'Shed', the word itself explains enough: these hairs you're losing are supposed to come back stronger. Unfortunately, reality is sometimes a bit different. I've been on propecia for nine months now and i seem to have lost a lot at the temples during this period. No sign of returning hairs here, except for a couple of tiny vellus/ terminal (i am not sure) at the left (=weakest) temple sprouting out/ still standing.
Then again, it totally depends on the person.