Cushing’s disease is one of the most common endocrine (i.e., hormone-related) diseases in dogs, and can interfere with your senior pet’s quality of life. Since hormones circulate throughout your pet’s body, Cushing's disease can have far-reaching effects on their body systems. Understanding this complex condition can help you manage your pet’s disease, so you can help them enjoy the best quality of life possible. 

What is Cushing’s disease in pets?

Your pet’s adrenal glands, located in their abdomen behind the kidneys, secrete hormones, including cortisol. Cushing’s disease, or hyperadrenocorticism, occurs when your pet’s adrenal glands produce too much cortisol. The excess can be harmful to your pet, despite cortisol’s importance for many body functions. A pituitary gland tumor that overproduces adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands, causes approximately 80% to 85% of Cushing’s disease cases. Cortisol-producing adrenal gland tumors can also form, but less commonly cause overproduction. 

While any pet can develop Cushing’s disease, some dog breeds have a higher incidence, including:

•Boston terriers

•Boxers

•Dachshunds

•Miniature poodles

•Staffordshire terriers

•Yorkshire terriers

Although Cushing’s disease is most common in middle-aged to older dogs, cats occasionally develop the condition. 

What are Cushing’s disease signs in pets?

Cushing’s disease signs are related to the way the excess cortisol affects various body systems, and may include:

•Lethargy

•Increased urination (i.e., polyuria)

•Increased water intake (i.e., polydipsia)

•Increased appetite (i.e., polyphagia)

•Abdominal enlargement 

•Heat intolerance

•Muscle weakness

•Panting

•Thin, fragile skin

•Hair loss

•Skin problems

Cats with Cushing’s disease typically develop extremely thin, fragile skin, and often have concurrent diabetes. If your middle-aged or older pet has signs consistent with Cushing’s disease, your family veterinarian should evaluate them for a possible diagnosis.

How is Cushing’s disease diagnosed in pets?

During your pet’s evaluation, your family veterinarian will perform a thorough physical exam and blood work, which may show abnormalities, such as increased cholesterol, glucose, and liver enzyme levels. Based on these findings, if your veterinarian suspects Cushing’s disease, they will perform more specialized testing, such as a low dose dexamethasone suppression (LDDS) test, ACTH stimulation, or a urine cortisol-to-creatinine ratio (UCCR). Further testing may be needed to determine whether a pituitary or adrenal tumor is causing your pet’s Cushing’s disease. 

How is Cushing’s disease treated in pets?

The goal of Cushing’s disease treatment is to reduce cortisol production, which can be accomplished by several methods:

Medication — Medications may be used to selectively destroy part of the adrenal gland, or suppress cortisol production. Titrating the correct dose to maintain cortisol levels in an appropriate range can be tricky, and cortisol deficiency (i.e., hypoadrenocorticism, or Addison’s disease) may occur. 

Radiation — Radiation therapy may be used to destroy or shrink a pituitary tumor. Radiation therapy has a high success rate, although concurrent medications may be needed while residual ACTH secretion decreases. Newer radiation techniques (i.e., CyberKnike) allow for more precise tumor targeting, and can treat tumors more quickly, with fewer side effects. 

Surgery — If an adrenal tumor is diagnosed, the affected adrenal gland may be surgically removed. However, hypoadrenocorticism will likely develop, and cause complications. Surgical removal of a diseased pituitary gland is possible, but the pituitary gland produces many hormones, and removal can lead to significant effects throughout the body. 

What is the prognosis for a pet with Cushing’s disease?

With proper treatment, pets can live for several years with Cushing’s disease, with a mean survival time of approximately two years. Radiation therapy is associated with a longer pet survival rate. If your pet has concurrent diseases, such as diabetes or a thyroid condition, they may complicate their treatment and impact their prognosis.