GHK Cu Peptide: Mechanism, Anti Aging Research, and Regenerative Benefits PDF) The Effect of the Human Plasma Molecule GHK Cu on Stem Cell Actions and Expression of Relevant Genes 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 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