What is the difference between HGH Fragment 176-191 and AOD-9604?

AOD-9604 is essentially HGH Fragment 176-191 with an additional tyrosine amino acid at the N-terminus. Both have similar fat-metabolising properties and mechanisms of action.

Does HGH Fragment build muscle?

Unlike full growth hormone, HGH Fragment 176-191 is not expected to promote muscle growth as it lacks the complete sequence necessary for growth-promoting effects. It is researched specifically for fat metabolism.

Is HGH Fragment 176-191 safe?

Limited human safety data exists. Preclinical studies suggest it may be well-tolerated, but long-term human safety is not established. It is not approved for human use.

Fact-checked by the Peptide Authority Editorial Board · Last reviewed: 1 February 2026

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Fat Loss & Metabolic•Updated 2026-02-01•4 min read

What Is HGH Fragment 176-191? Benefits, Research & Safety

A fragment of human growth hormone corresponding to amino acids 176-191, researched specifically for its fat-metabolising properties.

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Also known as:

HGH Frag

Fragment 176-191

Lipolytic Fragment

DAnimal/cell evidence onlyUK: Unlicensed (UK)WADA: Prohibited in sport

UK summary: Not a licensed UK medicine. C-terminal fragment of growth hormone marketed for selective fat loss. Conceptually distinct from full HGH but still captured by WADA growth-factor rules. Human evidence is weak.

Quick Facts

Overview

HGH Fragment 176-191 is a synthetic peptide corresponding to the C-terminal portion of human growth hormone (hGH), specifically amino acids 176 through 191. This region of the growth hormone molecule has been identified as containing the lipolytic (fat-burning) activity of the full hormone. The development of this fragment was based on research demonstrating that the fat-metabolising effects of growth hormone could be separated from its growth-promoting effects. By isolating this specific fragment, researchers aimed to harness the fat-loss benefits without the concerns associated with full growth hormone administration, such as effects on blood glucose, IGF-1 elevation, and tissue growth. Research has shown that HGH Fragment 176-191 can stimulate lipolysis (breakdown of fat) and inhibit lipogenesis (formation of new fat) without significantly affecting blood glucose levels or promoting growth. This makes it of interest for body composition research. HGH Fragment 176-191 is closely related to AOD-9604, which is essentially the same fragment with an additional tyrosine residue at the N-terminus. Both peptides share similar mechanisms and research applications. This peptide remains a research compound and is not approved for human therapeutic use.

Evidence standards summary

HGH Fragment 176-191 — evidence and risk at a glance

Twenty standard modules scored against the Peptide Authority evidence grading methodology. Missing modules indicate the field has not yet been characterised editorially — treat absences as uncertainty rather than reassurance.

01Evidence snapshot

DAnimal/cell evidence onlyOverall grade against our evidence grading methodology.

Not a licensed UK medicine. C-terminal fragment of growth hormone marketed for selective fat loss. Conceptually distinct from full HGH but still captured by WADA growth-factor rules. Human evidence is weak.

02Human evidence grade

DAnimal/cell evidence onlyStrength of evidence from published human trials.

03Preclinical evidence grade

CLimited human evidenceAnimal-model and in-vitro evidence quality.

04Regulatory status

UK: Not licensed for human use. Research compound only.
EU: Not approved for human therapeutic use.
Notes: HGH Fragment 176-191 is not approved by any regulatory authority for human use. It is available only as a research chemical.

05Approved medical uses

None in the UK or EU as a finished medicine. (Or: not yet documented; treat as absence rather than approval.)

06Unapproved / promotional claims

Targeted fat-loss without affecting muscle, glucose, or growth.
Stack safely with semaglutide for accelerated body recomposition.
FDA / MHRA approved as a 'safe' alternative to HGH.
Suitable for daily long-term home injection.

07Common internet claims

Marketed as the lipolytic fragment of HGH for cosmetic fat loss.
Sold by online retailers as 'HGH frag' alongside AOD-9604.
Promoted in bodybuilding cut-cycle stacks.

08Claim vs evidence

Claim	Evidence	Human evidence?	Regulatory concern	Safer wording
“Burns fat without HGH side effects”	D	Limited	High	Animal-model lipolytic effect is documented; meaningful human body-composition outcomes are not established.
“Permitted in sport (it's only a fragment)”	E	No	High	Prohibited under WADA growth-factors category; strict liability applies.

09Safety uncertainty score

High

Limited human safety data; meaningful uncertainty about rare or long-term effects.

10Known adverse signals

Injection-site reactions.
Headache, fatigue, nausea reported anecdotally.
Theoretical risk from chronic GH-fragment exposure (fluid retention, organ growth).
Unknown effects in combination with licensed GLP-1 medicines.

11Drug-interaction uncertainty

High

Interaction picture sparse; meaningful uncertainty when combined with other medicines.

12Anti-doping status

WADA: Prohibited in sportWADA strict-liability framing applies.

13UK legal position

UK: Unlicensed (UK)

Not licensed for human use. Research compound only.

Read the full UK legal guide → Peptides and athletes (UK)

14EU legal position

Not approved for human therapeutic use.

15What this page cannot tell you

Whether a UK-purchased vial actually contains HGH Fragment 176-191 at the labelled concentration.
Whether the AOD-9604 variant (which has a tyrosine on the N-terminus) is in the vial instead.
What clinically meaningful fat-loss effect (if any) it has in normal-weight adults.
What the WADA in-competition exposure looks like — growth-factor peptides are class-prohibited.

16Last reviewed

Last reviewed: 1 February 2026

Next review due: 1 February 2027

Spotted an error or something out of date? Send a correction.

17Citation quality score

CLimited human evidenceQuality of the sources we cite, graded against the evidence grading methodology.

18Research gaps

No published Phase 3 trials in healthy adults for cosmetic fat loss.
Long-term safety beyond a few weeks is unstudied.
Combination safety with GLP-1 agonists not assessed.
Human pharmacokinetic data is sparse.

19Safer alternatives / established care pathways

Licensed Wegovy (semaglutide) via NHS or GMC-registered prescriber.
Licensed Mounjaro (tirzepatide) via NHS specialist or registered private clinic.
Structured diet, resistance training, and cardio — the evidence-based body-recomposition stack.

20Doctor discussion prompts

Questions to ask a qualified clinician

These are starter questions you can adapt for a GP, specialist, pharmacist, or anti-doping advisor. The aim is to help you have a better-informed conversation — not to replace one.

Is HGH Fragment 176-191 a licensed UK medicine?
What are the WADA / UKAD anti-doping implications?
What licensed alternatives exist for fat-loss support?

Discovery & History

The development of HGH Fragment 176-191 arose from research into the structure-function relationships of human growth hormone. Scientists at Monash University in Australia, led by Professor Frank Ng, investigated which regions of the hGH molecule were responsible for its various biological activities. Research in the 1990s identified the C-terminal region (amino acids 176-191) as being particularly important for growth hormone's lipolytic activity. Studies demonstrated that this fragment could reduce body fat in obese mice without promoting growth or affecting IGF-1 levels. This work led to the development of both HGH Fragment 176-191 and the related compound AOD-9604 (which has an additional N-terminal tyrosine). The goal was to create compounds that could provide the fat-loss benefits of growth hormone without its broader hormonal effects. While HGH Fragment 176-191 has been extensively studied in preclinical models, human clinical data remains limited. AOD-9604, the closely related compound, has progressed further in clinical development.

Mechanism of Action

HGH Fragment 176-191 works through mechanisms distinct from full growth hormone: **Lipolysis Stimulation** The fragment stimulates the breakdown of triglycerides stored in adipose tissue, releasing fatty acids into the bloodstream for use as energy. This lipolytic effect occurs through activation of hormone-sensitive lipase in fat cells. **Lipogenesis Inhibition** Research suggests the fragment inhibits the formation of new fat from dietary carbohydrates and other substrates, potentially reducing fat storage. **Selective Fat Action** Unlike full growth hormone, the fragment appears to act primarily on adipose tissue without significant effects on muscle, bone, or other tissues that would respond to complete hGH. **IGF-1 Independence** HGH Fragment 176-191 does not appear to stimulate IGF-1 production, distinguishing its effects from those of full growth hormone and potentially reducing associated risks. **Glucose Neutrality** Studies suggest the fragment does not significantly affect blood glucose or insulin sensitivity, unlike full growth hormone which can impair glucose metabolism.

Researched Benefits

Based on preclinical and clinical research findings:

1
Stimulation of fat breakdown without affecting muscle tissue
2
Inhibition of new fat formation
3
No significant effect on blood glucose in studies
4
No stimulation of IGF-1 production
5
No growth-promoting effects observed
6
Potential for targeted fat reduction

Claim vs Evidence

How popular claims about HGH Fragment 176-191 stack up against the current research, graded using our public evidence grading methodology.

Claim	Evidence	Human evidence?	Regulatory concern	Safer wording
“Burns fat without HGH side effects”	D	Limited	High	Animal-model lipolytic effect is documented; meaningful human body-composition outcomes are not established.
“Permitted in sport (it's only a fragment)”	E	No	High	Prohibited under WADA growth-factors category; strict liability applies.

Theoretical Dosing & Protocols

⚠️ Educational Only: The following information is derived from research literature and is not a prescription or recommendation. No standardised human dosing exists. Always consult a qualified healthcare professional.

Theoretical Dosage	250-500 mcg per administration (based on research protocols)
Frequency	1-2 times daily, typically before cardio exercise
Duration	Variable in research settings; typically weeks to months
Notes	These are theoretical protocols derived from research literature. HGH Fragment 176-191 is not approved for human use. Any consideration of use should involve consultation with a qualified healthcare professional.

Administration Routes

Routes studied in research settings (educational only):

Subcutaneous injection

Half-Life	Stability
Short; approximately 30 minutes to a few hours	Lyophilised powder should be stored frozen; reconstituted solution refrigerated

Safety Profile & Known Risks

Commonly Reported Side Effects

Injection site reactions
Potential hypoglycaemia if used with insulin (theoretical)
Headache (reported anecdotally)

Rare Risks & Concerns

Long-term effects unknown in humans
Potential for contamination in non-pharmaceutical grade products
Effects on other metabolic parameters not fully characterised

Contraindications

Pregnancy and breastfeeding
Active malignancy
Diabetes (use with caution)
Children and adolescents

UK & EU Regulatory Context

🇬🇧 United Kingdom

Not licensed for human use. Research compound only.

🇪🇺 European Union

Not approved for human therapeutic use.

HGH Fragment 176-191 is not approved by any regulatory authority for human use. It is available only as a research chemical.

Clinical Studies Summary

Human Growth Hormone Fragment 176-191 Peptide Enhances the Toxicity of Doxorubicin-Loaded Chitosan Nanoparticles Against MCF-7 Breast Cancer Cells.

These dual-loaded Chitosan nanoparticles demonstrated greater anti-proliferative activity against a breast cancer cell line (MCF-7) than doxorubicin-loaded Chitosan. This dual-loading strategy may enhance the anticancer potency of doxorubicin and reduce the clinical side effects associated with non-target tissue exposure.

Drug Des Devel Ther. 2022View on PubMed

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Frequently Asked Questions

Questions to ask a qualified clinician about HGH Fragment 176-191