OBM Geriatrics The Effect of the Human Plasma Molecule GHK Cu on Stem Cell Actions and Expression of Relevant Genes 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 Frontiers Exploring the beneficial effects of GHK Cu on an experimental model of colitis and the underlying mechanisms GHK Cu vs AHK Cu: Which Copper Peptide Is More Effective? The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline GHK Cu as a multifunctional copper peptide: synthesis routes, process engineering and emerging applications Systems Microbiology and Biomanufacturing Springer Nature Link