My lower leg hair falls out during the winter. I know it's not due to socks because I wear dress socks in the summer as well. It happens like clockwork, starting around November and coming back April-ish. But since I started taking a Vitamin D supplement (8000 IU / day) 2 months ago, my leg hair has come back to summer levels. I've never had hair like this in the winter, not even as a teenager.
I also started eating Primally around the same time so it could be due to that as well. The reason I think it'd due to the Vit D is b/c I have normal leg hair during the summer despite eating total crap. I'm almost curious enough to do an experiment (start eating crap again, keep taking vit D) to see if it really is due to the Vit D, but I don't think it's worth it.