TRT and 'looksmaxxing': what gym TikTok gets wrong about testosterone

What did @landenm0ree actually say?

The creator argued that topical GHK-Cu is largely blocked by the skin barrier and delivers only cosmetic, surface-level effects, while injectable GHK-Cu "bypasses the skin barrier" and offers "significantly better bioavailability" by circulating systemically to signal repairs "where it actually matters." The takeaway was clear: injections win, full stop.

To be fair, he did add a disclaimer that this is "not medical advice" and encouraged viewers to do their own research. That matters, but it does not change the fact that 11,000 people just watched a confident bioavailability comparison for a research peptide that has never completed a Phase III clinical trial in humans. The framing here is more definitive than the actual evidence supports.

Does the science back this up?

Partially, but not as cleanly as the video implies. The skin-barrier argument is real, and the bioavailability advantage of injection over topical is broadly true for most peptides. Where the video oversimplifies is in treating GHK-Cu's systemic effects as established rather than preliminary.

GHK-Cu (glycyl-L-histidyl-L-lysine copper complex) has been studied since Pickart's foundational work in the 1970s and 1980s, primarily in vitro and in animal models. Pickart and Margolina (2018, Cosmetics) summarized decades of research showing GHK-Cu's role in wound healing, collagen synthesis, and anti-inflammatory signaling, but noted most robust data comes from cell cultures and rodent studies. Human clinical trials on injected GHK-Cu are essentially nonexistent in the peer-reviewed literature. The bioavailability claim for the injectable route is pharmacologically logical, but it is extrapolated from general peptide pharmacokinetics, not GHK-Cu-specific human injection data.

Topical GHK-Cu does have some legitimate cosmetic evidence. Leyden et al. (2018, Journal of Cosmetic Dermatology) found statistically significant improvements in skin laxity and wrinkle depth with a GHK-Cu-containing cream, which the creator somewhat dismisses.

What did they get wrong (or right)?

They got the directional logic right but overstated the certainty. Saying injectable GHK-Cu "has a lot more benefits" implies a clinical comparison exists. It does not.

What they got right: the skin barrier genuinely limits peptide absorption. Research on transdermal drug delivery consistently shows that peptides above roughly 500 daltons face significant penetration challenges. GHK-Cu's molecular weight sits around 340 daltons, which is actually on the favorable side, but the copper chelation and hydrophilicity still create real absorption barriers. So "most of it never gets to where it needs to go" is a reasonable generalization, not a fabrication.

What they got wrong, or at least glossed over: the claim that injectable GHK-Cu allows it to "circulate systematically and signal repairs where it actually matters" treats GHK-Cu like an FDA-approved drug with a documented mechanism and therapeutic endpoint in humans. It does not have that. GHK-Cu is currently a research compound. Injecting it subcutaneously, particularly from unregulated compounding or gray-market sources, carries contamination and sterility risks the video never mentions. That omission matters when your audience is "gymtok."

What should you actually know?

GHK-Cu is genuinely interesting science, but it is nowhere near the finish line for human therapeutic use. The gap between "promising in cell studies" and "proven systemic benefit in injected humans" is enormous, and this video does not acknowledge that gap at all.

If you are considering any form of GHK-Cu use, a few things are worth understanding. First, topical GHK-Cu is not useless. The dismissal here is too strong. For skin-specific outcomes, topical application has more actual human trial data than the injectable route does. Second, the source of any injectable peptide matters enormously. Compounded peptides are not FDA-approved, quality varies between suppliers, and sterility cannot be assumed. Third, "systemic signaling" is a mechanism that sounds compelling but is not well characterized in humans for this compound. The in vitro and animal data on GHK-Cu's role in wound healing and angiogenesis is real and worth watching, but extrapolating that to human subcutaneous injection outcomes is a significant leap. Anyone making this decision should be doing it under the supervision of a licensed clinician, not based on a 60-second TikTok.