HGH Fragment 176-191
Modified GH-fragment peptide
A 16-amino-acid C-terminal fragment of human growth hormone studied in lipolysis-related research.
Also referenced as: HGH Frag, AOD-9401
Overview
HGH Fragment 176-191 is a synthetic peptide corresponding to the C-terminal region (residues 176-191) of human growth hormone. This portion of the GH molecule was identified as carrying the hormone's lipolytic activity.
At a glance
What HGH Fragment 176-191 does
HGH Fragment 176-191 is the C-terminal fragment of human growth hormone corresponding to amino acids 176 through 191, the region of the GH molecule that carries its lipolytic (fat-mobilizing) activity. It is the parent structure behind AOD-9604, which is essentially this fragment with a stabilizing tyrosine added. Its studied action is stimulating the breakdown of stored fat: in adipocytes it promotes lipolysis and increases fat oxidation while, in research, discouraging the formation of new fat. Mechanistically the effect is attributed to modulation of the beta-3 adrenergic receptor pathway in adipose tissue, the same lipolytic route implicated for AOD-9604. The key design rationale, shared with its derivative, is that this fragment reproduces GH's fat-metabolizing effect while, in studies, not raising IGF-1, not promoting tissue growth, and not producing the glucose-handling and insulin-resistance effects associated with full-length growth hormone.
The evidence is predominantly preclinical. In animal and in-vitro models the fragment reduced body fat and increased fat oxidation via the beta-3 adrenergic mechanism, without the growth-signaling side effects of intact GH. Human data specific to the unmodified 176-191 fragment are limited, and most of the more developed clinical work (including a discontinued obesity trial program) was carried out on the stabilized AOD-9604 version rather than the raw fragment. So the honest framing is: a mechanistically plausible, GH-derived lipolytic peptide with supportive animal evidence, a favorable theoretical safety rationale (no IGF-1 elevation), but without robust human efficacy data in its own right.
Effects reported in research
- Stimulates lipolysis (mobilization/breakdown of stored fat) in adipocytes — the core studied action.
- Increases fat oxidation and reduced body fat in animal/in-vitro models.
- Discourages lipogenesis (new fat formation) in preclinical research.
- Acts via the beta-3 adrenergic receptor pathway in adipose tissue (mechanistic basis).
- Does NOT elevate IGF-1 or promote tissue growth, unlike full-length growth hormone (design rationale, study-supported).
- Did not impair glucose handling or induce insulin resistance the way intact GH can, in studies.
- Is the parent fragment of AOD-9604; most developed human clinical data come from that stabilized derivative, not the raw fragment.
- Human efficacy evidence for the unmodified fragment is limited — the effects rest mainly on preclinical data.
Effects listed reflect findings reported in the research literature — many in animal or in-vitro models. Listing an effect is not a claim of efficacy or a therapeutic indication in humans.
Mechanism of action
The fragment reproduces the C-terminal, lipolytic-associated region of GH while lacking the domains responsible for GH's growth-promoting and insulin-antagonizing actions. In preclinical models this region has been reported to stimulate fat breakdown (lipolysis) and reduce lipogenesis. It is not intact growth hormone and is not reported to reproduce GH's systemic growth effects.
Mechanistic description reflects published research-literature understanding. Much peptide research is preclinical (in-vitro or animal-model); mechanism in humans may differ and is not established for many compounds.
What it's studied for
Research contexts in which HGH Fragment 176-191 appears in the literature. Listing a research area is not a claim of efficacy or a therapeutic indication.
Key characteristics
- A peptide fragment of GH's C-terminal region (residues 176-191)
- Contains two cysteines that can form a disulfide-bridged loop
- AOD-9604 is a stabilized analog of this fragment with an added N-terminal tyrosine
- Studied for lipolytic activity without GH's growth/IGF-1 effects
- Not an approved therapeutic; used as a research compound
Reported research dosing reference only
Educational reference, not dosing guidance. The figures below summarize amounts reported in published research and research-community protocols, provided for educational and research context only. They are not medical advice, not a recommendation, and not instructions for human use. HGH Fragment 176-191 is a research compound.
Reported research figures are extrapolations from the published lipolysis literature rather than an established human regimen. These are figures reported for research context only, not dosing guidance for humans.
- Commonly-referenced research range: ~200-500 mcg/day (referenced to ~70 kg)
- Often described as split into two doses (AM/PM) due to short half-life
Very short half-life (~15-20 min) motivates split dosing in protocols. No human trials have established an official regimen; reference figures only.
How it compares
This is the native GH C-terminal fragment; AOD-9604 is its modified, tyrosine-extended analog. Both isolate lipolytic activity away from full GH signaling.
Commonly studied alongside
Compounds frequently researched together with HGH Fragment 176-191 in the literature. Cross-referenced for research context — not a usage or combination recommendation.
Handling & Stability
Lyophilized peptides are stored cold, protected from light, and reconstituted only at the time of intended in-vitro work.
- Avoid repeated freeze-thaw cycles
- Verify supplier lot and Certificate of Analysis
- Follow institutional lab-safety protocols
Analytical & COA Concepts
Reputable research suppliers publish a third-party Certificate of Analysis per batch. Key analytical concepts referenced in COAs include:
Category Context
HGH Fragment 176-191 sits in the Metabolic & Mitochondrial area of the PeptiDex library.
- Entry type: Research compound reference
- Browse the full library →
- Glossary of terms →
Where researchers source HGH Fragment 176-191
For researchers studying HGH Fragment 176-191, third-party suppliers such as Practically Natty Peptides offer research-grade material with third-party Certificates of Analysis and US-based shipping.
PeptiDex does not maintain a direct supplier listing for this compound. The link above goes to a third-party research-supplier directory.
Frequently asked questions
What is HGH Fragment 176-191?
HGH Fragment 176-191 is a synthetic peptide corresponding to the C-terminal lipolytic region (residues 176-191) of human growth hormone (native sequence LRIVQCRSVEGSCGF). Research identified this segment as carrying the fat-mobilizing activity of GH, while the diabetogenic IGF-1-driving activity resides in a different region (roughly 1-43).
How does HGH Fragment 176-191 differ from AOD-9604?
AOD-9604 is a stabilized analog of HGH Fragment 176-191: it adds an N-terminal tyrosine to the native fragment to improve stability and lipolytic activity. HGH Fragment 176-191 is the unmodified sequence. Both are studied for lipolysis, but the raw fragment is less characterized and has a very short duration.
What does the short half-life imply for research design?
The fragment has a very short half-life (reported ~15-20 minutes), which is why research protocols often describe split dosing (e.g., morning and evening) to maintain exposure. Its rapid clearance is an important consideration when designing pharmacodynamic experiments around lipolysis.
Does HGH Fragment 176-191 affect IGF-1 or blood glucose?
In animal studies the fragment stimulated lipolysis and inhibited lipogenesis without the growth-promoting or diabetogenic effects of full growth hormone, and without notable IGF-1 elevation. These are preclinical findings; no human clinical trials have established an official dosing regimen for the unmodified fragment.
How is HGH Fragment 176-191 stored and reconstituted?
It is supplied as a lyophilized powder and reconstituted with bacteriostatic or sterile water for laboratory handling. Lyophilized peptide is stored refrigerated or frozen; reconstituted solution is kept refrigerated and used within a limited window. Research-grade material carries a COA with HPLC purity and mass identity.
Answers are educational summaries of research-literature context and do not constitute medical advice. See the Research Library, COA guide, and Storage & Handling guide for more.