Cushing’s disease is an overproduction of steroids by the adrenal glands. The most common breeds to develop Cushing’s disease are poodles, dachshunds, beagles, boxers, and terrier breeds. Steriods are produced by the adrenal glands which are small glands that are located near the kidneys. The adrenal glands are told to produce steroids by a small gland at the base of the brain called the pituitary gland. The signaling hormone is called ACTH (See figure). The majority of dogs (80%) have an enlargement of the pituitary gland which excretes too much ACTH. This signals the adrenal glands to produce excessive steroids. The enlargement of the pituitary gland is benign and will not spread though in a small percentage of dogs it will become large enough to cause neurologic problems. In 20% of dogs (and usually larger breeds of dogs) there will be a tumor on the adrenal gland. 50% of these tumors are benign and 50% are malignant (cancers that will spread).
The most common symptoms associated with Cushing’s disease are increased drinking and urinations, panting, exercise intolerance or lethargy, increased appetite, pot bellied appearance, muscle wasting, and hair loss. Not all patients have every symptom and a number of these symptoms can be associated with other diseases. So if your pet is having any of these symptoms it is important to talk to your veterinarian about the symptoms to find out if Cushing’s disease is a possibility.
There are several tests that your veterinarian can do to diagnose Cushing’s disease including a 1 hour stimulation blood test, and urine test, and an 8 hr blood test. Once a diagnosis is made then it is important to determine if it is adrenal or pituitary associated. This can be done with an abdominal ultrasound or an 8 hour blood test.
Once you have a diagnosis a therapeutic protocol can be put into place. The recommend therapy for adrenal tumors is surgery. For pituitary associated Cushing’s there are several medications available. The two most commonly used are Lysodren and Trilostane. You should discuss with your doctor which of these medications would be best for your pet.
Cushing’s disease often severely affects the quality of life of the pet and the owner. Obtaining a diagnosis and then following through with therapy is one way that you can help your pet live the fullest life possible.
Article Brought To You By Heidi Allen, DVM, DACVIM