. ., MT 5/1/2010 8:02:51 PM This totally sounds like Hypothyroidism. Our dog has it, and we noticed symptoms at the age of 2. He started gaining a lot of weight, then lost hair on his bottom and stomach. We noticed that he became more and more lethargic, so we were off to the Veternarian. She looked him over and then said that she would simply test his blood and see if there is anything wrong. After 20 minutes or so, she came back and said that he wasn't even on the border line of having Hypothyroidism, he had it big time. If it was not treated, he would continue to gain weight, lose hair and get more lethargic. At first, I was scared, but the Vet said that daily medicine would make him feel better in no time. It's almost been 2 years since he was diagnosed, and we have noticed that he has been doing a lot better. All in all, Hypothyroidism is just a small disorder that can be treated easily. In fact, we noticed that our dog was feeling better as soon as he took the medicine.