hGH Fragment 176-191

hGH Fragment 176-191 is a synthetic peptide corresponding to amino acids 176 through 191 at the C-terminal end of the human growth hormone (hGH) molecule. This 16-amino-acid sequence was identified in research as the region of full-length GH responsible for the hormone's lipolytic (fat-burning) activity. By isolating and stabilizing this fragment, researchers produced a peptide that retains the fat-metabolism effects of growth hormone without the growth-promoting, insulin-desensitizing, or glucose-elevating properties of the intact molecule.

The mechanism of action is concentrated at the adipocyte level. hGH Fragment 176-191 binds to receptors on fat cell membranes that are coupled to adenylate cyclase, triggering an increase in intracellular cyclic AMP (cAMP). Elevated cAMP activates protein kinase A (PKA), which in turn phosphorylates and activates hormone-sensitive lipase (HSL) and adipose triglyceride lipase (ATGL). These lipases catalyze the hydrolysis of stored triglycerides into free fatty acids and glycerol, a process called lipolysis. Simultaneously, the fragment downregulates lipogenic enzymes including acetyl-CoA carboxylase, reducing the rate of new fat synthesis. The combined effect is a net shift toward fat mobilization and away from fat storage, particularly in visceral and abdominal depots.

Because this fragment lacks the domains of full-length hGH that stimulate the IGF-1 axis and promote cell proliferation and skeletal growth, it does not produce the side effects associated with exogenous GH therapy, including glucose dysregulation, joint pain, carpal tunnel syndrome, and acromegaloid features. This selectivity has made it an attractive research subject for targeted fat reduction. A clinical trial referenced in published research found that the lowest effective daily dose of 1 mg produced the greatest average fat loss, approximately 3 kg over three months, suggesting a non-linear dose-response relationship.

Published studies using oral and injectable forms of the fragment in both animal and early human models demonstrated significant reductions in lipogenic activity and corresponding increases in lipolytic activity in adipose tissue. Animal studies consistently showed reductions in body weight gain, with preferential loss from visceral fat rather than lean tissue. The fragment does not appear to impair insulin sensitivity or alter blood glucose homeostasis, which is a significant advantage over full-length GH and over many other lipolytic agents. It remains an unapproved research compound in the United States and most major regulatory jurisdictions.