What is Addison's disease?
Also known as hypoadrenocorticism, Addison’s disease is a potentially life-threatening deficiency in hormones produced by the adrenal glands.
These glands, located near the kidney, produce hormones such as steroids, which are stress hormones, and aldosterone, which regulates the body’s salt, sugar and water balance.
Dogs with insufficient levels of these hormones can become very unwell. Addison’s disease is more common in young to middle-aged dogs, particularly females.
What are the clinical signs of Addison's in dogs?
Signs of Addison’s in dogs typically include weakness, lethargy, lack of appetite, depression, reluctance to exercise, vomiting and diarrhoea. These may appear very suddenly and can be both intermittent and severe. Dogs suffering from the illness may also drink more and urinate more. It has been known for dogs with Addison’s to arrive at the vets extremely ill, in shock or collapsed, and almost in a coma. This is called an Addisonian crisis.
What causes Addison's in dogs?
Addison’s disease is usually caused by immune-mediated destruction of the adrenal glands. This means the dog’s immune system has become compromised and the adrenal glands have been damaged or attacked and therefore cannot produce enough hormones. Other less common causes include cancer and infections.
There are two types of Addison’s. The most common, or typical, form is due to a lack of both types of steroid hormones and can be fatal. The less common, or atypical, form of Addison’s is due to a lack of glucocorticoids alone.
How is Addison's disease in dogs diagnosed?
Dogs with suspected Addison’s often collapse due to dehydration, low sodium, high potassium, low blood sugar and high calcium. Diagnostic tests on kidneys may also show up as abnormal.
In general, these clinical signs are enough for the vet to start treatment until a final diagnosis is established.
A final diagnosis is made if and when the vet establishes very low levels of steroid hormone in the blood and usually by also performing a special ACTH stimulation test (ACTH stimulates the adrenal glands to produce steroid hormones) with a documented reduced response in terms of steroid production.
Is stress a factor in Addison's disease?
One of the reasons adrenal glands produce steroids is to help dogs deal with stress and illness. If a dog cannot make enough of these hormones they may not be able to deal with stress or their clinical signs will worsen when they are stressed. Stress is generally caused by a change in the dog’s routine. It’s important to minimise stress from your dog’s life.
Dogs who are very sick with Addison’s disease will require hospitalisation and intravenous fluids.
What is the treatment for Addison's?
Dogs who are very sick with Addison’s will require IV fluids and close monitoring in hospital of their electrolytes (sodium and potassium) and other blood parameters. High levels of potassium can cause abnormal heart rhythms and may be life-threatening. Once your pet has been stabilised in the hospital and a diagnosis has been established, they will likely be started on their long-term medication before going home.
Medication for Addison’s disease is needed for life and patients typically to do very well on it. Cases of typical Addison’s are treated with a combination of corticosteroids
(prednisolone) and mineralocorticoids. Mineralcorticoids maybe given by injection once a month or in tablet form. Dogs who only lack the corticosteroids (atypical cases), are only given prednisolone and monitored, although over time they might end up needing additional medication. Initially, when treatment is first started, your vet will need to recheck your pet’s blood paramenters regularly to ensure the medication is working. This close monitoring will be reduced over time.
What is the prognosis?
As long as dogs receive the appropriate treatment, they can live a long and happy life. It’s worth noting, however, that anything that prevents the dog from getting its medication is likely to result in an emergency. Dogs with Addison’s have a lower immune system so even minor illnesses can be life-threatening and may not respond as well to treatment. The stress brought on by such an illness could also lead rapidly to an Addisonian crisis, so prompt treatment of any illnesses is very important in dogs with Addison’s disease.