What Is HGH Fragment 176-191? A Research Overview

HGH Fragment 176-191 is a synthetic peptide corresponding to amino acids 176–191 at the C-terminus of human growth hormone (GH). It is studied in lipid-metabolism research as the region of the GH molecule associated with fat metabolism, and in preclinical models it has been reported to influence lipolysis without the growth-promoting or IGF-1 effects of the full-length GH molecule. This article is educational only. HGH Fragment 176-191 is a research chemical for research use only (RUO) — not a drug, supplement, or food, not approved by the FDA, and not for human consumption.

Quick facts

• Class: GH C-terminal peptide fragment (amino acids 176–191)
• Parent molecule: human growth hormone (somatotropin)
• Research focus: lipolysis and lipid-metabolism research in vitro and in animal models
• Closely related compound: AOD-9604 (a Tyr-modified analog of the same C-terminal region)

What is HGH Fragment 176-191?

Human growth hormone is a 191-amino-acid protein with several distinct functional regions. Early peptide-chemistry research set out to map which part of the molecule was responsible for its effect on fat metabolism. HGH Fragment 176-191 represents the C-terminal tail of that sequence — the final 16 residues — isolated and synthesized as a standalone peptide. The research interest comes from the idea that the lipid-metabolizing region of GH could be separated from the regions associated with growth and IGF-1 signaling, and studied on its own in model systems. This is a laboratory research question, not a statement about effects in humans.

What does the research show?

Most of the published, peer-reviewed work on this C-terminal region has used AOD-9604, a closely related synthetic analog built from essentially the same lipolytic domain of human GH (Tyr-hGH 177-191). These studies are preclinical — in vitro and in animal models — and should not be read as applying to people. In a study in Hormone Research, daily oral administration of the synthetic lipolytic domain (AOD-9604) to obese Zucker rats was associated with reduced body-weight gain and increased lipolytic activity in adipose tissue, and — unlike intact GH — was reported to have no adverse effect on insulin sensitivity in that model (Ng et al., 2000). A chronic-treatment study in Endocrinology reported that both GH and the lipolytic fragment increased fat metabolism in obese mice, and used beta-3 adrenergic receptor knock-out mice to probe the pathway involved (Heffernan et al., 2001). All of these results describe animal and laboratory systems only.

Mechanisms studied in the lab

• Lipolytic / β3-adrenergic pathway: preclinical work has examined the fragment’s association with the β3-adrenergic lipolytic pathway in adipocytes; one study reported that long-term effects on body weight and lipolysis were not seen in β3-AR knock-out mice.
• Adipose-tissue focus: research models measure lipolytic activity in fat tissue (e.g. glycerol and fatty-acid release in cultured adipocytes) as a readout.
• No IGF-1 effect in models: a stated rationale for studying the isolated fragment is that, in the model systems used, it acts on lipid metabolism without the IGF-1–associated growth signaling of full-length GH.

Research status

HGH Fragment 176-191 is not an approved drug and has no approved human use. It is handled strictly as a research chemical for in-vitro and laboratory investigation. Nothing in the published literature establishes safety or effect in humans, and this peptide is not intended to diagnose, treat, cure, or prevent any condition.

Related research peptides

Browse our full research peptide catalog, and read our educational overviews of AOD-9604 (the closely related GH-fragment lipolysis peptide that most of the published studies above actually used) and Tesamorelin (a GHRH analog studied in a different part of the GH axis).

FAQ

What is the difference between HGH Fragment 176-191 and AOD-9604? Both are built from the same C-terminal lipolytic region of human growth hormone. AOD-9604 is a modified analog (it adds an N-terminal tyrosine to the 177-191 sequence) and is the form used in most published lipolysis studies. HGH Fragment 176-191 refers to the unmodified 176–191 fragment. They are studied for the same general research question but are not identical molecules.

Is HGH Fragment 176-191 approved or safe for people? No. It is a research-use-only chemical with no FDA approval and no established human safety profile.

Why is it studied separately from full-length GH? Because researchers wanted to isolate the lipid-metabolism region of GH from the regions associated with growth and IGF-1 signaling, and study that region on its own in laboratory and animal models.

References

1. Ng FM, et al. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Horm Res. 2000.
2. Heffernan M, et al. Effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism in obese and beta3-AR knock-out mice. Endocrinology. 2001.

For research use only. Not a drug, supplement, cosmetic, or food; not for human or veterinary use. Statements have not been evaluated by the FDA.