HGH Fragment 176-191
Also known as: HGH Frag 176-191, HGH Fragment, GH Fragment 176-191, hGH 176-191, somatotropin fragment
3 notable studies · 4 references
TLDR
HGH Fragment 176-191 is a research-market name for a C-terminal growth-hormone fragment related to the experimentally studied hGH 177-191 sequence, which inhibited fat synthesis and reduced adiposity or weight gain in rodent studies, but controlled human weight-loss efficacy has not been established and it should not be treated as synonymous with the modified peptide AOD-9604.
Research Supports
- Studied for antilipogenic activity (inhibiting new fat synthesis) in animal adipose tissue
- Investigated for effects on body weight and adipose-tissue mass in obese mice
- Examined for effects on hepatic glycogen metabolism in rats
- Studied to help map which GH regions produce which metabolic effects
Observations Reported in Research
- Wu & Ng, 1993: antilipogenic activity similar to intact hGH, but no significant lipolysis by glycerol release
- Natera et al., 1994: reduced cumulative weight gain and adipose mass in obese mice
- 1978 rat study: altered hepatic glycogen synthase activity and glycerol-carbon incorporation into glycogen
- No controlled human efficacy evidence exists for this exact fragment
These are brief summaries of what the referenced research examined or reported — not conclusions about safety or effectiveness, and not medical advice. See Notable Studies and Sources & References below for the full context and citations.
At a Glance
Classification: Synthetic C-terminal human growth hormone-derived peptide fragment; experimental metabolic peptide
HGH Fragment 176-191 is marketed as a short peptide derived from the C-terminal region of human growth hormone. It's commonly described online as: “the fat-burning part of HGH.” That description is an oversimplification of some interesting older biochemistry. Researchers in the 1980s and 1990s investigated C-terminal GH fragments and found that hGH 177-191 could influence lipid and carbohydrate metabolism independently of the complete growth-hormone molecule. In obese mice, repeated hGH 177-191 reduced cumulative weight gain and adipose-tissue mass. But the critical Aminodex correction is: The classic published peptide is hGH 177-191. “HGH Fragment 176-191” is not automatically the same molecule, and neither is identical to AOD-9604.
What Is HGH Fragment 176-191?
Human growth hormone contains 191 amino acids. Researchers investigated whether different regions of GH could reproduce specific aspects of the complete hormone's biology. One region of particular interest was the C-terminal sequence: hGH 177-191. The classic synthetic peptide studied by Wu and Ng was: Leu-Arg-Ile-Val-Gln-Cys-Arg-Val-Ser-Glu-Gly-Ser-Cys-Gly-Phe. This sequence demonstrated antilipogenic activity—reducing formation/storage of new lipid—in experimental rat adipose tissue. Importantly, that particular experiment did not find significant lipolysis based on glycerol release. That's a useful correction to the common claim that the fragment simply “burns fat.”
What Are Researchers Studying?
Fat metabolism
C-terminal GH fragments were studied to determine which portions of GH contribute to its effects on adipose tissue. Synthetic hGH 177-191 inhibited lipogenesis in experimental systems. This suggests that some of GH's metabolic signaling can be reproduced by a small region of the parent hormone. It doesn't establish clinically meaningful human fat loss.
Body weight
In obese mice, chronic treatment with hGH 177-191 reduced cumulative body-weight gain and adipose-tissue mass. This is the animal result underlying much of the compound's later reputation. But note what the experiment demonstrated: less weight gain in genetically obese mice rather than proven weight loss in humans. Those are very different claims.
Lipogenesis
This is arguably the most defensible original research claim. The 1993 study found that hGH 177-191 possessed an antilipogenic effect comparable with intact hGH under the experimental conditions. Antilipogenesis means reducing the synthesis/storage of new fat. That isn't synonymous with directly breaking down existing adipose tissue.
Lipolysis
Here's where the literature gets particularly useful. Despite the modern "fat-burning fragment" label, the classic 1993 experiment found no significant lipolytic effect from hGH 177-191 using glycerol release from rat adipose tissue as the measure. Later research with the modified fragment AOD-9604 did report increased fat oxidation and lipolysis in obese mice. This is another reason not to merge the two compounds.
Glucose and glycogen metabolism
Research on hGH fragments goes back further than the obesity experiments. A 1978 rat study found that hGH 177-191 altered hepatic glycogen metabolism, including reducing active glycogen synthase and changing incorporation of glycerol carbon into glycogen. This reinforces that the C-terminal fragment has biological activity beyond a simplistic "fat burner" label.
Growth-hormone fragment biology
The original scientific question wasn't "Can we make a weight-loss peptide?" It was closer to "Which regions of growth hormone produce which biological effects?" That research helped establish that different GH sequences could produce different metabolic effects. AOD-9604 was subsequently developed as a modified C-terminal fragment intended to exploit that biology while avoiding unwanted actions of intact GH.
How Does It Work?
The precise mechanism remains incompletely defined. The historical evidence suggests that hGH 177-191 can: • suppress lipogenesis • influence adipose metabolism • affect hepatic glycogen metabolism. Importantly, the modified fragment AOD-9604 did not compete for the conventional hGH receptor in experimental work. Therefore the simplistic model: HGH fragment → weak GH receptor agonist → fat burning is probably wrong. The metabolic activity appears capable of occurring through mechanisms distinct from conventional full-length GH receptor signaling.
What Does the Research Show?
Human research
For the exact HGH Fragment 176-191/177-191 product identity commonly encountered in the research market: controlled human efficacy evidence is not established. The classic literature is predominantly: • rats • mice • adipose-tissue experiments • metabolic experiments. Human obesity development belongs primarily to AOD-9604, not unmodified hGH 177-191. And even there, as we covered in the separate AOD-9604 profile, the large human obesity program ultimately failed to establish significant weight-loss efficacy. So Aminodex should absolutely not borrow AOD-9604's human trials and place them under HGH Fragment 176-191.
Animal research
This is where the strongest direct evidence lies. Rat experiments hGH 177-191 showed antilipogenic activity and altered hepatic glycogen metabolism. Obese mice Repeated treatment reduced cumulative weight gain and adipose-tissue mass. Those findings support genuine biological activity. They do not establish human weight-loss efficacy.
In-vitro research
Experimental adipose-tissue work demonstrated: inhibition of lipogenesis without significant lipolysis under the conditions of the classic experiment. That's probably the single most important mechanistic nuance for this page.
Notable Studies
Antilipogenic Action of Synthetic C-Terminal Sequence 177-191 of Human Growth Hormone
in-vitroResearchers studied synthetic hGH 177-191 and found antilipogenic activity similar to intact hGH under the experimental conditions. However, the peptide did not produce significant lipolysis as measured by glycerol release from rat epididymal fat pads.
Limitations: Rat tissue and animal research, not humans. The experiment supports antilipogenic activity rather than the broader modern claim of clinically meaningful “fat burning.”
View publication →Reduction of Cumulative Body Weight Gain and Adipose Tissue Mass in Obese Mice: Response to Chronic Treatment With Synthetic hGH 177-191 Peptide
animalResearchers chronically administered synthetic hGH 177-191 to genetically obese mice. Treatment reduced cumulative body-weight gain and adipose-tissue mass and significantly inhibited adipose-tissue lipogenesis.
Limitations: Mouse study. Reduced weight gain in genetically obese mice doesn't establish weight-loss efficacy in humans.
View publication →Effects of Part Sequences of Human Growth Hormone on In Vivo Hepatic Glycogen Metabolism in the Rat
animalResearchers compared biologically active GH fragments and found that hGH 177-191 rapidly altered hepatic glycogen metabolism, including reducing active glycogen synthase and altering incorporation of glycerol carbon into glycogen.
Limitations: Old rat metabolic experiment with uncertain relevance to contemporary claims involving human fat loss.
View publication →What We Still Don't Know
• Whether HGH Fragment 176-191 produces meaningful human fat loss • Whether 176-191 and the historically studied 177-191 are pharmacologically equivalent • Human pharmacokinetics • Human dose-response relationships • Long-term human safety • Exact receptor/signaling mechanism • Whether human adipose tissue responds like rodent adipose tissue • Whether effects persist with chronic exposure • Whether it meaningfully affects glucose metabolism in humans • Whether research-market products actually contain the stated sequence • Whether commercial “HGH Frag 176-191” is sometimes actually AOD-9604.
Related Compounds
Recent publications
Latest titles from PubMed, not reviewed by Aminodex. Not an endorsement. See all on PubMed ↗
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Sources & References
- Wu Z, Ng FM. Antilipogenic action of synthetic C-terminal sequence 177-191 of human growth hormone. 1993.
- Natera SH, Jiang WJ, Ng FM. Reduction of cumulative body weight gain and adipose tissue mass in obese mice: response to chronic treatment with synthetic hGH 177-191 peptide. 1994.
- Effects of part sequences of human growth hormone on in vivo hepatic glycogen metabolism in the rat. 1978.
- Detection and in vitro metabolism of AOD9604.
Supplier Listings
A directory of relevant research suppliers for this compound is not yet available.