Human growth hormone is a 191-amino-acid protein produced by the pituitary gland. AOD-9604 contains only a small section from its C-terminal end.

The most precise sequence-based description is Tyr-hGH177–191. Some commercial pages call it hGH Fragment 176–191, but that wording obscures an important molecular difference from the native 176–191 sequence.

Native human-growth-hormone residue 176 is phenylalanine, whereas AOD-9604 begins with tyrosine. The two peptides therefore differ at their first residue and should not be treated as chemically identical.

AOD-9604 was designed to investigate whether the lipid-metabolism effects attributed to the C-terminal region of growth hormone could be separated from growth promotion and other actions of the complete protein.

It is not a complete growth-hormone molecule, a growth-hormone secretagogue or an analogue designed to stimulate the pituitary gland.

A label using one of these names does not establish that the product contains the correct sequence, disulphide bridge, salt form or peptide quantity.

Research-market sellers sometimes use “AOD-9604”, “HGH Frag” and “fragment 176–191” interchangeably without explaining that native hGH176–191 begins with phenylalanine while AOD-9604 begins with tyrosine.

AOD-9604 appears in Peptides UK catalogues as a lyophilised research vial, acetate-associated peptide, oral product, transdermal preparation or component of a multi-peptide blend.

Product descriptions frequently associate it with targeted fat loss, appetite control, increased metabolism, reduced abdominal fat, muscle definition, exercise recovery, cartilage repair and anti-ageing.

The strongest weight-related findings come from obese rodents rather than successful human weight-loss trials.

The largest controlled human obesity study did not show statistically significant weight loss at the tested doses. Development for obesity was then discontinued.

FDA also found no clinical evidence supporting the subcutaneous and transdermal routes used in many contemporary commercial descriptions.

Intact human growth hormone binds to growth-hormone receptors and influences growth, protein metabolism, glucose handling, fat metabolism and insulin-like growth factor 1.

AOD-9604 contains fewer than one tenth of the amino acids in complete growth hormone.

Cell experiments found that AOD-9604 did not displace labelled growth hormone from recombinant growth-hormone receptors under the tested conditions.

It also did not produce the same proliferation response in cells engineered to express growth-hormone receptors.

These findings suggest that conventional growth-hormone-receptor signalling is unlikely to explain its reported lipid effects.

The absence of conventional receptor binding does not establish that AOD-9604 is biologically inactive or free from endocrine, metabolic or immune-related risks.

FDA found inconsistent information in compounding nominations about whether the nominated substance was AOD-9604 free base or AOD-9604 acetate.

Some documents used a free-peptide formula while describing the material as the acetate form.

Because the molecule contains a disulphide bridge, reducing conditions can open the ring and produce altered peptide species.

Incorrect oxidation can also create intermolecular or scrambled disulphide bonds rather than the intended intramolecular bridge.

Lipolysis

Lipolysis is the process through which stored triglycerides are broken down into glycerol and free fatty acids.

Rodent studies reported higher plasma glycerol and increased lipolytic activity in adipose tissue after AOD-9604 exposure.

Lipogenesis

Lipogenesis refers to the formation and storage of new lipids.

Early experiments reported lower lipogenic activity in isolated adipose tissue and selected animal models.

Fat Oxidation

Indirect calorimetry in obese mice suggested that AOD-9604 increased fat oxidation and energy expenditure under the experimental conditions.

Beta-3 Adrenergic Signalling

One study compared ordinary obese mice with mice lacking beta-3 adrenergic receptors.

The longer-term body-weight and adipose-tissue effects were absent or reduced in receptor-knockout animals, suggesting that intact beta-3 signalling may contribute.

The peptide has not been established as a direct beta-3 receptor agonist, and the precise initiating molecular target remains unknown.

Growth-Hormone Receptors

AOD-9604 did not reproduce full growth-hormone receptor binding or cell-proliferation effects in selected laboratory assays.

This suggests a mechanism distinct from the conventional signalling pathway of intact growth hormone.

FDA noted methodological limitations in the animal literature, including incomplete dose-response assessment and uncertainty created by multiple statistical comparisons.

The molecular target responsible for the reported effects has not been established conclusively.

Early Intravenous Studies

Initial studies exposed small groups of healthy men or clinically obese men to single intravenous administrations.

These experiments focused primarily on tolerability and short-term metabolic measurements rather than long-term weight management.

Early Oral Studies

Oral capsules were assessed at several exposure levels in single-dose and repeated-dose studies.

Digestive symptoms, headache and other adverse events were reported, although the overall short-term tolerability profile was often described as similar to placebo.

Twelve-Week Phase-Two Study

A controlled study involving approximately 300 participants compared several oral exposure groups with placebo over 12 weeks.

The programme identified an irregular, non-linear pattern that prompted testing of lower amounts in a subsequent study.

An apparent signal from one study or exposure group does not establish effectiveness where it is not reproduced prospectively.

Largest Twenty-Four-Week Study

The final controlled obesity trial enrolled more than 500 participants and randomised approximately 500 after a placebo run-in period.

Participants received AOD-9604 or placebo alongside a diet and exercise programme.

No treatment group achieved a statistically significant improvement in weight loss compared with placebo.

The clinical programme for obesity was discontinued after the study failed to meet its efficacy objective.

Human Trial Measurements

Historical trial summaries reported no statistically significant differences in serum IGF-1 between AOD-9604 and placebo groups.

Selected participants were tested for antibodies, and no anti-AOD-9604 antibodies were detected in those subsets during the studies described.

What These Results Mean

The findings suggest that short-term exposure did not reproduce the conventional IGF-1 response expected from pharmacological full-length growth hormone.

They do not establish that every formulation, route, impurity profile or longer exposure is free from endocrine or immune-related effects.

Growth-Hormone-Receptor Evidence

Laboratory experiments found no conventional receptor-binding or receptor-dependent proliferation response under the tested conditions.

FDA nevertheless stated that it had not identified sufficient nonclinical evidence to validate every promotional claim concerning absent IGF-1 activity.

A 2015 study used 32 rabbits with collagenase-induced knee osteoarthritis.

The animals received intra-articular saline, hyaluronic acid, AOD-9604 or a combination of AOD-9604 and hyaluronic acid.

Researchers reported differences in gross cartilage appearance and histological scores, with the combination group producing the lowest degeneration scores under the study conditions.

This was an animal experiment involving direct administration into rabbit knee joints.

It did not establish pain relief, cartilage regeneration, disease modification or long-term safety in people with osteoarthritis.

FDA’s 2024 review did not identify clinical studies using AOD-9604 in people with osteoarthritis or osteoporosis.

Preclinical Pain Research

LAT8881 was assessed in rodent models of neuropathic pain after its obesity programme ended.

Experimental work proposed LANCL1 as a possible molecular target involved in neuronal stress pathways and pain signalling.

This proposed pain mechanism differs from the earlier beta-3 adrenergic explanation for lipid-metabolism findings.

Oral Neuropathic-Pain Trial

A randomised, double-blind crossover trial assessed oral LAT8881 in people with diabetic neuropathy or postherpetic neuralgia.

The primary pain-score comparison did not show superiority over placebo. The reported treatment difference was small and statistically non-significant.

Acute Migraine Study

A small crossover study investigated oral LAT8881 during acute migraine.

The protocol summary stated that the peptide was tolerated but did not significantly reduce migraine pain compared with placebo.

Exploratory Intravenous Radicular-Pain Study

A later small proof-of-concept study assessed intravenous LAT8881 in lumbar radicular pain.

Sponsor-reported results stated that the resting-pain primary endpoint was not improved.

An exploratory provoked-pain measure during straight-leg raising produced a possible short-term signal requiring larger independent confirmation.

• Positive weight findings come mainly from obese rodents.
• Animal metabolism differs from human obesity biology.
• The complete molecular target remains unresolved.
• Beta-3 adrenergic involvement does not prove direct receptor binding.
• The animal studies did not provide a complete dose-response programme.
• Some statistical analyses did not adjust adequately for multiple comparisons.
• Early human studies were primarily exploratory.
• The largest obesity trial did not show statistically significant weight loss.
• The obesity-development programme was discontinued.
• No established evidence supports targeted abdominal-fat loss.
• No human study established selective fat loss while preserving muscle.
• No human subcutaneous evidence was identified by FDA.
• No human transdermal evidence was identified by FDA.
• Oral evidence cannot validate injectable products.
• The rabbit cartilage study does not establish human joint repair.
• No clinical osteoarthritis study was identified by FDA.
• No clinical osteoporosis study was identified by FDA.
• The oral neuropathic-pain trial failed its primary endpoint.
• The small migraine study did not demonstrate significant pain relief.
• The later radicular-pain signal was exploratory.
• Human pharmacokinetic information remains incomplete.
• Long-term safety for chronic obesity treatment is not established.
• Immunogenicity risk is route and formulation dependent.
• Disulphide-bond reduction can produce degradation products.
• Scrambled disulphide bonds can create structurally different species.
• Commercial certificates may not assess aggregation.
• Certificates may not distinguish free peptide from acetate-associated material.
• Research-market products may not match clinical-trial material.

What a Meaningful AOD-9604 Certificate of Analysis Should Include

• Complete AOD-9604 or Tyr-hGH177–191 identity
• All sixteen amino-acid residues
• Confirmation of the N-terminal tyrosine
• Confirmation of the C-terminal phenylalanine
• Disulphide mapping between Cys7 and Cys14
• Observed intact molecular mass
• Tandem-MS sequence evidence
• Free-thiol or reduced-peptide assessment
• Declared free-peptide or acetate form
• Quantitative counterion measurement
• Net peptide-content assay
• Chromatographic purity
• Named and unknown impurity results
• Deletion-sequence assessment
• Scrambled-disulphide assessment
• Aggregate or higher-molecular-weight-species result
• Water-content result
• Residual-solvent results
• Elemental-impurity results where appropriate
• Finished-product batch number
• Testing-laboratory identity
• Analytical methods and acceptance criteria
• A clear statement of tests not performed

Why “99% HPLC” Is Not Enough

A high chromatographic purity percentage does not prove that the peptide contains the correct cysteine bridge.

A linear peptide, reduced peptide or incorrectly bridged peptide can differ biologically despite having the same basic amino-acid composition.

HPLC alone does not establish net peptide quantity, counterion content, aggregation, endotoxin control, sterility or human suitability.

Reported Human Adverse Events

Historical intravenous studies reported headache, fatigue, dizziness and euphoria among treatment-related events.

One participant experienced severe chest tightness or chest pain considered possibly related to treatment.

Oral studies reported headache and gastrointestinal symptoms including diarrhoea, nausea, abdominal discomfort, flatulence and altered taste.

FDA also reviewed serious events including cancers occurring during the obesity programme but stated that the available information was insufficient to determine whether AOD-9604 caused them.

Long-Term Safety

Obesity is a chronic condition that may require treatment lasting months or years.

FDA concluded that the available information was insufficient to support the safety of long-term repeated AOD-9604 exposure for obesity.

Nonclinical Signals

FDA’s assessment described signals relating to bone measurements in rats and possible liver effects in cynomolgus monkeys.

The agency also described equivocal findings in selected genotoxicity assessments.

These findings do not prove a specific human harm, but they prevent broad claims that the compound is demonstrably risk free.

Immunogenicity

AOD-9604 is sufficiently large and structurally complex to create potential immune-recognition concerns.

Aggregates and synthesis-related impurities may increase immunogenicity beyond that of correctly manufactured monomeric peptide.

FDA identified particular uncertainty for subcutaneous products because route-specific human information was absent.

Product-Quality Risks

• Incorrect amino-acid sequence
• Missing N-terminal tyrosine
• Deletion-sequence impurities
• Incomplete peptide coupling
• Reduced disulphide bond
• Scrambled disulphide bonds
• Intermolecular peptide cross-links
• Incorrect acetate or trifluoroacetate content
• Incorrect net peptide quantity
• Peptide aggregates
• Residual synthesis reagents
• Residual organic solvents
• Unverified microbiological quality
• Unverified bacterial-endotoxin control
• Certificates unrelated to the finished batch
• Degradation during uncontrolled storage or transport

Physical and Chemical Characterisation

FDA found that the submitted and publicly available information did not characterise peptide impurities, aggregates and critical finished-product attributes adequately.

Some submitted certificates lacked microbial and bacterial-endotoxin controls relevant to injectable products.

Historical Use

FDA found evidence that AOD-9604 had been marketed by wellness clinics and compounders, but the extent and conditions of use were unclear.

Online availability did not provide reliable evidence of quality, safety or clinical effectiveness.

Effectiveness

FDA concluded that evidence did not support AOD-9604 for obesity through any evaluated route.

Most identified studies did not show a benefit over placebo, and the final large study failed its weight-loss endpoint.

FDA did not identify human studies supporting the proposed subcutaneous or transdermal products.

Safety

FDA highlighted limited route-specific safety information, uncertain pharmacokinetics, possible serious adverse events, aggregation and immunogenicity concerns.

Advisory-Committee Vote

On 4 December 2024, the Pharmacy Compounding Advisory Committee considered AOD-9604 free base and AOD-9604 acetate together.

All 12 voting members voted against placing the substances on the 503A Bulks List.

How the MHRA Determines Whether a Product Is a Medicine

MHRA guidance states that a product may be medicinal when it is presented as preventing or treating disease.

A product may also be medicinal when it is intended to restore, correct or modify physiological functions through pharmacological, immunological or metabolic action.

Claims concerning fat loss, obesity, metabolism, cartilage repair, osteoarthritis, pain, hormone activity or body composition could contribute to medicinal-product classification.

The MHRA can consider website wording, product names, imagery, labels, testimonials, social-media posts, instructions and the complete commercial presentation.

“Research Use Only” Wording

A research disclaimer does not necessarily determine legal classification.

A product may still be treated as medicinal where the surrounding content encourages personal administration or promises physiological outcomes.

Advertising Restrictions

Regulation 279 of the Human Medicines Regulations restricts advertising medicinal products where the required marketing authorisation, registration or certificate is not in force.

This section provides general regulatory education and does not constitute legal advice.

The 2026 World Anti-Doping Agency Prohibited List includes growth hormone, its analogues and its fragments within section S2.

AOD-9604 and hGH176–191 are provided as express examples of prohibited growth-hormone fragments.

The prohibition applies at all times rather than only during competition.

A product being labelled for research, weight management or recovery does not alter its anti-doping status.

Athletes are responsible for prohibited substances found in their samples under the principle of strict liability.

Research-market products may also contain undeclared ingredients, creating additional anti-doping risks.

• Does the source provide the complete 16-residue sequence?
• Is the N-terminal tyrosine present?
• Is AOD-9604 correctly described as Tyr-hGH177–191 and distinguished from native hGH176–191?
• Is the Cys7-to-Cys14 disulphide bridge confirmed?
• Is the material free peptide or acetate associated?
• Is acetate being confused with covalent acetylation?
• Was identity confirmed by high-resolution mass spectrometry?
• Was sequence confirmed by tandem mass spectrometry?
• Were disulphide bonds mapped?
• Were reduced and scrambled forms assessed?
• Were aggregates measured?
• Was net peptide content quantified?
• Does the certificate match the finished batch?
• Was the cited experiment performed in mice, rats, rabbits or people?
• Was the outcome weight gain in an animal or weight loss in a person?
• Did the clinical trial include a placebo group?
• Did the largest trial meet its primary endpoint?
• Is an earlier subgroup being quoted while the final trial is omitted?
• Was the route oral, intravenous, subcutaneous or transdermal?
• Does the commercial route match the cited human study?
• Is rabbit cartilage histology being described as human cartilage repair?
• Was the pain finding a primary or exploratory endpoint?
• Was long-term safety assessed?
• Were antibodies tested in every participant or only a subset?
• Are FDA safety and compounding findings acknowledged?
• Is the WADA prohibition stated accurately?
• Is the claimed purpose authorised in the UK?
• Is the source selling the product it describes?