By age 30, your skin produces about 25% less collagen. By 40, that number can reach 40%. This decline affects more than just how your skin looks. It changes how it heals, Growth Hormone and Aging Endotext NCBI Bookshelf The GHK Cu delays aging in Caenorhabditis elegans via coordinated regulation of mitochondrial function and activation of DAF 16 SKN 1 pathways Biogerontology Springer Nature Link Copper Peptide (GHK Cu): Clinical Uses, Stability & Compounding Tips Growth Hormone and Aging Endotext NCBI Bookshelf Does GHK Cu Really Work? 40 Years of Research Reviewed