Addison's Disease
Addison's disease (hypoadrenocorticism) results from insufficient production of corticosteroids (cortisol and aldosterone) by the adrenal glands. It is often called 'the great pretender' due to its vague, waxing-and-waning clinical signs that mimic many other diseases. Acute adrenal crisis (Addisonian crisis) is a life-threatening emergency.
Symptoms & Signs
- Waxing and waning lethargy
- Intermittent vomiting and diarrhea
- Poor appetite
- Weight loss
- Muscle weakness
- Shaking or trembling
- Collapse (Addisonian crisis)
- Bradycardia
Causes & Risk Factors
Most commonly immune-mediated destruction of the adrenal cortex (primary Addison's). Less common causes include granulomatous disease, metastatic tumors, or iatrogenic (abrupt withdrawal of corticosteroids, mitotane overdose). Secondary Addison's results from pituitary dysfunction.
Diagnosis
ACTH stimulation test (gold standard): both pre- and post-ACTH cortisol levels are low. Electrolyte abnormalities (hyperkalemia, hyponatremia) in classic cases. Baseline cortisol <2 μg/dL is highly suggestive. ECG changes from hyperkalemia.
Treatment
Acute crisis: aggressive IV fluid therapy (0.9% NaCl), dexamethasone. Chronic management: monthly DOCP (desoxycorticosterone pivalate) injections for mineralocorticoid replacement, daily prednisone for glucocorticoid replacement. Stress-dose adjustments.
Prevention
No prevention for immune-mediated form. Gradual tapering of exogenous corticosteroids to prevent iatrogenic form. Careful monitoring during mitotane therapy for Cushing's disease.
Prognosis
Excellent with appropriate lifelong supplementation. Most dogs live normal lifespans with proper management. Requires owner education about stress dosing and emergency recognition.
Affected Breeds (2)
| Breed | Species | Size |
|---|---|---|
| Portuguese Water Dog | Dog | Medium |
| West Highland White Terrier | Dog | Small |