I never realized that it could possibly be the mirena, but this was one of my worst symptoms. I also had "spots" and always lots of hair "shedding" everywhere. I was also diagnosed with alopecia areata. Got a few shots and was told that it was due to stress. (What isn't?)
I had the Mirena taken out in September and since then no spots. I also switched to no Sodium Laurel Sulfate shampoos. (Look in the natural health section). Hair is growing back very nicely and can comb and wash hair with no falling out!!