30 Oathall Road

Haywards Heath 

West Sussex

RH16 3EQ

01444 440224



Emergencies for our registered Clients : 



Mon - Fri: 08:00 – 19:00
Sat: 08:30 – 13:00


VAT Reg. No. 760 1736 42

What is Addison’s Disease?

Addison’s, also known as hypoadrenocorticism, is a very severe hormone imbalance seen mainly in dogs. The symptoms are usually vague and non-specific until the dog suffers an Addisonian Crisis, at which point their life is in danger.

What causes it?

Lack of steroid hormones; substances that are made in your dog’s adrenal glands – two small structures, next to each kidney. There are two important steroid hormones in dogs:

  • Cortisol (the stress hormone), which has many effects on the body, but functions primarily to help dogs survive times of stress (one experiment showed that animals who couldn’t make cortisol were fine until they were stressed, then they rapidly became ill and died).
  • Aldosterone, which regulates the body’s water and salt balance. Normally, the body keeps the levels of potassium in the blood much lower (over twenty-five times less) than sodium; however, without aldosterone, the potassium level gets higher and higher.

The most common cause of Primary Addison’s is thought to be immune system damage to the adrenal glands, so they no longer make enough hormones (just like Type I Diabetes, where the pancreas no longer makes enough insulin). Other possibilities include tumours, or physical damage to both glands.More rarely, damage to the pituitary gland or certain tumours may cause Secondary Addison’s.
The third form is Iatrogenic Addison’s disease, which is most commonly due to high doses of steroid medication over a long time. Because the levels of artificial steroids in the blood are high, the adrenal glands stop making hormones – but if the medication is stopped too quickly, it results in a steroid deficiency until the adrenals can get back “into gear”. Other causes of Iatrogenic Addison’s include overdose with certain drugs (mitotane or trilostane).Addison’s can affect any dog, but is most common in young to middle-aged adult bitches.What are the symptoms?

Most of the time, a dog with Addison’s may seem fairly normal. However, they are likely to have subtle, waxing and waning symptoms, typically including intermittent vomiting, chronic fatigues, muscle weakness or shaking, and weight loss. These symptoms, however, often appear to improve on their own, only to recur later. Often, affected dogs are abnormally placid or quiet – but as the disease most often strikes in early adulthood, owners may confuse this with growing out of puppy behaviour.

Sooner or later, affected dogs will develop what is called an Addisonian Crisis. This usually starts with vomiting and/or diarrhoea, but fails to improve on its own, and rapidly

leads to collapse, dehydration, shock, heartbeat abnormalities and then death. In up to 30% of cases, an Addisonian Crisis is the first symptom.

How is it diagnosed?

The changes in the blood are very characteristic (a sodium to potassium ratio of under 25:1 and the absence of a stress-leukogram in the white blood cell counts) – dogs with this pattern are almost always Addisonian. However, a conclusive diagnosis requires a special blood test called an ACTH Stimulation Test.

Can it be treated?

Yes! In a Crisis, intravenous fluids can be used to reduce the dangerously high potassium level, and an injection of steroids (such as dexamethasone, to replace the cortisol) will temporarily stabilise the patient. Long term therapy requires replacement of both the cortisol and the aldosterone, and there are two options. The first is a human medication called fludrocortisone, which is a refrigerated tablet given daily, for life. The second is a very new drug (it has only become available in the last few months) which is a long-acting injection, given every 3-6 weeks (depending on the dog).

In both cases, regular monitoring with blood tests is needed until the optimum dose is achieved; thereafter, blood samples are only needed two or three times a year.
If untreated, the condition will eventually worsen and lead to an Addisonian Crisis.

If you think your dog may have any of these symptoms, make an appointment for them to be checked out by one of our vets. If you think they may be having an Addisonian Crisis, call us straight away – delaying treatment may put their life in danger.