HGH Fragment 191

What is HGH Fragment 191?

This represents human somatotropin in its native form: 191 amino acids in the precise sequence and tertiary structure found in pituitary-derived growth hormone. Produced through recombinant DNA technology in E. coli expression systems, this rHGH is structurally indistinguishable from endogenous GH, making it the unambiguous choice for studying growth hormone receptor binding, GH-mediated signal transduction, and the direct effects of somatotropin on target tissues.

Where secretagogues provide indirect GH elevation through endogenous release, direct GH application enables precise dose-response studies, receptor saturation experiments, and investigation of GH signaling independent of pituitary function. With over four decades of research characterizing GH's effects on IGF-1 production, lipolysis, protein synthesis, and tissue remodeling, this molecule remains central to endocrine and metabolic research.

Mechanism of Action

AOD-9604 represents the isolated C-terminal fragment of human growth hormone (amino acids 176-191) that retains lipolytic activity while lacking GH receptor binding capability. The peptide appears to stimulate lipolysis through β3-adrenergic receptor activation on adipocytes rather than through the JAK-STAT pathway used by full-length GH. Studies suggest AOD-9604 may mimic the conformational structure of a GH region that interacts with β3-AR, triggering adenylyl cyclase activation, cAMP elevation, and protein kinase A-mediated phosphorylation of hormone-sensitive lipase (HSL) and perilipin.

This mechanism explains the selective metabolic effects: by bypassing GH receptor, AOD-9604 avoids GH-mediated effects on IGF-1 production, glucose metabolism, and cell proliferation. The peptide demonstrates preferential action on abdominal adipocytes which express higher β3-AR density. Additionally, AOD-9604 may inhibit lipogenesis by reducing acetyl-CoA carboxylase activity. The tyrosine addition at the N-terminus (absent in native HGH 176-191) enhances stability and may contribute to receptor interaction. Unlike full GH, AOD-9604 shows no effects on blood glucose, insulin levels, or growth, making it a selective tool for studying GH-independent lipolytic pathways.

Key Research Findings

• Reduces body fat by 50% in genetically obese mice after 14 days treatment without affecting lean mass or food intake [Heffernan et al., 2001]
• Demonstrates 155% increase in lipolytic activity in isolated adipocytes at 10 μM concentration vs vehicle control [Ng et al., 2000]
• Shows no IGF-1 elevation or glucose/insulin changes across dose range 1-10 mg/day in phase 2 trials [Stenlof et al., 2000]
• Reduces visceral adipose tissue by 31% vs 12% placebo in 12-week obesity trial [Heffernan et al., 2005]
• Activates β3-adrenergic receptor signaling with EC50 of 4.2 μM in transfected cell lines [Ng et al., 2000]

Research Applications

• GH receptor binding and signaling
• IGF-1 pathway research
• Somatotropin receptor pharmacology
• Anabolic signaling mechanisms
• Direct GH effects vs. secretagogue comparison
• Protein synthesis research

Reconstitution & Use

Reconstitute with bacteriostatic water for laboratory use. For detailed reconstitution instructions and concentration ratios for your specific research application, see our reconstitution guide.

Storage & Handling

Store lyophilized at -20°C protected from light. Upon reconstitution with bacteriostatic water, maintain at 2-8°C and use within 14 days—shorter than peptide secretagogues due to protein aggregation susceptibility. Avoid agitation; gently swirl to dissolve.