What is Cushing’s Disease?

The adrenal glands are two small organs located near the kidneys that make hormones, which are chemicals that carry messages through the blood to help control how organs and cells work. Cushing’s Disease, also known as hyperadrenocorticism, occurs when the adrenal glands produce too much of the hormone cortisol. Cortisol is an important hormone for health, with functions including helping the body adapt to stress and regulating production and use of the nutrients required for a healthy skin and haircoat. However, too much cortisol in the body can cause problems.

What are signs my dog has Cushing’s Disease?

Dogs with Cushing’s Disease may have one or more of the following signs:

• Increased thirst (drinking more than normal)
• Increased urination (peeing more often than normal)
• Increased appetite
• Panting
• Hair loss
• Thin skin
• Large, low-hanging abdomen (potbelly)

Dogs with Cushing’s Disease often have changes to their bloodwork, including elevated liver values, higher than normal blood sugar and more platelets (clotting cells) in their blood. They may have high blood pressure or too much protein in the urine. Rarely, dogs with Cushing’s can develop calcinosis cutis (a severe skin disease), myotonia (a contraction of muscles), or a blood clot.

What are the causes of Cushing’s Disease?

In dogs, there are three causes of Cushing’s Disease:

• A tumor of a tiny part of the brain called the pituitary gland. The tumor is often benign (not cancerous) but signals the adrenal glands to make too much cortisol. This tumor is the most common cause of Cushing’s Disease, accounting for nearly 85% of cases.
• A tumor of the adrenal gland which may be benign or cancerous. The adrenal gland tumor produces more cortisol than the body needs.   
• Iatrogenic Cushing’s is caused by exposure to steroid medications. Steroid medications mimic the hormone cortisol in the body, and may be oral, injectable, or topical.  

Certain breeds of dogs may be more likely to develop Cushing’s Disease, including the Dachshund, Boxer, Beagle, and Boston terrier. The average age of a dog diagnosed with Cushing’s disease is 10 years old, but it can be found in both younger and older dogs.

How is Cushing’s Disease diagnosed?

There are two tests used to diagnose Cushing’s Disease:

• ACTH stimulation test
• Low-dose dexamethasone suppression test

Both tests measure whether too much cortisol is being made by the body.

Other tests may be used to determine whether the Cushing’s disease is caused by a pituitary tumor or an adrenal tumor. Those tests may include abdominal ultrasound, high-dose dexamethasone, suppression test, endogenous ACTH level, MRI, or CAT scan.

What is the treatment for Cushing’s disease?

For a pituitary tumor: The most common treatment option for a pituitary tumor causing Cushing’s Disease is oral medication. Trilostane (Vetoryl®) is a short acting medication that reduces the production of cortisol by the adrenal glands. Other medications that may be used include mitotane (Lysodren®), selegiline (Anipryl®) and ketoconazole.   These medications help manage the symptoms associated with Cushing’s disease, but do not cure the disease. For large pituitary tumors, radiation therapy may be an option for treatment.

For an adrenal tumor: Dogs with an adrenal tumor may be candidates for surgical removal of the adrenal gland. If surgery is not possible, the same medications used for dogs with a pituitary tumor may be used.

For iatrogenic Cushing’s: Dogs with iatrogenic Cushing’s Disease from long term use of steroid medications do not require medication for treatment of Cushing’s. Stopping or lowering the dose of the steroid medication will reduce the symptoms.

What is the prognosis for a dog with Cushing’s Disease?

Dogs being treated for Cushing’s Disease can live a long, healthy life. Most dogs live 2-3 years after diagnosis with some living much longer. Because Cushing’s Disease mainly affects older dogs, dogs may have other illnesses that are unrelated to Cushing’s. Regular monitoring of a dog’s symptoms as well as following the veterinarians recommendations for blood testing can help manage Cushing’s Disease and related complications.