Summary

HGH Fragment 176-191 is a synthetic peptide corresponding to amino acids 176–191 of human growth hormone (hGH), modified to enhance stability. It is researched for its potential to stimulate lipolysis (fat breakdown) without the broader metabolic and growth-promoting effects of full-length growth hormone. Evidence is primarily limited to animal and in vitro studies, with no published human clinical trials.

Mechanism

HGH Fragment 176-191 is proposed to stimulate lipolysis by activating hormone-sensitive lipase (HSL) in adipose tissue and inhibiting lipogenesis, potentially through beta-3 adrenergic receptor signalling pathways. Unlike full-length human growth hormone, the fragment does not appear to elevate IGF-1, affect blood glucose, or promote tissue growth. The selective lipolytic mechanism is based on preclinical (animal/in vitro) research and has not been confirmed in human studies.

Evidence base

Preclinical Evidence (Animal Models)

Research from the laboratory of Professor Frank Ng at Monash University identified the C-terminal region of hGH (residues 176–191/177–191) as responsible for lipolytic activity. In obese mouse models, administration of the fragment reduced body weight gain and fat mass without affecting food intake, blood glucose, insulin, or IGF-1 levels. Isolated adipose tissue preparations demonstrated direct lipolytic effects. These findings were published in peer-reviewed journals including Endocrinology (Ng et al., 2000).

Human Evidence

No published human clinical trials exist for HGH Fragment 176-191. The related peptide AOD-9604 (residues 177–191) completed Phase 2 trials, but those results cannot be directly extrapolated. All claims about human effects are unverified extrapolations from animal data.

Evidence Grade: Limited

Evidence is restricted to preclinical studies. No human pharmacokinetics, safety, or efficacy data have been published.

Protocols

Research use only — no human clinical dosing has been established.

In research communities, commonly discussed protocols (without clinical evidence) include:

  • Route: Subcutaneous injection
  • Dose: 250–500 mcg per administration (anecdotal, not clinically validated)
  • Frequency: 1–3 times daily, often timed around fasting or exercise
  • Cycle: 4–8 weeks, followed by time off
  • Site: Abdominal subcutaneous fat (no evidence supports site-specific lipolysis in humans)

These protocols are based on community discussion and extrapolation from animal studies, not clinical trials.

HGH Fragment 176-191 is not a licensed medicine in the UK and has no MHRA marketing authorisation. It is not a controlled substance under the Misuse of Drugs Act, but it is not approved for human use. It falls into a regulatory grey area: it may be sold for 'research purposes only' by vendors, but this does not constitute regulatory approval. The MHRA has taken action against vendors making therapeutic claims for unlicensed peptide products. Purchasing for research use is distinct from medicinal use.

Vendor notes

HGH Fragment 176-191 is available from several UK research peptide vendors. Verify COA availability and third-party purity testing before purchase. No specific vendor endorsements are made. See our Vendor Vetting Guide for supplier evaluation guidance.

References

  1. Ng FM, et al. A growth hormone fragment (hGH 177-191) with lipolytic activity in obese mice. Endocrinology. 2000;141(9):3284-3290. DOI: 10.1210/endo.141.9.7638.
  2. Heffernan M, Summers RJ, Thorburn A, et al. The reduced weight gain in AOD-9604-treated obese mice is not due to decreased energy intake. Endocrinology. 2001;142(1):151-159.
  3. Ng FM, Jiang WJ, Chua BH, et al. A modified hGH fragment peptide with lipolytic activity. Journal of Endocrinology. 2000;164(3):R1-R6.
  4. MHRA. Guidance on unlicensed medicines and borderline products. Medicines and Healthcare products Regulatory Agency, UK Government. Available at: gov.uk.