Hyperadrenocorticism (Cushing's Syndrome) in Cats

Hyperadrenocorticism or Cushing's syndrome is caused by an excessive production of glucocorticoids, namely cortisol, by the adrenal gland. Glucocorticoids are essential body hormones, but chronically elevated amounts may cause illness.

In about 80 percent of cats a small pituitary tumor at the base of the brain is the cause of the disease. This tumor secretes adrenocorticotropic hormone (ACTH or) that stimulates the adrenal gland to produce elevated cortisol levels. This type of Cushing's syndrome is also called pituitary dependent hyperadrenocorticism.

The remaining 20 percent of Cushing's disease is caused by a tumor of the adrenal cortex, which is the outer layer of adrenal gland. This is also called adrenal dependent hyperadrenocorticism.

Most cats with Cushing's syndrome are middle-aged or older (average 10 to 11 years) and approximately 70 percent are female.

There is no breed predilection. Cushing's syndrome is a rare disease in cats.

Over 90 percent of cats diagnosed with Cushing's disease have concurrent diabetes mellitus, commonly known as "sugar diabetes."

What to Watch For

The most common clinical signs of feline Cushing's syndrome are associated with the concurrent diabetes. These signs include:

Increased thirst

Increased urination

Increased appetite

Other symptoms include:

Fragile, easily bruised or torn skin

Symmetrical hair loss

Poor or ungroomed hair coat

Pot-bellied appearance

Generalized muscle wasting

Lethargy

Recurrent infections

Weight gain or loss

Diagnosis

Cushing's syndrome is not a diagnosis that should be made solely on the basis of laboratory testing. Both historical information and physical exam findings are equally important in establishing a diagnosis and directing appropriate laboratory testing. Since the majority of cats with Cushing's syndrome are insulin-resistant diabetics – which means they have a poor response to insulin – a poorly regulated diabetic may prompt a clinical suspicion of hyperadrenocorticism. Diagnostic tests include:

CBC (complete blood count)

Biochemical profile

Urinalysis with culture and sensitivity

Blood pressure evaluation

Radiographs of the chest and abdomen

Abdominal ultrasound

ACTH stimulation test

Dexamethasone suppression test

Combined dexamethasone suppression – ACTH stimulation test

ACTH Level

CT (computer tomography) or MRI (magnetic resonance imaging) of the abdomen

Treatment

Treatment options for feline Cushing's disease are much more limited than in the dog.

Medical therapy has proven to be of limited value in the control of the disease. Treatment with o, p-DDD (lysodren) and ketoconazole are generally ineffective. A third drug, metyrapone, has shown some occasional successful treatment.

Surgical treatment is the treatment of choice in feline Cushing's disease. Since pituitary dependent Cushing's disease causes bilateral adrenal enlargement, the most effective treatment option is the surgical removal of both adrenal glands. This is a difficult surgery that requires extensive postoperative care, usually at a referral institution or specialty hospital.

Adrenal tumors should also be treated surgically with a unilateral adrenalectomy, or removal of the affected adrenal gland. This surgery, as well, should be done at a referral institution with 24-hour care available.

Home Care

After the removal of both adrenal glands, cats continue on medication for the remainder of their lives. Follow your veterinarian's instructions very carefully when administrating medications.

Diabetic cats almost always have changes in their insulin requirements. Monitor for changes in water consumption and amount of urine produced.

In the immediate postoperative time, frequent blood tests are needed to monitor the cat's blood glucose and electrolytes. Insulin requirements and oral medications need to be adjusted on the basis of laboratory tests. Once stable, cats need to be evaluated at least several times a year.

Observe for any weakness, disorientation, lethargy, vomiting or diarrhea or any changes in your cat's attitude.

Preventative Care

Nothing can be done to prevent feline Cushing's disease, but knowing if your cat might be at risk of Cushing's disease is important for successful treatment. Early diagnosis and treatment leads to a better prognosis.

If your cat is a diabetic that is difficult to regulate, Cushing's syndrome (although rare) may be the cause.