How Does Finasteride Work?

I am a medical student and was wondering how finasteride works to give people a fuller appearance of hair.

In the Journal of the American Academy of Dermatology July 2006, Volume 55, Dr. Vera Price summarized the action of finasteride as follows:

“Long-term finasteride treatment led to sustained improvement in hair weight compared with placebo. Hair weight increased to a larger extent than hair count, implying that factors other than the number of hairs, such as increased growth rate (length) and thickness of hairs, contribute to the beneficial effects of finasteride in treated men.”

This is important, because what she implies is that the miniaturized hairs reverse. That is why it is so important to map out the scalp for miniaturization and to perform bulk measurements with the HAIRCHECK instrument. These two approaches used prior to starting finasteride (Propecia) gives us a baseline metric to determine the value of the treatment. I have seen people with miniaturization in the 80% range, reduce substantially to almost normal levels (under 20%). This is why everyone taking finasteride should be evaluated prior to starting the treatment by a doctor who understands this process clearly.