Also known as HGH Frag 176-191 · hGH 176-191 · Somatropin fragment 176-191
The lipolytic C-terminal fragment of human growth hormone — the parent peptide that AOD-9604 was engineered from.
Research refreshed
HGH Fragment 176-191 is a 16-amino-acid piece of human growth hormone — residues 176 to 191, the C-terminal tail that carries GH’s fat-metabolizing activity. Isolated from the rest of the hormone, it is studied for lipolysis without the growth-promoting or blood-sugar effects of full GH, and it is the direct structural parent of the engineered analog AOD-9604.
The idea behind HGH Fragment 176-191 is that growth hormone’s many effects are not all located in the same place on the molecule. Structure-activity work mapped GH’s fat-burning (lipolytic) activity to its C-terminal region, and the fragment spanning residues 176–191 was found to reproduce that effect on its own — while leaving behind the parts of GH responsible for growth signaling and the unwanted rise in blood glucose.
That makes the fragment a kind of natural experiment: a way to ask whether GH’s lipolysis can be separated from everything else it does. It is closed by a single disulfide bond between its two cysteines, and it is the peptide from which AOD-9604 was derived — AOD-9604 simply swaps the fragment’s N-terminal residue for a tyrosine to improve stability. It is a research compound and is not FDA-approved.
Proposed β3-adrenergic-mediated lipolysis; does not bind the GH receptor or raise IGF-1.
Behind every vial of HGH Fragment 176-191 is the same exacting pipeline every research peptide runs — but the chemistry plays out differently for this molecule. Here is how HGH Fragment 176-191, specifically, is brought into being.
On paper, HGH Fragment 176-191 is C78H123N23O22S2 — about 1,799.1 daltons of precisely arranged atoms. Before a single bond is made, the target sequence, salt form, and purity threshold are written down as the contract the finished material must meet.
Assembling HGH Fragment 176-191 means roughly 16 coupling cycles on the synthesizer — one protected residue added at a time, which is also 16 chances for an incomplete coupling to seed a deletion impurity. It also carries a disulfide bridge, an extra step beyond a plain chain that adds both capability and cost.
The crude mixture — HGH Fragment 176-191 plus its deletions and side products — is then separated on preparative HPLC, and where the cut is taken decides the difference between a genuinely pure peptide and a barely-passable one. HGH Fragment 176-191 carries 2 cysteines, whose thiols are oxidation-sensitive and can form disulfide links — reactive chemistry that purification has to control rather than ignore.
A real batch of HGH Fragment 176-191 proves itself: identity confirmed by mass spectrometry against its ~1,799.1 Da, purity read directly off an analytical HPLC trace, water and counterion content measured. That batch-specific certificate of analysis is the only honest way to know what is actually in a vial of HGH Fragment 176-191 — and a short, cold, accountable chain of custody is how that purity survives the trip to your bench.
The C-terminal hGH fragment (residues 176–191), made by solid-phase synthesis as a 16-residue peptide with a single disulfide loop between its two cysteines. The short chain assembles readily; forming and verifying that one disulfide correctly is the defining quality attribute — the same challenge as its analog AOD-9604.
Don't judge a vial by its cake. A fluffy, good-looking lyophilized powder reflects bulking agents and freeze-drying parameters — not purity. Insist on a batch-specific certificate of analysis.
It is a 16-amino-acid piece of human growth hormone (residues 176–191) that carries GH’s fat-metabolizing activity, studied for lipolysis without GH’s growth or blood-sugar effects.
HGH Fragment 176-191 is the parent peptide; AOD-9604 is the engineered version, differing by an added N-terminal tyrosine that improves stability.
No — the fragment is studied specifically because it reproduces GH’s lipolytic effect without binding the GH receptor or driving IGF-1.
No — it is a research compound, not FDA-approved. This page is a research and educational reference.
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