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What is Addisons Disease?
Addison's disease (otherwise known as 'hypoadrenocorticism') is a disorder
that can affect humans and dogs, and very occasionally cats. It is a lifelong
disease which can be tricky to diagnose, but can usually be well-controlled
with daily tablets.
Your dog has two glands called adrenal glands, one by each kidney,
which are responsible for producing natural steroids: mineralocorticoids
such as aldosterone, and corticosteroids such as cortisol. When these glands
don't function properly, the body's steroids aren't produced - this is Addison's
disease. Normally the reason for the adrenal glands not working is 'idiopathic'
(ie. the cause is unknown).
Addison's tends to affect dogs that are young-to-middle aged, and is more common in females. Your dog may show signs such as lethargy, anorexia, vomiting, weight loss and weakness.sometimes these signs may come and go which makes diagnosis more difficult, but sometimes they can cause collapse and an emergency situation.
Aldosterone is used in the body to control the amount of water in the blood, and also to balance the amount of potassium in the bloodstream. Addisonian dogs produce too little aldosterone, so can become dehydrated and have too much potassium in their blood which can cause problems with the beating of the heart. There is also not enough cortisol, which causes tiredness and anorexia.
Diagnosis
In order to diagnose your dog with this disease, blood tests will need to be done to look at different substances in the blood, including the levels of potassium and sodium. Addisonian dogs will normally have high potassium levels and low sodium levels, but the dehydration will also change other parameters in the blood. A urine sample may be analysed to see how concentrated it is, and your vet may want to ultrasound your dog (using sound waves to make a picture of your dog's organs when a probe is placed on your dog's skin) to look at the size of the adrenal glands.
These tests will suggest that a dog might have Addison's disease, but in order to confirm the diagnosis an 'ACTH stimulation test' will be done. This will require your dog to be kept in the hospital for a few hours, but just involves two blood tests with an injection of a drug an hour before the second one.
Treatment
If your dog is being treated after an 'Addisonian crisis' (a sudden collapse due
abnormalities of the levels of natural steroids causing dehydration, shock and possible heart problems), they will need to stay in the hospital on a drip for at least a few days to rebalance all the levels of substances in their blood.
More commonly, Addison's is diagnosed and treated before this happens and can be treated with daily tablets. 'Florinef' is the name of the tablet normally used, which contains an artificial steroid called fludrocortisone. This works like aldosterone to move excess potassium out of the bloodstream and into the urine, and also replaces most of the cortisol deficiency. It is important not to give too much Florinef and, in order to choose the correct dose, regular blood tests are needed to monitor your dog's levels of potassium and sodium. At first, blood tests will be needed every week or two, but these will become more infrequent as your dog settles onto the treatment. It is common for the necessary dosage of Florinef to increase over the first year of treatment, but after that it tends to be quite stable.
Dogs usually also need another steroid tablet at the start of treatment, called prednisolone. This replaces the rest of the deficiency in cortisol. However, the prednisolone dosage is decreased over the first couple of months, and then can often be stopped. If you know your dog is likely to become stressed, such as during a long car journey or on fireworks' night, you will need to give your dog a prednisolone tablet so she can cope with the stress. You will need to get to know your dog quite well to learn when extra prednisolone tablets are needed, but your vet will help you to understand when they are necessary.
It is very important that Florinef is kept in the fridge and that you never miss doses, so do plan ahead and remember that your vet will need 48 hours to look out a repeat prescription.
If you are treating your dog for Addison's disease and she seems unwell, is off her food or is not responding well after a prednisolone tablet, you will need to see your vet. Addison's disease does require commitment from the dog's owner, but with treatment there is an excellent prognosis for a full and happy life.
