Cushing’s disease is one of the most common medical disorders found in dogs. It results when a dog’s endocrine system malfunctions, leading to potentially life-threatening illnesses. These can include liver and kidney failure, diabetes, congestive heart failure, hypothyroidism, and chronic infections of the ears, eyes, skin, and gums.
The endocrine system is fascinating and incredibly complex. Made up of a group of glands and organs that produce and regulate hormones, it controls practically every function in the body. Two of these glands, the adrenals, sit above each kidney and produce a cocktail of steroid hormones that regulate body weight, assist in the production of white blood cells, maintain mineral balance, and ensure the health of skin and connective tissue.
One of the ingredients in this hormone cocktail is cortisol, which is responsible for the metabolism of proteins and carbohydrates. When the body produces too much cortisol, this is known as “hyperadrenocorticism” – more commonly known as Cushing’s disease.
Cushing’s disease usually strikes middle-age to older dogs, but younger dogs can also be affected. Although it can appear in any breed, certain breeds seem to be more prone to developing it than others. Labrador Retrievers, German Shepherds, Poodles, Beagles, Boxers, Australian Shepherds, Cocker Spaniels, Malteses, Dachshunds, and many of the Terrier breeds seem to show higher than average rates of Cushing’s disease.
What Causes Cushing’s Disease In Dogs?
There are 3 main conditions that can cause an overproduction of cortisol, leading to Cushing’s disease:
Pituitary Gland Tumor
The pituitary gland is located at the base of the brain and controls all hormone production in the body. Tumors in the pituitary can be either benign (non-cancerous) or malignant (cancerous). They can cause the pituitary to produce too much of a hormone called ACTH, which in turn stimulates the adrenal glands to overproduce cortisol.
This is the most common cause of Cushing’s disease in dogs, and is responsible for approximately 85-90% of cases. Many dogs with this form of Cushing’s disease can live normal lives for years, as long as they continue to take the proper medications and are monitored closely.
Adrenal Gland Tumor
Tumors in the adrenal glands may also be benign (called adenomas) or malignant (known as carcinomas). Adenomas may be surgically removed, and this usually cures the dog of Cushing’s disease. Surgery to remove a carcinoma in the adrenal gland may help for awhile, but these tumors tend to return, and the prognosis is much less favorable.
Excessive Cortisol from Prolonged Use of Steroids
This is referred to as “Iatrogenic Cushing’s disease.” It’s caused by the excessive use of oral or injectable corticosteroids, which are sometimes given to treat medical conditions such as allergies, arthritis, or inflammation. Common corticosteroids used in dogs include prednisone, dexamethasone, hydrocortisone, and Depo-Medrol.
Identifying the exact cause of a dog’s Cushing’s disease is important, because each type is treated differently.
Signs Of Cushing’s Disease In Dogs
Symptoms of Cushing’s disease in dogs are somewhat tricky, as they can mimic many other diseases and often appear to be connected to the normal aging process.
The most common signs include:
- Increased hunger
- Excessive panting
- Inability to sleep (insomnia)
- Increased thirst and urination
- “Pot-bellied” appearance (due to the body’s redistribution of fat directly to the abdomen)
- Hair loss
- Lack of energy
- Thinning of the skin
- Fat pad formation on the neck and shoulders
- Muscle weakness
- Darkening of the skin, or the appearance of blackheads
- Rough, white, scaly patches on the skin (particularly around the elbows)
Diagnosing Cushing’s Disease
If your veterinarian suspects that your dog has Cushing’s disease, he or she will do a complete physical exam, including blood work and urinalysis.
Your veterinarian will also run additional specialized tests to see if the cortisone level in your dog’s bloodstream is too high. These tests usually include a cortisol creatinine ratio test (run with a urine sample), and two blood tests: an ACTH stimulation test, and a low-dose dexamethasone suppression test. An abdominal ultrasound can also be done to view the adrenal glands to see if they are enlarged or if there’s a tumor present.
If your veterinarian positively confirms Cushing’s disease, further testing will be necessary to determine which type of Cushing’s disease is present. This will determine the cause so it can then be properly treated.
Treatment For Cushing’s Disease In Dogs
Depending on the type of Cushing’s disease diagnosed, treatment for dogs involves either oral medication for the remainder of the dog’s life, or surgical removal of the tumor (if one is present).
Dogs with a pituitary tumor are treated with drug therapy. This allows the Cushing’s disease to be managed, but it cannot be cured.
Dogs with an adrenal gland tumor are treated by surgical removal of the tumor, which involves major abdominal surgery. If the surgery is successful and the tumor is not cancerous, there is a good chance that the dog will be cured. If the tumor is cancerous, prognosis is usually poor. However, there are some cases where, if the tumor is very small and has not metastasized (spread to other parts of the body), the dog may be able to live for up to several years, depending on its overall condition.
Dogs with Cushing’s disease from an overuse of steroids are taken off all steroid medications in a very controlled, gradual manner. This avoids complications from suddenly stopping the medication (steroids need to be discontinued gradually to prevent shocking the body). Unfortunately, this may result in a recurrence of the condition that was being treated by the steroid in the first place, but Cushing’s disease is usually the greater of those two evils. Allergies, arthritis, or inflammation will then need to be treated with other non-steroidal options.
Early Detection Is Important
If your dog is middle-aged or older and is showing any signs of Cushing’s disease, make an appointment with your veterinarian as soon as possible. Although Cushing’s caused by a pituitary tumor cannot be cured, treatment can extend your dog’s lifespan and greatly increase his quality of life. And if your dog has Cushing’s from an adrenal tumor, the sooner surgery is performed to remove the tumor, the better.
Dogs who are taking lifelong medications for Cushing’s disease need to be closely monitored, and follow-up blood tests are very important – not only to ensure that their cortisol levels are in the correct range, but also to make sure they’re receiving the proper dosage of medication. If your dog has Cushing’s disease and is on medication, be sure to watch for any signs of an adverse reaction, including loss of appetite, vomiting, or diarrhea.
Cushing’s disease can be a life-threatening condition, but proper treatment can make all the difference. Although most dogs with Cushing’s disease cannot be cured, their quality of life can be improved and their lives extended for many years with early intervention.
Have you ever had a dog with Cushing’s disease? If so, what was your biggest challenge in managing the condition? Please share your experiences with us in the comments below!