Let me start by saying that we are very saddened that our 10 yr old sheltie passed today and I am simply looking for a more definitive reason. 2 yrs ago he was diagnosed with autoimmune deficiency and hypothyroid. was placed on long term steroids and thyroid meds. seemed to immediately respond. within the last several weeks has been disoriented, aggressive, and within the last week not able to get up on his own. has been at vet since tuesday afternoon and steadily got worse. Non-responsive and sudden onset of seizures.