Aesthetics Infinity Medical Institute GHK CU Beverly Hills Rejuvenation Center Copper Peptides Elmhurst IL Chicago Accelerated Aesthetics 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 vs AHK Cu: Which Copper Peptide Is More Effective?