Hypoadrenocorticism (Addison’s)

Disease

This condition occurs when the adrenal glands, two small glands
that are near the kidneys, don’t secrete enough hormones. The
most important hormones are mineralocorticoids and
glucocorticoids (cortisol). These hormones are responsible for
many of the body’s functions including the ability to use
glucose, dealing with stressful events and the maintenance of
normal levels of electrolytes such as sodium and potassium.
Addison’s occurs when there are insufficient levels of both
hormones or of just glucocorticoids.

Demographics

The condition is most common in young, female dogs but can
manifest later in life and in male dogs. Cats are rarely
affected.

Signs

Signs associated with insufficient production of these hormones
vary. It can be chronic and vague (known as “waxing and waning”
signs- good days and bad days) with recurrent periods of poor
appetite, vomiting, diarrhea and weakness or it can present
acutely with sudden collapse and shock. Its presentation can
mimic many other diseases including kidney, neurological and
gastrointestinal disease, and tests are needed to differentiate
Addison’s from other conditions.

Diagnosis

Routine blood tests can suggest this disease, especially when
there are low blood sugar levels, high calcium levels, low
sodium levels, high potassium levels and low red blood cell
counts. But patients with Addison’s may not have all of these
changes. The most definitive test to determine if a pet has
Addison’s or not is to do an ACTH stimulation test. This test
will indicate if the animal has normally functioning adrenal
glands or not. Two blood samples are obtained to measure
cortisol levels in response to the administration of a hormone
(adrenocorticotropic hormone). In normal dogs, there will be an
increase in blood cortisol levels between the first and second
samples. In dogs with Addison’s, the cortisol levels start low
and stay low since they can’t respond appropriately.

Treatment

The main goal of therapy is to replace the hormones that pets
with Addison’s can’t make. This can be done with an oral
medication called fludrocortisone (Florinef) that must be given
daily. It is mostly a mineralocorticoid, but it also has some
glucocorticoid activity. There is also an injectable medication
called desoxycortisone pivalate (DOCP) that can be given about
every 25 days, according to the pet’s needs. Since this is only
a mineralocorticoid, a small amount of an oral supplementation
of glucocorticoids in the form of prednisone or prednisolone
must be given daily or every other day. Every dog varies in its
response to medication and thus must be closely monitored,
especially in the initial phases until it can be determined how
that individual is responding. It is important that the pet
owner of a dog with Addison’s is aware that stress of travel,
grooming, boarding, surgery or other activities may necessitate
a temporary increase in the amount of glucocorticoids that help
the body cope with stress.

Monitoring

It is important to evaluate the pet clinically (i.e. energy
levels, resolution of signs of vomiting, etc) as well as with
laboratory tests such as electrolyte levels and kidney function.
At first, after the initiation of treatment, it may be necessary
to frequently check these levels. Once the pet is stabilized and
its needs for the medications are determined, checking the pet
every 4-6 months is usually sufficient.

Prognosis

At all times, the owner must stay vigilant for a decline in the
pet’s condition and recurrence of the previously noted signs.
With the appropriate medication and close monitoring from the
owner and veterinarian, pets with Addison’s can live a normal,
good quality of life. However, the pet owner must be prepared
for expenses associated with the medications (Florinef and DOCP
are both expensive) and with rechecking laboratory tests.

If there are any problems or questions, please contact your
veterinarian.

The above is general veterinary information. Do not begin
any course of treatment without consulting your regular
veterinarian. All animals should be examined at least once every
12 months.