It requires significant energy and oxygen to function, which makes it a primary site for the production of reactive oxygen species (ROS)
Delivery enhancers: Microneedle pretreatment increased GHK-Cu penetration in a preclinical study (PubMed)
That decline is part of why GHK-Cu became a target for skin, hair, and wound-healing research
Miczke A, Szuliska M, Hansdorfer-Korzon R, Krgielska-Narona M, Suliburska J, Walkowiak J, Bogdaski P (2016) Effects of Spirulina consumption on body weight, blood pressure, and endothelial function in overweight hypertensive Caucasians : a double-blind, placebo-controlled, randomized trial
Jarosiewicz et al
Biomarkers and Clinical Evidence for Glutathione Status Clinical assessment of glutathione utility relies on biomarkers of oxidative stress and antioxidant capacity