Addison’s disease, or hypoadrenocorticism, is a lack of adequate mineralocorticoid and/or corticosteroid production by the adrenal glands. The exact cause is not known; although, immune-mediated destruction is likely. The course is generally gradual with subtle signs first, only with stressful events. Full-on signs occur once the majority of both adrenal glands are lost. Young to middle-aged dogs are most often affected. Females have a higher incidence than males. Standard poodles and Portuguese Water Spaniels may be at a higher risk, but many breeds can be affected. This disease is rare in cats.
The major clinical signs include:
- lethargy,
- weakness,
- anorexia,
- vomiting,
- diarrhea,
- weight loss,
- increased drinking/urination, and
- potentially cardiovascular collapse.
Addison’s disease becomes life threatening when a crisis state occurs. In crisis, the patient is severely dehydrated and hypovolemic (having a decreased circulating blood volume) and cardiovascular collapse can occur, if aggressive treatment is not initiated.
Initial treatment largely entails aggressive fluid therapy, electrolyte control and steroid administration. Other symptomatic treatments for gastro-intestinal signs may be initiated. Basic blood work can yield a presumptive diagnosis, when considered with the animal’s presentation, but a definitive diagnosis requires a specific blood test. An ACTH stimulation test would be the definitive diagnostic of choice.
Long-term treatment involves oral and/or injectable mineralocorticoid and glucocorticoid supplementation. Often the doses of chronic medications must be altered several times before the ideal dose is found. Sometimes animals that have been treated at a constant dose for quite some time will require dose adjustment for one reason or another. Owners must always monitor their pet for clinical signs, as a crisis event can come on relatively rapidly. Stressful events (boarding at a kennel, grooming, veterinary visit, etc.) often necessitate a higher dose of steroid. Often, extra oral prednisone will be sent home with the patient for use when stress is anticipated.
The key to managing an Addisonian pet is acting early if clinical signs become apparent. It cannot be stressed enough that delay can lead to crisis and cardiovascular collapse