Dear Dr. Thompson: We have the sweetest 10-year-old medium-sized mixed breed dog that has recently been diagnosed with Cushing's disease. The vet administered blood tests in order to diagnose her symptoms and determined in March that her adrenal gland was responsible for the Cushing's. We began giving her Selegiline in March and increased the dosage last week. I am aware that it can take a few months to see improvement, but she is getting much worse. Can you offer any advice?
ANSWER: In Cushing's disease, the body overproduces the stress hormone cortisol. The resulting symptoms are all directly related to the excess of that hormone. The majority of cases involve a benign growth in the pituitary gland located in the bottom of the brain that sends excessive signals to the adrenal gland.
However, you mentioned that the blood tests suggested the primary problem is the adrenal gland. This is less common but carries a poorer prognosis becase it is usually a malignant growth overproducing the hormone. Blood tests are not foolproof in this regard and an ultrasound could help find a tumor.
Selegine showed some initial promise for dogs with the pituitary-dependent form when it was introduced years ago, but now it seems that only a small percentage of dogs respond to the medication. Lysodren has been the mainstay for treatment, but can be tricky at the outset due to side effects that can develop. Trilostane has been used for years in Europe to treat this disease and has recently been approved in the United States under the name Vetoryl. It is well-tolerated and is a very good option for smaller dogs to manage the disease. Ask your veterinarian which would be right for you.