F tier · safety concern
The unmodified 176-191 fragment has never been administered in a published human study and even its rodent literature was generated with a structurally different analogue, AOD-9604, whose own obesity programme was terminated for poor efficacy.
hgh fragment 176-191
HGH fragment 176-191 is the C-terminal 16 residues of human growth hormone, promoted on the basis of a fat-mobilising activity attributed to that region of the parent hormone. Published evidence for the unmodified fragment appears to extend no further than its identity as a sequence within growth hormone, because the animal and human data usually cited were generated with AOD-9604, a distinct analogue in which the N-terminal phenylalanine is replaced by tyrosine.
// we supply this one
available as a research reagent
≥ 99% HPLC · lyophilised powder · batch certificate published. Grade F above is our own and is not adjusted because we stock it.
the explanation
This is the last sixteen building blocks snipped off the end of the growth hormone protein, sold on the claim that this part is what burns fat without the growth effects. The catch is that the studies people point to were run on a slightly different molecule, and this exact peptide does not appear to have been tested in humans at all.
regulatory status
Not approved in any jurisdiction; research chemical; class prohibited in sport
HGH fragment 176-191 holds no marketing authorisation anywhere and is not a recognised medicine. Because it is a fragment of human growth hormone, distribution for human use in the United States engages the same prohibition that applies to hGH itself under 21 U.S.C. 333(e). Growth hormone fragments are anti-doping targets: the closely related analogue AOD-9604 is reported to remain banned in athletes and tested for in competition, and a dedicated study confirmed AOD-9604 does not interfere with WADA's hGH isoform immunoassay.
how it works · proposed mechanism
The proposed mechanism is a direct, growth-hormone-receptor-independent stimulation of fat oxidation localised to growth hormone's C-terminal region.
C-terminal lipolytic domain
Early work localised a fat-mobilising activity of growth hormone to a domain within its C-terminal region, which this fragment reproduces in isolation. The hypothesis is that the domain acts separately from the receptor-binding surfaces responsible for growth.
No IGF-1 elevation proposed
Lacking the helical faces that dimerise the growth hormone receptor, the fragment is not expected to raise IGF-1 or produce growth effects. This separation is the entire basis for marketing it as growth hormone's fat-loss action without growth hormone's liabilities.
Rodent data used analogue
Chronic-treatment studies in obese mice, obese Zucker rats and beta3-adrenergic-receptor knockout mice examined lipid metabolism and fat oxidation, but administered AOD-9604 rather than the unmodified 176-191 peptide. The mechanistic literature therefore characterises a related but non-identical compound.
what’s reported
evidence shape
6 sourcesThe composition of the cited literature by study type. This describes the shape of the evidence, not its quality — and it does not by itself set the grade.
⚠ the catch
Almost every claim made for this peptide rests on studies of AOD-9604, a different molecule in which the N-terminal phenylalanine is swapped for tyrosine. Even that analogue's record is unfavourable, with its obesity development programme terminated in 2007 after a 24-week trial showed poor efficacy.
key published findings
- Structural (human protein data): the marketed sequence FLRIVQCRSVEGSCGF corresponds exactly to residues 176-191 of the mature 191-residue GH1 chain (UniProt P01241) and retains the parent Cys182-Cys189 disulfide; PubChem CID 16131230 gives C78H123N23O22S2 and 1799.1 g/mol for the cyclic form.
- Rodent: Ng et al. (Horm Res 2000) conducted metabolic studies of the synthetic lipolytic domain in obese Zucker rats, and Heffernan et al. (Endocrinology 2001) examined chronic treatment effects on lipid metabolism in obese mice and beta3-adrenergic-receptor knockout mice - both using AOD-9604, the tyrosine-substituted analogue, rather than the unmodified fragment.
- Rabbit: Kwon and Park (Ann Clin Lab Sci 2015) tested intra-articular AOD-9604 with or without hyaluronic acid in a rabbit osteoarthritis model, again evaluating the analogue rather than the unmodified peptide.
- Literature audit: a PubMed search for AOD9604 returns 23 records comprising animal studies, analytical and doping-control methodology, and narrative reviews, with no indexed clinical efficacy trial of either AOD-9604 or the unmodified fragment.
- Human (analogue only, tertiary source): a 12-week randomized trial of AOD-9604 is reported to have produced approximately 1.8 kg greater weight loss than placebo, with development halted after a subsequent 24-week trial showed poor efficacy; the primary trial reports were not located as peer-reviewed publications.
limitations of the evidence
- No published study administers the unmodified fragment to humans, so there are no human pharmacokinetic, bioavailability or exposure data of any kind.
- The reported AOD-9604 obesity trial results could not be traced to primary peer-reviewed publications and rest on a tertiary source, so the effect sizes quoted should be treated as unconfirmed.
- Secondary and commercial literature routinely collapses the distinction between hGH 176-191 and AOD-9604, so any evidence attributed to the fragment must be checked against the molecule that was actually tested.
documented safety signals
- No published human safety data exist for the unmodified fragment; the absence of reported adverse events reflects an absence of study rather than demonstrated safety.
- Preparations sold under growth hormone fragment names have been the subject of forensic identification work by national authorities, indicating recurring uncertainty about what such products actually contain.
identity
| full name | Human growth hormone fragment 176-191 (hGH 176-191) |
| category | Growth Hormone |
| modality | peptide |
| formula | C78H123N23O22S2 |
| molar mass | 1799.1 g/mol |
| sequence | FLRIVQCRSVEGSCGF |
laboratory handling
| storage | Supplied as a lyophilised powder; research-grade peptide is generally stored desiccated at -20 °C and protected from light. |
| solubility | Soluble in water and in dilute aqueous acetic acid; the intramolecular Cys182-Cys189 disulfide makes it sensitive to reducing conditions. |
| co-studied with | No published study evaluates this fragment in combination with any other compound; combination claims have no evidence base. |
Handling information describes laboratory practice for a research reagent. It is not a preparation guide for use in humans.
the receipts
6 citedPubChem, National Library of Medicine · 2025 · official
Frontiers in Endocrinology · 2026 · review
Hormone Research · 2000 · preclinical
Endocrinology · 2001 · preclinical
Annals of Clinical and Laboratory Science · 2015 · preclinical
Wikipedia · 2026 · tertiary
Sources marked tertiary or press release are the weakest citations on this page.
others in Growth Hormone