I'm curious about the science on shedding. I don't mean why it happens, but whether there are known variances in its occurrence or the intensity of its occurrence depending on identifiable variances in subjects.
OP - what is your Norwood? How was your hair before you started propecia? Were you shedding before?
I started propecia two weeks ago and my results are the opposite. I was shedding massively before I went on propecia, and once I did, the shedding stopped. However, I would guess that the following could be the case:
I think I'm a Norwood 2.5/3 (not sure exactly), with all of my loss concentrated on the hairline and vertex. I had a huge "balding" shed right before I started to take propecia, and so lost a lot of the hairs that would have been shed once I started on propecia. Consequently, there may not be a whole lot of hairs left at the moment to go through a shedding cycle, which will probably come in a few months for me, if any of those lost hairs are coaxed into trying to come back.
It may even be better to have shedding at the beginning, as it might signal that you're going to save most of those hairs.
[*NB: the above is pure speculation, not based on any research*]