Addison's disease, also known as canine hypoadrenocorticism, occurs when a dog's adrenal glands don't produce sufficient corticosteroid hormones. These hormones aid the body in reactions to stress. When the body doesn't have enough of them, mildly stressful situations can cause huge problems in your dog. The adrenal glands are also responsible for balancing water, salt and sugar in the canine body.
Hypoadrenocorticism is far less common than its opposite condition, hyperadrenocorticism, or Cushing's disease, occurring when the adrenal glands produce too much hormone. Symptoms of hypoadrenocorticism might strike out of the blue, or appear gradually. Normally the dog's brain releases the adrenocorticotropic hormone (ACTH), which tells the adrenal glands to produce additional hormones. When the brain doesn't do its job informing the adrenal glands, or the glands don't react, hypoadrenocorticism results.
Although Addison's disease can occur in any dog, it's more common in certain breeds. These include the Portuguese water dog, standard and toy poodles, Nova Scotia duck tolling retrievers, bearded collie, Rottweiler, Great Dane, wheaten terrier, Labrador retriever and West Highland white terrier. Addison's disease affects females more often than males, with symptoms usually beginning before the age of 4.
Symptoms of Addison's disease run the gamut, one reason the condition is known as "the great imitator." Common signs of the disease include appetite loss, vomiting and diarrhea, hair loss, slow heart rate, lethargy, increased thirst and subsequent peeing, blood in the feces, tremors and collapse. Sometimes symptoms are vague enough that you don't even realize your dog is ill until she has an "Addisonian crisis"—going into shock and collapsing. This acute phase can prove fatal. In dogs with the chronic form of the disease, stress often provokes symptoms. Each dog is stressed by different things, but keeping to a regular routine can help.
Dogs experiencing an Addisonian crisis require hospitalization. They'll need intravenous fluids, as well as medications resembling cortisol, the primary corticosteroid produced by the adrenal glands. Dogs with chronic hypoadrenocorticism must take a daily hormone pill, or you must visit the vet each month for a hormone injection. As long as the dog is on medication, he can live a fairly normal life. However, if you know something stressful is in the cards—such as a stay in a boarding facility while you go on vacation, or a new addition to your family—ask your vet about giving him a higher dosage of hormones for that period.