GHK-Cu has the most developed evidence base of the peptides in the GLOW and KLOW blends, and it is also the one most often described loosely. This article covers what the molecule is, why the copper matters, and what the research does and does not show.
GHK is a tripeptide made of three amino acids in sequence: glycine, L-histidine and L-lysine. On its own it is written GHK; complexed with copper(II) it is written GHK-Cu.
The copper complex is responsible for the characteristic deep blue colour of the powder. That colour is a property of the coordinated copper ion, not an additive or a dye — a useful visual check, though not a substitute for analytical identity testing.
The copper binding is not incidental. GHK's affinity for copper(II) is high, and much of the research interest concerns the complex rather than the bare peptide.
GHK was first isolated from human plasma. It is a naturally occurring molecule rather than a synthetic construct, which distinguishes it from several other compounds in this field.
Reported plasma concentrations decline with age. That observation is frequently cited as the rationale for research interest, and it is an observation rather than a demonstrated mechanism of anything.
Research attention centres on interactions with components of the extracellular matrix — the structural scaffold surrounding cells — and on copper transport.
A substantial portion of the work is in cell culture. There is also a body of topical formulation research, where GHK-Cu appears as an active in cosmetic preparations and the questions concern stability, delivery through the skin barrier and formulation compatibility.
That topical context is worth noting because it is where most of the practical work has been done, and conclusions from it do not automatically transfer to other routes or contexts.
Two properties matter in practical laboratory work.
GHK-Cu is not a licensed medicine in the United Kingdom. Its appearance in cosmetic formulations is a distinct regulatory position from any medicinal use and should not be read as approval for one.
Claims about systemic effects extend well beyond the in-vitro and topical literature that makes up most of the evidence base. Where you see such claims, check what route and what model the cited work actually used.
This article is reference material describing published research. It is not medical advice, not a therapeutic claim, and contains no dosing or administration guidance.