Does GHK Cu Really Work? 40 Years of Research Reviewed Growth Hormone and Aging Endotext NCBI Bookshelf GHK Cu Copper Peptide Therapy for Skin & Hair in Southlake, TX 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 naturally occurring peptide GHK reverses age related fibrosis by modulating myofibroblast function He Aging Pathobiology and Therapeutics