HGH Fragment 176-191 5mg

What is HGH Fragment 176-191 ?

HGH Fragment 176-191, also sold as HGH Frag 176-191, is a 16-residue peptide from the C-terminal end of human growth hormone. The sequence on its certificate is YLRIVQCRSVEGSCGF. Each 5mg vial holds white lyophilised powder.

Native human growth hormone has phenylalanine at position 176, so its 176-191 stretch reads FLRIVQCRSVEGSCGF. The peptide sold under this name carries tyrosine at that first position instead. That makes it Tyr-hGH(177-191), the same primary sequence as AOD-9604.

The cysteines at positions 7 and 14 (hGH residues 182 and 189) can form the disulfide bridge that closes the hormone's small C-terminal loop. Ogru and colleagues (J Pept Res, 2000) solved the solution structure of that cyclic 177-191 peptide by NMR.

HGH Fragment 176-191 Research Applications

• Early fragment work : in rats, hGH 172-191 to 178-191 fragments raised blood glucose and insulin, while 179-191 was inert (Ng and Bornstein, 1978).
• Adipose tissue : the 177-191 domain (AOD9401) stimulated hormone-sensitive lipase and inhibited acetyl-CoA carboxylase in rat fat, without inducing insulin resistance (Ng et al., J Mol Endocrinol, 2000).
• Beta-3 receptors : AOD9604 raised beta-3-adrenergic receptor RNA in obese mice, though its lipolytic action did not run directly through that receptor (Heffernan et al., Endocrinology, 2001).
• Drug delivery : the fragment increased the toxicity of doxorubicin-loaded chitosan nanoparticles to MCF-7 breast cancer cells (Habibullah et al., Drug Des Devel Ther, 2022).

Typical uses are lipolysis and lipogenesis assays in adipocyte and hepatocyte preparations, and structure-activity work on the C-terminal loop. The human clinical data belong to AOD-9604, not to this product, and efficacy was never established. No marketing authorisation exists anywhere.

HGH Fragment 176-191 vs AOD-9604

AOD-9604 is Tyr-hGH(177-191): residues 177 to 191 with a tyrosine added at the N-terminus. The peptide sold as HGH Fragment 176-191, including this batch, has that same sequence, YLRIVQCRSVEGSCGF. The native hGH 176-191 sequence would start with phenylalanine instead. So the two names describe one primary structure and differ in the literature attached to each. AOD-9604 carried the clinical programme to phase 2b. The fragment name appears in early synthetic fragment work and in a 2022 drug-delivery study.

Research Overview

HGH Fragment 176-191 is the C-terminal 16-residue sequence of human growth hormone, residues 176 to 191 of the 191-residue protein, sequence Tyr-Leu-Arg-Ile-Val-Gln-Cys-Arg-Ser-Val-Glu-Gly-Ser-Cys-Gly-Phe (YLRIVQCRSVEGSCGF), molecular formula C₇₈H₁₂₅N₂₃O₂₃S₂, molecular weight 1817.09 g/mol, CAS 66004-57-1. Because residue 176 of the intact hormone is a tyrosine, the fragment is sequence-identical to AOD-9604, the hexadecapeptide Tyr-hGH(177-191) that Metabolic Pharmaceuticals developed from the same region. The two cysteine residues, at fragment positions 7 and 14 (hGH residues 182 and 189), form the intrachain disulfide bridge that closes the small C-terminal loop of the native hormone, the conformation characterised by Ogru and colleagues (J Pept Res, 2000).

Research has focused on this region as the lipolytic domain of the parent hormone: the segment credited with its lipid-mobilising activity, separable from its growth-promoting and diabetogenic actions. The early work is the synthetic C-terminal fragment programme of Ng and Bornstein (Am J Physiol, 1978), and the fuller metabolic characterisation comes from the AOD-9401 and AOD-9604 literature on the same sequence, including molecular and cellular studies in Zucker fatty rats (Ng et al., J Mol Endocrinol, 2000) and chronic treatment work in obese mice and beta-3-adrenergic receptor knock-out mice reporting reduced body weight and body fat without IGF-1-mediated growth effects (Heffernan et al., Endocrinology, 2001). Its modified derivative AOD-9604 is among the most studied analogues of the fragment and reached phase 2b clinical development, with six randomised trials summarised by Stier and colleagues (J Endocrinol Metab, 2013). A separate modern line uses the unmodified fragment in drug-delivery research, where Habibullah and colleagues (Drug Des Devel Ther, 2022) reported that the peptide enhanced the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells.

It is worth being direct about the state of the evidence. The human clinical data belong to AOD-9604, not to the unmodified fragment, and even there efficacy was never established: the phase 2b programme was wound down and no marketing authorisation exists anywhere.

Storage and Reconstitution

Keep sealed vials at -20°C, away from light and moisture, and move them to the freezer on receipt. After reconstitution, keep the solution at 2-8°C and use it within 4 weeks, or freeze single-use aliquots at -20°C and thaw each once. Keep vials tightly sealed with little headspace and away from oxidising agents.

Vials are sold on their own, without bacteriostatic water for mixing or other supplies.

How to reconstitute and handle

Bring the vial to room temperature and swab both stoppers with alcohol. Add bacteriostatic water slowly down the inside wall, never onto the powder, and swirl until the solution is clear and colourless. Do not shake or vortex. The two cysteines are the oxidation-prone sites, so limit air in the vial and reseal promptly. Discard a vial that stays turbid. Label it with the date, volume and concentration, then refrigerate.

• The cysteines at positions 7 and 14 form an intrachain disulfide bridge, and oxidation of that bridge is the degradation route to design against: minimise headspace and stopper-open time, keep solutions cold, and prepare single-use aliquots rather than repeatedly accessing one vial.

For the full method, see the peptide reconstitution guide and the reconstitution calculator.

Research References

• Hyperglycemic action of synthetic C-terminal fragments of human growth hormone (Ng and Bornstein, Am J Physiol, 1978)
• Molecular and cellular actions of a structural domain of human growth hormone (AOD9401) on lipid metabolism in Zucker fatty rats (Ng et al., J Mol Endocrinol, 2000)
• The effects of human GH and its lipolytic fragment (AOD9604) on lipid metabolism following chronic treatment in obese mice and beta(3)-AR knock-out mice (Heffernan et al., Endocrinology, 2001)
• The conformational and biological analysis of a cyclic anti-obesity peptide from the C-terminal domain of human growth hormone (Ogru et al., J Pept Res, 2000)
• Human growth hormone fragment 176-191 peptide enhances the toxicity of doxorubicin-loaded chitosan nanoparticles against MCF-7 breast cancer cells (Habibullah et al., Drug Des Devel Ther, 2022)

Published research on HGH Fragment 176-191 is indexed on PubMed. See our full UK buyer's guide for HGH Fragment 176-191.