Addison's Disease
This information is not meant to be a substitute for veterinary
care. Always follow the instructions provided by your veterinarian.
Addison’s disease (hypoadrenocorticism) is caused by a lower than
normal production of hormones, such as cortisol, by the adrenal glands.
The adrenals are small glands that are located near the kidneys. Adrenal
hormones are necessary to control salt, sugar and water balance in the
body.
Addison’s disease occurs less commonly than the opposite condition,
Cushing’s disease (overproduction of cortisol)
in dogs, and is rare in cats.
Addison’s disease occurs most commonly in young to middle-aged female
dogs. The average age is about 4 years old. The signs of Addison’s disease
may be severe and appear suddenly, or may occur intermittently and vary in
severity. Signs may include weakness, depression, lack of appetite,
vomiting, diarrhea, and occasionally increased thirst (polydipsia) and
increased urine production (polyuria).
When a pet is stressed, their adrenal glands produce more cortisol, which
helps them deal with the stress. Because dogs with Addison’s disease cannot
make enough cortisol, they cannot deal with stress, so the signs may occur
or worsen when stressed. What a dog finds stressful depends upon his/her
temperament. For many dogs, any change in their day-to-day routine, such as
being boarded or having house guests, is stressful and may precipitate or
worsen signs of Addison’s disease.
On examination of dogs with Addison’s disease one may see depression,
weakness, dehydration, weak pulses and sometimes a slow, irregular heart
rate. Routine laboratory tests often show a low blood sodium and high blood
potassium. Loss of water, in vomit and diarrhea, can lead to dehydration.
Severe dehydration increases waste products in the blood (creatinine and
blood urea nitrogen = BUN) that are normally eliminated by the kidneys.
Addison’s disease can be confused with primary kidney disease. Some dogs
with Addison’s disease have low blood sugar. See
What Do Those Lab Tests Mean? for additional
information about laboratory tests.
Sick dogs often show a pattern of changes in their white blood cells
(WBCs) called a stress leukogram. This pattern of changes in the WBCs is
caused by cortisol. The absence of a stress leukogram in a sick dog may be a
clue to consider Addison’s disease. The urine is often dilute.
Increased blood potassium can cause life-threatening abnormalities in the
heart rhythm. These abnormalities can cause the heart rate to be slow and
irregular and can be seen on an electrocardiogram (ECG).
X-rays of dogs with Addison’s disease do not show any specific
abnormalities. The heart may appear smaller than normal and rarely the
esophagus (tube from mouth to stomach) can be enlarged.
The history, physical examination, and initial laboratory tests provide
suspicion for Addison’s disease, but a more specific test, an ACTH
challenge, should be performed to confirm the disease .
There are two stages of treatment for Addison’s disease; in-hospital
treatment and long term treatment. Very sick dogs with Addison’s disease
require intravenous fluids, cortisol-like drugs and drugs to neutralize the
effects of potassium on the heart.
Long-term treatment involves the administration of hormones in one of two
forms; either a daily pill or a shot that is given about every 25 days.
Because dogs with Addison’s disease cannot produce more cortisol in response
to stress, stress should be minimized whenever possible. It may be necessary
to increase the amount of hormones given during periods of stress (e.g.
boarding, surgery, travel, etc.).
With appropriate treatment for Addison’s disease, dogs can live a long and
happy life.
Washington State University assumes no liability for injury to you or
your pet incurred by following these descriptions or procedures.
Last Edited: Dec 21, 2007 4:48 PM
