All information below describes the compound's chemical identity, laboratory handling, and the published research literature. It describes molecular targets and results in laboratory and animal models only — not effects in humans — and is not evidence of any human benefit.
What Is HGH Fragment 176-191?
HGH Fragment 176-191 is a synthetic peptide corresponding to residues 176 through 191 of the C-terminal region of the human growth hormone (hGH) sequence. It does not occur freely in nature as an isolated molecule; it is a synthetic fragment reproducing a defined portion of the parent hormone. As a short C-terminal fragment, its structure is distinct from full-length growth hormone, and it has been used as a subject of preclinical laboratory investigation into lipid-metabolism and metabolic-signaling systems.
It is supplied as a reference compound for in vitro and animal research use only. The sections below summarize its chemical identity, laboratory handling, the molecular targets and model systems examined in the published literature, and the primary references — without describing outcomes, efficacy, or effects in humans.
Research Targets & Pathways
Published preclinical literature has examined HGH Fragment 176-191 in relation to several molecular systems. These are pathway associations reported in laboratory and animal models; refer to the cited studies for methods and findings.
- Lipid-metabolism / lipolytic pathways — examined in relation to triglyceride and fatty-acid metabolism in isolated-adipocyte assay systems.
- Adipocyte signaling — studied in relation to adipose-tissue regulatory mechanisms in rodent fat-cell models.
- Beta-3 adrenergic receptor (β3-AR) — examined in relation to β3-AR messenger-RNA expression in adipose tissue.
- Energy-homeostasis pathways — investigated in relation to resting energy expenditure and fat-oxidation measures.
- Glucose / insulin axis — examined in relation to glucose-tolerance and insulin-sensitivity indices as metabolic reference measures.
- Growth-hormone-receptor binding — characterized in relation to the receptor-binding profile of the C-terminal fragment, distinct from the signaling attributed to full-length growth hormone.
- Serum IGF-1 — assayed as a reference measure in metabolic-safety comparisons against intact growth hormone.
Model Systems Studied
HGH Fragment 176-191 has been used as a test compound across a range of published preclinical model systems, primarily in rodents and in vitro cell assays. Refer to the cited literature for study designs, endpoints, and findings.
- In vitro adipocyte assays — isolated rat and murine fat-cell preparations; glycerol-release lipolysis assays.
- Diet-induced obesity models — obese mouse and rat models, including body-composition assessment by DEXA scanning.
- Genetic knock-out model — beta(3)-adrenergic-receptor knock-out mice.
- Metabolic phenotyping — indirect calorimetry in obese murine models.
- Receptor & signaling assays — receptor-binding and cell-signaling systems.
- Musculoskeletal model — rabbit intra-articular osteoarthritis model (studied with the closely related modified fragment AOD9604).
- Human pharmacokinetic study — a Phase I oral-dosing pharmacokinetic study of the related analogue AOD9604.
Note: much of the fat-metabolism literature was generated using the closely related modified fragment AOD9604, and the majority of the mechanistic evidence derives from preclinical rodent models; no randomized controlled human trials have replicated the reported findings to date.
Molecular & Technical Profile
C78H123N23O23S2 | MW 1817.12 g/mol | CAS 66004-57-7 | Fragment: residues 176–191 of the human growth hormone C-terminal region
Storage, Reconstitution & Working Concentrations
Storage, reconstitution, and working-concentration values are general laboratory guidance for in vitro and animal research; always confirm against the lot-specific Certificate of Analysis. Note: much of the published fat-metabolism data was generated with the related analogue AOD9604, and independent human replication remains limited.
Current Research Status
As of the time of this writing, HGH Fragment 176-191 has not been approved by the U.S. Food and Drug Administration (FDA) or other regulatory bodies for any human therapeutic use. The available evidence base is primarily preclinical, derived from rodent and in vitro models, and a substantial portion was generated using the closely related modified fragment AOD9604. Translation to human clinical contexts has not been established through controlled clinical trials. The research-grade material supplied by Explicit Research is a reference compound for laboratory research use only and is not an approved drug product. Ongoing research continues to characterize the compound's mechanistic profile and identify which experimental findings may have translational relevance.
Research FAQ
Is HGH Fragment 176-191 approved for human use?
No. HGH Fragment 176-191 has not been approved by the FDA or other regulatory bodies for any human therapeutic use. The evidence base is preclinical (rodent and in vitro models), and the compound is supplied for laboratory research use only — not for human consumption.
What is HGH Fragment 176-191's molecular formula and structure?
A synthetic peptide corresponding to residues 176–191 of the C-terminal region of human growth hormone — molecular formula C78H123N23O23S2, MW 1817.12 g/mol, CAS 66004-57-7.
How is HGH Fragment 176-191 stored and reconstituted?
Store lyophilized at −20°C, protected from light and moisture. Reconstitute in sterile or bacteriostatic water (or 0.9% saline); store the reconstituted solution at 2–8°C for up to ~28 days, freeze aliquots at −80°C for long-term, and avoid repeated freeze–thaw.
What targets and model systems has HGH Fragment 176-191 been studied in?
Preclinical work has examined lipid-metabolism and lipolytic pathways, β3-adrenergic-receptor expression, and glucose/insulin measures across isolated adipocyte assays, diet-induced obese rodent models, and receptor-binding systems. Much of this literature used the related modified fragment AOD9604; note the preclinical-rodent caveat above.
Selected References
- Ng et al. — Hyperglycemic activity of synthetic C-terminal hGH fragments measured in rat bioassay. Am J Physiol, 1978.
- Ng et al. — Lipolytic activity of synthetic C-terminal fragments of hGH mapped by in vitro fat-cell assay. FEBS Lett, 1983.
- Heffernan et al. — Structural requirements of the C-terminal hGH region for receptor binding vs. lipolytic activity assessed in isolated adipocytes. J Endocrinol, 1989.
- Ng et al. — In vitro lipolytic activity of hGH C-terminal peptides quantified by glycerol release in isolated rat adipocytes. J Endocrinol, 1995.
- Ng et al. — Dose-response lipolytic activity of AOD9604 measured in isolated murine adipocytes and compared to full-length GH. Biochem Biophys Res Commun, 1997.
- Heffernan et al. — Lipolytic potency of AOD9604 compared to full-length GH measured by fat mass and adipocyte triglyceride assay in rodent models. Int J Obes Relat Metab Disord, 1999.
- Heffernan et al. — Beta-3 adrenergic receptor mRNA expression in adipose tissue quantified by RT-PCR, and resting energy expenditure by indirect calorimetry, in obese vs. lean murine models. J Endocrinol, 2000.
- Heffernan et al. — Total body weight and fat mass measured by DEXA scanning in diet-induced obese rodents without caloric restriction. Int J Obes, 2001.
- Heffernan et al. — Role of the beta(3)-adrenergic receptor in AOD9604-mediated lipid changes confirmed in knock-out mouse model by indirect calorimetry. Endocrinology, 2001.
- Stier et al. — Oral bioavailability, pharmacokinetic profile, and Phase I safety endpoints of AOD9604 measured in a human volunteer dosing study. Clin Pharmacokinet, 2006.
- Moon et al. — Cartilage and joint markers assessed after intra-articular injection of AOD9604 with or without hyaluronic acid in a rabbit osteoarthritis model. Ann Clin Lab Sci, 2015.
- Bhatt et al. — Helical peptide antagonist of the human growth hormone receptor characterized by binding and structural assays. Endocrinology, 2026.
- Massey et al. — Peptide applications in orthopaedics reviewed across cell-culture, animal, and clinical study designs. J Am Acad Orthop Surg Glob Res Rev, 2026.
- Davey et al. — Safety and regulatory status of approved and unapproved peptides for musculoskeletal use reviewed across clinical and preclinical literature. Sports Med, 2026.