Blood chemistry screening does not test for Cushings. Tests to diagnose Cushings include:
Urine Cortisol:Creatinine Ratio (screening test)
Low Dose Dexamethasone Suppression Test
ACTH Stimulation Test
Here is a good link on Cushings:
http://www.kateconnick.com/library/cushingsdisease.html
What concerns me about Cushings isn't hair loss or increased drinking/urinating or appetite increase, but other serious consequences:
"Left untreated, Cushing's disease will progress. As excess cortisol is immunosuppressive, Cushingoid dogs are prone to various infections. They are also predisposed to developing hypothyroidism, pancreatitis, diabetes, seizures, hypertension, congestive heart failure, blood clots (thromboembolism), and liver and kidney failure." - Copied from above site.
I had no idea that Cushings could cause heart failure and pulmonary hypertension until a friend's Maltese went into heart failure with severe pulmonary hypertension. My cardiologist found that the dog had undiagnosed Cushings and the pulmonary thromboemboli (blood clots) which resulted caused his heart failure and severe lung disease. The first cardiologist missed it and simply thought the heart failure was due to acquired valvular disease but the cause was actually Cushings. There have also been many dogs with kidney failure as a result of Cushings that I've known in my kidney disease yahoo group.
I understand your dilemma regarding quality of life with the SM symptoms, but (as I said earlier) I'd want to very clearly understand all of the possible ramifications of untreated Cushings since daily prednisone is likely to cause this disease. And I'd want to figure out how often to test and how to monitor. This is why long term steroid therapy is done with alternate day dosing.
Pat
It may be (I don't know her weight) that the vet feels that the dose is low enough not to be immunosuppressive - but I'd want to have a discussion about all the pros and cons.