Is Fragment 176-191 safe?

There is no human safety data. Animal studies have not reported significant adverse effects. As an unmodified GH fragment, it may be less stable than AOD-9604. The absence of human data means the safety profile is unknown.

Does it actually burn fat?

Animal studies show it stimulates lipolysis and inhibits lipogenesis without affecting blood glucose or IGF-1. However, no human trials have been conducted. The related compound AOD-9604 was tested in humans but the effect was modest.

How is it different from AOD-9604?

AOD-9604 is a modified version of Fragment 176-191 with an added tyrosine residue for improved molecular stability. AOD-9604 has been through Phase IIb human clinical trials. Fragment 176-191 has no human studies.

No. Fragment 176-191 is not FDA-approved for any indication. It remains an investigational research compound. It is not currently on the FDA Category 2 restricted compounding list.

Why does it have so few studies?

AOD-9604, the modified and more stable version, became the focus of clinical development at Monash University. Fragment 176-191 was the precursor concept but was not advanced through clinical trials itself. Most research attention shifted to AOD-9604.

What does the research show about: Animal studies show Fragment 176-191 stimulates lipolysis and inhibits lipogenes?

Animal studies show Fragment 176-191 stimulates lipolysis and inhibits lipogenesis without affecting IGF-1, insulin, or blood glucose levels. This metabolic selectivity was the original rationale for isolating this GH region. The concept is scientifically valid

What does the research show about: No human clinical trials exist for Fragment 176-191. The evidence base is entire?

No human clinical trials exist for Fragment 176-191. The evidence base is entirely preclinical. With only 17 published studies, this is among the smallest evidence bases in the PSI registry

What does the research show about: AOD-9604, a modified version of this fragment with an added tyrosine residue, is?

AOD-9604, a modified version of this fragment with an added tyrosine residue, is the compound that was actually taken through clinical development. AOD-9604 has Phase IIb human data. Fragment 176-191 was the precursor concept

What does the research show about: The fragment does not appear to affect blood glucose or promote growth, unlike f?

The fragment does not appear to affect blood glucose or promote growth, unlike full-length growth hormone. This metabolic safety profile in animals is the primary theoretical advantage over GH therapy

reviewed april 2026|next review october 2026|88 physicians psi has verified|17 published studies

HGH Fragment 176-191

Fragment 176-191 is the C-terminal fragment of human growth hormone (amino acids 176-191) studied for selective fat metabolism without the growth-promoting or blood-sugar-raising effects of the full hormone, and the precursor concept to the clinically developed AOD-9604.

Evidence landscape: 17 published studies

17 published items. 1 human study and 11 animal studies indexed. One of the smallest evidence bases on this platform. The clinically developed version is AOD-9604.

1 Human
11 Animal
5 Reviews

Isolates the fat-burning region of growth hormone (amino acids 176-191) to stimulate lipolysis without the growth-promoting or blood-sugar-raising effects of the full hormone.

AOD-9604, a modified version with an added tyrosine for stability, is the compound that actually advanced through human clinical trials (Phase IIb). Fragment 176-191 itself has never been tested in humans.

Only 17 published studies, all from animal models (preclinical). One of the smallest evidence bases on this platform.

PSI Assessment

The scientific concept behind Fragment 176-191 is valid: isolate the fat-burning region of growth hormone (amino acids 176-191) to stimulate lipolysis without the growth-promoting or blood-sugar-raising effects of the full hormone. AOD-9604, a modified version of this fragment with an added tyrosine for stability, was the compound that actually advanced through human clinical trials. Fragment 176-191 itself has never been tested in humans. With 17 published studies, all from animal models (preclinical), it has one of the smallest evidence bases on this platform.

The precursor concept to AOD-9604. Valid scientific rationale for selective lipolysis. Controlled human trials have not been conducted for this specific fragment.

The mechanism is selective lipolysis through the beta-3 adrenergic pathway. Fragment 176-191 corresponds to the C-terminal region of growth hormone responsible for fat metabolism. It stimulates fat breakdown without activating the JAK2/STAT5 growth signaling cascade or elevating IGF-1, meaning it does not produce the growth-promoting or diabetogenic effects of full GH. AOD-9604 adds an N-terminal tyrosine to this fragment for improved molecular stability and was the version that entered clinical development.

What the evidence supports

Fragment 176-191 selectively stimulates lipolysis in animal models without affecting IGF-1, insulin, or blood glucose. The beta-3 adrenergic pathway mechanism is documented. The GH fragment concept - isolating fat metabolism from growth-promoting effects - is validated by AOD-9604's Phase IIb human data.

What is not yet established

Whether Fragment 176-191 produces meaningful fat loss in humans. Controlled clinical trials have not been conducted for this specific fragment. Whether it is equivalent to AOD-9604 in efficacy and safety. Whether either fragment can compete with GLP-1 agonists for clinical fat loss.

Research Evidence

The findings below cover the selective lipolysis data from animal models, the AOD-9604 relationship, and the evidence base limitations.

Evidence by condition

Evidence dimensions across Fragment 176-191's investigated conditions. All evidence is from animal models (preclinical). Controlled clinical data for this specific fragment has not been published.

Condition	Mechanism	Animal evidence	Human evidence	Replication
Fat Loss
Metabolic Safety
Cartilage Research

Animal studies (preclinical) show Fragment 176-191 selectively stimulates lipolysis and inhibits lipogenesis without affecting IGF-1, insulin, or blood glucose levels. The metabolic selectivity was the original rationale for isolating this GH region.

The concept is scientifically valid. Whether the lipolytic effect is clinically meaningful in humans is completely unknown because controlled human studies have not been conducted for this specific fragment.

AOD-9604, a modified version of Fragment 176-191 with an added tyrosine residue for improved molecular stability, was developed at Monash University and advanced through Phase IIb human clinical trials. The modification was made because the unmodified fragment had stability concerns.

AOD-9604 has the human data that Fragment 176-191 lacks. The Phase IIb results showed modest fat loss effects. Fragment 176-191 was the precursor concept but was not advanced into clinical development.

With only 17 published studies and no human clinical trials, Fragment 176-191 has one of the smallest evidence bases on this platform. The research is entirely from animal models (preclinical).

Marketing claims about Fragment 176-191 far exceed what the evidence supports. The clinically developed version is AOD-9604, and even AOD-9604's Phase IIb results showed modest effects.

1 Human|11 Animal|5 Reviews

View all 17 indexed studies

How HGH Fragment 176-191 Works

Fragment 176-191 is the C-terminal portion of human growth hormone (amino acids 176-191) that interacts with adipose tissue to stimulate fat breakdown through the beta-3 adrenergic pathway.

Fragment 176-191 is the part of growth hormone that talks to fat cells. It tells them to release stored fat and stop storing new fat. The key benefit is that it does this without triggering the other effects of growth hormone, like raising blood sugar or making things grow.

For a more detailed view of the biology, here is what researchers have observed at the molecular level.

Fragment 176-191 corresponds to the C-terminal region of human growth hormone responsible for fat metabolism. It stimulates lipolysis through beta-3 adrenergic receptor-mediated pathways and inhibits acetyl-CoA carboxylase, reducing de novo lipogenesis. Unlike full-length GH, this fragment does not bind the classical GH receptor in a way that activates JAK2/STAT5 growth signaling, IGF-1 production, or insulin resistance pathways. AOD-9604 adds a tyrosine at the N-terminus for improved molecular stability.

What is HGH Fragment 176-191 being studied for?

Researchers are studying HGH Fragment 176-191 across several health conditions. Each condition below is labeled with the strength of evidence that exists for that specific use, not for HGH Fragment 176-191 overall. This means a compound can have human studies for one condition but only animal data for another.

Fat Loss

·Animal Studies

Animal studies (preclinical) show Fragment 176-191 stimulates lipolysis and inhibits lipogenesis. The effect is attributed to the C-terminal region of GH that interacts with fat tissue independently of the GH receptor.

Limitations: All data is from animal models. No human clinical trials have been conducted. The magnitude of fat loss in humans is completely unknown. AOD-9604 (the modified version) had modest Phase IIb results.

Metabolic Safety

·Animal Studies

Animal data suggests the fragment does not affect blood glucose or IGF-1 levels, unlike full-length GH. This is the primary theoretical advantage over GH therapy.

Limitations: Metabolic safety in humans has not been evaluated. Whether the fragment maintains this selectivity in human physiology is unknown.

Cartilage Research

·Preclinical

Very limited data from animal models (preclinical) suggests possible cartilage protective effects. The evidence is insufficient to draw conclusions.

Limitations: The evidence base is extremely thin. No mechanistic pathway has been clearly defined.

Safety and Regulatory Status

FDA Status: Not FDA-approved for any indication.

Availability: Not currently on the FDA Category 2 restricted list. Available through specialty pharmacies where a licensed pharmacist prepares a medicine from ingredients for an individual patient.

Human Safety Data: No human safety data exists. Animal studies have not reported significant adverse effects.

Fragment 176-191 has no human safety data. Animal studies have not reported significant toxicity. As an unmodified GH fragment, it may be less stable than AOD-9604 (which includes a tyrosine modification for improved stability).

Peptide Structure

Technical molecular data for researchers and clinicians.

Questions and Comparisons

Questions the evidence raises for a HGH Fragment 176-191 discussion.

Comparison and Related Research

Fragment 176-191 is most often compared with AOD-9604 (modified version with human trial data), semaglutide (FDA-approved, vastly superior efficacy), and tesamorelin (FDA-approved GHRH analog).

Head-to-head comparisons

Full research comparisons covering HGH Fragment 176-191 and another peptide side by side.

HGH Fragment 176-191 vs AOD-9604

Both are HGH fragments targeting fat metabolism. AOD-9604 is a modified version. What the difference means, and why neither proved effective in trials.

View full comparison

Related compounds

AOD-9604 Semaglutide Tesamorelin

Frequently Asked Questions

References

Each citation links to the original study on PubMed, the U.S. National Library of Medicine database.

1.Chronic treatment study comparing the lipolytic fragment (AOD9604/fragment 176-191) to full-length growth hormone in obese mice. The fragment reduced body fat without the diabetogenic effects associated with full GH, demonstrating that fat-reducing activity can be separated from GH's metabolic side effects.Heffernan M et al., 2001 in Endocrinology. View on PubMed
2.Characterized the metabolic profile of the synthetic GH fragment AOD9604 in animal models. The fragment stimulated fat breakdown (lipolysis) and inhibited new fat formation (lipogenesis) without affecting blood sugar levels or IGF-1 production.Ng FM et al., 2000 in Horm Res. View on PubMed
3.Early characterization study identifying the specific C-terminal region of growth hormone responsible for fat metabolism effects. The synthetic fragment inhibited lipogenesis in animal fat tissue, establishing that this short peptide sequence retains the anti-fat-accumulation activity of the full hormone.Wu Z et al., 1993 in Biochem Mol Biol Int. View on PubMed
4.Tested oral delivery of the GH lipolytic fragment in obese mice, a notable finding since most peptides are destroyed during digestion. Oral administration reduced body fat gain and improved lipid profiles without affecting IGF-1 or insulin levels.Heffernan MA et al., 2000 in Am J Physiol Endocrinol Metab. View on PubMed

Medical Disclaimer

This content is for educational and informational purposes only and does not constitute medical advice. The information presented reflects published research as indexed by PSI and should not be used to make treatment decisions. Always consult a qualified healthcare provider before starting, stopping, or modifying any treatment.