# GHK gene-expression claims

> GHK gene claims, examined | Bare MD Aesthetics — Bare MD Aesthetics examines the 31.2% gene-expression claim for GHK, its threshold and its distance from a cosmetic result.

Why a large molecular footprint can be fascinating while leaving the cosmetic question open.

## The threshold behind 31.2%

The [gene-data review](https://pmc.ncbi.nlm.nih.gov/articles/PMC6073405/) describes GHK-associated changes in approximately 31.2% of human genes at a threshold of 50% or greater change in expression. Gene expression concerns how actively genes are being read by cells; it is the activity being compared in this analysis.

Among the affected genes, the [review reports](https://pmc.ncbi.nlm.nih.gov/articles/PMC6073405/) increased expression for 59% and decreased expression for 41%. The underlying work draws on a gene-expression database, with cell-culture validation. I understand the excitement. A wide signature offers many possible lines of investigation, especially when tissue repair is the subject.

The leap from signature size to a desirable outcome troubles me. The percentage counts gene-expression changes at the stated threshold. It supplies no percentage improvement in skin, no measure of a person's age and no answer to which topical preparation would produce a visible effect.

## The much-repeated gene total

The [same entry's account of the gene analysis](https://pmc.ncbi.nlm.nih.gov/articles/PMC6073405/) flags the often-quoted figure of about 4,000 genes as an extrapolation. The table using the threshold of at least 50% change reports on the order of 2,100 genes.

That is the part of the story I would put in larger type. A threshold determines what enters the count. Moving between a threshold-specific table and a broader extrapolation without saying so can make a molecular result seem more settled than its description warrants.

The pathways named in the review sustain my curiosity: tissue repair, protein quality control, DNA repair and antioxidant programmes. Their names are a set of research leads. Whether changing their expression gives a particular person a desirable skin outcome remains a separate experiment.

## The age-decline argument

The [skin-regeneration review](https://pmc.ncbi.nlm.nih.gov/articles/PMC4508379/) reports plasma GHK declining from about 200 ng/mL at age 20 to about 80 ng/mL by age 60. This concerns GHK in blood plasma. It is easy to see why that observation appeals to an aesthetic imagination concerned with age.

I still need a demonstrated connection between that observation and an intervention's outcome. An age-associated difference by itself does not show that replacing a substance restores younger skin. The cited review's topical and cell-culture findings need to be assessed as their own evidence, with their own preparations and endpoints.

For a cosmetic claim, I would return to a skin measurement before borrowing the grandeur of the gene story. The [collagen studies](/collagen) are smaller in ambition and closer to the question this bulletin is asking. The gene analysis still gives me plenty of experiments to wonder about.

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I examine the material details of skin in published research at Bare MD Aesthetics, an editorial bulletin with no treatment business behind its name and no medical advice in its pages.