correct but it will help you to keep the reamining and in part re-thicken your lost hair.
the term losing hair is not correct; the hair that you are losing they would have fallen anyway; the gear is just accelerating the process (defluvium). Once you lose your hair always other hair replace the lost one ; the difference between normal people and people prone to hairloss is that the hair that replace your lost hair are gradually more thin and this process continue until the follicle stop producing them.
So although propecia will not work immediately will help you to make thicker the hair that will replace your lost one.