Addison's disease (Hypoadrenocorticism)
Addison's disease is also known as hypoadrenocorticism. It is an
insufficient production of adrenal hormones by the adrenal gland.
Since these hormones are essential for life, this is an extremely
serious disease and it must be treated as such.
Adrenal insufficiency can be primary or secondary. Primary
adrenocorticism affects salt/potassium balance in the body and
glucorticoid as well. Secondary adrenocorticism usually only affects
the glucocorticoids. It is not known why primary adrenocorticism
occurs but it may be an immune mediated process. Secondary
adrenocorticism probably occurs most often when prednisone or other
cortisone being administered for medical reasons are suddenly
withdrawn. It can occur as a result of pituitary cancer or some
other process that interferes with production of hormones that
stimulate the adrenal glands.
Most dogs with Addison's disease initially have gastrointestinal
disturbances like vomiting. Lethargy it also a common early sign.
Poor appetite can occur as well. These are pretty vague signs and it
is extremely easy to miss this disease. More severe signs occur when
a dog with hypoadrenocorticism is stressed or when potassium levels
get high enough to interfere with heart function. Dogs with this
problem will sometimes suffer severe shock symptoms when stressed,
which can lead to a rapid death.
When potassium levels get high heart arrhythmias occur or even heart
stoppage which also is fatal. In some cases, especially secondary
Addison's disease, there are no detectable electrolyte changes.
This disease can be picked up by changes in the ratio between sodium
or potassium by accident at times. When this happens it is still
extremely important to treat for it. It is confirmed by an ACTH
response test -- administration of this hormone should stimulate
production of adrenal hormones. If this does not occur then
hypoadrenocorticism is present. In cases in which the electrolyte
levels are normal this is the only test for the problem and it will
be missed unless it is looked for specifically. At times this
disease can be hard to differentiate from renal failure because the
symptoms and even the bloodwork can be similar ---- so the ACTH
response test may be necessary to differentiate them.
Treatment for this disease is usually done by oral administration of
fludrocortisone acetate (Flurinaf), salting the food, and
administration of corticosteroids like prednisone. In a crisis
situation this disorder must be treated more aggressively with
intravenous fluids, IV glucocorticoids and correction of acid/base
balances.
You have to pay close attention to a dog with this problem. Don't
ignore any changes in appetite, GI disturbances or anything else
that makes you think your dog is ill. If you work with your vet and
are careful about following his or her directions this disease has a
good prognosis when it is discovered before a crisis occurs.
