HGH Fragment 176-191
Educational information only — not medical advice. Many listed compounds are not FDA-approved for human use. Consult a licensed clinician before starting, changing, or stopping any protocol.
Overview
HGH Fragment 176-191 is a synthetic peptide made up of the amino acids at the C-terminal end (positions 176 to 191) of human growth hormone. Structure-function research on growth hormone found that its fat-mobilizing, or lipolytic, activity is concentrated largely in this short C-terminal region, while the hormone’s growth-promoting and blood-sugar-related effects appear to reside elsewhere in the molecule.
The idea behind isolating this fragment is to retain the fat-metabolizing behavior of growth hormone while leaving out the region associated with insulin resistance and unwanted tissue growth. For that reason it is most often discussed in a fat-loss and body-composition context.
It is closely related to — but distinct from — AOD-9604, a modified analog of the same domain that carries an extra tyrosine residue. Much of the published preclinical work was performed on that AOD-9604 version, so the two are frequently discussed together.
How it works
In animal studies, growth hormone’s C-terminal fragment has been reported to stimulate lipolysis (the breakdown of stored fat) and to increase fat oxidation without producing the rise in blood sugar seen with the full hormone. Researchers have noted that the fragment does not appear to bind the growth hormone receptor, suggesting it acts through a different route.
Some of this work points to the beta-3 adrenergic receptor — the main fat-cell receptor involved in lipolysis — as part of the pathway, alongside effects on the enzymes that govern fat storage and fat breakdown. The precise mechanism in humans is not established.
Reported benefits
- Mobilization and oxidation of stored fat (studied primarily in obese-mouse models)
- Reduced body-weight gain without the blood-sugar elevation associated with full growth hormone
- Interest as a fat-targeted alternative that does not act through the growth hormone receptor
These are reported and studied effects, not guaranteed outcomes, and the strongest data is preclinical.
Considerations & side effects
Human evidence is limited. Clinical trials of the closely related AOD-9604 analog reported a safety profile broadly similar to placebo but did not demonstrate weight loss strong enough to support approval as a medicine, and the unmodified 176-191 fragment itself has not been characterized in robust human trials. As a result, its long-term safety in people is not well established.
Reported side effects are generally mild and can include injection-site irritation. Product purity varies widely in the research-chemical market, and the fragment is not a substitute for evaluation and treatment by a qualified clinician.
Frequently asked
What is HGH Fragment 176-191?
A synthetic peptide corresponding to the C-terminal 176-191 region of human growth hormone. Research suggests this region carries much of GH's fat-mobilizing (lipolytic) activity, while omitting the parts of the hormone linked to blood-sugar and growth-promoting effects.
Is HGH Fragment 176-191 FDA-approved?
No. It is not approved by the FDA or any major regulator for human therapeutic use, and is sold for research purposes only.
How is it different from AOD-9604?
AOD-9604 is a modified analog of this same C-terminal domain, carrying an added tyrosine at one end. The two are closely related but not identical, and much of the published animal research was actually conducted on the AOD-9604 version.
Is there human clinical evidence for fat loss?
Most published data comes from animal models. Human trials of the closely related AOD-9604 analog did not show weight-loss results strong enough to support it as an approved drug, so human evidence for fat loss remains limited.
How is it typically administered?
Most commonly by subcutaneous injection after reconstitution with bacteriostatic water.
References
- Heffernan M, et al. Increase of fat oxidation and weight loss in obese mice caused by chronic treatment with human growth hormone or a modified C-terminal fragment. ↗
- Heffernan M, et al. The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism in obese mice and beta(3)-AR knock-out mice. ↗
- Wu Z, Ng FM. Antilipogenic action of synthetic C-terminal sequence 177-191 of human growth hormone. ↗
Related compounds
Anti-Obesity Drug fragment of HGH (176-191). Targets fat metabolism without affecting blood sugar or growth.
Small molecule NNMT enzyme inhibitor. Increases NAD+ levels in fat cells, promoting energy expenditure and reducing fat accumulation without affecting appetite.
Prohibitin-targeting peptidomimetic designed to selectively disrupt blood supply to white adipose tissue. Highly experimental anti-obesity compound. Clinical development discontinued due to renal side effects.