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 The tripeptide GHKCu complex ameliorates lipopolysaccharideinduced acute lung injury in mice Oncotarget Expression and Purification of Recombinant GHK Tripeptides Are Able to Protect against Acute Cardiotoxicity from Exposure to Waterborne Copper in Zebrafish Synergy of GHKCu and hyaluronic acid on collagen IV upregulation via fibroblast and exvivo skin tests Jiang 2023 Journal of Cosmetic Dermatology Wiley Online Library GHK Cu: The Regenerative Peptide for Skin, Hair, and Healing Pulse & Remedy