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:
Other symptoms include:
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:
Treatment of Hyperadrenocorticism in Cats
Treatment options for feline Cushing’s disease are much more limited than in the dog.
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.
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:
The diagnosis of feline Cushing’s syndrome is very difficult to achieve accurately. The diagnosis should always be made on the basis of the clinical suspicion and then supported with the appropriate diagnostics. The most common reason to suspect feline Cushing’s syndrome is insulin-resistant diabetes. Diagnostic tests that are important in evaluating a potential cat with Cushing’s syndrome include:
Feline hyperadrenocorticism is a very debilitating disease. Stabilizing any secondary complicating diseases should be attempted before treating the Cushing’s disease. Concurrent urinary tract infections require antibiotics. Diabetes is often difficult to regulate appropriately, but attempts to stabilize and decrease blood sugar to the safest levels should be attempted. Since feline Cushing’s syndrome is so uncommon, only a limited number of cats have been managed. Medical therapy with a variety of drugs has been shown to be of only limited value. The surgical option seems to provide the best long-term prognosis for these cats. Treatment options that have been tried include:
If pituitary dependent Cushing’s disease is confirmed, then both adrenals are removed. Intravenous fluids are given aggressively, as well as intravenous nutrition. In the diabetic patient, the blood sugar needs to be carefully monitored, and fast acting regular insulin is given as needed. Postoperative antibiotics are commonly given, as sepsis (blood infection) is a common complication. Blood electrolytes (specifically potassium, sodium and chloride) need to be monitored closely and medication adjusted to stabilize their levels. Managing the postoperative cat is challenging and usually requires specialized care.
Home Care of the Cat with Cushing’s Disease
Optimal treatment for your pet requires a combination of home and professional care. Follow-up can be critical, especially if your pet does not rapidly improve. Administer all prescribed medications as directed. Alert your veterinarian if you are experiencing problems treating your pet.
The surgical treatment of removing both adrenal glands in the cat with Cushing’s disease creates another condition, Addison’s disease (hypoadrenocorticism), which requires life long medications and very close monitoring.
Glucocorticoid therapy with prednisone will be required since your cat is no longer producing cortisol. It is usually possible to decrease the dose of prednisone down eventually to very small maintenance dosages. When decreasing the dose it is important to monitor for increased lethargy, anorexia or weakness. Notifying your veterinarian and increasing the prednisone dose usually improves the symptoms if they are being caused by a cortisol deficiency.
Additionally, life long replacement therapy with the mineralocorticoid, fludrocortisone acetate (Florinef) is required. This drug maintains the normal electrolyte balance of sodium, potassium and chloride. Frequent blood tests are needed, especially for the first few weeks postoperatively. Adjustments in medication are made on the basis of the electrolyte results. Florinef is increased if the blood potassium is elevated. If needed, salt may be added to the diet to elevate blood sodium and chloride levels.
Injectable mineralocorticoids (desoxycorticosterone pivalate or DOCP) can be given as a monthly injection instead of the daily oral medications.
Since most cats are diabetics, the blood sugar level will need to be closely followed. Once the Cushing’s disease is controlled, it is common for insulin requirements to decrease dramatically. Watch for changes in drinking, urination and attitude. You will need to work closely with your veterinarian to decrease insulin dosages and to avoid a hypoglycemic (low blood sugar) event. Watch for weakness, disorientation or seizures, as they may indicate a low blood sugar.
After the first several weeks postoperatively, the long-term prognosis is good.