What is Cushing’s Disease in Dogs?

According to the WSU College of Veterinary Medicine, over 100,000 dogs are diagnosed with Cushing’s disease each year in the United States alone. This common chronic condition, usually diagnosed in middle-aged dogs, can cause mild to severe symptoms and complications. 

Learn how to spot potential signs of Cushing’s, how this condition can affect your dog’s health, and how Cushing’s disease is diagnosed and treated in dogs.
 

What is Cushing’s Disease?

Cushing’s syndrome, also known as hyperadrenocorticism, is one of the most common endocrine disorders diagnosed in dogs. In dogs with Cushing’s syndrome, the adrenal glands, located above each kidney, produce too much of the stress hormone cortisol. 

Cushing’s syndrome in dogs has three primary causes: a tumor of the pituitary gland, an adrenal gland tumor, or long-term use of a steroid medication. 

When Cushing’s syndrome is associated with an adrenal or pituitary gland tumor, it’s known as Cushing’s disease. Cushing’s disease is a form of Cushing’s syndrome. 

According to the Merck Veterinary Manual, around 85% of cases of Cushing’s disease in dogs are caused by a tumor on the pituitary gland, which is located at the center of the brain. 

The pituitary tumor begins to overproduce adrenocorticotropic hormone (ACTH), a hormone that travels through the bloodstream and signals the adrenal glands to produce cortisol.

The remaining 15% of Cushing’s disease cases are caused by a tumor on the adrenal gland itself, directly causing the overproduction of cortisol.
 

What Are The Symptoms of Cushing’s Disease in Dogs?

Cushing’s disease causes the overproduction of cortisol, an important hormone that facilitates the body’s response to stress or danger. Cortisol increases blood sugar, controls inflammation, and aids energy metabolism.

Cushing’s disease can interfere with kidney function, causing increased drinking and increased urination. It can also cause long-term kidney damage. Some dogs also become more susceptible to urinary tract infections. Always make sure your dog has access to fresh, clean water and allow them to go outside often.

Dogs with Cushing’s disease may have a patchy, thinning coat that grows slowly. Their skin can also become thinner, and they may become more susceptible to skin infections. 

Cortisol is an important hormone for energy metabolism. In dogs with excess cortisol, changes in appetite, especially increased appetite and weight gain, are common. Some dogs also have a pot-bellied appearance, which can be due to fat storage in the abdomen and organ enlargement.

Dogs with Cushing’s disease can become lethargic. Cortisol draws protein from the muscles, causing muscle wasting and weakness. Excessive panting is also common. 

These symptoms are nonspecific, often associated with other health conditions. If your dog is drinking more water or urinating more often, experiencing hair loss or skin infections, recurring urinary tract infections, or changes in appetite or energy, seek your veterinarian as soon as possible. These signs are often associated with old age but can indicate a treatable health issue like Cushing’s disease. 
 

How Is Cushing’s Disease Diagnosed?

Cushing’s disease can be difficult to diagnose, as false negatives and inconsistent test results are common. If your dog shows signs of hyperadrenocorticism, your veterinarian will likely begin with bloodwork and urinalysis to look for markers like increased liver enzymes or an increased urine cortisol creatinine ratio. 

Risk factors like your dog’s age, breed, and sex may also be taken into consideration. Boston Terriers, Boxers, Beagles, Dachshunds, Miniature Poodles, and German Shepherds are more susceptible than other breeds. 

Your veterinarian may conduct an ACTH stimulation test if Cushing's disease is suspected. Your veterinarian will take a blood sample before and after administering a synthetic form of the ACTH hormone. A dramatic increase in blood cortisol indicates a positive result.

A low-dose dexamethasone suppression test can also be used to diagnose Cushing’s disease. Your veterinarian will take a blood sample before and after administering dexamethasone, a medication that suppresses the production of cortisol in healthy dogs but will fail to reduce blood cortisol in dogs with Cushing’s disease.

Your veterinarian may also use abdominal X-rays, sonographs, MRI, or CT scans to determine whether there is a tumor of the pituitary or adrenal glands.
 

What’s The Prognosis for Dogs with Cushing’s Disease?

Cushing’s disease is rarely curable, but it can be treated with lifelong use of medication. 

The most commonly prescribed medication for dogs with Cushing’s disease is trilostane, brand name Vetoryl® because it’s FDA-approved, usually well tolerated, and helps improve symptoms and quality of life. 

Trilostane in Vetoryl^® blocks an enzyme that the adrenal glands need to produce cortisol. Pet parents may see improvement in as little as one week. Your veterinarian will need to see your dog every three months to monitor your dog’s progress and to determine if their current dosage is right for them.

Early treatment is key to helping prevent and manage complications. Around 10 percent of dogs with Cushing’s disease have or will eventually develop diabetes. Dogs with Cushing’s disease are also prone to recurring skin and urinary tract infections, kidney damage, pancreatitis, blood clots, high blood pressure, and skin and coat issues.

Tumors of the pituitary or adrenal gland can be benign or malignant. In dogs with pituitary-dependent Cushing’s disease, the tumor can grow to affect surrounding brain tissue, leading to neurological issues like seizures. If the tumor is malignant or growing, surgery or radiation may be needed.