ADDISON'S DISEASE
What is Addison's Disease?
The correct medical term for this disease is Hypoadrenocorticism. This term
means that there is diminished or lowered hormone production from the outer
part or cortex of the adrenal gland.
What are the adrenal glands?
The adrenal glands are paired glands situated adjacent to the kidneys. Each
gland essentially consists of an outer cortex and an inner medulla. The glands
produce several vital substances which regulate a variety of body functions
and are necessary to sustain life. The most widely known of these substances
is cortisol, commonly called cortisone, produced by the outer part of the adrenal
cortex. Also produced by the cortex and equally important is aldosterone which
is a mineralocorticoid hormone. This hormone regulates the electrolyte and water
balance of the body and is involved in the excretion of potassium and retention
of sodium.
Deficiency of this hormone together with cortisol is referred to as Addison's
Disease.
What causes the disease?
In the dog the main causes are usually the result of direct injury to the tissue
due to hemorrhage, infection or certain auto immune conditions.
Thus primary hypoadenocorticoism can be immune mediated. It can also sometimes
occur when treating Cushing's Disease which can be thought of as the opposite
situation (hyperadrenocorticism) where too much cortisol and aldosterone are
produced.
Addisons disease can also occur if a dog has been treated with cortisone for
any reason on a long term basis and this is suddenly withdrawn. Another cause
can involve the pituitary gland in the brain.
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What are the clinical signs?
Signs are usually vague and nonspecific. They are commonly seen in animals
with more common medical disorders, for example, chronic gastroenteritis
or renal diseases. There may be vomiting and weight loss. A waxing and
waning course with diarrhea, sometimes increased thirst and urination
is not unusual. Intermittent shaking episodes are also characteristic.
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These animals will often respond to nonspecific medical intervention, for example
the administration of fluids by injection and also administration of corticosteroids.
Addisonian Crisis
Sometimes the condition takes on a much more acute form. There is sudden weakness,
vomiting and diarrhea, sometimes with collapse. This is an Addisonian crisis.
Under these circumstances urgent hospitalization will be necessary for a short
time.
How is it diagnosed?
Laboratory tests are necessary, often involving serial blood samples. Your
dog will probably have to be admitted for the day for the necessary tests.
What does treatment involve?
Once diagnosis has been positively established most dogs can be successfully
stabilized with oral treatment usually in the form of tablets.
Diet and activity levels do not usually have to be materially altered.
In the majority of cases even following an Addisonian crisis the condition
can be stabilized
It will be necessary to monitor progress carefully, particularly at the start
of treatment and this may involve occasionally staying with your vet for the
day.
It must be emphasized that lifelong replacement of both the glucocorticoids
and mineralocorticoids may be necessary. Some of these tablets may have to be
increased during periods of stress, such as when traveling or if the dog is
kenneled or has to undergo surgery. In addition your vet will have to see your
pet at fairly frequent intervals to check that stabilization is satisfactory.
This may involve further blood tests.
Prognosis
The vast majority of patients with Addison's Disease have a good to excellent
prognosis once the diagnosis has been established and they have been stabilized
with the appropriate drugs.
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