Fragment 176–191

Fragment 176–191 refers to a C-terminal segment of human growth hormone marketed through research-peptide and wellness channels for fat loss. AOD-9604 is a closely related engineered compound with an added stabilizing amino acid. Although vendors often conflate the names, the modified compound and the unmodified fragment are distinct evidence subjects.

The hypothesis is that growth hormone’s fat-storage effects can be isolated in its tail without reproducing the full hormone’s growth or glucose effects. Rat work located anti-lipogenic activity in the C-terminal region. The tested hGH 177–191 peptide, a close relative rather than exactly the marketed 176–191 fragment, matched whole growth hormone’s anti-lipogenic activity in the rat-fat-pad experiment reported by Wu and Ng in 1993, but did not significantly stimulate lipolysis. This comparison concerned inhibition of fat storage in animal tissue, rather than human weight loss.

More detailed experimental findings concern AOD-9604. In obese Zucker rats, it reduced weight gain by more than 50% over 19 days and increased adipose lipolysis without the insulin-sensitivity impairment seen with intact growth hormone. In obese mice it increased fat oxidation and circulating glycerol, did not compete at the growth-hormone receptor and did not stimulate cell proliferation. Those AOD findings are not human proof for the unmodified fragment.

Fragment 176–191 has no FDA-approved drug or recognized compounding status in the published account and is sold as a gray-market research chemical. Metabolic Pharmaceuticals’ AOD-9604 obesity program ended in 2007 after insufficient efficacy. Growth-hormone fragments, including hGH 176–191, are prohibited at all times under WADA rules.

No controlled human fat-loss trial of the bare fragment is described in these reports. Its rationale rests on laboratory and animal work. The nearest human obesity data concern AOD-9604:

The later negative result limits the case for this related development program. Neither trial establishes benefit, a clinical dose or safety for unmodified Fragment 176–191.