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Addison's Disease in Dogs

overview

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What is Addison's disease?

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Hypoadrenocorticism, more commonly known as "Addison's disease", is characterised by the lack of production of the steroid hormone cortisol by the adrenal glands, which sit next to the kidneys. This causes various effects in the body which, if untreated, can be dangerous or even fatal. Often there is no inciting cause for why the adrenal glands stop functioning normally, but some breeds seem to be predisposed. The majority of cases of Addison's disease can be successfully managed, however treatment is lifelong as the condition is not curable.

symptoms

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What are the symptoms of Addison's disease?

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Dogs with Addison's disease can present with either chronic (slow onset) or acute (sudden onset) symptoms. The disease is most commonly seen in female, young to middle aged dogs, particularly poodles, bearded collies and cocker spaniels.

Chronic symptoms are typically "waxing and waning", and can include:

• Inappetence
• Lethargy
• Vomiting or diarrhoea
• Weight loss
• Excessive thirst
• Abdominal pain
• Restlessness

Commonly chronic Addison's disease is difficult to diagnose as the symptoms are so non-specific.

Acute cases present collapsed with a very slow heart rate, low temperature, abdominal pain and often vomiting and/or diarrhoea. This is an emergency requiring rapid treatment.

diagnosis

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What tests are used to diagnose Addison's disease?

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Diagnosis of Addison's can be challenging; in chronic cases symptoms are often vague and variable.

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General blood work

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Addison's commonly causes low sodium and high potassium on blood work. In acute cases, kidney levels may be elevated due to dehydration and low blood pressure.

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Urinalysis

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Dogs with Addison's often have dilute urine despite dehydration. This change is not specific for Addison's disease however, as many conditions cause dilute urine.

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Cortisol

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The level of cortisol can be measured in the blood; a low result suggests Addison's disease. Again, this is not specific so an ACTH stimulation test must be performed to confirm the diagnosis.

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ACTH Stimulation Test

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This involves two cortisol tests, with a small dose of synthetic hormone administered in between. For most dogs this will cause their cortisol to increase dramatically, but a dog with Addison's will show no response. This confirms the diagnosis.

Often cortisol and ACTH stimulation tests must be sent to an external lab to be processed, meaning it can be up to a week before your vet has a result. In acute cases, we sometimes have to take samples but treat on an assumed diagnosis while we await results.

treatment

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How is Addison's disease treated?

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Dogs presenting collapsed need urgent treatment to stabilise them, and often need several days in hospital on fluids and intravenous medication while they start to respond to treatment.

Management of Addison's requires us to administer the hormones that aren't being produced. This is done using an injection every 28 days, combined with a low daily dose of oral steroids. Both are needed for successful management.

It's important to check the levels of sodium and potassium in the blood regularly to ensure the dose is correct - this is initially done 10 days after the first injection and then regularly between doses. Some dogs need a lower dose long-term, or a longer interval between doses. Once stable, blood can be checked every 3-6 months.

Patients with Addison's disease can't make additional steroid to respond to stress. To compensate oral steroids may need increasing if a stressful event is anticipated – your vet will advise you.

outlook

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What is the outlook of Addison's disease?

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The prognosis for dogs with Addison's is good, however, medication is life-long, and it is important to give the injection when it is due rather than a few days earlier or later.