Overview

Fragment 176-191 is a synthetic peptide derived from the C-terminal region of human growth hormone, specifically comprising amino acids 176 through 191 of the hGH molecule. This 16-amino acid sequence represents the lipolytic domain of growth hormone and has been studied for its potential metabolic effects.

Early research from the 1970s and 1980s identified this fragment as having hyperglycemic properties, meaning it may increase blood glucose levels. More recent investigations have explored its potential applications in cancer research, particularly as an adjuvant to enhance chemotherapy effectiveness.

The peptide is prohibited by the World Anti-Doping Agency (WADA) and is not approved for human therapeutic use in any jurisdiction. Despite limited clinical data, it has gained attention in research contexts for its potential metabolic effects.

Mechanism of Action

Fragment 176-191 is believed to retain some of the metabolic activities of full-length growth hormone while potentially having reduced effects on insulin-like growth factor-1 (IGF-1) production. Research suggests the peptide may:

• Glucose Metabolism: Studies from 1978 and 1982 demonstrated that synthetic C-terminal fragments of human growth hormone, including the 176-191 sequence, can produce hyperglycemic effects through mechanisms that may involve interference with glucose uptake or insulin sensitivity.

• Cellular Targeting: Recent research has investigated its use as a targeting mechanism for drug delivery systems. A 2022 study showed that Fragment 176-191 could enhance the cytotoxicity of doxorubicin-loaded nanoparticles against breast cancer cells, suggesting it may have cell-specific binding properties.

• Metabolic Signaling: The peptide may interact with growth hormone receptors or related signaling pathways, though the exact mechanisms remain under investigation.

The precise molecular targets and downstream effects of Fragment 176-191 require further elucidation through controlled human studies.

Research Summary

4 papers found on PubMed. 4 clinical trials registered, though none specifically investigate Fragment 176-191.

Key Studies

Hyperglycemic Effects (1978-1982) Two foundational studies published in the American Journal of Physiology and Biochimica et Biophysica Acta established that synthetic C-terminal fragments of human growth hormone, including the 176-191 sequence, can produce significant hyperglycemic effects. These studies demonstrated that the fragment maintains some metabolic activity of the parent hormone.

Cancer Research Applications (2022) A study published in Drug Design, Development and Therapy investigated Fragment 176-191 as a targeting peptide for drug delivery. The research showed that when conjugated to chitosan nanoparticles loaded with doxorubicin, the fragment enhanced cytotoxicity against MCF-7 breast cancer cells, suggesting potential applications in targeted cancer therapy.

Doping Concerns (2026) A critical review in The Journal of Sports Medicine and Physical Fitness discussed the use of peptides including Fragment 176-191 in recreational and professional sports, highlighting concerns about their use as performance-enhancing substances and the challenges of detection.

Research Gaps

• No dedicated human clinical trials for Fragment 176-191
• Limited safety data in human populations
• Unclear optimal dosing parameters
• Unknown long-term effects

Dosage Guidelines

Note: The following information is based on theoretical frameworks and research protocols, not clinical recommendations. Fragment 176-191 is not approved for human use.

Research Protocols:

• Studies have used varying concentrations in cell culture and animal models
• Optimal human dosing parameters remain unknown
• Bioavailability and pharmacokinetics not established in humans

Safety Profile

The safety profile of Fragment 176-191 in humans is not well established due to limited clinical data. Potential considerations based on available research include:

Metabolic Effects:

• May cause hyperglycemia based on early research
• Potential interactions with glucose metabolism
• Unknown effects on insulin sensitivity

General Considerations:

• No established human safety data
• Unknown drug interactions
• Potential for allergic reactions as with any peptide
• Long-term effects completely unknown

Monitoring Recommendations (if used in research contexts):

• Blood glucose monitoring
• Liver function assessment
• Kidney function evaluation
• Regular health screenings

Contraindications:

• Diabetes or glucose intolerance
• Active malignancy
• Pregnancy or breastfeeding
• Age under 18 years

Stacking

Information provided for research and educational purposes only.

Fragment 176-191 has been discussed in research contexts alongside other growth hormone-related compounds, though no formal combination studies exist:

Theoretical Combinations:

• With Growth Hormone Secretagogues: May be combined with GHRH analogs like Sermorelin or GHRP compounds, though interactions unknown
• Metabolic Compounds: Theoretical synergy with other metabolic peptides, but safety and efficacy not established

Important Considerations:

• No clinical data on combination use
• Potential for increased side effects
• Unknown drug interactions
• Regulatory status prohibits non-research use

Research Recommendations: Any combination use should only occur in controlled research settings with appropriate medical oversight and institutional review board approval.

References

1. Human Growth Hormone Fragment 176-191 Peptide Enhances the Toxicity of Doxorubicin-Loaded Chitosan Nanoparticles Against MCF-7 Breast Cancer Cells. (2022). Drug design, development and therapy. DOI PubMed
2. Hyperglycemic action of synthetic C-terminal fragments of human growth hormone. (1978). The American journal of physiology. DOI PubMed
3. A new era of doping? Use of peptide and peptide-analog drugs in recreational and professional sport and bodybuilding: a critical review. (2026). The Journal of sports medicine and physical fitness. DOI PubMed
4. The mechanism of the hyperglycaemic action of synthetic peptides related to the C-terminal sequence of human growth hormone. (1982). Biochimica et biophysica acta. DOI PubMed