-026-02437-0
- Potential role of new therapies in modifying cardiovascular risk in overweight patients with metabolic risk factors.Obesity (Silver Spring) 2006.PubMed 16931496 · doi:10.1038/oby.2006.294
- Obesity drugs in clinical development.Curr Opin Investig Drugs 2006.PubMed 16625817
- Current updates in the medical management of obesity.Recent Pat Endocr Metab Immune Drug Discov 2012.PubMed 22435392 · doi:10.2174/187221412800604644
- Analytical approaches for the detection of emerging therapeutics and non-approved drugs in human doping controls.J Pharm Biomed Anal 2014.PubMed 24906629 · doi:10.1016/j.jpba.2014.05.020
- [Obesity: a review of currently used antiobesity drugs and new compounds in clinical development].Postepy Hig Med Dosw (Online) 2007.PubMed 17971763
- 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
- 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
- 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
- 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
- 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
- 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
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.