I went to a doctor about my hair thinning and she said I had miniaturization

What I want to know is if this can be reversed with Propecia and if it can, how long will it take.  I am 22 years old. 

Advanced miniaturization often does not reverse, but early miniaturization is what finasteride works best on. When it works well, it is usually in a male under 26 years of age. That means you are a good candidate for real benefit. It generally takes about one year to see the value of this drug.