What Is Addison's Disease?
Addison's disease (hypoadrenocorticism) is the inability of the adrenal cortex to produce adequate cortisol (a glucocorticoid) and aldosterone (a mineralocorticoid). Without these hormones, the body cannot regulate metabolism, respond to stress, or maintain electrolyte balance (sodium and potassium).
The most common form is primary — immune-mediated destruction of the adrenal cortex. The secondary form occurs when the pituitary gland fails to stimulate the adrenals; aldosterone production is usually preserved in this form.
Symptoms: The Great Imitator
Addison's is notorious for non-specific, waxing-and-waning symptoms that mimic dozens of other conditions:
- Lethargy and progressive muscle weakness.
- Intermittent vomiting and diarrhoea (occasionally with blood).
- Weight loss and loss of appetite.
- Shaking and feeling cold.
- Polydipsia (drinking excessively) and polyuria (urinating frequently).
- Episodes that appear to resolve spontaneously and then return.
Addisonian Crisis — Veterinary Emergency
Under physical stress (infection, surgery, trauma) or spontaneously, a dog can enter an Addisonian crisis: sudden collapse, weak and slow pulse (bradycardia from hyperkalaemia), hypovolaemic shock and hypothermia. This is an immediate veterinary emergency — without intensive IV fluid therapy and emergency corticosteroids the dog can die within hours.
Diagnosis
- Biochemistry and electrolytes: a Na⁺/K⁺ ratio below 27:1 (normal 27–40:1) is strongly suggestive. Azotaemia, hypoglycaemia and hypercalcaemia are also common.
- ACTH stimulation test (gold standard): cortisol is measured before and 60 minutes after synthetic cosyntropin. Post-stimulation cortisol below 55 nmol/L confirms the diagnosis.
- ECG: in crisis, to assess hyperkalaemia-induced arrhythmias.
- Abdominal ultrasound: adrenal glands are often atrophic.
Lifelong Treatment
Maintenance therapy:
- Mineralocorticoid: desoxycorticosterone pivalate (DOCP, monthly injection) or daily oral fludrocortisone. Replaces aldosterone and regulates sodium/potassium.
- Glucocorticoid: prednisolone at a physiological low dose (0.1–0.2 mg/kg/day).
- Electrolyte monitoring: every 1–3 months initially until the dose is stabilised, then every six months.
Stress rule: during stressful situations (travel, illness, surgery, thunderstorms), double or triple the glucocorticoid dose preventively. Inform any vet treating your dog that it has Addison's before any procedure.
Prognosis
Excellent with appropriate treatment. Most dogs with well-managed Addison's live a completely normal life. The main risk remains the unrecognised crisis — which is why owners must know the warning signs and act immediately.
Keep your dog's medication, doses and monitoring appointments logged in Purzi. In an emergency room, the on-duty vet can immediately see what your dog takes — that saves critical minutes.