Cushings Syndrome is the resulting set of symptoms observed when the body is exposed to excess cortisone (or related hormones) over a long period of time. Cortisone, or more correctly Cortisol, is a hormone produced by the adrenal glands which are located atop the kidneys. Cortisol is stored in the adrenal gland and released in times of stress where it helps our bodies prepare for a fight or flight situation. It adjusts the metabolism to expect physical exertion by mobilizing fat and sugar stores and retaining sodium and water. It puts us in a state of break down so that our stored resources can be used quickly. If the body is exposed to this hormone most of the time instead of during short stressful periods, the state of break down becomes debilitating.
There are several mechanisms which can lead to Cushings syndrome and, as they are treated differently, it is important to determine which one is at work in a given animal.
In the normal body, the pituitary gland, located at the base of the brain, can detect when cortisol levels in the blood are declining. In response, the pituitary secretes a stimulating substance which causes the adrenal gland to release more cortisol. When the pituitary gland detects that cortisol levels are again appropriate, it stops its stimulatory message.
You can think of the pituitary gland as a sort of a thermostat for cortisol. This raising and lowering of cortisol blood level is regulated throughout the day and occurs rapidly.
1) PITUITARY-DEPENDENT CUSHING'S SYNDROME
This accounts for 85% of dogs with Cushing's syndrome. Basically, the pituitary gland grows a tumor, generally microscopic and generally benign. This tumor, however, over-produces its stimulatory message thus leading to enlargement of both adrenal glands and an over-production of cortisone. Occasionally (10% of pituitary-dependent Cushing's dogs), these benign pituitary tumors are large enough to compress the brain. In these cases, neurological signs may be observed; these cases are unusual but very hard to treat.
2) ADRENAL-DEPENDENT CUSHING'S SYNDROME
In 15% of dogs with Cushing's syndrome, an adrenal tumor is directly over-producing cortisone. The tumor is often large enough to see with radiographs or ultrasound and may be malignant.
3) OVERUSE OF CORTISONE-TYPE HORMONES
Cortisone derivatives may well be the most over-used drugs in veterinary medicine. Their anti-inflammatory actions soothes such common maladies as allergic skin disease (especially flea allergic dermatitis) and degenerative arthritis. Relief is usually rapid and and many owners find themselves requesting "cortisone" shots or pills over and over again. In time, Cushing's syndrome results, not from any inherent disease in the pet's system but from the effects of the hormones given.
The pituitary gland perceives the high steroid levels yielded by the medication and does not send a stimulation to the adrenal glands. In time, the adrenal glands atrophy and are not able to release cortisone for a period of three months after the medication is discontinued. To allow the adrenal to gradually recover, cortisone pills are usually prescribed in a decreasing dose and an owner should never discontinue the pills suddenly.
Commonly prescribed cortisone derivatives include: vetalog, azium, prednisone, prednisolone, dexamethasone, depomedrol and others.
DOES YOUR DOG HAVE CUSHINGS SYNDROME?
There are many clinical signs associated with Cushings syndrome (also called hyperadrenocorticism) in the dog. These signs usually come on very gradually and, because of this slow onset, these changes are often written off as part of the normal aging process. The following is a list of common symptoms which an owner might observe in their pet at home.
DRINKING EXCESSIVELY/URINATING EXCESSIVELY/INCONTINENCE
Owners often notice that lately the water bowl must be filled more frequently than in the past. Some dogs are unable to hold their bladder all night and begin crying to go outside during the night when previously this was unnecessary. Also, urinary tract infections may also be detected and true urine leaking may be observed.
HOW MUCH WATER CONSUMPTION IS NORMAL?
Each day a dog should drink about one cup of water for each ten pounds of body weight.
INCREASED OR EVEN RAVENOUS APPETITE
This symptom often leads dogs to beg incessantly or steal food from the garbage. It is important for an owner not to be fooled by the pets good appetite; eating well is not necessarily a sign of normal health.
This symptom, present in over 90% of Cushings syndrome dogs, results from hormonal redistribution of body fat plus a breakdown of abdominal musculature.
Muscle protein is broken down in Cushings syndrome. The result may be seen as exercise intolerance, lethargy, or reluctance to jump up on furniture or climb stairs.
The classical signs of endocrine (hormonal) skin diseases are:
Another condition of the skin which may be observed is called Calcinosis Cutis, in which calcium deposits occur within the skin. These are raised, hard, almost rock-like areas which can occur almost anywhere on the body.
Some other notable findings might include: excessive panting and shortness of breath, infertility, extreme muscle stiffness (called pseudomyotonia - a very very rare symptom in Cushings disease), and high blood pressure.
WHEN CATS DEVELOP CUSHINGS DISEASE
In the cat, the clinical features of Cushings disease are similar to those in the dog: excess water consumption, muscle wasting, pot-bellied appearance, thin coat, and skin abnormalities. Some cats develop a peculiar curling-in of their ear tips. An important difference to note is that while only 10% of dogs with Cushings disease develop diabetes mellitus, 80% of cats with Cushings disease develop diabetes mellitus. Diabetes in an animal with Cushings disease is very difficult to control until the Cushings disease is controlled.
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