Addison's Disease in Dogs

Addison's disease when diagnosed and treated correctly means your four legged friend will be able to lead an active and normal life much like any other dog even if they do have the condition. But what exactly is this disease? Addison's disease is also known as adrenal insufficiency or hypoadrenocorticism. Unfortunately, it has symptoms that are commonly seen in other ailments and diseases which makes it harder for vets to diagnose the condition.

As a result vets have to go through a process of elimination before they can correctly diagnose Addison's disease. However, as soon as your pet is put on the correct medication, there is no reason why they cannot live a full and normal life just like any other dog although they would need to be put on medication for the rest of their lives.

What Goes Wrong To Cause the Condition?

There's an adrenal gland on both kidneys which are made up of two layers being the cortex and the medulla. The cortex forms the outer layer and its function is to secrete corticosteroid hormones, namely cortisol and aldosterone. The second layer is called the medulla, this forms part of the sympathetic nervous system and its function is to secrete adrenaline (epinephrine). The medulla is not normally affected by Addison's disease whereas the cortex is and ceases to produce the necessary hormones.

Three Types of Addison's Disease

There are three types of Addison's disease being primary, secondary and atypical.

• Primary and atypical Addison's Disease: Normally the result of damage to the adrenal glands due to abnormal activity in the body's immune system – this is called immune-mediated so if you hear a vet referring to Addison's Disease in this way, you will be familiar with the term
• Secondary Addison's Disease: This is caused due to failure of the pituitary gland which stimulates the adrenal glands with a hormone called adrenocorticotropic (ACTH)

It is very important to determine which sort of Addison's Disease has been diagnosed and then to know just what treatment your dog is receiving for the condition from your vet.

A Difficult Disease to Diagnose

It can be hard to recognise the symptoms of Addison's disease because they can be a quite vague. The problems start because these can often be confused with many other health related problems in dogs. However, the first signs to watch out for are listlessness or sometimes your dog may seem depressed. A lot owners describe their pets as just 'seeming off colour' - they lose that sparkle they normally have in their eyes. If your dog goes off their food, this could be another sign there is something very wrong especially if your pet is normally a healthy eater.

Signs To Look Out For

Apart from your pet acting a 'bit off' and not being interested in their food, other symptoms like vomiting and diarrhoea are also common. Very often dogs feel pain in their hind quarters and suffer generalised muscle weakness. This may become evident when they go to jump up on something and just can't do it. You may also notice your pet shivering and they may even have bouts of tremors. If you see any of these signs, then it's time to get your pet checked out by a vet as quickly as you can.

It's not uncommon for the symptoms to vanish and then come back again. The problem really starts as this could happen over a period of months or even years which is another reason for the disease to be so hard to diagnose. Unfortunately, over time the adrenal glands get weaker and therefore dogs can eventualy suffer an acute episode called an Addisonian crisis.

What Happens in an Addisonian Crisis?

Should a dog suffer an Addisonian crisis, their potassium levels rise and this disrupts normal heart function. One condition known as arrhythmia may happen as a result of this, and then blood pressure drops often to extremely low levels. Kidney function is affected too and what is known as creatinine and BUN levels become elevated. If this happens, then renal failure will follow as kidneys are unable to function effectively.

To cope with renal failure, dogs are normally put on an IV in order to keep them hydrated, and this often works with animals recovering almost miraculously. As a result vets then know the problem first started due to adrenal glands not doing their job properly - hence Addison's disease is diagnosed and not a kidney complaint that shows very similar symptoms.

How to Know The Condition is Actually Addison's Disease

Electrolyte levels and especially levels of sodium (Na) and potassium (K) cause the greatest worry when the condition starts to take hold. Not only is it important for a vet to look at these two electrolyte values but the ratio between them too. If a dog is suffering from Addison's disease, changes in ratios and levels of electrolytes is a sure indication of the condition.

However, this is not a definitive test because if a dog is suffering from secondary and/or atypical hypoadrenocorticism, then electrolyte levels may not change at all. In order to achieve a definitive diagnosis, a vet will give the dog a response test or a ACTH. This checks whether the adrenal glands are indeed producing the necessary corticosteroid hormone cortisol.

The test is relatively simple with the vet taking an initial blood test to check cortisol levels. The dog is then injected with a pituitary hormone ACTH which encourages the adrenal glands to produce the much needed cortisol. After a short period of time(usually around one hour), the vet will do a second blood test to check levels of cortisol for a second time. This test indicates if the adrenal glands are indeed functioning properly or not as the case may be – and will determine whether your dog has indeed got Addison's disease.

If your dog has been prescribed any glucocorticoids which includes predinsone for any other health issues – you need to tell your vet because it will affect the results of a ACTH test – dexamtheasone, on the other hand will not affect the test.

What Medication Will My Dog Have to Take?

Addison's disease can be treated with several different medicines. The first being a mineralocorticoid which replaces a hormone called aldosterone and it is this that will maintain the correct electrolyte levels in your dogs' body. It's one medicine can be administered either orally or in injection form.

Cortisol and glucocorticoids also need to be replaced because adrenal glands have stopped working. Vets normally administer an oral medication called hydrocortisone to replace these valuable hormones.

When a vet diagnoses atypical and secondary Addison’s disease the glucocorticoid is the only medication given to a dog with either of these types of the condition because electrolyte levels are rarely affected.

Can a Dog With Addison's Disease Live a Normal Life?

Dogs with the condition can lead normal, active and long lives but they will need to be on medication the whole time. Their condition would also need to be monitored and as a owner, by keeping a close eye on your pet, you can soon tell if things have changed or not. You get to know your pet extremely well over time and this enables you to recognise early signs of any changes in their condition. Working closely with your vet there is no reason at all why your four legged friend can't carry on doing the things they love best – and that's being a healthy happy dog!