Article showing reduction of DHT in scalp from finasteride at different doses

https://pubmed.ncbi.nlm.nih.gov/10495374/

https://www.sciencedirect.com/science/article/pii/S0022202X15529357

Both of these articles show the relationship between finasteride and the dose as it impacts the skin concentrations of finasteride.  Of course we want to know how much finasteride is getting to our hair follicles, so it is surprising that low doses are getting significant levels of drug at the hair follicle levels