If you have been reading about obesity research and want a single page that covers the useful parts, this is it: definitions, context, how it is studied, and the questions that come up repeatedly.
Last reviewed on 2026-01-27. Where a claim depends on a specific study, the study is described rather than over-claimed.
Identity and purity are commonly checked with reversed-phase high-performance liquid chromatography and mass spectrometry. RP-HPLC separates the peptide from related impurities and can estimate purity by peak area. Mass spectrometry confirms molecular mass and helps detect sequence variants or truncations. Some laboratories use amino acid analysis or peptide mapping for additional characterization. No single method proves biological activity; these techniques establish chemical identity and purity only. They also require suitable reference standards for confident comparison.
Commercial AOD-9604 may vary in purity, counterion content, and residual moisture. Certificates of analysis often report HPLC purity, mass confirmation, and appearance, but testing methods differ between suppliers. Independent verification is sometimes used because labeled content may not match actual peptide amount. Stability under different pH and temperature conditions is not fully standardized across studies. Researchers generally treat lyophilized material as the reference form for weighing and reconstitution. Moisture content can affect accurate mass measurement.
AOD-9604 is typically supplied as a lyophilized white to off-white powder. In this form, it is relatively stable when kept cool, dry, and protected from light. Common storage recommendations place it at −20 °C or below for long-term retention. Reconstituted solutions are less stable and are often kept at 2–8 °C for short periods. Freeze-thaw cycles should be minimized because they can promote aggregation or loss of peptide content. Vials are usually sealed under inert gas to reduce oxidation.
AOD-9604 is a synthetic peptide modeled on the C-terminal region of human growth hormone. It corresponds to residues 176-191 of the 191-amino-acid hGH sequence. The fragment is not the full hormone and lacks the receptor-binding region associated with growth and metabolic effects of hGH. Researchers developed it to isolate a specific portion of hGH for study. Its exact sequence and length are often stated in peptide catalogs and patents.
The peptide is frequently described as a growth hormone fragment, although it is chemically distinct from full-length hGH. AOD-9604 contains 16 amino acids and includes two cysteine residues that can form an intramolecular disulfide bond. In solution, this structural feature can influence folding, aggregation, and stability. Published descriptions sometimes call it hGH 176-191 or AOD9604, with spacing and capitalization varying. Such naming differences can complicate literature searches, database entries, and product verification.
Researchers have studied the fragment in cell and animal models to understand its metabolic actions. Some experiments report effects on fat breakdown and fat storage pathways, but the underlying mechanism remains incompletely defined. AOD-9604 does not appear to stimulate the same broad growth hormone receptor signaling as full-length hGH. Whether its observed activities arise from direct receptor interactions or downstream metabolic changes is an open question. Results from different assays are not always consistent.
| Property | Value | Notes |
|---|---|---|
| Appearance | White to off-white powder | Lyophilized form; may appear as cake |
| Solubility class | Water-soluble | Often reconstituted in aqueous buffer |
| Typical storage temperature | −20 °C or below | Protect from light and moisture |
| Typical analytical method | RP-HPLC and mass spectrometry | Used for purity and identity |
| Common synonyms | AOD-9604; AOD9604; hGH fragment 176-191 | Research name and fragment description |
AOD-9604 has been investigated primarily as a potential treatment for obesity and related metabolic conditions. Early laboratory work examined its effects on fat cells, and later studies moved into animal models and human clinical trials. Some trials reportedly reached Phase II, but the program did not lead to an approved medicine. Published summaries often note that weight-loss results were modest or inconsistent. The full trial data are not all publicly available in detail.
Regulatory treatment of AOD-9604 has varied. In sports anti-doping, the peptide became widely discussed during a 2013 investigation into an Australian professional sports club. Authorities at the time debated whether it fell under prohibitions on growth hormone and related substances. Later clarifications and updated lists have addressed the compound in different ways. Anyone seeking current status should consult the latest applicable rules, and commercial supply for human use is not authorized in major markets.
Research interest in AOD-9604 often focuses on whether it can influence lipid metabolism without the growth-promoting or glucose-related effects of full-length hGH. This question remains unresolved, and findings depend on model, dose, and measurement method. Some reviews treat the peptide as a historical obesity candidate rather than an active therapeutic. Others cite it in discussions of peptide fragments, metabolic signaling, and performance-enhancing substances. Clear conclusions are limited by the small number of rigorous, independent human studies.
The compound has been studied as a potential treatment for obesity and related metabolic conditions. Published trials have examined changes in body weight, fat mass, and safety markers over limited durations. Results have been mixed or modest, and no large-scale outcome trials are established. Regulatory agencies in several countries have not approved it as a therapeutic drug. Some commercial products have been marketed outside regulated pharmaceutical channels, which raises questions about quality and claims.
In the scientific literature, AOD-9604 appears in reviews of growth hormone fragments and in discussions of peptide-based metabolic research. Some sources distinguish it from growth hormone itself, while others group it with compounds marketed for weight management. The evidence base is small compared with approved obesity medications. Questions about long-term efficacy and clinical relevance remain open, and independent replication of key findings is limited. Most published reports are early-stage and exploratory.
Proposed mechanism focuses on lipolysis, the breakdown of stored triglycerides into free fatty acids and glycerol. AOD-9604 is thought to act on adipose tissue without stimulating appetite or affecting blood sugar in the same way as growth hormone. Laboratory studies report increased fat oxidation in some models. The precise receptor interactions and signaling pathways remain incompletely characterized. Researchers have proposed that the peptide may influence fat mobilization through pathways distinct from the full hormone.
Research has examined whether the peptide affects fat mass independently of growth hormone's other actions. Early animal studies suggested reductions in body fat, but species differences and small sample sizes limit interpretation. Human studies have generally been short and have not consistently shown large effects. Some trials measured body composition, lipid profiles, and safety parameters, but the overall picture is one of suggestive yet inconclusive metabolic activity. Findings vary across study populations and protocols.
A central uncertainty is whether observed metabolic changes translate into meaningful clinical benefits. Study designs vary in dose, duration, and participant characteristics, making comparisons difficult. Independent replication is limited, and the field lacks consensus on optimal endpoints or treatment duration. Ongoing or future studies may clarify mechanism and effect size, but current evidence does not establish a clear therapeutic role. Researchers often call for larger, longer, and better-controlled trials, while questions remain about which patient groups might respond.
Tendons are viscoelastic structures, which means they exhibit both elastic and viscous behaviour. When stretched, tendons exhibit typical "soft tissue" behavior. The force-extension, or stress-strain curve starts with a very low stiffness region, as the crimp structure straightens and the collagen fibres align suggesting negative Poisson's ratio in the fibres of the tendon. More recently, tests carried out in vivo (through MRI) and ex vivo (through mechanical testing of various cadaveric tendon tissue) have shown that healthy tendons are highly anisotropic and exhibit a negative Poisson's ratio (auxetic) in some planes when stretched up to 2% along their length, i.e. within their normal range of motion. After this 'toe' region, the structure becomes significantly stiffer, and has a linear stress-strain curve until it begins to fail. The mechanical properties of tendons vary widely, as they are matched to the functional requirements of the tendon. The energy storing tendons tend to be more elastic, or less stiff, so they can more easily store energy, whilst the stiffer positional tendons tend to be a little more viscoelastic, and less elastic, so they can provide finer control of movement. A typical energy storing tendon will fail at around 12–15% strain, and a stress in the region of 100–150 MPa, although some tendons are notably more extensible than this, for example the superficial digital flexor in the horse, which stretches in excess of 20% when galloping. Positional tendons can fail at strains as low as 6–8%, but can have moduli in the region of 700–1000 MPa.
=== Extraction === Extraction is performed with either water or acid solutions at appropriate temperatures. All industrial processes are based on neutral or acid pH values because although alkali treatments speed up conversion, they also promote degradation processes. Acidic extraction conditions are extensively used in the industry, but the degree of acid varies with different processes. This extraction step is a multistage process, and the extraction temperature usually is increased in later extraction steps, which ensures minimum thermal degradation of the extracted gelatin.
=== Safety concerns === Hydrolyzed collagen, like gelatin, is made from animal by-products from the meat industry or sometimes animal carcasses removed and cleared by knackers, including skin, bones, and connective tissue. In 1997, the U.S. Food and Drug Administration (FDA), with support from the TSE (transmissible spongiform encephalopathy) Advisory Committee, began monitoring the potential risk of transmitting animal diseases, especially bovine spongiform encephalopathy (BSE), commonly known as mad cow disease. An FDA study from that year stated: "... steps such as heat, alkaline treatment, and filtration could be effective in reducing the level of contaminating TSE agents; however, scientific evidence is insufficient at this time to demonstrate that these treatments would effectively remove the BSE infectious agent if present in the source material." On 18 March 2016, the FDA finalized three previously issued interim final rules designed to further reduce the potential risk of BSE in human food. The final rule clarified that "gelatin is not considered a prohibited cattle material if it is manufactured using the customary industry processes specified." The Scientific Steering Committee (SSC) of the European Union in 2003 stated that the risk associated with bovine bone gelatin is very low or zero.
Sources: en.wikipedia.org
Other 1,2- and 1,3-dithiols give related 1,3-dithiolanes (five-membered) and 1,3-dithianes (six-membered rings). Diols such as ethylene glycol undergo analogous reactions to give 1,3-dioxolanes. One distinguishing feature of the dithiolanes and dithianes derived from aldehydes is that the methyne group can be deprotonated and the resulting carbanion alkylated. 1,2-Ethanedithiol has been used as a scavenger in peptide cleavage synthesis. Like 1,3-propanedithiol, 1,2-ethanedithiol readily forms metal thiolate complexes. Illustrative is the synthesis of the derivative diiron ethanedithiolate hexacarbonyl upon reaction with triiron dodecacarbonyl: Fe3(CO)12 + C2H4(SH)2 → Fe2(S2C2H4)(CO)6 + H2 + Fe(CO)5 + CO Ethane-1,1-dithiol
If the corneal stroma develops visually significant opacity, irregularity, or edema, a cornea of a deceased donor can be transplanted. Because there are no blood vessels in the cornea, there are also few problems with rejection of the new cornea. When a cornea is needed for transplant, as from an eye bank, the best procedure is to remove the cornea from the eyeball, preventing the cornea from absorbing the aqueous humor. There is a global shortage of corneal donations, severely limiting the availability of corneal transplants across most of the world. A 2016 study found that 12.7 million visually impaired people were in need of a corneal transplant, with only 1 cornea available for every 70 needed. Many countries have years-long waitlists for corneal transplant surgery due to the shortage of donated corneas. Only a handful of countries consistently have a large enough supply of donated corneas to meet local demand without a waitlist, including the United States, Italy, and Sri Lanka.
== Clinical significance == Mutations in the COL3A1 gene cause vascular Ehlers-Danlos syndrome (vEDS; OMIM 130050), classified under this name in the 2017 International Classification of the Ehlers–Danlos Syndromes and formerly designated EDS type IV. It is the most severe form of EDS, since patients often die suddenly due to rupture of large arteries or other hollow organs. A few patients with arterial aneurysms without clear signs of EDS have also been found to have COL3A1 mutations. More recently, mutations in COL3A1 have also been identified in patients with severe brain anomalies suggesting that type III collagen is important for the normal development of the brain during embryogenesis. This phenotype resembles the cortical malformation caused by loss-of-function mutations in ADGRG1 (formerly GPR56; OMIM 604110), the gene encoding adhesion G protein-coupled receptor G1. Type III collagen is a known ligand for this receptor, linking the finding to a shared brain-development pathway. The first single base mutation in the COL3A1 gene was reported in 1989 in a patient with vEDS and changed a glycine amino acid to a serine Since then, more than 600 different variants have been reported in the COL3A1 gene. About 2/3 of these mutations change a glycine amino acid to another amino acid in the triple-helical region of the protein chain. A large number of RNA splicing mutations have also been identified.
Sources: en.wikipedia.org
Lyophilized powder is commonly stored at −20 °C or below, protected from light and moisture. Reconstituted solutions are typically kept refrigerated and used within a limited period.
Reversed-phase HPLC and mass spectrometry are standard checks. They confirm peptide purity and molecular mass, but they do not by themselves demonstrate biological activity.
Synthesis, purification, and handling conditions can differ, leading to variations in purity and salt content. Certificates of analysis help, but independent testing is often needed for verification.
No, it is a synthetic peptide fragment corresponding to a small portion of hGH. It is not the full 191-amino-acid hormone and does not reproduce all of hGH's effects.