HGH Fragment 176-191

Research-Grade

HGH Fragment 176-191 (HGH Frag) is a synthetic peptide corresponding to the C-terminal portion of human growth hormone, spanning amino acids 176 through 191. This region was identified in the 1990s as the segment responsible for GH's fat-metabolizing properties, independent of its anabolic and IGF-1-stimulating effects. The fragment was extensively studied by researchers at Monash University (Melbourne), who demonstrated that this 16-amino-acid sequence could stimulate lipolysis in adipose tissue at a rate 12.5 times greater than full-length GH, without the hyperglycemic effects that limit therapeutic GH use in obesity. The mechanism is distinct from full-length GH: HGH Frag 176-191 does not bind to the growth hormone receptor in the canonical manner. Instead, it appears to interact with a beta-3 adrenergic receptor pathway, stimulating hormone-sensitive lipase (HSL) activity and inhibiting lipogenesis. This means it promotes fat breakdown while preventing new fat storage — without affecting blood glucose, IGF-1 levels, or protein synthesis. In preclinical studies, the fragment reduced body fat in obese mice without altering food intake or lean mass. A Phase 2 clinical trial (AOD-9604, the acetylated oral form) showed statistically significant weight loss vs. placebo in obese subjects, though the effect size was modest. The oral formulation AOD-9604 received GRAS (Generally Recognized As Safe) status from the FDA in 2014 for use in food products. Limitations are significant: the fragment has poor oral bioavailability in its native form (hence the AOD-9604 modification), the clinical weight loss data is modest compared to GLP-1 agonists, and research-grade injectable Frag 176-191 remains in regulatory gray zones. It does not produce the dramatic body composition changes that its in vitro lipolysis data might suggest.