Also known as: hGH 176-191, HGH Frag, Lipolytic Fragment
Half-life: ~30 minutes
Last reviewed: · Published:
HGH Fragment 176-191 is the synthetic peptide corresponding to amino acids 176-191 of the human growth hormone molecule — the C-terminal region responsible for its fat-metabolizing activity. Like its close cousin AOD-9604 (which is HGH Fragment 177-191 with an added N-terminal tyrosine), this peptide isolates the lipolytic effects of GH from its growth-promoting, insulin-disrupting, and IGF-1-elevating effects. It stimulates lipolysis (breakdown of stored triglycerides) and inhibits lipogenesis (new fat formation), apparently through a calcium-dependent pathway that is distinct from the GH receptor.
The distinction from AOD-9604 matters: AOD-9604 was specifically engineered with an added tyrosine residue to facilitate radio-iodination during the original Monash University research program, and is the version with clinical-trial and FDA GRAS data behind it. HGH Fragment 176-191 is the un-modified parent sequence, sold by research-chemical vendors and used widely in the wellness community. The two peptides are pharmacologically very similar but not identical; most published clinical and animal data refer specifically to AOD-9604 rather than the bare 176-191 fragment.
Because the fragment does not bind the GH receptor, it does not raise IGF-1, does not affect blood glucose, and does not produce the appetite, water retention, or carpal-tunnel symptoms associated with exogenous HGH. This makes it a popular cut-phase peptide, frequently stacked with CJC-1295 / Ipamorelin combinations to combine localized fat metabolism with broader GH-axis support.
The lipolytic activity of growth hormone's C-terminal region was characterized through structure-function studies of HGH conducted from the late 1980s onward. Researchers showed that the 176-191 region retained the fat-metabolizing activity of the full molecule while losing its diabetogenic effects. This work directly led to the development of AOD-9604 at Monash University in the late 1990s by Frank Ng's group. The unmodified 176-191 fragment entered the research-chemical market alongside AOD-9604 and has remained popular as a more economical alternative.
HGH Fragment 176-191 is generally well-tolerated at typical research doses. Because it does not activate the GH receptor, the classic GH-related side effects (carpal tunnel, water retention, insulin resistance) are absent. Most reports describe at most mild injection-site reactions. Human safety data specific to the unmodified fragment is much thinner than for AOD-9604, but the close structural similarity supports a generally favorable profile. As with any fat-loss peptide, results are heaviest when paired with a calorie-controlled diet and resistance training.
Dose Range
250-500 mcg
Frequency
Once daily, morning, on an empty stomach (SubQ)
Duration
8-12 weeks
Dose Range
250 mcg
Frequency
Twice daily (morning + pre-cardio), fasted
Duration
8-12 weeks
Dosing information is for educational purposes only. Consult a healthcare professional before using any peptide.
Typical Vial Size
5 mg
Water Type
Bacteriostatic water (BAC water)
Mixing Volume
2 mL
Half-Life
~30 minutes
Molecular Weight
1817.1 Da
Store reconstituted vial refrigerated at 2-8°C. Use within 28 days. Best administered on an empty stomach 30-60 minutes before fasted cardio for maximum lipolytic effect.
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FDA Status
Not FDA approved. Distinct from AOD-9604, which holds GRAS status as a food additive.
Legal Status
Unregulated research chemical. Prohibited by WADA.
USA
Not approvedResearch-only; sold as a research chemical
EU
Not approvedNot authorized as medicinal product
UK
Not approvedClassified as research chemical
Australia
Not approvedTGA has not evaluated
Canada
Not approvedNot authorized for human use
Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R
Endocrinology (2000)
Foundational work characterizing the C-terminal hGH fragment (176-191 / 177-191) and its retained lipolytic activity in the absence of growth-promoting effects, providing the rationale for both this peptide and AOD-9604.
View Study →Heffernan M, Summers RJ, Thorburn A, Ogru E, Gianello R, Jiang WJ, Ng FM
Obesity Research (2001)
Demonstrated that the engineered version of this fragment (AOD-9604) stimulates fat metabolism via a GH-receptor-independent mechanism without altering glucose or insulin homeostasis — most likely also applicable to the bare 176-191 fragment.
View Study →Wu Z, Bidlingmaier M, Friess SC, Kirk SE, Buchfelder M, Schopohl J, Strasburger CJ
Journal of Endocrinological Investigation (2003)
Investigation of the C-terminal hGH sequence's lipolytic effects, supporting the broader hypothesis that the 176-191 region is responsible for GH's fat-mobilizing activity independent of the receptor-mediated growth pathway.
View Study →Fat-metabolizing fragment of human growth hormone without growth-promoting effects.
Long-acting growth hormone releasing hormone analog for sustained GH and IGF-1 elevation.
Selective growth hormone secretagogue with minimal side effects.
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