AOD-9604 vs HGH Fragment 176-191: Same Region, Different Names

Few compound pairs cause as much confusion as these two. Some sources treat them as rivals, others as the same thing under two labels. The clearest way to sort it out is to go back to where the fragment came from and what each name was meant to describe.

The C-terminal region of growth hormone

Human growth hormone is a 191-amino-acid protein. Most of its growth-promoting activity depends on binding the growth hormone receptor, which involves large surfaces of the folded protein. In the 1990s, researchers at Monash University in Australia investigated whether a small piece from the very end of the chain, roughly residues 176 to 191, could account for growth hormone’s effects on fat metabolism on its own.

That stretch contains two cysteines, at positions 182 and 189 in the parent protein, which form a disulfide bond and close the fragment into a small loop. In rodent studies, synthetic versions of this region stimulated lipolysis and reduced lipogenesis in fat tissue without the receptor binding that drives growth.

Where the AOD-9604 name comes from

AOD-9604 is the development code given to one specific version of that fragment: the 177-191 sequence with a tyrosine added at the N-terminal end. The added tyrosine sits where residue 176 would be, so the finished peptide spans the same 16 positions as “fragment 176-191”. This is why many suppliers list the two names with the same amino-acid sequence.

The name AOD-9604 is tied to the development program and its published animal work, such as the 2001 Endocrinology study by Heffernan and colleagues in obese mice. “Fragment 176-191” is a descriptive label for the region itself, and it is used more loosely across the market.

So what actually differs?

When two products carry these names, the meaningful differences, if any, tend to show up in the details rather than the headline:

• Residue at position one. Check whether the sequence begins with tyrosine (Y). That is the defining feature of AOD-9604.
• Disulfide bond. The cysteine pair can be present as a closed loop or as free thiols. The two forms have slightly different masses.
• C-terminal form. Whether the end is a free acid or an amide changes the molecular weight by about one dalton.
• Counter-ion and peptide content. Salt form affects how much of the powder is actually peptide. Our article on net peptide content explains why.

What preclinical work has looked at

Published research on this fragment has focused on fat metabolism in rodents: lipolysis in isolated adipocytes, fat mass in diet-induced obese mice, and whether the effects depend on β3-adrenergic receptors. A recurring finding is that the fragment does not raise IGF-1 the way intact growth hormone does, which is why it became a tool for separating growth hormone’s metabolic effects from its growth effects.

That separation is the main reason labs choose it. If your question is about adipocyte metabolism and you want to exclude the growth hormone receptor and IGF-1 signalling, a C-terminal fragment gives you a way to ask it.

A quick verification checklist

Keeping it in scope

The research described here is preclinical and mechanistic. It does not describe effects in people, and Resolve materials are for laboratory research only. Current lot documentation for AOD-9604 is on the COA / Lab Reports page, and the Research Use Only policy sets out how our materials may be used.