GHK Cu Copper Peptide Neck & Face Serum GHK Cu Topical Cream 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 Helloskin GHK Cu 1% Triple Peptide Regenerative Serum Hormone Free Copper GHK+ Facial Serum with Cycloastragenol