Procollagen responses in treated subjects
This percentage describes people with a recorded response. I want that subject left visible.
The reported proportions
A review of topical GHK reports increased procollagen synthesis in 70% of GHK-Cu-treated subjects, versus 50% for vitamin C and 40% for retinoic acid. Procollagen is a precursor in collagen production. These are proportions of subjects with an increase in synthesis.
I appreciate a human measurement with a biological subject. But the sentence becomes a different claim if the proportion of people responding is retold as the size of their improvement. The reported proportions provide no basis for calling this a 70% reduction in wrinkles.
Those distinctions can sound fussy until a number starts travelling. A percentage needs something to be a percentage of. Here that something is the group of treated subjects, classified by a synthesis response.
Permeability and modification
The review also identifies poor stratum-corneum permeability as a central challenge for topical GHK. It evaluates palmitoylation, a chemical modification, and microneedle pretreatment as delivery strategies. The topic has more moving parts than a peptide name suggests.
Preparation and outcome both deserve some of that excitement. I favour connecting the human outcome as closely as possible to the substance that reached the relevant tissue. That is a request for a more complete explanation, not a reason to discard the finding.
A separate human endpoint
The hair-count trial gives another human endpoint and another preparation: a combination of GHK with 5-aminolevulinic acid. The count concerns hair, and the preparation contains both ingredients. I leave those differences standing, even when a peptide name is shared.
These papers give my curiosity both room and boundaries. A broad molecular signal can occupy the imagination while a modestly framed human finding gives it a much more exact question to answer.