Effects of GH IGF on the Aging Mitochondria Before vs. after 3 months of GHK Cu peptide therapy smoother texture, more even tone, and skin that looks healthier overall. Small peptide, big difference GHK Cu Peptide Therapy: The Definitive Clinical Guide to Gene Modulation, Protocols, and Efficacy The Effect of the Human Peptide GHK on Gene Expression Relevant to Nervous System Function and Cognitive Decline Pharmacogenomics of insulin like growth factor I generation during GH treatment in children with GH deficiency or Turner syndrome The Pharmacogenomics Journal