Cushing's disease can affect humans, horses and cats; however, it is typically most common in older dogs. Thus, Cushing's disease is an ailment that thousands of dogs and their owners must deal with.
Named after Harvey Cushing, the American neurosurgeon who first described the disease in humans in the early 20th century, Cushing's disease can result when part of the endocrine system in the body is not functioning properly.
The main function of the body's endocrine system is to produce and secrete numerous hormones that regulate growth, metabolism, tissue function and sleep, among other functions. Major glands that are part of this endocrine system include the adrenal glands, the pancreas, and the thyroid gland, to name just three.
Cortisol, a hormone produced by the adrenal glands, is a natural steroid, which in proper amounts helps the body regulate tissue and skin structure and promotes a healthy body weight. When too much cortisol is produced, hyperadrenocorticism, more commonly known as Cushing's disease, can occur. Unfortunately, when too much cortisol is produced the entire immune system is compromised, leaving the sufferer susceptible to infection and disease.
A tumor in the adrenal gland or the pituitary gland can also cause Cushing's. In some situations, where this is the cause, surgical removal of the tumor can correct the condition.
Symptoms of Cushing's disease in dogs include an increase in appetite, thirst, and blood pressure. Additional symptoms include a bulging abdomen or a potbelly appearance, lumps under the skin, hair loss and muscle weakness. An affected dog may pant heavily. Hair loss is also common in many cases.
Because the symptoms of Cushing's disease often vary widely, diagnosis can be difficult, requiring multiple blood and urine tests to reach a proper identification. If the disease is caused by a growth or tumor, x-rays or an ultrasonography test will help in diagnosis.
Once Cushing's disease has been confirmed, surgery is an option for the treatment of a tumor. However, the risks of surgery are significant and you and your veterinarian may opt for medication first as overproduction of cortisol can often be slowed with medications.
Cushing's disease alone is rarely fatal. However, because the disease compromises the animal's immune system, your dog will be more susceptible to other diseases and infections. In addition, Cushing's can greatly reduce quality of life, in which case you will be faced with some tough decisions about treatment. Be sure your vet knows your wishes concerning your pet and how aggressive you want the treatment to be for your dog.
Approximately 100,000 dogs are diagnosed with Cushing's disease each year in the United States, according to the Washington State University College of Veterinary Medicine. The disease is much rarer in cats and humans. Smaller dogs with Cushing's more commonly have pituitary tumors, whereas in larger dogs the tumor is more often in the adrenal gland. However, the most common cause of Cushing's disease in dogs is a benign tumor in the pituitary gland. More rarely a malignant tumor causes Cushing's.
Certain dog breeds -- Beagles, Boston Terriers, Boxers, Dachshunds, German Shepherds, Jack Russell Terriers, Poodles, Staffordshire Bull Terriers and Yorkshire Terriers -- are more likely than other dog breeds to suffer with this disease. In addition, based on what researchers currently know about this disease, female dogs appear to have a higher risk of developing Cushing's disease.
As always, if you have questions about Cushing's disease or any other medical condition that might affect your pet, ask a vet.
FDA: Consumer Updates, Treating Cushing's Disease in Dogs
Washington State University College of Veterinary Medicine: Cushing's Disease