Resetting Skin Genome Back to Health Naturally with GHK Springer Nature Link Copper Peptides Elmhurst IL Chicago Accelerated Aesthetics 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 GHK Cu Peptide Therapy: The Definitive Clinical Guide to Gene Modulation, Protocols, and Efficacy GHK Cu: The Peptide That Transforms Skin and Tissue Health Calibrate Hydration