Cushing's Disease is a condition in which the adrenal glands overproduce certain hormones. The 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. Decreased or excessive production of these substances may be life-threatening.
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 type of Cushing’s Disease because the various forms are treated differently and have different prognoses.
The most common clinical signs associated with Cushing's Disease are an 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.
A number of tests are necessary to diagnose and confirm Cushing's Disease. The two most common tests to detect Cushing’s Disease are the ACTH Stimulation Test and the Low-Dose Dexamethasone Suppression Test. Other tests are needed to decide which form of the disease is present. An ultrasound examination can be a valuable part of the testing process. This permits visualization of the adrenal glands and determines their size and the presence of a tumor. Although some of these tests are somewhat expensive, they are necessary.
Iatrogenic Cushing's Disease: Treatment of this form requires a discontinuation of the steroid that is being given. This must be done in a very controlled manner so that other complications do not occur. Unfortunately, it usually results in a recurrence of the disease that was being treated by the steroid. 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 is a high risk surgery, if 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 patients can be 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 drugs commonly used: Anipryl and Lysodren™. Anipryl is the only drug approved by the FDA to treat canine Cushing’s Disease. Anipryl is given daily and has little, if any, side effects. Few blood tests are required when using this medication. Anipryl works directly on the pituitary gland, helping produce more of the hormones that may be diminished with Cushing’s Disease. Most pets with uncomplicated Cushing’s Disease (no complications such as diabetes mellitus, etc.) can be treated with Anipryl and most clinical signs will resolve. If a pet does not improve after two to three months of Anipryl therapy, Lysodren™ therapy is often recommended.
Lysodren™ is the primary drug used to destroy the abnormal adrenal gland tissue. Lysodren™ 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 with either treatment, 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 brain can be the limiting factor in survival.
Treatment of this form involves an initiating phase and a maintenance phase. The initiating phase arrests the disease and restores the dog to a more normal state. Some of the clinical signs, especially increased food and water intake, should stop within the first 1-3 weeks. Other signs, such as a poor hair coat or a bloated abdomen, may take several weeks or months to correct. The maintenance phase represents the phase of long-term therapy. This phase lasts the rest of the dog's life.
You must continually monitor your dog's food and water intake. We expect both to return to a normal level. Water intake should be less than 1 oz per pound (66 cc per kilogram) of body weight per day, but don't limit the water if your dog needs to drink more. Your dog should drink _________________ ounces (__________cc) per day. The amount of food should also be measured each day. At least two feedings per day are preferred.
When regulated, your dog will take Lysodren™ approximately once weekly. An ACTH stimulation test will be necessary about every 3-4 months to be sure that regulation is satisfactory. At the appropriate time, the specifics of the maintenance phase will be explained.
Give _________ tablet(s) every ________ days.
This client information sheet is based on material written by Ernest E. Ward Jr., DVM. © Copyright 2002 Lifelearn Inc. Used with permission under license. May 1, 2018.