• Iatrogenic - Iatrogenic Cushing's Disease means that the excess of cortisone has resulted from excessive administration of cortisone. This may occur from oral or injectable medications. Although the injections or tablets were given for a legitimate medical reason, their excess is now detrimental. This situation is corrected by slowly removing the medication(s) under the supervision of a veterinarian.
• Adrenal gland tumor - Cushing's Disease may be the result of a benign or malignant tumor of the adrenal gland. If benign, surgical removal cures the disease. If malignant, surgery may help for a while, but the prognosis is less favorable than for a benign tumor. Medical therapy is not usually effective for adrenal tumors.
• Pituitary gland tumor - The most common cause of Cushing's Disease (85% of all cases) is a tumor of the pituitary gland. The tumor may be either benign or malignant. The tumor causes the pituitary to overproduce a hormone that stimulates the adrenal glands. This results in excessive cortisone secretion. The tumor may be either microscopic or quite large. Depending on the size of the tumor, the presence of signs other than Cushing's will be variable. Generally, if the activity of the adrenal gland can be controlled with medication, the dog will live a relatively normal life. Unfortunately, this is sometimes not the case and with time growth of the pituitary tumor would give the patient a less favorable prognosis.

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. A pot-bellied appearance may also develop as the muscles of the abdominal wall become weaker and liver becomes larger. 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. The primary one is the ACTH Stimulation Test. Other tests are needed to decide which form of the disease is present. These tests may include abdominal ultrasound and a dexamethasone suppression tests. Although some of these tests are somewhat expensive, they are necessary as the treatments for the different forms of this disease are quite different. Additional laboratory tests will usually be recommended at the time of initial evaluation to assess possible complications, such as urinary tract infections.

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.

• Adrenal Tumor: If an adrenal tumor is suspected, surgery is indicated to attempt to remove the tumor. Unfortunately the location of the adrenal glands makes this surgery very challenging, but our surgery service is accustomed to such challenges. If it is successful and the tumor is not malignant, there is a good chance that the dog will regain normal health.
• Pituitary Tumor: Treatment of the pituitary-induced form of Cushing's Disease is based on medical management. Because the pituitary gland cannot be removed due to its location, the drug, Lysodren™, is used to destroy the adrenal tissue’s ability to respond to the pituitary tumor. Lysodren™ is also known as mitotane. If not enough drug is used, the adrenal gland continues to produce too much cortisol and the disease continues. If too much is used, most or all of the adrenal gland may be destroyed, which can cause your dog to seriously ill and require immediate medical attention. Therefore, careful monitoring of your 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.