GHK-Cu

GHK is a three–amino-acid sequence (glycine-histidine-lysine) that binds copper, forming the GHK-Cu complex. Levels fall with age. In lab and skin studies it appears to stimulate collagen, elastin, and glycosaminoglycan synthesis, support wound healing, and modulate thousands of genes involved in tissue remodeling and repair. Most evidence concerns the skin because that is where it has actually been applied in people.

GHK-Cu has more human data than the rest of this cluster, but with important caveats: the human studies are predominantly small, topical, cosmetic trials — often industry-adjacent — measuring skin appearance and firmness rather than the deep tissue, tendon, or systemic outcomes some users seek. Injectable use is essentially unstudied in humans. So the honest grade is "real but narrow" human evidence for skin, and little to nothing for the bigger regenerative claims.

• Improved skin firmness, elasticity, and appearance in topical cosmetic trials
• Stimulation of collagen and glycosaminoglycan synthesis in skin studies
• Wound-healing and tissue-remodeling activity in lab and animal models
• Antioxidant and anti-inflammatory gene-modulating effects in vitro

• Human evidence is mostly topical and cosmetic — systemic/injectable use is unstudied
• Copper exposure from high or injected doses is a theoretical safety concern
• Many positive studies are small or industry-linked
• Topical irritation possible in sensitive individuals

OTC supplement. Sold over the counter as a dietary supplement or cosmetic ingredient.

Goals studied: Skin anti-aging, Tendon & ligament repair

Does GHK-Cu actually have human evidence?

Yes, more than most peptides in this cluster — but it is mostly small topical cosmetic studies on skin appearance, not trials of deep-tissue or systemic regeneration.

Is topical or injectable GHK-Cu better studied?

Topical, by a wide margin. Injectable GHK-Cu is essentially unstudied in humans, so the safety and efficacy of that route are unknown.

1. [1]
   Regenerative and Protective Actions of the GHK-Cu Peptide in the Light of the New Gene Data

   Pickart L, Margolina A · International Journal of Molecular Sciences · 2018 · PMID 29986520 · model: in-vitro

   Revue documentant la modulation par le GHK-Cu de milliers de gènes humains liés à la réparation tissulaire et à la défense antioxydante.

2. [2]
   GHK Peptide as a Natural Modulator of Multiple Cellular Pathways in Skin Regeneration

   Pickart L, Vasquez-Soltero JM, Margolina A · BioMed Research International · 2015 · PMID 26236730 · model: in-vitro

   Revue des effets du GHK sur le collagène, les fibroblastes et les voies de réparation cutanée à concentrations nanomolaires.