HGH Fragment 176-191
Metabolic & GLP-1Research Use OnlyLast reviewed: September 28, 2026
Quick Facts
- What it is
- A synthetic peptide matching amino acids 176–191 of human growth hormone — the C-terminal region associated with fat metabolism. The related analogue AOD-9604 adds a stabilising tyrosine, and it is AOD-9604 that went through clinical development.
- How it's taken
- Not established — the published routes are experimental animal routes, injected in the 1978 rat study and oral in the AOD9604 animal work
- Half-life
- Not characterized in humans for the bare fragment — no published pharmacokinetic study was located
- Typical research dose
- No validated dose — no controlled human trial has been published to establish one
- Research status
- Not FDA- or EMA-approved. The Phase 2 obesity programme ran under the AOD-9604 name, published no efficacy results, and has no ClinicalTrials.gov registration.
On this page
- 1.Where to source HGH Fragment 176-191
- 2.What is HGH Fragment 176-191?
- 3.How is HGH Fragment 176-191 proposed to work?
- 4.What does the research on HGH Fragment 176-191 show?
- 5.How is HGH Fragment 176-191 dosed, and what is known about safety?
- 6.What are the limitations of HGH Fragment 176-191 research?
- 7.HGH Fragment 176-191 FAQ
- 8.References
- 9.Published Studies
Where to source HGH Fragment 176-191
HGH Fragment 176-191 has no approved medical use and is sold by specialty research peptide vendors as material for laboratory use only. Both 2026 reviews cited on this page raise uncertainty about product composition in unregulated supply chains, and this compound has a specific version of that problem: vendors sell the bare fragment and AOD-9604 under names that published sources use interchangeably. A Certificate of Analysis is the only check a buyer has on which one is in the vial.
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What is HGH Fragment 176-191?
HGH Fragment 176-191 is a synthetic peptide matching amino acids 176 to 191 of human growth hormone — the C-terminal end of the hormone, and the region associated with its effect on fat rather than with its growth-promoting effects. The idea behind it is a good one: isolate growth hormone's lipolytic action and leave behind the IGF-1 stimulation and the wider endocrine effects that come with the whole hormone.
Most of what is said about this compound is evidence about a different one. The fat-loss studies, the mechanism work and the clinical development all belong to AOD-9604, the same region with a stabilising tyrosine added. The literature on the bare 176-191 sequence that vendors sell under this name comes to two papers: a 1978 study in rats, and a 2022 cell-culture study about delivering a cancer drug. The 1978 one is the only in-vivo look at this exact sequence, and what it found was raised blood glucose and reduced insulin sensitivity — not fat loss. New to peptide research? Start with the basics
Reported in the cited studies: a short-lived rise in blood glucose, a more sustained rise in plasma insulin, and significantly reduced insulin sensitivity for the fragments containing 178-191, in normal rats [1]; reduced body weight and body fat in obese mice and a mechanism not routed through the β3-adrenergic receptor, for AOD9604 [2]; increased lipolytic activity in animals after oral AOD9604 [3]; and, in two independent 2026 clinical reviews, placement among unapproved peptides sold direct to consumers with scarce human safety data [4][5].
Other metabolic compounds in the library include AOD-9604, MOTS-c and 5-Amino-1MQ.
How is HGH Fragment 176-191 proposed to work?
The rationale is straightforward and genuinely interesting: separate growth hormone's effect on fat from the rest of what growth hormone does. Whether the bare fragment achieves that is a separate question from whether the rationale is sound.
- The lipolytic-domain idea [2][3]. The C-terminal end of human growth hormone was identified as the region carrying its effect on fat metabolism. A synthetic peptide covering that region was expected to reproduce the fat-loss effect without stimulating IGF-1 or producing growth hormone's broader endocrine effects.
- Not through the β3-adrenergic receptor [2]. Chronic treatment reduced body weight and body fat in obese mice, and the effect persisted in β3-adrenergic-receptor knock-out mice — so the authors concluded the action of both hGH and AOD9604 is not mediated directly through that receptor in fat cells (Heffernan et al. 2001).
- Increased lipolytic activity in animals [3]. An oral dose of AOD9604 at 500 µg/kg for 19 days was reported to raise lipolytic activity (Ng et al. 2000).
- What the 1978 study found for this exact sequence [1]. hGH 176-191 given to normal rats produced a short-lived rise in blood glucose and a more sustained rise in plasma insulin, and fragments containing the 178-191 sequence significantly reduced insulin sensitivity (Ng and Bornstein 1978). That is a metabolic effect of the fragment, and it runs in the opposite direction from the one it is marketed for.
What does the research on HGH Fragment 176-191 show?
The decisive thing to understand about this compound is a naming problem with real consequences. Almost all the favourable research is on AOD-9604, a modified version. The literature on the bare 176-191 sequence that vendors sell is three papers, one of them from 1978 and one of them about cancer-drug delivery.
- On the exact sequence, in vivo: one study, from 1978 [1]. Normal rats, six C-terminal fragments compared, and the finding for 176-191 is hyperglycaemic — raised blood glucose, raised plasma insulin, reduced insulin sensitivity for the fragments containing 178-191 (Ng and Bornstein 1978).
- On the exact sequence, in vitro: one study, and not about metabolism [6]. The fragment used as a tumour-targeting ligand on doxorubicin-loaded nanoparticles against MCF-7 breast cancer cells (Habibullah et al. 2022).
- On AOD-9604, in animals: the fat-loss record [2][3]. Reduced body weight and body fat in obese mice, increased lipolytic activity, and a mechanism not routed through the β3-adrenergic receptor. Real results, about a different molecule.
- On AOD-9604, in humans: no published efficacy trial. The anti-obesity programme reached Phase 2 and Prof. Peptide could find no peer-reviewed publication of its efficacy results — that compound's own profile covers its human record, including where the record stops.
- Registry check: zero. A ClinicalTrials.gov search returns no studies for AOD-9604, AOD9604, or the growth hormone fragment 176-191. The same query run against semaglutide returns 788 and against tesamorelin 24, so the zero is a finding about this compound and not a broken search.
- Independent clinical reviews, 2026 [4][5]. Two reviews published this year place this compound among unapproved peptides sold direct to consumers, note that rigorous human safety data for the group are scarce, and list dysglycaemia among the class's reported adverse effects.
How is HGH Fragment 176-191 dosed, and what is known about safety?
No approved or validated dose exists, and the safety picture is reported in the same section because the two are inseparable here: the study that best characterises what this sequence does in a living animal is also the one that found an unwanted metabolic effect.
The published regimens are animal regimens: a single 5 nmol/kg dose in the 1978 rat study [1], and an oral 500 µg/kg daily dose for 19 days in the AOD9604 animal work [3]. Neither converts to a human schedule, and no controlled human trial of either compound has been published that would establish one, so Prof. Peptide publishes no dose, frequency or route. On safety, three things are on the record and belong together. First, hGH 176-191 raised blood glucose and plasma insulin in normal rats, and fragments containing 178-191 significantly reduced insulin sensitivity on tolerance testing [1] — a compound sold for metabolic improvement, with a published in-vivo finding pointing the other way. Second, two independent 2026 reviews report that rigorous human safety data for this class of unapproved peptides are scarce, and list dysglycaemia, endocrine and metabolic disturbance, fluid retention, musculoskeletal symptoms and injection-site reactions among the adverse effects reported across it [4][5]. Third, those same reviews raise uncertainty about product composition and dose in unregulated supply chains, which is a safety question about the vial as much as about the molecule. Research vendors sell this as lyophilised material labelled for laboratory use only; a Certificate of Analysis is the only identity and purity check available to a buyer.
What are the limitations of HGH Fragment 176-191 research?
The favourable evidence and the product on sale are not about the same molecule. Fat loss in obese mice, increased lipolysis, the β3-receptor-independent mechanism — all of that is AOD-9604 research. The compound sold as HGH Fragment 176-191 has, in the literature located here, one in-vivo study from 1978 and one cell-culture study about cancer-drug delivery.
That 1978 study is not supportive. It is titled for a hyperglycaemic action, and what it reports for this sequence is raised blood glucose, raised plasma insulin, and reduced insulin sensitivity for the fragments containing 178-191. A single rat study from 1978 is thin evidence in either direction — but it is the direct evidence that exists, and reporting the mouse fat-loss data while omitting it would misrepresent the record.
The human record is an absence, not a negative and not a positive. The anti-obesity programme reached Phase 2 and no peer-reviewed publication of its efficacy results could be found; the registry search returns zero studies against working controls. A development programme that stops without a published trial is weak evidence on its own terms, and it is not the same thing as a trial that succeeded and went unreported.
Naming is a genuine hazard with this compound. Published sources use “AOD9604” and “hGH 176-191” interchangeably while vendors sell them as two products, so a claim read in one place attaches easily to a vial bought in another. Prof. Peptide keeps a separate AOD-9604 profile for that reason, and each page reports its own compound's evidence.
HGH Fragment 176-191 FAQ
What is HGH Fragment 176-191?
HGH Fragment 176-191 is a synthetic peptide corresponding to amino acids 176 to 191 of human growth hormone — the C-terminal end of the hormone, and the region associated with its effect on fat metabolism rather than with its growth-promoting effects. It is sold by research peptide vendors under that name. The closely related compound AOD-9604 is the same region with a stabilising tyrosine added, and it is AOD-9604, not the bare fragment, that went through clinical development.
What happened to the obesity trials?
The honest answer is that the results were never published. AOD-9604 was developed as an anti-obesity drug by Metabolic Pharmaceuticals and taken into Phase 2, and Prof. Peptide could find no peer-reviewed publication of that programme's efficacy results — the outcome reached the public through company and industry disclosure rather than through a journal. There is also no registration for AOD-9604, AOD9604 or the fragment on ClinicalTrials.gov: a search of the registry returns zero studies, against 788 for semaglutide and 24 for tesamorelin on the same query. A drug programme that ends without a published trial and without a registry entry is not a positive result that was merely under-reported.
Is HGH Fragment 176-191 the same as AOD-9604?
The names are used interchangeably in the literature and they are not quite the same thing. A 2026 review in Frontiers in Endocrinology writes "AOD9604 (hGH 176-191)" as if they were one compound; Prof. Peptide's own AOD-9604 profile describes AOD-9604 as the 176-191 region with a stabilising tyrosine added. Both descriptions appear in published sources. What matters for a reader is that vendors sell two different products under two names, the clinical work was done under the AOD-9604 name, and the only in-vivo study of the bare 176-191 sequence located here is from 1978.
Is HGH Fragment 176-191 FDA-approved?
No. Neither the fragment nor AOD-9604 is approved by the FDA or the EMA for any indication. It is sold as research-use-only material. Two independent 2026 reviews place it in the category of unapproved peptides marketed direct to consumers, one of them describing a "gray market" of compounds operating largely outside regulatory oversight.
Is there a standard HGH Fragment 176-191 dose?
There is no approved or validated dose. The 1978 rat study used a single 5 nmol/kg dose in an experimental protocol, and the AOD-9604 animal work used its own oral regimens; neither is a human schedule. Prof. Peptide publishes no dosing figure for this compound, because no controlled human trial of it has been published to establish one.
References
- Ng FM, Bornstein J. Hyperglycemic action of synthetic C-terminal fragments of human growth hormone. Am J Physiol. 1978;234(5):E521-E526. doi:10.1152/ajpendo.1978.234.5.E521. PMID 645904. https://pubmed.ncbi.nlm.nih.gov/645904/
- Heffernan M, Summers RJ, Thorburn A, et al. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice. Endocrinology. 2001;142(12):5182-5189. doi:10.1210/endo.142.12.8522. PMID 11713213. https://pubmed.ncbi.nlm.nih.gov/11713213/
- Ng FM, Sun J, Sharma L, et al. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Horm Res. 2000;53(6):274-278. doi:10.1159/000053183. PMID 11146367. https://pubmed.ncbi.nlm.nih.gov/11146367/
- Dominikowski A, Rękoś Z, Olejarz M, et al. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026;17:1822475. doi:10.3389/fendo.2026.1822475. PMID 42395176. https://pubmed.ncbi.nlm.nih.gov/42395176/
- Mendias CL, Awan TM. Safety and efficacy of approved and unapproved peptide therapies for musculoskeletal injuries and athletic performance. Sports Med. 2026;56(8):1921-1935. doi:10.1007/s40279-026-02437-0. PMID 41966639. https://pubmed.ncbi.nlm.nih.gov/41966639/
- Habibullah MM, Mohan S, Syed NK, et al. Human growth hormone fragment 176-191 peptide enhances the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells. Drug Des Devel Ther. 2022;16:1963-1974. doi:10.2147/DDDT.S367586. PMID 35783198. https://pubmed.ncbi.nlm.nih.gov/35783198/
Published Studies
Plain-English summaries of the peer-reviewed studies behind the statements above. Click any title to read the source paper. Two of the six test the 176-191 sequence itself; the rest test the AOD-9604 analogue or review the class.
Ng FM, Bornstein J.
The only in-vivo study located that tests the 176-191 sequence itself by name, rather than a modified analogue of it. Six synthetic C-terminal fragments of human growth hormone — 172-191, 176-191, 177-191, 178-191, 179-191 and 180-191 — were given to normal rats. Four of them, including 176-191, produced a short-lived rise in blood glucose and a more sustained rise in plasma insulin; the two shortest were inert. A single 5 nmol/kg dose of the peptides containing the 178-191 sequence significantly reduced the animals' insulin sensitivity on intravenous insulin tolerance testing. Note what this paper is titled and what it measured: the effect it establishes for this sequence is on glucose and insulin, and it is not a favourable one.
Heffernan M, Summers RJ, Thorburn A, et al.
Chronic treatment of obese mice with human growth hormone or with AOD9604 reduced body weight and body fat. The experiment's real contribution is mechanistic: by repeating the work in β3-adrenergic-receptor knock-out mice and still seeing the effect, the authors concluded the actions of both hGH and AOD9604 are not mediated directly through the β3-AR found in fat cells. This is the mouse work the compound's fat-loss reputation is built on — and it is work on AOD9604, not on the bare fragment.
Ng FM, Sun J, Sharma L, et al.
An earlier animal study of the synthetic lipolytic domain, reporting increased lipolytic activity after an oral dose of AOD9604 at 500 µg/kg body weight for 19 days. Same caveat as above: the compound tested is the AOD9604 analogue. Prof. Peptide's separate AOD-9604 profile covers that compound's own record, including its human study, in full.
Dominikowski A, Rękoś Z, Olejarz M, et al.
An independent narrative review from Poznan University of Medical Sciences, written for clinicians seeing patients who self-administer these compounds. It names the GH fragment — written there as "AOD9604 (hGH 176-191)" — among the peptides most commonly encountered in online self-administration protocols, and stratifies the whole class into evidence tiers running from regulatory-grade randomized trial data down to a complete absence of human studies. Reported adverse effects across the class include endocrine and metabolic disturbances, dysglycaemia, fluid retention, musculoskeletal symptoms and injection-site reactions, alongside uncertainty about product composition and dose in unregulated supply chains.
Mendias CL, Awan TM.
A second independent 2026 review, covering AOD-9604 among a list of approved and unapproved peptides marketed direct to patients. Its summary judgement on the unapproved group is worth quoting in substance: many demonstrate favourable tissue-repair and metabolic outcomes in animal models, but rigorous human safety data are scarce and there is potential for serious harm. It also discusses the placebo effect as a mediator of reported peptide efficacy, and the role of social media in amplifying it.
Habibullah MM, Mohan S, Syed NK, et al.
Included because it is one of the very few papers that names the bare 176-191 peptide in its own title. It is a drug-delivery study, not a metabolic one: the fragment is used as a tumour-targeting ligand on doxorubicin-loaded chitosan nanoparticles, tested against MCF-7 breast cancer cells in culture. It tells a reader nothing about fat loss, and is listed here so the small literature on this exact sequence is represented completely rather than selectively.
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