Hyperadrenocorticism (Cushing’s Syndrome) in Cats

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Cushing’s Syndrome in Cats

Hyperadrenocorticism, or commonly called Cushing’s syndrome or Cushing’s disease, 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 of Hyperadrenocorticism in Cats

    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 of Hyperadrenocorticism in Cats

    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.

    In-depth Information on Hyperadrenocorticism in Cats

    The adrenal glands are two small endocrine organs located near each kidney. The glands have two separate parts: the cortex (outer layer) and the medulla (inner layer). The adrenal cortex is the layer that is responsible for glucocorticoid or cortisol production. Normally, the adrenal gland’s production of glucocorticoids is regulated by higher functions in the brain. The area of the brain called the hypothalamus secretes the hormone CRH (corticotrophin releasing hormone). CRH then stimulates the pituitary gland to produce ACTH (adrenocorticotropic hormone), which in turn stimulates the production of glucocorticoids by the adrenal cortex. Elevated glucocorticoid levels normally lead to suppression of ACTH production, thus maintaining homeostasis.

    In feline Cushing’s disease, elevated cortisol levels are caused by either a pituitary tumor producing increased ACTH or by an adrenocortical tumor directly producing elevations in cortisol. Chronically elevated cortisol levels may predispose a cat to become a diabetic; cause muscle atrophy and weakness; cause skin to be more fragile – even to the extent of bruising or tearing with minor manipulation; cause suppression of the immune system; and changes in the body conformation.

    Other diseases that might cause similar clinical signs include:

  • Diabetes mellitus. The vast majority of cats that have Cushing’s disease are diabetic. If a cat is not a diabetic, it is unlikely (but possible) that the disease is cushingoid.
  • Feline acromegaly. Acromegaly or an excess of growth hormone is caused by a growth hormone secreting tumor in the pituitary gland. Cats usually present as insulin resistant diabetics with body conformational changes. Typical changes include an increase in the cat’s head and paw size. The lower jaw may also protrude.
  • Hyperthyroidism. Elevated levels of thyroid hormones may cause cats to eat and drink excessively, urinate more and lose weight. Hyperthyroid cats may also have poor hair coats and have generalized muscle atrophy.
  • Liver disease may cause an enlarged liver and a protruding abdomen. Many cats drink excessively and have a poor hair coat with liver disease.
  • Feline fragile skin syndrome. Fragile skin syndrome is a condition that causes the cat’s skin becomes thinner and weaker. It may be associated with metabolic or neoplastic conditions. Its exact cause is unknown.
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