The Granby Animal Clinic, Inc.
CANINE CUSHING'S DISEASE
What is Cushing's Disease?
Cushing's Disease is a disease in which the adrenal glands overproduce certain hormones. Another medical term for this disease is hyperadrenocorticism.
The adrenal glands produce several vital substances which regulate a variety of body functions and are necessary to sustain life. The most widely known of these substances is cortisol, commonly known as cortisone. Either deficient production or excessive production of these substances may be life threatening.
How does this disease occur?
There are three mechanisms by which this disease can occur. Regardless of the cause, the clinical signs are essentially the same. It is important to identify the cause, however, because the various forms are treated differently and have different prognoses.
What are the clinical signs?
The most common clinical signs associated with Cushing's Disease are a tremendous increase in appetite, water consumption, and urination. Lethargy, or lack of activity, and a poor hair coat are also common. Many of these dogs develop a bloated appearance to their abdomen due to an increase of fat within the abdominal organs and a stretching of the abdominal wall as the organs get heavier. The pot-bellied appearance also develops because the muscles of the abdominal wall become weaker. Panting is another common finding with this disease.
How is it diagnosed?
A number of tests are necessary to diagnose and confirm Cushing's Disease. Some tests help to diagnose the disease, other tests help to determine what form of Cushings is present. The ACTH Stimulation Test and the Low-Dose Dexamethasone Suppression Test are frequently used to diagnose Cushings and the High-Dose Dexamthasone Test is used to determine the type of Cushings. An ultrasound examination can also be a valuable part of the testing process. Ultrasonic examination permits visualization of the adrenal glands and determines their size. Although some of these tests are somewhat expensive, they are necessary.
What are the treatment options?
· Iatrogenic Cushing's Disease: Treatment of this form requires a discontinuation of the cortisone that is being given. This must be done in a very controlled manner so that other consequences do not occur. Unfortunately, it usually results in a recurrence of the disease that was being treated by the cortisone. Because there may have been adverse effects on the adrenal glands, treatment is also needed to correct that problem.
· Adrenal Tumor. Treatment of an adrenal tumor requires major surgery. Although this surgery is dangerous to the dog, if it is successful and the tumor is not malignant, there is a good chance that the dog will regain normal health. If surgery is not an option, some of these can be well managed with the medication discussed next.
· Pituitary Tumor: Treatment of the pituitary-induced form of Cushing's Disease is the most complicated. There are two medications that are commonly used to treat Cushings. Anipryl can be used early on in the disease if no severe signs are present. If your dog has severe signs or does not respond to Anipryl, the drug, Lysodrenä, is used. The drug is used to destroy the abnormal adrenal tissue. Lysodrenä is also known as mitotane or o,p'-DDD. If not enough drug is used, the abnormal tissue persists and the disease continues. If too much is used, most or all of the adrenal cortex will be destroyed, which can be life-threatening. Therefore, careful monitoring of the dog is necessary in order to achieve good results. Because the pituitary is not being affected by the treatment, it continues to stimulate the adrenal gland. This means that continued treatment is necessary. Although a cure is not achieved, control is possible for many years if the tumor is small. If the tumor is large, local effects of the tumor invading surrounding tissues in the head can be the limiting factor in survival.