HGH Fragment 176-191

01 · What it is

The residue numbers on this product do not match the residue numbers in the research it is sold on.

The compound with the fat-loss research programme is AOD-9604, and the anti-doping literature states its structure without ambiguity: the C-terminal fragment of human growth hormone from amino acids 177 to 191, with an additional tyrosine residue at the N-terminus ¹². Not 176. Not without a tyrosine.

Searching PubMed for the exact designation “growth hormone fragment 176-191” returns one paper. It is a 2022 study in which the peptide was used to enhance the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells ¹⁴. An oncology drug-delivery paper. Not a fat-loss study, not a metabolic study, not a human trial.

This guide located no study of fat loss, weight loss, or lipolysis conducted on a compound designated 176-191. The three rodent lipolysis studies that everything in this market rests on ^6,7,8 were conducted on AOD-9604 and describe it as such.

Two possibilities, and this guide cannot distinguish them. Either “176-191” is a loose or erroneous label for the same molecule described as 177–191 plus tyrosine, or products sold under the two names are not the same substance. No published analysis of any product sold under either name was located, so nobody has checked.

This project has now found several compounds whose commercial name is absent from PubMed’s phrase index. This case is different and worse in one specific way: the name is present, attached to a real peptide used in a real experiment, and that experiment has nothing to do with what the product is sold for.

02 · Evidence at a glance

Evidence grade

Preclinical — no human trial located; no metabolic study under this designation located

Papers matching this exact designation

One — a 2022 breast cancer nanoparticle study ¹⁴

What that paper did

Used the peptide to enhance toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 cells ¹⁴

AOD-9604’s published structure

hGH residues 177–191 plus an N-terminal tyrosine ¹²

Metabolic studies under the 176-191 designation

None located

Metabolic studies under the AOD-9604 designation

Three rodent studies, 2000–2001 ^6,7,8

Human trials, either designation

None located

Product analysis

None located

Other hGH fragments studied

32–38 ⁴; 44–91 ⁵; A-II ²; 14 kDa ¹⁵ — with differing and in one case opposite effects

hGH fragment 44–91

Produces insulin resistance and hyperinsulinaemia in the rat ⁵

Contemporary framing

Named among unapproved peptides marketed direct to patients ¹⁸; among GH-axis agents used in self-administration ¹⁷

Regulatory status

No marketing authorisation located

03 · Mechanism of action

The claimed mechanism belongs to a differently numbered molecule

The proposition sold with this name is that the C-terminal region of growth hormone carries its lipolytic activity and can be used without the rest of the hormone. That proposition was tested — on AOD-9604 ^6,7,8, a synthetic analogue of the lipolytic domain, in obese Zucker rats and obese mice.

This is the sixth or seventh instance in this project of a compound whose mechanistic case is borrowed wholesale from a related but non-identical molecule. It is the most consequential instance, because here the two molecules differ by a defined and stated amount: one residue at the N-terminal boundary, plus an added tyrosine ¹².

Why one residue is not a rounding error

The growth hormone fragment literature is a fifty-year record of different fragments doing different and sometimes opposing things.

Fragment 44–91 produces insulin resistance and hyperinsulinaemia in the rat ⁵. Fragment 32–38 increases glucose uptake in the conscious dog ⁴. A fragment designated A-II shows somatomedin-like bioactivity on chick cartilage and human fibroblasts ². The residue boundaries of one such fragment had to be revised after re-sequencing, in a 1975 paper correcting the published amino acid sequence of an active fragment of bovine growth hormone ¹.

That last point is worth its own sentence. The field has already had to correct a fragment’s stated sequence once. Residue numbering in this literature is not decorative and has been wrong before. A 14-kilodalton fragment inhibits angiogenesis and tumour metastasis ¹⁵. Intact growth hormone and growth hormone fragment both stimulate T-lymphocyte proliferation in vitro ³.

Two fragments of the same hormone have opposite effects on insulin sensitivity. That is the argument against treating residue boundaries as approximate, and it does not depend on any claim about what this particular compound does.

The one thing published under this exact name

In the 2022 study, the peptide was used as a component enhancing the cytotoxicity of a doxorubicin-loaded chitosan nanoparticle system against a breast cancer cell line ¹⁴.

A peptide that enhances a cytotoxic drug’s action on cancer cells is doing something, and what it is doing has no established relationship to adipose tissue. This guide reports the study for what it is and draws no inference from it in either direction.

04 · Key research findings

There are no fat-loss findings to report under this designation.

This section normally summarises what has been shown. Here the honest content is the absence, and the surrounding literature a reader might otherwise mistake for evidence about it.

Breast cancer nanoparticles, 2022. Human growth hormone fragment 176-191 peptide enhanced the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells ¹⁴.

The only located paper using this exact designation. Its subject is drug delivery in oncology.

AOD-9604 in obese Zucker rats, 2000. A synthetic analogue of the lipolytic domain of human growth hormone; adipose tissue of treated animals showed increased lipolytic activity ⁶.

AOD-9604 in obese mice, 2001. Chronic treatment with human growth hormone or a modified C-terminal fragment increased fat oxidation and produced weight loss, with increased in vivo fat oxidation and increased plasma glycerol. In vitro assays addressed whether effects were hGH-receptor-mediated and whether the peptide could drive cell proliferation through that receptor ⁷.

AOD-9604 in obese and knockout mice, 2001. Both human growth hormone and the lipolytic fragment induced weight loss and increased lipolytic sensitivity after long-term treatment, in a design including beta-3 adrenergic receptor knockout mice ⁸.

The synthesis: these three studies are the entire preclinical fat-loss case for this market, they are twenty-five years old, they are in rodents, and they were conducted on a molecule the literature describes with different residue numbers than the product label carries.

Structure and detection, 2015. AOD9604 is the C-terminal fragment of human growth hormone from amino acids 177–191 with an additional tyrosine at the N-terminus; a detection method and a stable metabolite were characterised ¹². The compound appears in sports drug-testing reviews ¹³.

Development history. A 2004 review reported phase IIa obesity trials underway as of February 2002 ⁹; contemporaneous reviews surveyed the obesity pipeline ¹⁰ and patent landscape ¹¹. No resulting human trial publication was located under either designation.

Contemporary reviews, 2026. A sports medicine review covers unapproved peptides marketed direct to patients including AOD-9604 ¹⁸; a GH-IGF1 axis review is framed around the gap between clinical evidence and patient self-administration ¹⁷; an orthopaedic review groups AOD-9604 with growth hormone secretagogues ¹⁶, which on the structural evidence ¹² it is not.

Three 2026 reviews treat this family of compounds as a clinical management problem created by a market, rather than as therapeutic candidates. That is where the literature has arrived.

05 · Evidence overview

06 · Safety profile

There is no safety data for a compound under this designation, beyond a cell-culture study in which it was used to increase the toxicity of a chemotherapy agent ¹⁴.

Animal data. None under this designation. The rodent studies belong to AOD-9604 ^6,7,8. No dedicated toxicology study was retrieved for either designation.

Human data. None located, under either designation.

What is genuinely unknown, and it is nearly everything. Four items.

What the substance is. The published numbering for the researched compound is 177–191 plus a tyrosine ¹². Whether material sold as 176-191 is that molecule, a molecule differing by one residue and lacking the tyrosine, or something else, is not established by anything this guide located.

Whether the metabolic effect transfers. If the molecules differ, the rodent lipolysis results do not automatically apply. The fragment literature shows that different fragments of this hormone produce different and sometimes opposite metabolic effects ^4,5.

Proliferative potential. The 2001 study asked whether the fragment can drive cell proliferation through the growth hormone receptor ⁷; this guide read that the question was posed and did not read the answer. Growth hormone stimulates lymphocyte proliferation in vitro ³, and the one study using this exact designation concerns cancer cells ¹⁴. None of that establishes harm; all of it establishes that the question is open and load-bearing.

Product identity. No published analysis of any product sold under this name was located.

07 · US regulatory status

Current as of 7 September 2026. This guide located no marketing authorisation under this designation or for AOD-9604 in any jurisdiction. A 2026 review describes AOD-9604 among unapproved peptides marketed direct to patients ¹⁸.

This guide has not consulted FDA, EMA or any other regulatory record, and makes no statement about any agency’s determinations.

An unapproved drug cannot lawfully be supplied for human use in the United States outside an authorised clinical trial or a formal expanded-access pathway.

A validated anti-doping detection method exists for AOD9604 ^12,13. Competitors should consult the current Prohibited List directly rather than rely on secondary summaries, including this one.

08 · Limitations of the evidence

1. The residue numbering does not match. The researched compound is published as 177–191 with an added N-terminal tyrosine ¹²; the product designation is 176-191. This guide cannot resolve whether that is a labelling convention or a difference in substance, and treats it as unresolved rather than assuming equivalence.
2. The single paper using this exact designation is an oncology drug-delivery study ¹⁴, not a metabolic one. Citing it as evidence for a fat-loss claim would be a category error.
3. The entire fat-loss case is borrowed from three rodent studies of a differently designated compound ^6,7,8, now twenty-five years old.
4. No human trial was located under either designation, despite a 2004 report of phase IIa trials underway since 2002 ⁹.
5. The fragment literature demonstrates non-equivalence between fragments ^2,3,4,5,15, including one fragment that produces insulin resistance ⁵. This is cited to establish that residue boundaries matter, not to attribute any effect to this compound.
6. The proliferation question is open ⁷ and unanswered in what this guide read.
7. No dedicated toxicology study was retrieved.
8. No independent product analysis was located, so nothing can be said about what is in anything sold under this name.
9. A 2026 review misclassifies the underlying compound as a growth hormone secretagogue ¹⁶. Where reviews contradict primary structural sources, this guide follows the primary source.
10. This guide and the AOD-9604 guide share a single PubMed search, of which twenty of 43 records were examined. A search designed specifically around the 176-191 designation might return more, and running one is a verification item.
11. This guide has read abstracts, not full texts, for every source cited, and two are indexed without abstracts.

09 · Legal and regulatory appendix

This appendix applies to every compound in this family and is reproduced in each guide.

Approval status. This guide located no marketing authorisation under this designation. Supplying or administering an unapproved drug for human use is unlawful in the United States and in most other jurisdictions outside an authorised trial or expanded-access pathway. This guide does not describe how to obtain the compound and takes no position on any supplier.

Products sold under this name. Material sold under this designation has no established relationship to the material used in the studies cited here, and the published residue numbering differs from the designation on the label. This guide located no published analysis of the identity, purity, concentration, sterility or contamination status of any such product.

Research-use labelling. Material labelled for laboratory research use is not manufactured, tested, or released to the standards applied to medicines intended for people, and such labelling does not make administration lawful or safe.

What this guide is. A description of the published peer-reviewed literature, written for readers who want to understand the state of the evidence. It is not medical advice, not a recommendation, not an endorsement, and not a substitute for a clinician who can assess an individual situation.

Editorial position. Arkham Labs publishes independently and earns through disclosed referral links. That commercial relationship is disclosed on every page carrying such a link and on the editorial standards page. It does not alter what the evidence says, and this guide reports that the name on this product does not match the name in its research.

10 · References

1. Yamasaki N, Shimanaka J, Sonenberg M. Studies on the common active site of growth hormone. Revision of the amino acid sequence of an active fragment of bovine growth hormone. J Biol Chem. 1975 Apr 10;250(7):2510–2514.

   PMID 1123321 ↗

2. Hubbard JR, Liberti JP. Somatomedin-like bioactivities of a growth hormone fragment on embryonic chick cartilage and cultured human fibroblasts. Biochim Biophys Acta. 1980 Jan 17;627(2):207–214.

   PMID 7350924 ↗

3. Mercola KE, Cline MJ, Golde DW. Growth hormone stimulation of normal and leukemic human T-lymphocyte proliferation in vitro. Blood. 1981 Aug;58(2):337–340.

   PMID 6972789 ↗

4. Stevenson RW, Stebbing N, Jones T, Carr K, Jones PM, Hii C, Cherrington AD. The synthetic human growth hormone fragment (32-38) increases glucose uptake in the conscious dog. Acta Endocrinol (Copenh). 1988 Apr;117(4):457–462.

   PMID 3291525 ↗

5. Hettiarachchi M, Watkinson A, Leung KC, Sinha YN, Ho KK, Kraegen EW. Human growth hormone fragment (hGH44-91) produces insulin resistance and hyperinsulinemia but is less potent than 22 kDa hGH in the rat. Endocrine. 1997 Feb;6(1):47–52.

   PMID 9225115 ↗

6. Ng FM, Sun J, Sharma L, Libinaka R, Jiang WJ, Gianello R. Metabolic studies of a synthetic lipolytic domain (AOD9604) of human growth hormone. Horm Res. 2000;53(6):274–278.

   PMID 11146367 ↗

7. Heffernan MA, Thorburn AW, Fam B, Summers R, Conway-Campbell B, Waters MJ, Ng FM. Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment. Int J Obes Relat Metab Disord. 2001 Oct;25(10):1442–1449.

   PMID 11673763 ↗

8. Heffernan M, Summers RJ, Thorburn A, Ogru E, Gianello R, Jiang WJ, Ng FM. 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 Dec;142(12):5182–5189.

   PMID 11713213 ↗

9. Wilding J. AOD-9604 Metabolic. Curr Opin Investig Drugs. 2004 Apr;5(4):436–440. Review.

   PMID 15134286 ↗

10. Halford JC. Obesity drugs in clinical development. Curr Opin Investig Drugs. 2006 Apr;7(4):312–318. Review.

    PMID 16625817 ↗

11. Khan A, Raza S, Khan Y, Aksoy T, Khan M, Weinberger Y, Goldman J. Current updates in the medical management of obesity. Recent Pat Endocr Metab Immune Drug Discov. 2012 May;6(2):117–128. Review.

    PMID 22435392 ↗

12. Cox HD, Smeal SJ, Hughes CM, Cox JE, Eichner D. Detection and in vitro metabolism of AOD9604. Drug Test Anal. 2015 Jan;7(1):31–38.

    PMID 25208511 ↗

13. Schänzer W, Thevis M. Human sports drug testing by mass spectrometry. Mass Spectrom Rev. 2017 Jan;36(1):16–46. Review.

    PMID 26213263 ↗

14. Habibullah MM, Mohan S, Syed NK, Makeen HA, Jamal QMS, Alothaid H, Bantun F, Alhazmi A, Hakamy A, Kaabi YA, Samlan G, Lohani M, Thangavel N, Al-Kasim MA. Human growth hormone fragment 176-191 peptide enhances the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells. Drug Des Devel Ther. 2022 Jun 27;16:1963–1974.

    PMID 35783198 ↗

15. Shaker BT, Ismail AA, Salih R, Hadj Kacem H, Rahmani M, Struman I, Bajou K. The 14-kilodalton human growth hormone fragment a potent inhibitor of angiogenesis and tumor metastasis. Int J Mol Sci. 2023 May 17;24(10):8877.

    PMID 37240223 ↗

16. Rahman OF, Lee SJ, Seeds WA. Therapeutic peptides in orthopaedics: applications, challenges, and future directions. J Am Acad Orthop Surg Glob Res Rev. 2026 Jan 2;10(1):e25.00236. Review.

    PMID 41490200 ↗

17. Dominikowski A, Rękoś Z, Olejarz M, Szczepanek-Parulska E, Domin R, Ruchała M. The emerging landscape of performance-enhancing peptides modulating GH-IGF1 axis: bridging the gap between clinical evidence and patient self-administration. Front Endocrinol (Lausanne). 2026 Jun 18;17:1822475. Review.

    PMID 42395176 ↗

18. Mendias CL, Awan TM. Safety and efficacy of approved and unapproved peptide therapies for musculoskeletal injuries and athletic performance. Sports Med. 2026 Aug;56(8):1921–1935. Review.

    PMID 41966639 ↗