HGH Fragment 176-191

VANDL Labs

$34.99

5mg vial · vial

HGH Fragment 176-191's proposed mechanism of action is grounded in the structural dissection of the native human growth hormone molecule. Full-length hGH (residues 1-191) is a 22 kDa peptide that binds two distinct functional domains to the growth hormone receptor (GHR), triggering receptor dimerisation and activation of the JAK2/STAT5 signalling cascade. This pathway mediates both the anabolic and growth-promoting effects of hGH (via hepatic IGF-1 production) and certain direct lipolytic effects in adipose tissue. The challenge with using full-length hGH therapeutically for obesity or body composition is that chronic supraphysiological hGH administration raises concerns about acromegaly, insulin resistance, diabetes, cardiovascular strain, carpal tunnel syndrome, and possibly cancer — concerns reflected in tight regulatory controls on hGH prescription for adult indications.

The Monash group's insight was that the lipolytic and anti-lipogenic activity of hGH appears to be largely mediated by the C-terminal region (approximately residues 176-191), while the growth-promoting activity is mediated by other regions including residues important for GHR binding. By isolating the 15-amino-acid C-terminal fragment and adding a stabilising N-terminal tyrosine, Ng and colleagues created AOD-9604 — a molecule that, in preclinical studies, retains the lipolytic and anti-lipogenic signalling of the parent hormone while failing to activate the growth-promoting IGF-1 pathway. In principle, this would allow chronic fat-loss dosing without the acromegaly or cancer concerns of full-length hGH.

Proposed mechanism at the adipocyte level:

1. Stimulation of lipolysis. AOD-9604 is reported in cell-culture and animal studies to increase cAMP production in adipocytes, activating hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL), resulting in increased breakdown of stored triglycerides to free fatty acids and glycerol. This is the same downstream signalling as beta-adrenergic receptor activation (catecholamines, clenbuterol, yohimbine) but reportedly achieved without direct adrenergic receptor binding.

2. Inhibition of lipogenesis. Concurrent with stimulating fat breakdown, AOD-9604 has been reported to inhibit fatty acid synthesis and adipocyte triglyceride accumulation, shifting net adipose tissue balance toward catabolism.

3. Absence of GHR-mediated growth signalling. Critically, the preclinical data indicate that AOD-9604 does NOT activate the JAK2/STAT5 pathway in the growth-promoting manner of full-length hGH, and does not measurably raise serum IGF-1 at therapeutic doses. This is the mechanistic basis for the claim that AOD-9604 produces fat loss without the growth side effects of hGH.

4. Proposed receptor. The specific receptor mediating AOD-9604's lipolytic effects has not been definitively identified. It is not the canonical growth hormone receptor (GHR). Some work suggests a distinct "lipolytic receptor" on adipocytes, but this receptor has not been characterised at the molecular level, and the possibility remains that AOD-9604's effects are mediated indirectly (e.g., through weak interaction with multiple adipocyte receptors) rather than through a single specific target.

Joint and cartilage claims. Secondary claims about AOD-9604 benefiting cartilage and joint tissue derive from limited preclinical work suggesting effects on chondrocyte function and potential synergy with hyaluronic acid in intra-articular applications. These are more speculative than the adipose tissue claims. Rigorous human clinical trials establishing joint benefit do not exist.

What AOD-9604 does NOT do:

• It does NOT meaningfully raise serum IGF-1 (by design).
• It does NOT produce the subjective "hGH effects" (improved sleep, skin changes, well-being reports) that users attribute to full-length hGH or GH secretagogues like CJC-1295 and ipamorelin.
• It does NOT stimulate muscle growth (hypertrophy) through IGF-1-mediated mechanisms.
• It does NOT suppress endogenous GH secretion through negative feedback (because it does not engage the feedback loop).
• It does NOT activate the GLP-1 or GIP receptors that underlie the large-effect weight-loss drugs semaglutide and tirzepatide.

Oral vs. injectable bioavailability. Metabolic Pharmaceuticals pursued an oral formulation of AOD-9604 because the small peptide size (16 residues) and relative stability made oral absorption plausible. The Phase 2b trial used oral AOD-9604, and the failed primary endpoint applied to oral dosing. Current peptide-clinic and research-chemical use is typically subcutaneous injection, which has different pharmacokinetics (higher bioavailability, different exposure profile) than the tested oral formulation. This means the existing negative clinical trial data do not strictly apply to the subcutaneous dosing regimens commonly used today — but it also means that subcutaneous AOD-9604 has essentially NO placebo-controlled clinical data supporting its efficacy. The mechanism-of-action logic remains the same; the clinical validation does not.

HGH Fragment 176-191 (also written HGH Frag 176-191, hGH Fragment 176-191, and frequently appearing in clinical literature as AOD-9604 — "Anti-Obesity Drug 9604") is a synthetic peptide corresponding to the C-terminal 15-amino-acid region of the 191-amino-acid human growth hormone (hGH) molecule, with an additional N-terminal tyrosine residue added for stability and biological activity. The sequence spans residues 176 through 191 of native hGH plus the tyrosine cap, giving the designation "Tyr-hGH 176-191." It was developed in the 1990s at Monash University (Melbourne, Australia) under the direction of F.M. Ng and colleagues, and subsequently licensed to Metabolic Pharmaceuticals (later acquired by Calzada Ltd), which pursued clinical development for obesity indications. The core hypothesis driving its development was that the C-terminal region of hGH carries the lipolytic (fat-burning) and anti-lipogenic activity of the parent molecule while being separable from the IGF-1-mediated growth-promoting effects that raise cancer, diabetes, and acromegaly concerns when full-length recombinant hGH is used chronically.

That separation is real in cell culture and rodent studies. Ng and colleagues demonstrated in the 1990s that HGH 176-191 stimulates lipolysis in isolated adipocytes, reduces body fat in genetically obese mice, and does so without measurably raising serum IGF-1 or activating the JAK2/STAT5 pathway in the growth-promoting way that intact hGH does. This work formed the scientific foundation for AOD-9604's clinical development as a potential obesity drug. Between approximately 2002 and 2008, Metabolic Pharmaceuticals conducted a series of Phase I and Phase II trials in humans, evaluating doses ranging from 100 mcg to 1 mg daily via subcutaneous injection and, in later studies, oral formulations.

The critical fact users should understand is that AOD-9604 failed its key clinical trials. The 2007 Phase 2b trial (n≈534) evaluated AOD-9604 at doses up to 1 mg/day orally in obese adults over 24 weeks, and the primary endpoint — placebo-adjusted weight loss — was not met. The difference from placebo was small and not statistically significant. Metabolic Pharmaceuticals subsequently abandoned AOD-9604's development as an anti-obesity drug, and no regulatory agency (FDA, EMA, TGA, PMDA, Health Canada) has ever approved AOD-9604 for any indication. It is not an approved medicine anywhere in the world. The Australian TGA briefly granted AOD-9604 GRAS-like "listable" status as a cosmetic ingredient — a classification that does not imply clinical efficacy or safety for systemic therapeutic use — but this is a regulatory footnote, not a clinical endorsement.

Notwithstanding the clinical trial failure, HGH Fragment 176-191 has acquired a significant following in the compounding pharmacy, peptide clinic, and research-chemical markets, primarily for claimed fat loss, joint health, and body recomposition effects. Compounding pharmacies in the United States have at times supplied AOD-9604 as an ingredient in custom formulations prescribed by longevity-medicine and functional-medicine physicians, though the FDA has issued guidance restricting compounding of peptides without an established USP or NF monograph, and the regulatory landscape for AOD-9604 compounding has tightened substantially since 2023. In the unregulated research-peptide market, HGH Fragment 176-191 is widely sold as an injectable peptide, typically at prices substantially lower than brand-name weight-loss medications.

The problem users must grapple with is that the best-controlled human data on AOD-9604 showed it did not produce clinically meaningful weight loss. This is in stark contrast to the current standard of care for obesity, which includes the GLP-1 receptor agonists — semaglutide (Wegovy, Ozempic) and the dual GIP/GLP-1 agonist tirzepatide (Zepbound, Mounjaro) — which produce 15-22% placebo-adjusted weight loss in 68-72 week randomised trials (STEP and SURMOUNT programmes), approved by the FDA, EMA, and global regulators for chronic weight management. These drugs have transformed obesity medicine in the 2020s. AOD-9604, by comparison, produced a weight-loss effect of approximately 2.8 kg vs. placebo in 12-week trials that did not reach the threshold for regulatory approval. The gap is not subtle; it is a categorical difference between an evidence-based treatment and a compound that failed its key trials.

A more honest framing of AOD-9604 in 2026 is this: it is a rationally designed peptide fragment with plausible preclinical biology that did not translate to a clinically meaningful anti-obesity effect in humans. It may have subtle metabolic effects at commonly used research doses, but these have not been established in adequately powered, placebo-controlled trials. Users considering AOD-9604 for fat loss should first ask whether they have exhausted evidence-based options: GLP-1/GIP agonists for those meeting BMI criteria; structured diet and exercise programs with documented adherence support; evaluation of thyroid, cortisol, and metabolic status; and, where indicated, bariatric surgery consultation. Adding an unregulated peptide that failed its clinical trials is a substantially weaker option than any of these. For joint-health claims — a secondary use popularised in peptide-clinic marketing — there are no adequately powered trials establishing AOD-9604 efficacy for osteoarthritis or cartilage repair, and the evidence-based options (physical therapy, weight reduction, NSAIDs, intra-articular corticosteroids, and for eligible patients, joint replacement) remain the appropriate first-line. BPC-157 and TB-500 are sometimes discussed alongside AOD-9604 for joint and tissue-repair claims, but they share similar limitations in the evidence base.

For the remainder of this page, we present the mechanism, studies, and protocols that users and compounding pharmacists have worked with — with the repeated caveat that none of this substitutes for a failed key trial result and the absence of any regulatory approval.

IUPAC Name

Tyr-hGH(176-191)

CAS Number

66004-57-7

Molecular Formula

C78H123N23O23S2

Molecular Mass

1817.12 g/mol

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