Most authorities agree that Cushing’s should not be treated unless the dog is displaying clinical signs of disease. Once that happens, the treatment protocol will depend upon which of the three forms of the disease is present.
Iatrogenic Cushing’s disease is caused by excessive or prolonged administration of corticosteroid drugs. This form of Cushing’s can be treated, and usually cured, by tapering and slowly weaning the animal off of these medications, if possible.
Naturally occurring Cushing’s disease, which is caused by functional tumors on either the adrenal or pituitary glands, can only be treated through surgery or with life-long medication. Adrenal tumors normally require surgical removal, which is highly effective unless the tumors have metastasized. Unfortunately, few of the naturally occurring Cushing’s cases are caused by adrenal tumors. The majority of dogs with Cushing’s have tumors on their pituitary gland. At the present time, pituitary tumors are not normally removable surgically.
Medical treatments for Cushing’s disease are available, although the protocols are complex. Certain drugs, including Mitotane (Lysodren), Ketoconazole, L-Deprenyl (Anipryl) and Trilostane (Vetoryl), have been used to treat Cushing’s with varied success, by suppressing production of corticosteroids. Each of these drugs can carry serious adverse side effects, and most can be administered only under a veterinarian’s strict supervision. Blood tests should be run periodically to ensure that any chemotherapy is not causing or contributing to other medical problems. Despite the risk of side effects, supervised medical treatment options can improve and prolong the quality of life for dogs affected by Cushing’s disease. Radiation may also be an option in some cases.
The prognosis for dogs with Cushing’s disease is variable. If an adrenal tumor is the underlying cause of the condition and can be successfully removed, the prognosis is quite good. However, if a pituitary tumor is involved and the only treatment is chemotherapy, the prognosis is guarded.