Cushing’s Disease in Cats and Dogs – What You Need to Know

Cortisol is a naturally produced hormone that helps the body respond to stress (“fight or flight” response). When the endocrine system produces too much cortisol (hypercortisolism), it can cause clinical signs of illness that collectively are called Cushing’s syndrome or Cushing’s disease, but the disease is better termed hyperadrenocorticism (HAC).  

Causes of Cushing’s Disease 

It may be caused by a tumor (which can be malignant or benign) on the adrenal gland which is located in the abdomen near the kidney. It may also be caused by a benign growth on the pituitary gland, located at the base of the brain, that produces too much of a hormone that stimulates the production of cortisol by the adrenal gland.  

Signs that resemble naturally occurring Cushing’s disease may also occur with glucocorticoid administrations and may result in Iatrogenic Cushing’s Disease. Oral or injectable steroids given for medical reasons may lead to side effects that are the clinical signs of Cushing’s. Sometimes these signs are expected, but continued use of steroids may result in clinical signs of Cushing’s.  

What are the Signs of Cushing’s Disease in Cats and Dogs? 

Cushing’s Disease can affect dogs and cats. It is extraordinarily rare in cats. Cushing’s Disease occurs more commonly in small breed dogs, including Miniature Poodle, Dachshund, Boxer, Boston Terrier, and Beagle, that are over the age of 6.  

Clinical signs may include: 

• Increased thirst, urination, and appetite 
• Panting and heat intolerance 
• Potbelly appearance, lethargy, and muscle weakness 
• Urinary tract and skin infections   
• Calcinosis cutis 

Pets that have Cushing’s are also at higher risk for developing:  

• Blood clots – mainly involving the lungs, legs, and brain 
• Secondary infections of the lungs, skin, bladder, and kidneys 
• Inflammation of the pancreas (pancreatitis) 
• High blood pressure (systemic hypertension) 

How is Cushing’s Disease Diagnosed?  

Cushing’s can be difficult to diagnose, especially in the early stages of the disease when clinical signs are vague or absent, or if your pet has other conditions that may affect signs or laboratory work results. Your veterinarian will recommend special blood and urine tests for a diagnosis. They may also recommend an ultrasound to examine the adrenal glands and other abdomen organs. Occasionally, your veterinarian may perform an MRI or CT scan of the head to examine the pituitary gland.

How is Cushing’s Disease Treated?  

Treatment options differ depending on whether your pet has the syndrome due to a problem with their pituitary or adrenal glands. 

The most common (about 75-85%) form of Cushing’s is pituitary-dependent, which is not curable but can be managed to improve your pet’s quality of life. This version of Cushing’s is generally treated with medications, such as Vetoryl® (trilostane). Occasionally, Lysodren® (miotane) is still used. These medications may be needed for your pet’s lifetime. While each medication works differently, they both decrease the amount of cortisol produced by the adrenal glands. Less commonly, radiation may be used if a pituitary tumor is large and causes neurologic signs.   

The 15-25% of pets that have adrenal-dependent Cushing’s are generally treated with surgery to remove the adrenal tumor. Medication is also used. If the entire tumor is removed and it is not malignant, there is a good chance that your pet will regain normal health. 

If your pet has Iatrogenic Cushing’s Disease, treatment is to slowly discontinue steroids and secondary problems are managed. The disease being treated by steroid therapy may recur and hormone replacement therapy may be needed for the adrenal glands.  

What to Expect After Treatment Begins 

Once your pet begins taking medication, you should see improvements in many signs over a few weeks. Because medications are lifelong, your veterinarian will closely monitor your pet to ensure the medication is working and dosing is optimized. 

When a pet has Cushing’s Disease, ACTH is a hormone produced in excess by the pituitary gland, which stimulates the adrenal glands to produce cortisol. To ensure your pet receives the best medication dosage, your veterinarian may use an ACTH Stimulation Test. The test is generally performed within two weeks after therapy begins and every few weeks thereafter until your pet is receiving the right amount of medication for their individual needs. Once the correct dosage is established, they are typically evaluated every three to four months.  

Contact your veterinarian if you notice any of the following signs after your pet begins Cushing’s treatment: 

• Changes in appetite, including eating slower or not finishing a meal 
• Vomiting or diarrhea 
• Decreased activity and increased sleeping 

While Cushing’s Disease is not curable, treatment can help your pet feel better and improve their quality of life.