Cushing's disease can occur in various species of animals but it is most commonly seen in dogs. This disease affects the adrenal glands which are part of the endocrine system. If left untreated, this disease can be life threatening so it's vital for dog owners to recognize the signs and know what kind of treatment their pets may require.
What Is Cushing's Disease in Dogs?
Cushing's disease is also known as Cushing's syndrome and hyperadrenocorticism. It is a disease that affects the adrenal glands of a dog and results in an overproduction of a natural steroid called cortisol or cortisone. Cortisol is the body's main stress hormone and affects most cells. It does a variety of different things including playing a role in regulating blood sugar levels, reducing inflammation, and controlling blood pressure, just to name a few. Cortisol is even responsible for the body's "fight or flight" response. If too much cortisol is produced, multiple systems in a dog's body are unable to work properly. Addison's disease is the opposite of Cushing's disease.
Since Cushing's disease affects a multitude of bodily systems, various signs of this disease may be seen.
Signs of Cushing's Disease in Dogs
- Increased thirst
- Increased urination
- Increased appetite
- Thinning hair coat
- Thinning, fragile skin
- Lack of energy
- Excessive panting
- Skin infections
- Pot-belly appearance
Dogs with Cushing's disease often appear as though they have a distended abdomen or pot-bellied appearance and are losing their fur. These symptoms are seen in many dogs with Cushing's disease but an increase in thirst and urination are also commonly observed. Frequently emptied water bowls and urinary accidents in the house are indications of these symptoms.
Some dogs with Cushing's will also have an increase in appetite, a decrease in energy, and excessively pant for no apparent reason. Finally, thin skin that is sometimes compared to tissue paper alongside reoccurent skin infections may be seen in dogs with Cushing's disease. Excessive cortisol levels in a dog can cause all of these visible changes and issues.
Causes of Cushing's Disease in Dogs
There are three causes of Cushing's disease in dogs.
- Pituitary Gland Tumor - The pituitary gland stimulates the adrenal glands to produce cortisol so if there is a tumor on the pituitary, it may tell the adrenal glands to make too much of this natural steroid. This is called pituitary-dependent Cushing's disease and is the most common type of Cushing's disease.
- Adrenal Gland Tumor - If a tumor develops on one or both adrenal glands, it may produce too much cortisol resulting in Cushing's disease. This is called adrenal-dependent Cushing's disease.
- Prolonged Steroid Use - If steroids are taken regularly and for a long period of time to manage things like allergies and other issues, they can cause issues with the adrenal glands. This is called iatrogenic Cushing's disease.
Diagnosing Cushing's Disease in Dogs
Your veterinarian will perform a full physical examination and obtain a medical history on your dog. If Cushing's disease is suspected, blood work will be run. Specific blood tests called ACTH stimulation and low-dose dexamethasone suppression (LDDS) tests are performed to check for Cushing's disease in addition to a routine complete blood count (CBC) and chemistry profile to check organ function and to rule out other diseases. These blood tests will tell your veterinarian how well the adrenal glands are working but other tests may need to be done to confirm what type of Cushing's disease your dog has. Checking endogenous ACTH levels, and performing a high-dose dexamethasone suppression (HDDS) test, a urine cortisol:creatinine ratio, or a 17-hydroxyprogesterone response to ACTH administration test may also be neeeded to determine if your dog has adrenal-dependent or pituitary-dependent Cushing's disease. Finally, an abdominal ultrasound may be recommended in order to visualize your dog's adrenal glands.
Treatment of Cushing's Disease in Dogs
If the Cushing's disease is diagnosed as being pituitary-dependent, lifelong oral medications will need to be given. Trilostane (Vetoryl®) and mitotane (Lysodren®) are two drugs that are commonly used to treat pituitary-dependent Cushing's disease in dogs.
If the Cushing's disease is diagnosed as being adrenal-dependent, surgery to remove the tumor may be recommended. If the entire tumor is able to be removed surgically, most dogs return to normal without lifelong medications. If the tumor is not able to be surgically removed, some dogs may be able to be managed with medications.
Iatrogenic Cushing's disease will require a discontinuation of the steroids that have been given. This needs to occur slowly so as to not cause further issues but the disease that was being treated by the steroids often reoccurs. This then warrants not only management of the disease that was previously being treated by steroids but also treatment of the Cushing's disease that was caused by the steroids with the use of medications.
Dog Breeds Prone to Developing Cushing's Disease
While any dog can have Cushing's disease, certain breeds are more likely than others to develop it as they age. These breeds include:
- Staffordshire Terriers
- Boston Terriers
- Yorkshire Terriers
- German Shepherds
- Dandie Dinmonts
- Labrador Retrievers
- Australian Shepherds
- Cocker Spaniels
How to Prevent Cushing's Disease in Dogs
Most Cushing's disease is caused by a tumor on the pituitary or adrenal glands and there is unfortunately no way to prevent these from occurring. But since the third type of Cushing's disease is caused by excessive and lengthy steroid use, you can help prevent iatrogenic Cushing's disease by discussing whether or not there are other options available to help manage your dog's ailments besides than steroids.