What Is AOD-9604? The HGH Fragment 176-191 Explained for Researchers

AOD-9604 HGH fragment 176-191 lipolysis adipose research peptide Durham Peptides Canada

AOD-9604 is one of the more interesting molecules in metabolic peptide research because of the question that produced it: can you isolate the fat-metabolism effects of growth hormone without the rest of growth hormone's biology? Full-length human growth hormone (hGH) affects lipolysis, but it also drives IGF-1 production, influences glucose metabolism, and has broad somatotropic (growth-promoting) effects. AOD-9604 was designed as an answer — a small fragment of the growth-hormone molecule that retains the lipolytic region while leaving the rest behind.

This article explains what AOD-9604 is, how it was developed, its proposed mechanism, and what researchers examine. For Canadian researchers, Durham Peptides carries AOD-9604 5mg as a research peptide (currently subject to stock availability — see the product page's "Notify When Available" function). Nothing here is medical, dosing, or therapeutic guidance.

The Origin: Isolating Growth Hormone's "Fat" Region

AOD-9604 — short for "Anti-Obesity Drug 9604" — was developed by Metabolic Pharmaceuticals Ltd. in Australia during the 1990s. The research premise was that the lipolytic (fat-mobilizing) activity of growth hormone is localized to a specific region of the molecule: the C-terminal domain, specifically residues 176-191. By synthesizing just that fragment — with a small modification — researchers aimed to capture the lipolytic effect while excluding the IGF-1-driven and somatotropic effects associated with the full hormone.

AOD-9604 went on to complete six human clinical trials involving over 900 participants — an unusually extensive clinical history for a research peptide. The research story is therefore well-characterized, though, as discussed below, the clinical efficacy results were mixed.

The Molecular Structure

Durham Peptides' AOD-9604 is a synthetic hexadecapeptide (16 amino acids):

• Sequence: Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe (disulfide bridge: Cys7-Cys14)

• Molecular formula: C₇₈H₁₂₃N₂₃O₂₃S₂

• Molecular weight: 1,815.12 g/mol

• CAS number: 221231-10-3

• PubChem CID: 71300630

• Common synonyms: Tyr-hGH Fragment 176-191, HGH Frag 176-191, Lipotropin

Two structural features matter. First, the molecule corresponds to hGH residues 176-191 with a tyrosine added at the N-terminus (the "Tyr-" prefix). Second, it carries an intramolecular disulfide bridge between Cys7 and Cys14, which gives the fragment conformational stability.

The Proposed Mechanism: Lipolysis Without IGF-1

The defining research feature of AOD-9604 is that its proposed mechanism operates

independently of the IGF-1 receptor and the hGH receptor. Full-length growth hormone exerts many of its effects through hGH-receptor signaling and downstream IGF-1; AOD-9604 is studied for stimulating lipolysis through a distinct route that does not engage that axis. Areas of mechanistic investigation include:

• β₃-adrenergic receptor upregulation in adipocyte (fat-cell) models

• Stimulation of lipolysis (breakdown of stored fat) and inhibition of lipogenesis (storage of new fat) in white and brown adipose tissue

• IGF-1 independence — selective metabolic effects without the somatotropic signaling of full hGH

This IGF-1-independent profile is what distinguishes AOD-9604 in the research literature and why it is studied as a tool for examining lipolysis in isolation from growth-hormone's broader effects.

A Note on the Clinical Record

Honesty about the research record matters. While AOD-9604's preclinical lipolysis data in animal models was encouraging, the later human clinical trials for obesity did not demonstrate the strong weight-reduction efficacy the early work suggested. This is part of why AOD-9604 remains a research compound rather than an approved therapeutic. For researchers, that mixed record is itself informative — it makes AOD-9604 a useful tool for studying the gap between preclinical lipolytic mechanisms and whole-organism metabolic outcomes. Researchers should treat it as a mechanistically interesting compound with an instructive (not triumphant) clinical history.

Beyond Fat Metabolism: Cartilage Research

A secondary area of AOD-9604 investigation is cartilage and joint biology. Some preclinical research has examined the fragment in models of cartilage regeneration, separate from its lipolytic studies. This is a smaller branch of the literature but reflects the broader interest in growth-hormone-fragment biology.

What Researchers Examine

• β₃-adrenergic receptor upregulation in adipocyte models

• Lipolysis and lipogenesis-inhibition in white and brown adipose tissue

• Comparative analysis versus full-length hGH on lipolytic activity

• IGF-1 independence and selective metabolic effects

• Cartilage regeneration and joint biology in preclinical models

How AOD-9604 Relates to Other Metabolic Research Peptides

AOD-9604 occupies a different mechanistic niche from the incretin peptides that dominate current metabolic research. Where semaglutide, tirzepatide, and retatrutide act on GLP-1/GIP/glucagon receptors to influence appetite, insulin, and energy expenditure, AOD-9604 acts on adipose-tissue lipolysis through a growth-hormone-fragment mechanism. They're studied for related research questions (fat metabolism) through entirely different pathways. For the direct comparison, see AOD-9604 vs Semaglutide vs Tirzepatide.

Quality and Storage

Durham Peptides' AOD-9604 is supplied as a 5mg lyophilized peptide, Janoshik-verified to ≥99% purity by HPLC with mass-spec identity confirmation and a verifiable COA key. Storage: 2–8°C short-term, -20°C long-term, protected from light and moisture; reconstitute in bacteriostatic water. See How to Read a Janoshik COA and the peptide calculator for reconstitution math.

Frequently Asked Questions

What is AOD-9604? A synthetic 16-amino-acid fragment of human growth hormone (residues 176-191, with an added N-terminal tyrosine), studied for selective lipolytic activity independent of the IGF-1 receptor.

What does AOD-9604 stand for? "Anti-Obesity Drug 9604," reflecting its original development by Metabolic Pharmaceuticals as a candidate for fat-metabolism research.

Is AOD-9604 the same as HGH fragment 176-191? Essentially yes — AOD-9604 is the Tyr-modified form of hGH fragment 176-191, with an added N-terminal tyrosine and a Cys7-Cys14 disulfide bridge.

How is AOD-9604 different from growth hormone? It's a small fragment that retains the lipolytic region of GH but is studied for acting independently of the IGF-1 and hGH-receptor pathways, so it doesn't carry GH's broader somatotropic effects.

Did AOD-9604 work in clinical trials? It completed six human trials with over 900 participants, but later obesity trials did not show the strong efficacy early work suggested — which is why it remains a research compound.

Where can I buy AOD-9604 in Canada? Durham Peptides carries AOD-9604 5mg for laboratory use only, subject to stock availability (use the product page's "Notify When Available" function).

Final Thoughts

AOD-9604 is a compound built on a clean idea — isolate growth hormone's lipolytic region and study fat metabolism without the rest of GH biology. Its preclinical mechanism is well-characterized and its IGF-1 independence makes it a distinctive research tool, even as its clinical efficacy record remains mixed. For Canadian researchers, Durham Peptides supplies AOD-9604 5mg, Janoshik-verified.

For how it compares to the incretin peptides, see AOD-9604 vs Semaglutide vs Tirzepatide. Browse the metabolic research category at durhampeptides.ca/category/metabolic-research-peptides.

Selected Research References

1. Heffernan MA, Thorburn AW, Fam B, et al. Increase of Fat Oxidation and Weight Loss in Obese Mice Caused by Chronic Treatment with Human Growth Hormone or a Modified C-Terminal Fragment (AOD-9604). International Journal of Obesity. 2001. https://pubmed.ncbi.nlm.nih.gov/11713213/

2. Ng FM, Sun J, Sharma L, et al. Metabolic Studies of a Synthetic Lipolytic Domain (AOD9604) of Human Growth Hormone. Hormone Research. 2000. https://pubmed.ncbi.nlm.nih.gov/11146367/

3. Stier H, Vos E, Kenley D. Safety and Tolerability of the Hexadecapeptide AOD9604 in Humans. Journal of Endocrinology and Metabolism. 2013. https://pubmed.ncbi.nlm.nih.gov/23510750/

All products sold by Durham Peptides are for research and laboratory use only. They are not intended for human or animal consumption, diagnosis, treatment, cure, or prevention of any disease.