Cushing’s disease, also called hyperadrenocorticism, is an endocrine system disorder seen commonly in dogs and rarely in cats. Hyperadrenocorticism occurs when the body produces too much cortisol, an essential hormone produced by the adrenal glands in times of stress, even after the stressor, such as pain or infection, has gone.

What causes Cushing’s disease in dogs?

Three types of Cushing’s disease are seen in dogs, each with different causes and prognoses.

• Pituitary gland tumors cause 85% to 90% of Cushing’s cases. A tumor forms on the pituitary gland, located at the base of the brain, and stimulates the gland into producing an overabundance of a hormone that triggers the adrenal gland to generate cortisol. Your pet’s prognosis depends on the tumor, which can be benign or malignant, small or large. Even a benign, but large, tumor can interfere with normal brain function and cause neurologic signs. A benign, small tumor offers the best prognosis, because the disease can be managed with medication and your pet can enjoy a high quality of life for many years.
• Adrenal gland tumors can form on one or both adrenal glands and trigger excess cortisol production. These tumors are a less common cause of Cushing’s disease, but prognosis is also dependent on whether the tumor is benign or malignant. A benign adenoma can be removed surgically and cured, but removing a malignant carcinoma helps only for a limited time.
• Steroid use can be a problem for pets who are given the drug for a prolonged period or in excessive amounts. Corticosteroids can adversely affect a pet’s normal body function, resulting in iatrogenic Cushing’s disease.

What are the signs of Cushing’s disease in dogs?

Regardless of the cause, the signs are the same. If your pet has excess cortisol in his or her body, you may notice the following:

• Excessive thirst
• Excessive urination
• Excessive hunger

These three Cushing’s disease signs are known as the three P’s—polydipsia, polyuria, and polyphagia. However, other diseases, such as diabetes, also routinely show these signs, so a thorough physical exam is necessary to pick up on other signals, including:

• Pot-bellied appearance
• Poor hair coat
• Lethargy
• Thin skin
• Muscle loss
• Panting
• Hyperpigmentation
• Chronic skin or urinary infections
• Poor skin healing

How is Cushing’s disease diagnosed in dogs?

In addition to your pet’s physical appearance and behavior at home, several tests can confirm a Cushing’s disease diagnosis. If your pet has other diseases, or is in the early disease stages, an accurate diagnosis may be difficult, but we can perform special blood and urine tests to evaluate cortisol levels and the body’s response to steroid administration. An abdominal ultrasound may be recommended to check for adrenal tumors.

How is canine Cushing’s disease treated?

Depending on the cause, your pet may require medical or surgical treatment.

• Pituitary-dependent forms are not curable, but can often be managed with lifelong medication. Your pet will need follow-up blood work to evaluate the response to medication, and whether a dose change is indicated or a change of medication is needed. If a pituitary-based tumor is growing, radiation treatment may be recommended to treat neurologic signs.
• Adrenal-dependent forms usually require surgery and can be cured with tumor removal. Medications may also be necessary.

• Iatrogenic-based forms resolve once steroid administration is discontinued. Unfortunately, that may allow the disease process being suppressed, such as autoimmune issues, allergies, or asthma, to flare up again.

Our highly qualified team of board-certified internal medicine veterinary specialists is well-equipped to handle any diagnostic testing and treatment of a pet with Cushing’s disease. Your primary veterinarian may refer your pet to our care if he or she is a challenging case, or the practice is not equipped for the additional testing or treatment needed. Contact us if you think your pet may benefit from a consultation with one of our board-certified internal medicine specialists.