HGH Fragment 176-191

What is HGH Fragment 176-191?

HGH Fragment 176-191 is the native 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, written YLRIVQCRSVEGSCGF, molecular weight 1817.09 g/mol, CAS 66004-57-1. Research has focused on this region as the lipolytic domain of the parent hormone, the segment credited with its lipid-mobilising activity and separable from its growth-promoting and diabetogenic actions, a separation first explored with synthetic C-terminal fragments by Ng and Bornstein (Am J Physiol, 1978). 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 'cyclic anti-obesity peptide' conformation characterised by NMR in the analysis of Ogru and colleagues (J Pept Res, 2000). Because residue 176 of the intact hormone is itself a tyrosine, the fragment is sequence-identical to AOD-9604, the hexadecapeptide written Tyr-hGH(177-191) that Metabolic Pharmaceuticals developed from the same region; described as a modified derivative of the fragment, AOD-9604 is among the most studied analogues of the region and reached phase 2b clinical development. Supplied as lyophilised powder for in-vitro research use only, not a licensed medicine anywhere.

HGH Fragment 176-191 vs AOD-9604

The two compounds share the same sixteen residues, the same intrachain disulfide bridge and the same folded loop; what separates them is provenance and the literature attached to each name, not primary structure. HGH Fragment 176-191 is the native sequence, residues 176 to 191 exactly as they occur at the C-terminus of the 191-residue human growth hormone, with the N-terminal tyrosine occurring naturally at position 176. AOD-9604 is the developed hexadecapeptide written Tyr-hGH(177-191), the fifteen residues from position 177 onward with a tyrosine added at the N-terminus for stability. Because that added tyrosine is precisely the native residue 176, the two are sequence-identical, YLRIVQCRSVEGSCGF in both cases, and both carry the disulfide between the cysteines at positions 7 and 14 that closes the native C-terminal loop (Ogru et al., J Pept Res, 2000). The practical difference is the literature each name maps onto. The unmodified fragment appears in the early synthetic C-terminal fragment work (Ng and Bornstein, Am J Physiol, 1978; Bornstein et al., Acta Endocrinol, 1983) and in a modern drug-delivery study (Habibullah et al., Drug Des Devel Ther, 2022), whereas AOD-9604 is the developed candidate that carried the clinical programme, six randomised trials summarised by Stier and colleagues (J Endocrinol Metab, 2013). Researchers choosing between them are mostly choosing which name maps to which literature; the peptide chain is the same.

HGH Fragment 176-191 Research Applications

HGH Fragment 176-191 is used in metabolic research on the C-terminal lipolytic domain of human growth hormone: lipolysis and lipogenesis assays in adipocyte and hepatocyte preparations, structure-activity work on the disulfide-constrained C-terminal loop, and study designs that separate the lipid-mobilising activity of hGH from its growth-promoting and diabetogenic actions. The foundation is the synthetic C-terminal fragment work of Ng and Bornstein (Am J Physiol, 1978), who reported hyperglycaemic activity for synthetic C-terminal sequences, and Bornstein and colleagues (Acta Endocrinol, 1983), who reported inhibition of acetyl-CoA carboxylase by a carboxyl-terminal part sequence acting through a second messenger. The fuller metabolic characterisation comes from the AOD-9401 and AOD-9604 literature on the same sequence: Ng and colleagues (J Mol Endocrinol, 2000) described the molecular and cellular actions on lipid metabolism in Zucker fatty rats, Heffernan and colleagues (Am J Physiol Endocrinol Metab, 2000) reported altered lipid metabolism after oral administration in rodents, and the group's chronic treatment study in obese mice and beta-3-adrenergic receptor knock-out mice (Endocrinology, 2001) reported reduced body weight and body fat with restoration of beta-3-adrenergic receptor expression, without raising IGF-1 or impairing glucose handling. A separate modern line uses the unmodified fragment itself in drug delivery: 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. The honest boundary: the human clinical literature belongs to AOD-9604 rather than to the unmodified fragment, human efficacy was never established, the phase 2b programme was wound down without a marketing authorisation anywhere, and material supplied here is for in-vitro laboratory research only.

Reconstitution Guide

Allow the vial to reach room temperature, then sterilise the rubber stopper of both the peptide vial and the bacteriostatic water vial with an alcohol swab. Slowly draw bacteriostatic water into a sterile syringe and inject it gently down the inner glass wall of the peptide vial, never directly onto the lyophilised cake. Swirl the vial slowly in a circular motion until the powder is fully dissolved and the solution is clear and colourless; never shake or vortex, as mechanical shear and foaming degrade the peptide. The fragment carries two cysteine residues, at positions 7 and 14, which form the intrachain disulfide bridge of the native C-terminal loop, so treat oxidation as the degradation route to design against: work efficiently, avoid introducing excess air into the vial, and re-seal promptly after each draw. Use sterile, pyrogen-free consumables throughout and work in a laminar flow hood where available. If the solution appears turbid or the cake fails to dissolve completely, discard the vial rather than forcing dissolution. Record the reconstitution date, solvent volume and resulting concentration on the vial label, then refrigerate immediately. For in-vitro laboratory research use only.

See our full peptide reconstitution guide and reconstitution calculator for step-by-step protocol.

Storage Instructions

Store lyophilised vials at -20°C, protected from light and moisture, for long-term stability of up to 24 months; the lyophilised cake tolerates short transit at ambient temperature but should be moved to the freezer on receipt. Once reconstituted with bacteriostatic water, hold the solution at 2-8°C (standard refrigerator) and use within approximately 4 weeks, as hydrolysis proceeds once the peptide is in solution. For longer storage, prepare single-use aliquots at -20°C and thaw each aliquot only once; repeated freeze-thaw cycles are the fastest route to aggregation and loss of intact material. The degradation route to design against is oxidation of the intrachain disulfide between the cysteines at positions 7 and 14: keep vials tightly sealed with minimal headspace, protect from light, and never store the solution in contact with oxidising agents. Handle under sterile laboratory conditions throughout, and keep the batch number and certificate of analysis on file for experimental records. For in-vitro laboratory research use only.

Frequently Asked Questions

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)

Related Research Compounds

• → AOD-9604 5mg
• → Sermorelin 5mg
• → Bacteriostatic Water 10ml