Cushing's Disease (Hyperadrenocorticism) in Cats

Key Takeaways

Hyperadrenocorticism or Cushing’s disease occurs as a result of excessive cortisol levels. It is a rare condition in cats.

• Cushing’s syndrome can be caused by one of various factors

• The most common cause of Cushing’s syndrome in cats is an overactive pituitary gland as a result of a tumor

• Other possible causes are excessive administration of steroid-containing medication and an adrenal gland tumor

• A large percentage of diagnosed cats have diabetes mellitus

• The prognosis for Cushing’s syndrome is guarded

• Treatment generally involves lifelong medication and regular monitoring

• Cushing’s syndrome can be life-threatening if diagnosis and treatment are significantly delayed (months)

A Closer Look: What is Hyperadrenocorticism in Cats?

Cortisol is a steroid hormone that suppresses inflammation. It is manufactured by and stored in the adrenal glands (which are located in the kidneys) and is naturally released in times of stress. Cortisol production is regulated by the pituitary gland in the brain.

Cushing’s syndrome can be classified into:

ACTH-dependent Cushing's syndrome involves the pituitary gland. Adrenocorticotropic hormone (ACTH) is produced by the pituitary gland to stimulate adrenal gland activity. When small pituitary gland tumors increase the production of ACTH, cortisol levels go up without regulation. 

ACTH-independent Cushing's syndrome involves the adrenal gland. This occurs when the adrenal cortex produces an excess of cortisol hormone independently from the pituitary gland. Adrenal tumors are the most common cause of this form of Cushing's syndrome.

Iatrogenic Cushing's syndrome is caused by prolonged or high-dose administration of steroid-containing drugs.

Risk Factors

Elevated levels of cortisol cause a number of symptoms that significantly decrease quality of life. Cushing’s syndrome is rare in cats, but if left untreated it can be life-threatening, as such it must be treated as an emergency. 

Pituitary gland tumors are the most common cause of feline Cushing's syndrome. 

Middle-aged and older cats are more likely to develop Cushing’s syndrome due to a tumor. Cats of any age receiving high doses of steroids are at risk of developing Cushing’s disease spontaneously.

Possible Causes

Cushing's syndrome is caused by excessive amounts of cortisol hormones in the animal's system.

The excessive production of steroid hormones can be caused by one of three underlying conditions:

• Pituitary gland tumor  • Adrenal gland tumor  • Excessive administration of steroid-containing drugs

Main Symptoms

Main symptoms of Cushing’s syndrome:

• Excessive thirst • Excessive urination • Increased appetite • Poor coat condition • Hair loss

• Fragile skin • Weakness • Lethargy

Testing and Diagnosis

Cushing’s syndrome is very rare in cats. It requires specialized blood testing to diagnose. Common diagnostic tools include:

• Blood tests, including cortisol levels and hormone response tests • Urinalysis • Hormone level test 

• Diagnostic imaging 

Treatment depends on the underlying cause.

Steps to Recovery

Treatment for ACTH-dependent hyperadrenocorticism involves:

• Radiotherapy medication • Medication to reduce the production of cortisol

Treatment for ACTH-independent hyperadrenaocorticism involves the surgical removal of one or both adrenal glands. Surgery is the only treatment option for adrenal gland tumors, as they do not respond to chemotherapy. 

Treatment for iatrogenic hyperadrenocorticism involves weaning off the steroid-containing medication. 

The prognosis for Cushing's syndrome varies depending on the type. Once diagnosed, the animal may require life-long medication and monitoring.

Prevention

Cushing’s syndrome is not contagious. Cushing’s syndrome is unpreventable. Cats with Cushing’s syndrome are likely to suffer from diabetes mellitus. Testing for Cushing’s syndrome is advised for diabetic cats.

Is Hyperadrenocorticism Common in Cats?

Cushing’s disease is a rare condition in cats.

Typical Treatment

• Weaning off steroid-containing medication  • Surgery  • Chemotherapy • Radiotherapy 

• Cortisol reducing medication