HGH Fragment 176-191

In the early 1990s, Frank Ng's group at Monash established that the fat-related actions of growth hormone could be reproduced by a short synthetic peptide of its C-terminal sequence, residues 177-191: it was antilipogenic in fat tissue [3], it altered glucose transport in rat fat cells [5], and given chronically to obese mice it reduced cumulative body weight gain and adipose mass [1].

That is essentially the whole case for this peptide, and it is the same body of work that underpins AOD-9604, which is this fragment with an N-terminal tyrosine attached for stability. The later and better-documented experiments — 30 days of oral dosing in ob/ob mice with reduced weight gain, increased lipolysis and increased energy expenditure; loss of the chronic effect in beta-3 adrenergic receptor knockout mice — were done on the tyrosinated form [2][6]. Findings for one are routinely quoted for the other.

Why it is interesting in principle. Growth hormone mobilises fat, but it also raises IGF-1, causes fluid retention and worsens insulin sensitivity. If the fat-mobilising activity lives in a separable domain, a peptide of that domain should give the first without the rest. In animals it does [3].

Why that is not enough. No human trial of hGH fragment 176-191 has been published, for weight, fat, or anything else. The only human material in this literature is isolated adipose tissue [2]. A 2026 review of the peptides sold for physique purposes places this fragment among those with no human evidence [4]. A related caution sits in the oldest papers: synthetic peptides from this region of growth hormone have a hyperglycaemic action of their own in animals [7].

The fragment acts on fat cells, increasing lipolysis and suppressing lipogenesis [2][3]. Both growth hormone and this fragment restore the suppressed expression of the beta-3 adrenergic receptor — the main lipolytic receptor on fat cells — in obese mice, which would be a tidy explanation. But in beta-3 knockout mice the chronic weight and lipolysis effects disappear while an acute dose still raises energy expenditure and fat oxidation, so the peptide is not acting directly through that receptor [6].

No receptor for the fragment has been identified. The mechanism, three decades on, is a set of observed effects on fat tissue without a target.

The peptide is residues 176-191 of human growth hormone — 15 amino acids, including the disulfide-closed loop of the parent hormone [3]. The variant with an N-terminal tyrosine is AOD-9604. Sellers use the two names loosely, and some products labelled as one contain the other; there is no way to tell from a label. Peptides of this size are detectable in doping control [8].

No human safety data exist, because no human study has been published. The animal work reports no toxicity but was not designed to look for it [1][2].

Two things in the preclinical literature are worth carrying forward: peptides from this region of growth hormone raise blood glucose in animals [7], and the fragment changes glucose transport in fat cells [5]. Neither has been examined in people. A 2026 clinical review of this class notes that products bought outside a pharmacy frequently do not match their labels, which is a separate and more immediate risk [4].

No interaction data in humans or animals for this fragment. No interactions with other compounds on this site have been documented.