sudden weight loss - toy poodle

Question
we have two toy poodles - butch and sandance, both just over 8 years old.  butch has lost about 2 lbs on his formerly 9-lb. frame within the the last two months.  the vet has checked his thyroid and found his numbers to be low.  she also tested a fecal sample which came back negative for worms.  his senior dog blood tests came back normal, except his white cell count is slightly higher.  his appetite has increased.  other than sudden weight loss and increased appetite, butch has high energy, lively (and lovely!) personality, is his usual adorable self -- he's just wasting away, and we're very anxioius about it.  our vet took another sample of blood and sent it to a lab in california for a more extensive test for thyroid disorder, and we're awaiting those results.  my husband and i are very anxious and very puzzled.  have you ever seen anything like this?  can you offer guidance about what might be causing this sudden weight loss?

Answer
There are many, many things that can cause weight loss in a dog.
Mysthenia gravis for one, addisons disease, hyperthroidism (rare),Pancreatic acinar atrophy and cancers. I am not sure why the vet is zeroing in on the thryoid but low thyroid causes weight gain, not weight loss. I think that if you are not getting the answers you want that you should seek a second opinion and do it soon. Too much body mass loss is hard to recover from.
The higher white blood count is a red flag in this case as it can indicate that the body is trying to fight off something inside.
Has he had any scans done for tumors? These usually are the cause of weight loss in other unexplained scenarios and you don't want to wait to long to find out if that is what he has.

I hope you can get some answers soon. Please keep me posted.