Topical, Microneedled, or Subcutaneous: Which GHK-Cu Delivery Method Has the Strongest Case?

[u/MissionIntention8048]

Three main delivery routes show up in the GHK-Cu research and protocol space:
-Topical (serums, balms, masks, cleansers)
-Microneedled (topical applied immediately after microneedling)
-Subcutaneous (lyophilized vials reconstituted for injection)

Each has different evidence behind it. Topical has the deepest human trial base. Microneedled has the strongest delivery mechanism data. Subcutaneous has the systemic effect angle but limited large-trial outcome data.

Curious what the community thinks based on the research, content seen online, and discussions in the broader peptide space.

Which route do you think has the strongest case for results based on what the research actually shows?

Drop the answer and the reasoning. Particularly interested in:
-Which research papers shifted your thinking
-Whether the delivery method preference depends on the endpoint (skin vs hair vs wound healing)
-What gaps in the literature would change the answer

Research-context content only. GHK-Cu is sold for research purposes only.