Defy GHK Cu (glycyl L histidyl L lysine) is a naturally occurring copper binding peptide found in human plasma. As levels decline with age, so may its support of the biological processes involved in collagen production, skin GHK Cu Peptide Therapy: The Definitive Clinical Guide to Gene Modulation, Protocols, and Efficacy GHK Cu in the NAD+ Push Patch: A Smarter Way to Stimulate Collagen, He Hi, Finch GHK Cu Peptides: Unlocking the Copper Peptide Revolution in Skin Care