My dog was just diagnosed with hypothyroidism. She is a terrier mix and is only mildly aggressive if there are treats around, etc. However, the vet explained to me that many, many times when something like what happened to Roxy occurs, it could very well be a case of hypothyroidism. GSD's, Rotties, Goldens are all predisposed apparently. I really hope everyone will be ok. You will all be in my thoughts.