It mainly depends of your genetics, for instance me no men in my family is bald even at 80 years old, which makes no effect for my hair, I take it wihout Proscar and any help without problem, if youre 25 and your hair alrready started thinning out and you havent yet took any anabolics like dbol, test and many other it will simply speed the process.. It doesnt make it happen on its own though.