Cushing's Disease (Hyperadrenocorticism)

Cushing's Disease, or Hyperadrenocorticism, is the production of an excess of adrenal hormone, or, more particularly, corticosteroids. Cushing's 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 that are located atop the kidneys. Cortisol is stored in the adrenal gland and is released in times of stress as 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. However, ifthe body is exposed to this hormone most of the time instead of only for short stressful periods, the state of break down becomes debilitating. There are several mechanisms that can lead to Cushing's syndrome and, as they are treated differently, it is important to determine which one is at work in a given animal. 

Cushing's Disease is diagnosed by both a full physical exam, and a series of blood panels done by a veterinarian. In the normal body, the pituitary

 gland, which is 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, called ACTH, 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 via ACTH secretion and it occurs rapidly.

*Pituitary-Dependent Cushing's Syndrome
This form of Cushing's accounts for 85% of dogs with Cushing's syndrome. Basically, the pituitary gland grows a small tumor. The tumor is generally too small to cause any trouble and is usually a benign tumor. This tumor, however, over-produces ACTH, thus leading to over-stimulation and enlargement of both adrenal glands and an over-production of cortisone. Occasionally, in about 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 hard to treat.

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. There is little or no production of ACTH from the pituitary gland, and as a result the opposite adrenal gland is usually atrophied or small.

Symptoms

There are many clinical signs associated with Cushing’s syndrome 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 pet’s “good appetite;” eating well is not necessarily a sign of normal health.

POT-BELLIED APPEARANCE

This symptom, present in over 90% of Cushing’s syndrome dogs, results from hormonal redistribution of body fat plus a breakdown of abdominal musculature.

MUSCLE WEAKNESS

Muscle protein is broken down in Cushing’s syndrome. The result may be seen as exercise intolerance, lethargy, or reluctance to jump up on furniture or climb stairs.

SKIN DISEASE

The classical signs of endocrine (hormonal) skin diseases are:

*Hair loss on the main body sparing the head and legs
*Thin, wrinkled skin with poor wound healing
*Hair that does not grow back after clipping.  
*Blackheads and darkening of the skin, especially on the abdomen.
*Persistent or recurring skin infections (especially if the dog is not itchy during times when the skin infection is cleared).
*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, and high blood pressure.

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