Male Baldness Info

Hello, im 19 and i just started self medicating with Finasteride as im showing male pattern baldness ive just started off with 0.5mg I was just wondering if this stuff can cause you permanent infertility?
Also does anyone know what the best dose would be, ive read allot of different studies saying that 0.2mg is almost identical to using 5mg and others saying 1mg is the best, im not quite sure what to believee.
Thanks for the help

I am a 62-year-old male. Five years ago, I rather suddenly lost a strip of hair on one side of my head (actually starting with a patch of lost hair in the eyebrow, and extending up past the crown).
It has never come back despite treatment by a dermatologist and attention to diet, rest, combating stress, etc.
Does anyone have any ideas as to what could cause this type of hair loss, clearly unrelated to typical male pattern baldness?