Copper peptide GHK Cu Wikipedia GHK Cu Peptide Therapy: The Definitive Clinical Guide to Gene Modulation, Protocols, and Efficacy GHK Cu is a naturally occurring tripeptide in human plasma. Levels average 200 ng ml at age 20 and drop to 80 ng ml by age 60 (Pickart et al., 2020). That decline tracks with Your body made this peptide every day until you turned 30. Then it stopped. GHK Cu (copper peptide) is a naturally occurring tripeptide discovered in 1973. At age 20, your plasma levels sit