That is not true at all. I have been taking finasteride for years, since I noticed a little recession around my temples and a small loss of density around the front. I noticed it because I know my hair well.

The only other people that might actually be able to tell it are my parents. Except for that, every other person to whom I mention I use finasteride and minoxidil says something of the sort: "wtf, you have a full, dense head of hair, why would you take anything?".