Cushings disease is most commonly diagnosed with blood work. A cbc/chemistry and what is called a low dose dexamethasone suppression test. Cushings disease is an over production of cortisone from the adrenal gland or the pituitary.
A sonogram can be helpful in identifing an adrenal tumor.
A high dose dexamethasone suppression test can be done after the low dose to help identify origin (adrenal or pituitary.) If the tumor is adrenal, sometimes it can be removed surgically. Pituitary tumors are usually not removed and are treated with medications. The newest medication being used is not FDA approved in the USA. It had been used widely overseas and is also used here.The medication is called trilostane. It is the safest treatment with the fewest side effects. Most symptoms of the disease will resolve within 2 months of starting the medication. The medication is used long term. periodic blood work is done while on trilostane to monitor Sodium and potassium levels to make sure that they are not being adversly effected. (that could cause Addisons disease- where cortisone levels are too low) However, should this happen, this will usually resolve once the trilostane is stopped. Symptoms of cushings disease are usually but not limited to :an increase in thirst and urination,
increased appetite, bloated pot belly look, increased panting, fur thinning on the torso.

hope this was helpful to you. please let me know if I can answer anyting else for you. best of luck