Cushing's Disease in a Geriatric Dog

Cushing’s disease is most common in older dogs, and some breeds are more prone to it than others. Poodles, dachshunds, boxers, beagles and Boston terriers are among those most likely to suffer from Cushing’s disease as they get older. Research also indicates that female dogs are more vulnerable to developing Cushing’s disease than male dogs. While it does manifest more commonly in certain breeds and genders, no dog is immune.

There are two known causes that lead to one of two distinct forms of Cushing’s disease. The first and most common form is pituitary-dependent hyperadrenocorticism and is caused by a tumor in the dog’s pituitary gland. The second form of Cushing’s disease is called adrenal-based hyperadrenocorticism and is caused by a tumor in the adrenal gland.

Some animal health experts claim that there is a third form of the disease, iatrogenic Cushing’s disease, which is caused by administering high doses of steroids but resolves itself when steroid use is discontinued.

Cushing’s disease often goes unnoticed or misdiagnosed for prolonged periods of time because the symptoms are so similar to those of the natural aging process or other health conditions.

Two of the most common symptoms of Cushing’s disease include increased water consumption and increased appetite. More than 80 percent of dogs suffering from Cushing’s disease display one or both of these symptoms. Increased water consumption leads to increased urination, which sometimes causes previously housebroken dogs to have accidents. However, many pet parents mistakenly dismiss this symptom as a natural part of aging. Increased appetite is also commonly overlooked by pet parents who tend to consider a strong appetite to be a sign of a healthy pet.

Panting, hair loss, and muscle weakness are other clinical symptoms of Cushing’s disease that generally get confused for natural aging. Cushing’s disease can also cause lumps and discoloring of the skin.

The most distinguishable symptom of Cushing’s disease in older dogs is a bulging abdomen. As fat in the abdominal area shifts and abdominal muscle mass weakens, dogs suffering from Cushing’s disease may develop abdominal enlargement that gives them a pot-bellied appearance.

While routine bloodwork and urinalysis tests may suggest the presence of Cushing’s disease, additional lab tests are needed to provide a more accurate diagnosis. Some of the screening and diagnostic tests that veterinarians recommend for suspected cases of Cushing’s disease include a urine cortisol/creatine ratio test, an ACTH stimulation test, and high- and low-dose dexamethasone suppression tests. Since there is no one test to diagnose Cushing’s disease, an accurate diagnosis is often challenging.

Treatment depends on the form of the disease and the health of the dog. Many complications can arise when treating older dogs with weakened immune systems. Adrenal tumors are sometimes surgically removed, whereas pituitary tumors are more likely to be treated with chemotherapy. The ideal treatment plan for a dog with Cushing’s disease is one that aims to improve the dog’s comfort and quality of life. While dogs suffering from Cushing’s may not be cured, the disease can be managed effectively enough to maintain good quality of life for many years after diagnosis.