Hi- I had the Mirena from May 07-Nov 09 and suffered a lot of hair loss during that period, as well as numerous other symptoms. As soon as I realised what was causing all of my problems I had the Mirena removed and thankfully I haven't suffered from hair loss since.
I agree with some of the other posters that problems with the Mirena are caused by silicone in the device- as many of my symptoms were exactly the same as those of silicone poisoning.