Addison's Disease in Dogs: The Sneaky Diagnosis
Addison's disease — hypoadrenocorticism — is the mirror image of Cushing's disease. Where Cushing's means too much cortisol, Addison's means too little. The adrenal glands fail to produce adequate cortisol and often aldosterone, the hormone that regulates sodium and potassium. Without these hormones, the body can't manage stress or maintain normal electrolyte balance. The disease is called "the great pretender" because its episodic, vague symptoms are easily attributed to dozens of other conditions for months before the right diagnosis is made.
| Sign Type | What You See |
|---|---|
| Chronic (waxing/waning) | Lethargy, vomiting, diarrhea, poor appetite, weight loss, weakness |
| Acute crisis | Collapse, severe weakness, low heart rate, low blood pressure — emergency |
| Bloodwork clues | High potassium, low sodium (Na:K ratio below 27 is highly suspicious) |
Diagnosis: The ACTH Stimulation Test
Addison's is confirmed with an ACTH stimulation test — cortisol is measured before and after synthetic ACTH injection. A dog with Addison's produces little to no cortisol response. The classic bloodwork finding is an elevated potassium-to-sodium ratio (the Na:K ratio), which should prompt testing even if the dog doesn't look critically ill. Electrolyte panels from annual wellness bloodwork sometimes catch the abnormality incidentally.
Management: Lifelong but Manageable
Most dogs receive monthly injections of DOCP (desoxycorticosterone pivalate, brand name Percorten) to replace the mineralocorticoid aldosterone, plus daily low-dose oral prednisone to replace cortisol. Stress dosing (tripling the prednisone dose) is required during illness, surgery, or major stressors. Dogs on appropriate therapy live normal, active lives. Carrying a "stress dose" of prednisone with a medical alert tag is advised for Addisonian dogs.
Frequently Asked Questions
What are the signs of Addison's disease in dogs?
Signs are vague and wax and wane: lethargy, vomiting, diarrhea, poor appetite, weakness, and shaking. Many dogs are repeatedly treated for 'GI issues' before Addison's is diagnosed. An Addisonian crisis (collapse, severe weakness, low blood pressure) is the acute emergency form.
Is Addison's disease treatable in dogs?
Yes — Addison's is manageable with lifelong medication. Most dogs do extremely well and live normal lifespans. Treatment typically involves monthly injections of DOCP and daily oral prednisone.
Which breeds are prone to Addison's disease?
Standard Poodles, Portuguese Water Dogs, Nova Scotia Duck Tolling Retrievers, Bearded Collies, and Great Danes have elevated prevalence. Female dogs are diagnosed more often than males. Middle-aged dogs are most commonly affected.