Glossary
Addison's disease
A hormone disease in which the adrenal glands make too little cortisol and often too little aldosterone, causing vague illness and sometimes crisis.
Also called: Addisons, hypoadrenocorticism, adrenal insufficiency, the great pretender
In Addison's disease, or hypoadrenocorticism, the adrenal glands stop producing enough of the hormones that handle stress and balance salts in the body. It usually affects young to middle-aged dogs, more often females, and breeds such as the Poodle and the Portuguese Water Dog are known to be at risk.
Signs are vague and come and go, which is why it is nicknamed the great pretender. They include lethargy, poor appetite, vomiting, diarrhea, weakness, shaking and weight loss, and a dog can seem to improve with fluids and then relapse.
An Addisonian crisis, with collapse, a slow heart rate and shock, is an emergency. Blood tests that check electrolytes and an adrenal hormone test confirm it. It is the opposite of Cushing's disease. A veterinarian manages it for life.
Last reviewed November 8, 2026