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 University of Washington Study: Natural Molecule Counters Sleep Deprivation's Impact on Learning and Memory NMN Copper Tripeptide 1 (GHK Cu): The Premier Anti Aging Ingredient for Skincare Formulators Titan Biotech Ltd. Sublingual GHK Cu TruHealth Physical Therapy The glycyl l histidyl l lysine Cu2+ tripeptide complex attenuates lung inflammation and fibrosis in silicosis by targeting peroxiredoxin 6 ScienceDirect