My vet says my dog has Addison’s disease – what is it?

Addison's disease was named after Thomas Addison, who discovered the human version, which we also know as hypoadrenocorticism. It is a very severe excessive hormone imbalance, and in the Animal World, found mainly in dogs. In itself, the signs are non-specific unless the dog has an Addisonian Crisis. If this happens the dog's life can be in serious danger. This Pets4Homes article is going to look deeper at the symptoms, causes, and treatment of the disease.

What causes it?

The cause of Addison's disease is the deficiency of steroid hormones in the body. These are normally made in the adrenal glands, which are located next to the dog's kidneys. Every animal has steroid hormones, and in the dog, there are two important hormones:

• Cortisol is known as the stress hormone. This steroid hormone has a range of effects on the dog, but it has one main purpose - to help the dog when it is stressed, by combating it.
• Aldosterone - this steroid hormone regulates water and electrolytes/salt in the body. Its function, when working efficiently is to keep potassium in the dog's blood, lower than the sodium (salt) content in it. If the body does not produce Aldosterone, potassium levels raise constantly higher.

Are there different types of the disease?

Yes, there is. In fact, there are three known types of Addison's disease:

• Primary Addison's
• Secondary Addison's
• Iatrogenic Addison's

Primary Addison's

This is the most common type of the disease. It is concerned with damage to the adrenal glands - particularly immune damage. It means the glands may no longer produce enough of the steroid hormones. Other reasons the glands may not make enough hormones can be due to tumours or even that they have been damaged physically.

Secondary Addison's

This type of the disease is the most uncommon. I can be caused by specific tumours or damage to the pituitary gland. This gland is found in the base of the brain and is a pea-sized organ. Among other functions, it stimulates other glands (such as the adrenals) to produce hormones.

Iatrogenic Addison's

This form of the disease is common with high doses of steroid treatment over a long period of time. It's due to the level of the synthetic steroids in the blood, causing the adrenal glands to cease producing hormones. The synthetic steroids need to be reduced gradually, otherwise, there is a lack of proper steroids until the adrenal glands start producing again.

The disease can affect any breed of dog; however, research has found that the most common age range is in younger to mid-aged bitches.

What do I need to look for?

Although much of the time you may not notice any signs that your dog has the disease, as they can seem normal. The disease does have small signs and symptoms though, and an owner of a dog with Addison's will come to recognise the signs as part of the disease. The symptoms include occasional:

• Vomiting
• Lethargy
• Weakness in the muscles
• Shaking
• Weight loss

The above seems to improve without any treatment after a short time but can happen again later. Dogs with Addison's are quite often quieter than normal and seemingly laid-back, the problem arises because the age Addison's disease normally happens. The quieter behaviour is often put down to the dog leaving puppyhood and becoming an adult.

In time dogs carrying the disease will display an Addisonian Crisis - which normally starts with symptoms that do not improve in time. Vomiting and diarrhoea are the usual first symptoms. These can then escalate quickly to:

• Collapse
• Dehydration
• Heart rate changes
• Shock
• Death

Sadly, an Addisonian Crisis is often the first sign the owner will know about the disease. In up to 30% of cases, there are no other indications.

How does the vet know it's definitely Addison's?

The tell-tale signs are shown with blood tests. Results that show a sodium to potassium ratio of under 25:1 along with a white cell count that shows no presence of the stress cell, are predominately carrying the disease.

A specialist test can confirm the findings and give a positive result. Blood is taken for something called an ATCH Stimulation Test. This is the only test available that can show if the dog is carrying Addison's.

ATCH (adrenocorticotropic hormone) is produced in the pituitary gland and this stimulates the adrenal glands to produce the Cortisol steroid. In the test, synthetic ACTH is used to mirror the stimulation effect. If the adrenal glands fail to produce Cortisol, then the dog is classed as an Addison's dog.

What treatment can a dog with Addison's get?

The good news it there is treatment available for the disease. If the dog is having an Addisonian Crisis, the first treatment is to dilute the potassium in the blood and reduce it from a dangerous level. This is achieved by the use of intravenous fluids, with the dog on a drip. To make sure the dog becomes stabilised - even temporarily, they will also be given an injection of a drug such as dexamethasone, which will replace the missing Cortisol.

For a long-term plan, the steroids need replacing in the dog's bloodstream. For giving them the cortisol and aldosterone they need to stabilise and let them lead a good life, there are presently two options available.

• Tablet therapy.
• Injection therapy.

Tablet therapy

The tablet is actually a human medication (many licensed animal drugs start out as human drugs), it is called fludrocortisone and the tablets require to be kept in a refrigerator. Tablet therapy means the dog needs to be dosed every day, for the rest of their lives.

Injection therapy

This therapy is very new - the drug has only been available recently. It is called Desoxycorticosterone Pivalate or DOCP and is injected every 3 to 6 weeks, according to how the dog responds.

For either treatment, blood tests are taken at regular intervals, until the dog is stable, then monitoring blood tests taken several times a year. If treatment ceases, the dog will eventually have an Addisonian Crisis.

Conclusion

Addison's is a complex disease, but if your dog exhibits any of these symptoms, don't delay - please seek the advice of your vet. A dog having an Addisonian Crisis has their life at risk.