"Research finds finasteride causes penis shrinkage in rats"
>A new study in the Journal of Sexual Medicine finds that male rats receiving oral finasteride treatment for four weeks had a 25% reduction in the weight of their penis (corpora cavernosa).
Effects of oral finasteride on erectile function in a rat model:
https://pubmed.ncbi.nlm.nih.gov/22375859/

>Rodents have long been the preferred species of lab animals in biomedical research, with sporadic experiments on common brown rats stemming back 150 years. Though laboratory animal research continues to pose ethical questions, particularly with respect to animal welfare, the scientific achievements linked to lab rats are innumerous. This primarily relates to the extraordinary anatomical, genetic, and physiological similarities between humans and rodents.
https://www.kentscientific.com/blog/why-rats-used-research/

Three of forty men developed bilateral gynecomastia upon ketoconazole treatment. This appears to be a direct drug effect on breast tissue."
>Gynecomastia with Ketoconazole
https://pmc.ncbi.nlm.nih.gov/articles/PMC181611/

the results shown in rat testing suggest the need for human clinical trials. it should be highly concerning that preliminary trials show a large incidence and 25% shrinkage of penile tissue.
it's very well medically established that finasteride reduces the size of the prostate, which is also male reproductive tissue by 20%.
it's also very well established that penile tissue in humans is responsive to dht.
rodent studies are showing penile tissue (the same kind as prostate tissue) shrinks by roughly the same amount.
this is highly concerning.