What is Addison’s disease?
Addison’s disease (also called hypoadrenocorticism) is a disorder where the adrenal glands, which sit near each kidney, don’t produce enough hormones.
Two important hormones are affected:
- Cortisol – a stress hormone (glucocorticoid) important for energy and metabolism.
- Aldosterone – a hormone (mineralocorticoid) that regulates salt, water, and electrolyte balance.
In most dogs, Addison’s disease develops when the immune system mistakenly attacks the adrenal glands. Less common causes include infections, cancer, or certain medications.
Some breeds have a higher risk, including Standard Poodles, Bearded Collies, Nova Scotia Duck Tolling Retrievers, Portuguese Water Dogs, Great Danes, and Labrador Retrievers.
What are the Clinical Signs?
Dogs suffering from Addison’s disease usually have vague and non-specific clinical signs. Early or mild signs may include:
- Lethargy (low energy)
- Decreased appetite
- Vomiting or diarrhoea (intermittent or recurring)
- Weight loss
- Increased thirst and urination
- Shivering or weakness
Dogs may appear unwell, and these symptoms may wax and wane. Eventually, if the disease is not diagnosed, dogs may become severely unwell in a phenomenon known as an Addisonian crisis. Signs associated with a Addisonian Crisis include:
- Collapse
- Dehydration
- Vomiting and diarrhoea
- Heart disturbances
An Addisonian crisis is considered a medical emergency, and immediate hospitalisation and treatment is needed.
How is it Diagnosed?
A patient’s clinical history, clinical signs and routine blood tests may suggest that a dog is suffering from Addison’s disease. However, the most definitive diagnostic test for Addison’s disease is the ACTH stimulation test. ACTH is a hormone naturally produced by the body’s pituitary gland (located in the brain) and signals to the adrenal glands to produce cortisol. This test involves a short stay at McLaren Vale Veterinary Surgery for a few hours, and the following:
- A blood sample is taken to measure baseline cortisol.
- A synthetic ACTH injection is given. This stimulates the production of cortisol by the dog’s adrenal glands.
- A second blood sample is taken 1–2 hours later.
- Cortisol levels in the two blood samples are measured and compared.
How is Addison’s disease treated?
As Addison’s disease results from an insufficiency of hormones, treatment revolves around replacement of the missing hormones.
Mineralocorticoid Replacement (to control the body’s electrolyte balance):
- Option 1 - Fludrocortisone (Florinef) - an oral medication given once or twice daily.
- Monitoring blood tests: Frequent initial blood testing to ensure the correct dosage is given, then 2–4 times per year.
- May need dose adjustments over time
- Possible side effects: increased thirst and urination.
- Option 2 - Desoxycorticosterone pivalate (DOCP) – Also known as Percorten-V or Zycortal. This is a long-acting injection which needs to be given every 28 days.
- Given every 28 days (some owners can learn to administer at home)
- Blood tests at start, then once or twice yearly long-term.
- Often provides more stable electrolyte control than Florinef.
Glucocorticoid Replacement (cortisol support):
- Prednisolone tablets – usually once daily.
- Dogs on Florinef may need low doses.
- Dogs on DOCP always need prednisolone.
- Doses must be increased during stress (boarding, surgery, travel, illness).
What is the prognosis for patients with Addison’s disease?
Dogs with Addison’s disease have an excellent when managed appropriately. If medications are not given correctly, or appropriate monitoring does not occur, a life-threatening Addisonian crisis could occur.