Quick answer
AOD-9604 is a synthetic peptide (about 1.8 kDa) made of human growth hormone residues 177-191 plus an N-terminal tyrosine, studied as a narrow probe of lipid-metabolism signaling in cell and animal models.
- Structure: Tyr-hGH(177-191), 16 residues with one intramolecular disulfide bond
- Mechanism: proposed lipid-handling signaling in adipocyte models, independent of the full GH receptor response; primary target not firmly established
- Evidence: cell-culture and rodent studies only
- Handling: avoid reducing agents; concentration = mg ÷ mL; use the reconstitution calculator
- Research use: For laboratory research use only; not for human consumption.
What AOD-9604 is
For laboratory research use only; not for human consumption.
AOD-9604 is a synthetic peptide corresponding to the C-terminal region of human growth hormone (hGH), residues 177-191, with an added N-terminal tyrosine. Counting that extra residue, the molecule is 16 amino acids long, although some sources describe it as a "15-residue" fragment because the native segment it reproduces is 15 residues. Its mass is about 1.8 kDa. It is best understood as an isolation tool: a way to probe one narrow behavior attributed to growth hormone, lipid-metabolism signaling in model adipocyte systems, without engaging the receptor-activating machinery of the full 191-residue hormone.
| Property | AOD-9604 |
|---|---|
| Class | Modified C-terminal fragment of human growth hormone |
| Parent segment | hGH residues 177-191, plus an N-terminal tyrosine |
| Sequence | Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe |
| Approximate molecular weight | About 1.8 kDa |
| Key structural feature | Intramolecular disulfide bond between the two cysteines |
| Supplied form | Lyophilized powder |
| Evidence base | Cell-culture and animal-model studies; earlier investigational history |
It is distinct from growth-hormone secretagogues such as ipamorelin and sermorelin, which act upstream to trigger endogenous hormone release. AOD-9604 acts, if the proposed model is correct, downstream of that release step and does not depend on it. A plain-language orientation is in AOD-9604 peptide explained, and the catalog entry is the AOD-9604 research vial.
Discovery and history
AOD-9604 grew out of a broader scientific effort to dissect human growth hormone into functional pieces. Growth hormone is a 191-residue protein with multiple overlapping functions. Instead of studying the intact molecule, investigators asked whether discrete regions carried separable activities, a reductionist strategy that produced this modified fragment as a research tool.
Why the C-terminal region
Attention fell on the C-terminal portion because it was linked to lipid-metabolism readouts that appeared distinct from the hormone's classic growth-promoting signaling. That observation is the premise of the fragment's mechanism of action. Early structure-activity work explored whether a short segment could reproduce a narrow slice of hormone behavior without the full receptor-activating response.
From native fragment to defined analog
The unmodified hGH(177-191) fragment was the starting point. Adding an N-terminal tyrosine helped define the molecule as a discrete, reproducible research entity, and it also provides an aromatic, UV-absorbing handle that is convenient for analytical detection. The resulting compound is identified by a specific sequence rather than an ill-defined mixture. Those structural details are covered in AOD-9604 chemical structure and synthesis. The compound was developed in Australia and advanced through preclinical and early investigational work in the late 1990s and 2000s by groups interested in metabolic research, which is why it appears frequently in the literature.
What the history does not establish
A development record is not proof of a current research hypothesis. Progress through successive stages of investigation shows that the compound was sufficiently well defined to test, but historical attention does not validate every proposed pathway or endpoint. Older summaries often blend biochemical observations, animal-model findings and development goals; treating those evidence types separately gives a clearer account of what AOD-9604 has and has not shown. Modern work still needs suitable comparators, verified material and assays that can separate fragment-specific effects from nonspecific changes in cell state. The longer chronology is in AOD-9604 discovery and history.
Chemical structure and synthesis
The core of AOD-9604 reproduces the portion of growth hormone associated with the lipid-metabolism signaling discussed below. Because it represents only the C-terminal segment, it deliberately omits the residues responsible for the hormone's receptor-activating region. It is therefore a fragment, not a functional hormone mimic.
The added tyrosine
The N-terminal tyrosine is the defining engineering choice. Its aromatic side chain changes the molecule's physicochemical fingerprint, gives a UV-absorbing handle for detection, and creates an analytical signature distinct from unmodified hGH(177-191). How single-residue choices reshape a peptide's identity is outlined in understanding amino acid sequences.
The disulfide bond
The two cysteines in the sequence form an intramolecular disulfide bridge, creating a small loop. This is the critical structural feature for handling: reducing agents such as DTT or TCEP would break it, so diluents and buffers need care, and gentle handling avoids scrambling the disulfide pairing.
Solid-phase synthesis, purification and freeze-drying
At sixteen residues, AOD-9604 is well suited to standard Fmoc solid-phase peptide synthesis. The chain is assembled stepwise on a resin support, one protected amino acid at a time, then cleaved and deprotected, with the disulfide formed by controlled oxidation. Crude material contains truncated and deletion sequences, which are removed by preparative reversed-phase chromatography. The purified peptide is converted to a stable powder by freeze-drying, the process described in what is lyophilization. Short sequences like this are accessible to conventional synthesizers without the recombinant expression needed for larger proteins.
Sequence-dependent stability
As for any short linear or loop-containing peptide, stability depends on sequence, terminal chemistry, residual moisture and the surrounding matrix. Oxidation, deamidation, hydrolysis and disulfide exchange are the general degradation routes considered during method development, though their relative importance must be established experimentally for each preparation. Stability studies therefore compare chromatographic profiles over time instead of assuming that a lyophilized appearance guarantees intact material. Reference standards and repeat mass measurements help distinguish true degradation products from synthesis-related impurities, which matters when small sequence variants could be mistaken for the intended fragment. See also the dedicated chemistry article.
Mechanism of action
The proposed mechanism concerns how a growth-hormone C-terminal fragment might influence lipid-metabolism readouts in model systems while lacking the full hormone's receptor-activation profile. Several observations are reported, but the primary molecular target has not been established as firmly as the canonical growth-hormone receptor pathway.
| Question | Proposed answer in the literature | Confidence |
|---|---|---|
| Does it activate the GH receptor like intact GH? | No; it is not expected to engage the receptor the way the full hormone does | Consistent with the design rationale |
| What cellular readouts are studied? | Markers of lipolytic and lipogenic balance in cultured adipocyte preparations | Assay- and model-dependent |
| Does it release endogenous GH? | No; it is not a secretagogue and bypasses the release step | Consistent across descriptions |
| What is its primary molecular target? | Not firmly established | Open question |
Fragment-specific activity and adipocyte signaling
Because AOD-9604 represents only the C-terminal region, it is hypothesized to engage lipid-metabolism pathways in model adipocytes without reproducing the full GH signaling cascade or its receptor-mediated growth effects. This separation of activities is what makes the fragment attractive as an experimental probe. Observed changes are model-system observations tied to assay conditions, not statements about whole-organism metabolism.
Contrast with secretagogues
Ghrelin-receptor secretagogues such as ipamorelin and GHRH analogs such as sermorelin raise circulating growth hormone by acting upstream; see sermorelin mechanism of action for the contrast. AOD-9604 is studied instead as a downstream metabolic probe. The two categories therefore answer very different experimental questions even though both relate to the GH axis.
Open mechanistic questions
Changes in lipid-handling markers can support a pathway hypothesis but do not by themselves identify direct binding partners. Informative studies would pair phenotypic endpoints with receptor screening, pathway inhibitors, gene-expression analysis and loss-of-function controls; concordance across these approaches is stronger evidence than any single assay. Until such evidence converges, AOD-9604 is most accurately described as a fragment with proposed metabolic signaling activity in models, not a ligand with a fully mapped target. In-vitro concentrations are set by assay design, and vehicle controls and characterized material are essential because the proposed effects are subtle and model-dependent. More is in AOD-9604 mechanism of action.
Preclinical research findings
Preclinical characterization means controlled cell and animal studies, not conclusions about people. The central design logic is to test whether a short fragment can retain a distinct research profile detached from the parent molecule's broader effects. The same minimal-sequence logic is shared by small regulatory peptides such as KPV.
| Model system | Typical endpoints | Interpretation notes |
|---|---|---|
| Cultured adipocyte preparations | Biochemical markers of lipid handling at defined concentrations | Cleanest system; conditions held constant, but lacks whole-organism regulation |
| Other cultured cell preparations | Signaling readouts; absence of full GH-receptor response | Useful for confirming that the fragment is not a receptor-activating hormone mimic |
| Rodent models | Metabolic endpoints and tolerability parameters within the experimental design | Controlled in-vivo observation; not directly transferable to other species |
| Analytical comparison studies | Identity, purity, stability profiles across lots | Establishes what was actually tested |
Cell-culture systems
Adipocyte and other cultured preparations are the primary substrate for characterizing the fragment. Investigators can hold conditions constant and observe lipid-metabolism-related readouts at defined concentrations, isolating the fragment's behavior from the many confounders present in whole organisms.
Animal-model observations
Rodent models have been used to examine the fragment under controlled in-vivo conditions. Studies typically look at metabolic endpoints and tolerability parameters within the experimental design, always as model observations rather than translational claims.
Endpoints and readouts
Typical endpoints include biochemical markers of lipid handling, changes in relevant signaling readouts and confirmation that the fragment does not reproduce the full growth-hormone receptor response. Reproducibility across these endpoints depends heavily on well-characterized material, which is why identity verification through a certificate of analysis is emphasized.
Building a stronger evidence chain
A rigorous program connects molecular identity, cell-level activity and whole-model observations without treating them as interchangeable. Analytical confirmation establishes what was tested; orthogonal cell assays ask whether a repeatable signal appears; model studies examine whether related endpoints remain detectable amid physiological feedback. Negative findings are informative because they define the fragment's boundaries and discourage selective reporting. Replication across laboratories, platforms and independently characterized lots would strengthen confidence further. This matters especially for AOD-9604 because its proposed activity is narrower and less canonically mapped than signaling by intact growth hormone. Further summary: AOD-9604 preclinical research.
All findings reflect controlled model systems. Cell cultures lack whole-organism regulation, and animal models do not translate directly to any other species.
Handling, reconstitution and storage
AOD-9604 is a modified growth-hormone fragment of about 1.8 kDa with an intramolecular disulfide bond. This section is laboratory handling information only; the full article is AOD-9604 reconstitution and storage, and the generic method is in the lyophilized-peptide reconstitution guide.
What makes it different to handle
The disulfide bridge is the critical feature. Reducing agents would break it, so check what else is in a diluent or buffer. Gentle handling prevents scrambling of the disulfide pairing. Disulfide-containing peptides can undergo exchange at higher pH, so the conservative approach is storage near neutral or slightly acidic conditions, cold and aliquoted.
Preparing a stock solution
- Let the vial reach room temperature before opening, and use sterile technique.
- Add bacteriostatic water slowly down the inside wall of the vial, not onto the cake.
- Dissolve by swirling. Do not vortex or shake.
- Label the vial with concentration and date.
Concentration is peptide mass divided by diluent volume. The reconstitution calculator performs the arithmetic.
| Vial mass | Diluent added | Resulting concentration |
|---|---|---|
| 5 mg | 1 mL | 5 mg/mL |
| 5 mg | 2 mL | 2.5 mg/mL |
| 10 mg | 2 mL | 5 mg/mL |
These are arithmetic examples for stock planning only. Always confirm the labeled mass of the vial in hand.
Storage
The lyophilized powder is the most stable form and should be kept cold, dry and away from light until needed. After reconstitution keep the solution refrigerated, minimize freeze-thaw cycling and prefer small single-use aliquots. General cold-chain principles are in storing research peptides.
Purity, COA and quality
Because closely related sequences share many properties, fragment identity is easy to get wrong. A lot record for AOD-9604 should show both purity and identity, and mass spectrometry matters in particular because it confirms that the extra tyrosine is present and distinguishes the compound from nearby native hGH fragments.
| Test | Question answered | What to check for AOD-9604 |
|---|---|---|
| Reversed-phase HPLC | What fraction is the main component? | One dominant peak with a stated purity and a real chromatogram |
| Mass spectrometry | Is the mass correct? | Observed mass consistent with about 1.8 kDa including the tyrosine |
| Lot traceability | Does the document match the vial? | Lot number identical on vial and certificate |
| Stability profile | Has the material changed? | No unexplained new peaks over time in repeat runs |
Certificates are published on the COA page. Learn to read them in how to read a COA and HPLC vs. mass spectrometry; compound-specific detail is in AOD-9604 purity testing. For sourcing considerations see where to buy AOD-9604 for research, or go to the AOD-9604 product page. Record lot number, storage conditions and reconstitution date with every dataset so an unexpected result can be traced back to the reagent.
Related compounds and comparisons
AOD-9604 is conceptually related to growth-hormone-axis tools but occupies a different niche. The comparisons below are about experimental role, not relative performance.
| Compound | Role | Contrast with AOD-9604 | Read more |
|---|---|---|---|
| Ipamorelin | Ghrelin-receptor secretagogue | Acts upstream to trigger GH release; AOD-9604 is a fragment probe | Ipamorelin overview |
| Sermorelin | GHRH analog | Acts on the pituitary release step | Sermorelin overview |
| KPV | Short tripeptide regulatory fragment | Shares the minimal-sequence design logic | KPV overview |
Researchers sometimes pair a secretagogue and a downstream fragment in separate arms to ask which readouts depend on hormone release and which do not. That design requires matched vehicle controls, because a fragment with no receptor-activating region and a releasing peptide have very different expected time courses. Keep the two evidence bodies separate when reporting. Frequently asked questions are collected in the AOD-9604 research FAQ.
Frequently asked questions
What part of growth hormone does AOD-9604 correspond to?
The C-terminal region, residues 177-191 of human growth hormone, with an added N-terminal tyrosine.
Does AOD-9604 trigger the same response as full-length growth hormone?
No. It lacks the receptor-activating region of the hormone and is not expected to activate the GH receptor the way intact GH does, which is why it is studied as a narrow metabolic probe.
How does it differ from secretagogues such as sermorelin or ipamorelin?
Secretagogues act upstream to trigger endogenous GH release. AOD-9604 is studied as a downstream probe that does not rely on a release event.
Why does the molecule have an added tyrosine?
The N-terminal tyrosine helps define the analog as a discrete entity, adds a UV-absorbing handle for detection and gives it an analytical signature distinct from the native fragment.
What model systems is it studied in?
Primarily cultured adipocyte preparations and rodent models, always as controlled-model observation.
Is the molecular target of AOD-9604 known?
Not firmly. Lipid-handling readouts have been reported, but the primary receptor or binding partner has not been established as firmly as the canonical GH receptor pathway.
Why does the disulfide bond matter for handling?
Reducing agents such as DTT or TCEP can break it, and higher pH can promote disulfide exchange, so diluents, buffers and storage conditions should be chosen accordingly.
How do I calculate the concentration of a reconstituted stock?
Divide the peptide mass in the vial by the diluent volume: 5 mg in 2 mL gives 2.5 mg/mL. The calculator performs the same arithmetic.
How should AOD-9604 be stored?
Lyophilized powder cold, dry and protected from light. After reconstitution, keep it refrigerated, limit freeze-thaw cycles and prefer small aliquots.
What documentation should accompany a research lot?
A lot-specific certificate of analysis showing HPLC purity with a chromatogram and a mass-spectrometry result confirming identity, matched to the lot number on the vial.
Research use only. For laboratory research use only; not for human consumption. Nothing in this guide is usage guidance; concentration arithmetic describes laboratory stock preparation only.
References
- Heffernan M, 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.