GHK Cu vs NAD+: Which Longevity Peptide Should You Take or Stack? The somatostatin secreting pancreatic cell in health and disease Nature Reviews Endocrinology You started using a GHK Cu peptide serum on your face and now , The things no one tells you., Yes, the injections can hurt like a bitch. , Heres the thing Ive found it works even better topically, GHK CU Soma Chems Thermodynamically stable ionic liquid microemulsions pioneer pathways for topical delivery and peptide application ScienceDirect