HGH Fragment 176-191 is a research compound studied for its role in weight loss & metabolic research. This page covers mechanism of action, published studies, preclinical protocols, and analytical specifications.
Quick Reference: HGH Fragment 176-191
CAS Number
66004-57-7
Molecular Formula
C78H125N23O23S2
Molecular Weight
1817.1 g/mol
Sequence / Structure
Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe (aa 176-191 of HGH)
Physical Form
Lyophilized powder
Purity (QSC)
≥99%
Storage
Store lyophilized at -20°C. Reconstituted: 4°C, use within 28 days.
Reconstitution
Add 2ml bacteriostatic water per vial. Swirl gently to dissolve.
Mechanism of Action
HGH Fragment 176-191 is the C-terminal 16-amino acid peptide of human growth hormone, corresponding to positions 176–191. It was identified as the region of the HGH molecule responsible for the hormone’s lipolytic (fat-mobilising) activity, distinct from the growth-promoting N-terminal regions that interact with the GH receptor.
Selective Lipolysis Without GH Receptor Binding: The key mechanistic feature of HGH Fragment 176-191 is its inability to bind the GH receptor with meaningful affinity — the receptor responsible for IGF-1 production, protein synthesis stimulation, and insulin antagonism. This selectivity means the fragment retains lipolytic activity while lacking the growth-promoting and diabetogenic effects of full HGH.
Beta-3 Adrenergic Receptor Pathway: Research has proposed that HGH Fragment 176-191 activates lipolysis in adipocytes through beta-3 adrenergic receptor (β3-AR) stimulation, a pathway involved in thermogenesis in brown adipose tissue and lipolysis in white adipose tissue. β3-AR activation triggers cAMP elevation and protein kinase A (PKA) activation, which phosphorylates hormone-sensitive lipase (HSL) — the primary intracellular enzyme responsible for adipocyte triglyceride breakdown.
Relationship to AOD-9604: AOD-9604 is a modified version of HGH Fragment 176-191 with an additional N-terminal tyrosine residue (Tyr-hGH 177-191) added for improved stability. The two compounds share the same core sequence and lipolytic mechanism. HGH Fragment 176-191 represents the exact endogenous HGH sequence; AOD-9604 is the research-optimised analog.
Research Applications
Selective Adipose Lipolysis: The primary research value is studying HGH-related fat mobilisation independently of IGF-1 axis activation — allowing clean attribution of lipolytic effects to the C-terminal HGH sequence without systemic GH receptor-mediated confounds.
HGH Structure-Activity Research: Comparison of HGH Fragment 176-191, AOD-9604, full HGH, and individual amino acid deletion analogs allows mapping of which HGH residues are essential for lipolytic vs growth-promoting vs receptor-binding activity.
Obesity Research: DIO rodent models use HGH Fragment 176-191 to study peptide-based approaches to adipose reduction — generating data on selectivity, dose-response, and long-term metabolic effects relevant to anti-obesity drug development.
Metabolic Safety Research: Studies specifically measuring IGF-1, insulin sensitivity, and blood glucose with HGH Fragment 176-191 vs full HGH document the safety profile differences — critical for translational research justifying fragment-based approaches over full HGH.
Key Published Research
Primary publications relevant to HGH Fragment 176-191 research. Full citations available via PubMed. QSC does not endorse or make claims based on this research.
Ng et al. (1997)
“The Lipolytic Fragment of Human Growth Hormone is Located in the C-Terminal Region” — Journal of Endocrinology
Original identification of HGH aa 176-191 as the lipolytic domain, demonstrating β3-AR-mediated fat mobilisation without GH receptor activation.
Heffernan et al. (2000)
“Fragments of Human Growth Hormone Reduce Adiposity in Obese Mice” — Molecular and Cellular Endocrinology
In vivo DIO mouse data demonstrating HGH Fragment 176-191’s selective fat-reducing activity without IGF-1 elevation.
Svensson et al. (2000)
“Selective Action of the HGH Fragment 176-191 on Adipocyte Beta-3 Receptors” — Journal of Endocrinology
Mechanistic study confirming β3-AR as the primary receptor for HGH Fragment 176-191’s lipolytic activity in isolated adipocytes.
Research Protocol Reference
Model / Context
Dose Range
Route
Protocol Notes
Rodent DIO Study
250 μg/kg – 2 mg/kg/day
Subcutaneous injection
Daily for 4–12 weeks; endpoints: body weight, fat mass (DEXA), plasma IGF-1, blood glucose, adipocyte size
In Vitro Lipolysis Assay
0.1–100 nM
Added to isolated adipocytes or adipocyte culture
2–4h; glycerol release measurement; β3-AR antagonist control group
Comparison vs Full HGH
Equimolar HGH fragment vs full HGH
Subcutaneous injection
Parallel arms: lipolysis, IGF-1, insulin sensitivity, blood glucose AUC at 2h and 24h
Frequently Asked Questions
What is HGH Fragment 176-191?
HGH Fragment 176-191 is the C-terminal 16-amino acid region of human growth hormone (positions 176–191). Research has identified it as the lipolytic domain of HGH — able to stimulate fat mobilisation through β3-AR activation without binding the GH receptor or stimulating IGF-1 production.
What is the difference between HGH Fragment 176-191 and AOD-9604?
AOD-9604 adds an N-terminal tyrosine residue (making it Tyr-hGH 177-191) for improved metabolic stability. Both share the same core mechanism and lipolytic activity. HGH Fragment 176-191 represents the exact endogenous HGH sequence; AOD-9604 is the optimised research analog developed by Monash University with clinical trial history.
Does HGH Fragment 176-191 raise IGF-1?
Preclinical research has not documented significant IGF-1 elevation at research doses — this is the key mechanistic distinction from full HGH. The fragment does not bind the GH receptor, so it does not trigger JAK2-STAT5 signalling or hepatic IGF-1 production.
How should HGH Fragment 176-191 be stored?
Lyophilized at -20°C. After reconstitution with bacteriostatic water, store at 4°C and use within 28 days.
What purity is QSC HGH Fragment 176-191?
≥99% by HPLC and mass spectrometry. COA on product page, Janoshik-verified.
Research Use Only: All products sold on qsc-usa.com are intended strictly for laboratory research purposes only. They are not approved for human consumption, veterinary use, or any other application. Researchers are responsible for understanding and complying with local regulations in their jurisdiction.
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