There's a lot of enthusiasm in peptide communities and a lot of motivated reasoning. Here's a framework I use for evaluating any peptide claim for enhancement:
Is there a plausible biological mechanism? (Does the peptide interact with receptors or pathways that could produce the claimed effect in the target tissue?)
What's the evidence quality? (Cell culture
Is the target tissue actually responsive? (A peptide that causes muscle growth doesn't automatically cause penile tissue growth — different receptor expression.)
What are the delivery challenges? (Topical absorption, peptide degradation in GI tract, local vs systemic distribution all affect whether the active compound reaches the target tissue.)
What's the risk profile? (GHK-Cu topical: very safe. IGF-1 systemic: significant risk. Know what you're working with.)
Apply this framework and most enhancement peptide claims survive step 1 but struggle at step 2 or 3.
— SkepticalScienceSteve