GHK Cu is the compound your body made at 25 and quietly stopped making. Most people find it in overpriced serums. Few understand what it actually does, or what happens when you're not GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? Selected Biomarkers Revealed Potential Skin Toxicity Caused by Certain Copper Compounds Scientific Reports GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link