AOD-9604 is a modified, synthetic analogue derived from the same C-terminal region of human growth hormone (hGH) as HGH Fragment 176-191. However, these are not identical compounds. HGH Fragment 176-191 is the unmodified 16-amino acid sequence corresponding to residues 176-191 of the full 191-amino acid hGH molecule [1], [2]. AOD-9604 was developed from the same region but carries a structural modification – a tyrosine substitution – distinguishing it from the native fragment [3]. Some sources describe AOD-9604 as being derived from, or a modified version of, hGH residues 177-191, rather than specifically 176-191. This reflects slight variability in how the parent region is defined across different literature [3], [4].
This shared origin is the primary reason why these two compounds are frequently confused or linked in commercial and online content. According to Wikipedia's evidence summary, HGH Fragment 176-191 „was incorrectly represented as a lipolytic peptide fragment based on the extrapolation of clinical data regarding AOD9604„. It also notes that ”unlike AOD9604, hGH frag 176-191 has not been studied in humans" [1].
This is the single most important distinction to carry over from any comparison of these two compounds. Research findings for AOD-9604 do not automatically apply to the unmodified fragment, even though they originate from the same region of the hormone.
Comparison of mechanisms
Lipolysis and fat metabolism. AOD-9604 has been investigated in animal models specifically for its effects on lipid metabolism. In one study, both full-length hGH and AOD-9604 reduced weight gain in obese mice over a 14-day treatment period. This effect was associated with increased fat oxidation and elevated plasma glycerol, a marker of lipolysis [3].
A separate study showed that daily oral administration of AOD-9604 to obese Zucker rats for 19 days reduced weight gain by more than 50% compared with controls, with a corresponding increase in lipolytic activity in adipose tissue [4].
By way of comparison, no animal or human studies identified in these reviews tested unmodified HGH Fragment 176-191 for lipolytic or fat-oxidising effects. The only study that actually tested this exact unmodified sequence analysed its effect on blood glucose and insulin in rats, not fat metabolism [5].
Does either increase IGF-1 or affect growth pathways? Research into AOD-9604 indicates that, unlike full-length hGH, it does not compete for binding to the hGH receptor and does not promote cell proliferation via this receptor pathway [3]. This is presented in the literature as a key reason why AOD-9604 has garnered interest as a potential treatment for obesity separate from hGH itself.
None of the studies identified here directly measured IGF-1 levels after administration of AOD-9604 or HGH Fragment 176-191. For the unmodified fragment 176-191 specifically, no studies on IGF-1 or growth pathway effects were identified at all.
History of research and clinical trials
AOD-9604. The reviewed studies identified in this review consist of animal studies. These include chronic treatment studies in obese and lean mice, including beta(3)-adrenergic receptor knockout mice [3]. There is also an oral dosing study in obese Zucker rats [4] and a study of the conformational and biological properties of an anti-obesity cyclic peptide derived from the same C-terminal domain of hGH [6].
Separately, a few commercial and industry websites browsed during the course of these studies, not peer-reviewed journal sources, state that AOD-9604 has undergone human clinical trials. This includes claims of Phase II/III obesity trials conducted in Australia [7]. These claims could not be independently verified against peer-reviewed clinical trial publication from the sources gathered for this article. They should therefore be treated as vendor or industry claims, not confirmed peer-reviewed clinical evidence. Readers interested in verifying specific human trial data for AOD-9604 should consult clinical trial registries (such as ClinicalTrials.gov) or peer-reviewed publications directly.
HGH Fragment 176-191. The research base is narrower and does not include any study focused on obesity or unmodified fragment fat loss. Identified peer-reviewed studies consist of a 1978 rat study regarding blood glucose and insulin effects [5] and a 2022 in vitro/in silico study using the peptide as a component of an anti-cancer drug delivery nanoparticle system, unrelated to weight loss [8]. No clinical trials of any phase were identified for the unmodified fragment.
Comparison of study design and methods of administration. Animal studies of AOD-9604 used chronic intraperitoneal administration for 14 days in one instance [3] and daily oral administration for 19 days in another [4] – notably, one of the few studies of peptides in this research area testing the oral rather than injectable route. A rat study of HGH Fragment 176-191 used a single intravenous dose [5]. These differences in administration route, duration, and species mean that the two sets of studies are not directly comparable in design, beyond testing different (though related) compounds.
Side-by-side effectiveness data
| HGH Fragment 176-191 (unmodified) | AOD-9604 | |
|---|---|---|
| Clinical data on humans regarding fat loss | None identified | No peer-reviewed [3] or independently verified reviews identified in this review; vendor sources claim human trials took place [7], unverified herein. |
| Animal data regarding fat loss/lipolysis | None identified | Reduced weight gain and increased markers of fat oxidation/lipolysis in obese mice [3]; reduced weight gain in obese rats by oral dosing [4] |
| Evidence of mechanism | Unestablished for fat metabolism; one study shows glucose/insulin effects [5] | A proposed lipolytic mechanism distinct from hGH receptor binding [3] |
| IGF-1/growth pathway data | None identified | No direct measurement of the unidentified entity; it has been reported as not binding to the hGH receptor nor promoting proliferation [3] |
Where is the evidence strong vs anecdotal for each: For AOD-9604, there is real peer-reviewed animal evidence supporting a fat oxidation and weight reduction effect in mice and rats. This represents a significantly stronger evidence base than exists for the unmodified fragment. It is important to note, however, that this is still preclinical, animal evidence – not confirmed human clinical evidence, in the sources reviewed here.
For HGH Fragment 176-191, no peer-reviewed evidence of fat loss exists in either animals or humans. Any claims of fat loss attributed to this specific compound in commercial or anecdotal contexts are not supported by studies identified in this review. They most likely reflect confusion with data for AOD-9604.
Comparison of security and regulatory status
Approval status. Based on the reviewed sources, neither compound is approved by the US Food and Drug Administration (FDA) or the European Medicines Agency (EMA) for any medical use. Both are typically marketed as „research chemicals” rather than licensed pharmaceutical products in the US, EU, UK and Australia. Regulatory status may vary by country and can change over time; this is not legal advice, and readers should consult the relevant national drug regulator for current, authoritative information.
Reported side effect profiles. For AOD-9604, identified animal studies noted something worthy of remark. Unlike hGH, it did not induce elevated blood sugar or reduce insulin secretion during chronic treatment in mice [3]. No human adverse event data specific to AOD-9604 were identified in the peer-reviewed sources collected here.
For HGH Fragment 176-191, the only relevant animal study noted a transient increase in blood glucose, a more sustained increase in insulin, and decreased insulin sensitivity following a single dose in rats [5]. No human safety data exist for either compound in these studies.
A broader 2026 review of growth hormone axis peptides as a class, which specifically refers to „growth hormone (GH) fragment – AOD9604 (hGH 176–191)”, notes something about adverse effects reported within this general category of unregulated compounds. These include endocrine and metabolic disturbances, fluid retention, musculoskeletal symptoms, and injection site reactions. However, this reflects the entire class broadly — unconfirmed, compound-specific human data for neither AOD-9604 nor the unmodified fragment individually [9].
Frequently asked questions
Is AOD-9604 the same as HGH Fragment 176-191?
No. They share their origin in the same C-terminal region of human growth hormone. AOD-9604 is, however, a structurally modified analogue, carrying a tyrosine substitution, whereas HGH Fragment 176-191 is an unmodified native sequence [1], [3].
What is the difference between AOD-9604 and HGH Fragment 176-191?
The key differences are structural (modification of AOD-9604 versus native sequence) and evidential. AOD-9604 has peer-reviewed animal studies supporting effects on fat oxidation and weight gain in obese rodents [3], [4]. Unmodified HGH Fragment 176-191 lacks such studies and has not been studied in humans at all [1], [5].
Which has stronger clinical support?
Based on the reviewed sources, no compound has confirmed, peer-reviewed clinical trial data in humans. AOD-9604 has a stronger preclinical (animal) research base specific to fat metabolism than HGH Fragment 176-191, which has no fat metabolism research at all. Claims of completed human trials for AOD-9604 appear in industry and vendor sources but have not been independently verified against peer-reviewed publications for these studies [7].
AOD-9604 vs HGH Fragment 176-191 for fat loss — which is better supported by research?
AOD-9604 has reviewed animal data suggesting a fat oxidation and weight reduction effect [3], [4]. HGH Fragment 176-191 has no reviewed fat loss data of any kind, either in animals or humans, based on the sources gathered for this review [1], [5]. This distinction does not establish AOD-9604 as proven effective in humans—only that its preclinical evidence base is more developed than that for the unmodified fragment.
Disclaimer
Neither AOD-9604 nor HGH Fragment 176-191 are approved by the US Food and Drug Administration, the European Medicines Agency, or any equivalent regulatory body for human medical use. Confirmed peer-reviewed human clinical trial data for either compound could not be identified from the sources reviewed for this article. The evidence base described for AOD-9604 consists of preclinical (animal) studies, and claims of human trials found in industry or vendor sources have not been independently verified. HGH Fragment 176-191 specifically has not been studied in humans at all. This article is provided for general educational and informational purposes only. It does not constitute medical advice and should not be relied upon as a basis for decisions to use, purchase, or administer any compound.
References
[1] Wikipedia contributors. (2025, December 30). HGH Fragment 176–191. Wikipedia, The Free Encyclopaedia. https://en.wikipedia.org/wiki/HGH_Fragment_176%E2%80%93191
[2] National Centre for Biotechnology Information. (2026, July 18). PubChem Compound Summary for CID 172966176, HGH Fragment 176-191. PubChem. https://pubchem.ncbi.nlm.nih.gov/compound/172966176
[3] Heffernan, M., Summers, R. J., Thorburn, A., Ogru, E., Gianello, R., Jiang, W. J., & Ng, F. M. (2001). 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, 142(12), 5182–5189. https://doi.org/10.1210/endo.142.12.8522
[4] Ng, F. M., Sun, J., Sharma, L., Libinaka, R., Jiang, W. J., & Gianello, R. (2000). Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Hormone Research, 53(6), 274–278. https://doi.org/10.1159/000053183
[5] Ng, F. M., & Bornstein, J. (1978). Hyperglycaemic action of synthetic C-terminal fragments of human growth hormone. American Journal of Physiology, 234(5), E521–E526. https://doi.org/10.1152/ajpendo.1978.234.5.E521
[6] Ogru, E., Heffernan, M., Jiang, W. J., Thorburn, A., & Aird, S. D. (2000). The conformational and biological analysis of a cyclic anti-obesity peptide from the C-terminal domain of human growth hormone. The Journal of Peptide Research, 56(4), 260–267. https://pubmed.ncbi.nlm.nih.gov/11152298/
Phoenix Peptide Labs. (n.d.). Metabolic and Energy Research: AOD9604. Retrieved from phoenixpeptidelabs.com. [Industry/vendor source; claims from human trials have not been independently verified against peer-reviewed publications.]
[8] Habibullah, M. M., Mohan, S., Syed, N. K., Makeen, H. A., Jamal, Q. M. S., Alothaid, H., Bantun, F., Alhazmi, A., Hakamy, A., Kaabi, Y. A., Samlan, G., Lohani, M., Thangavel, N., & Al-Kasim, M. A. (2022). Human growth hormone fragment 176-191 peptide enhances the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells. Drug Design, Development and Therapy, 16, 1963–1974. https://doi.org/10.2147/DDDT.S367586
[9] Dominikowski, A., Rękoś, Z., Olejarz, M., Szczepanek-Parulska, E., Domin, R., & Ruchała, M. (2026). The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: Bridging the gap between clinical evidence and patient self-administration. Frontiers in Endocrinology, 17, 1822475. https://doi.org/10.3389/fendo.2026.1822475