hGH Fragment 176-191: Native C-Terminal Fragment of Growth Hormone
Unmodified C-terminal fragment of human growth hormone. Rodent lipolysis data; no approved human use. Closely related to AOD-9604.
🐀 Animal
- Full name
- hGH fragment 176-191
- Class
- Native 16-residue C-terminal peptide of hGH
- Half-life
- Minutes in circulation
- Route
- Subcutaneous (research)
- Developer
- Academic research groups
- Regulatory status
- Not a registered medicine; WADA-banned for athletes
What it is
The 176-191 fragment is the native C-terminal 16 amino-acid portion of human growth hormone. Isolation and characterisation in the 1990s showed that it retained lipolytic activity in rodents without the growth-promoting effects of the full hormone. AOD-9604 is a tyrosine-modified commercial analogue of this fragment.
How it works
In rodent adipocytes the fragment increased lipolysis and β-adrenergic responsiveness without binding the hGH receptor in a productive fashion. This apparent dissociation of lipolysis from growth was the scientific interest.
In humans the mechanism is unclear: the fragment does not appreciably activate the hGH receptor and convincing evidence of fat loss in human trials is lacking.
What the research shows
Pre-clinical studies are the foundation; human data for the native fragment (rather than AOD-9604) are sparse.
Ng FM et al. (1990s) — rodent lipolytic activity
Ng F.M. et al., Horm Res 1994;42:66–72. 🐀 Animal
Purified 176-191 fragment administered to obese mice and lean rats.
Increased lipolysis and reduced fat mass at multiple doses; no IGF-1 response.
Limitations: Species-specific GH biology; no mechanistic confirmation in human tissue.
Heffernan MA et al. (2001) — mouse adipose tissue mechanism
Heffernan M.A. et al., Eur J Endocrinol 2001;144:491–498. 🐀 Animal
Mechanistic studies in mouse adipose tissue showed increased β₃-adrenoceptor expression.
These effects were the basis for subsequent human AOD-9604 development — which failed to replicate the fat-loss effect.
Limitations: Mechanism did not translate to humans.
Safety and limitations
Because no human programme exists for the native fragment, safety data come from the closely-related AOD-9604 trials. Short-term human exposure showed no significant changes in IGF-1, glucose, or insulin. Grey-market purity and dose accuracy are the main real-world risks.
Banned by WADA under the category of “peptide hormones and their releasing factors”.