Addison's Disease -
hypoadrenocorticism
(5min read)
Although Addison’s disease can be a very serious disease the changes it causes can be very subtle in the early stages. The signs of the disease are variable and often vague. It is important to get an early diagnosis because, with treatment, affected animals can lead a normal and full life.
What is addison's disease?
Addison’s disease occurs when dogs fail to produce enough of the hormone, cortisol and in some cases, the hormone, aldosterone. The other name for Addison’s disease is hypoadrenocorticism.
In the normal dog, cortisol and aldosterone are produced by the adrenal glands, (which are located just in front of the kidneys). Scientists think that cortisol has hundreds of possible effects in the body. Because cortisol is so vital to health, the amount of cortisol produced by the adrenal glands is precisely balanced. Cortisol production is regulated by hormones produced in the brain (from the pituitary) which stimulate the adrenal glands. When the adrenal glands receive the signal from the pituitary they respond by producing cortisol. Cortisol’s most important job is to help the body respond to stress. In Addison’s disease the body is unable to produce enough cortisol and affected animals may become ill at times of stress.
Aldosterone helps maintain blood pressure and the water and salt balance in the body by helping the kidneys retain sodium and excrete potassium. When aldosterone production falls too low, the kidneys are not able to regulate salt and water balance, causing abnormal electrolyte levels and the blood volume and blood pressure to drop.
What causes Addison's?
Addison’s disease is usually caused by damage to the adrenal glands. Most cases of Addison’s disease are caused by the gradual destruction of the outer layer of the adrenal glands, by the body’s own immune system.
Common Signs of Addison's Disease
The steroid hormones affect almost every tissue in the body and the signs of Addison’s disease can be diverse. The signs of adrenal insufficiency usually begin gradually. The most common clinical signs are:
Waxing and waning gastrointestinal signs (vomiting and/or diarrhoea).
Lethargy (tiredness), weakness, exercise intolerance
Loss of appetite
How would I know if my pet had Addison's ?
The signs of Addison’s disease are extremely variable and can be subtle in the early stages. Addison’s disease usually affects younger dogs and females are more at risk than males. In some breeds of dog eg Standard Poodles and Bearded Collies, the disease is more common. Many owners do not recognize the signs of Addison’s disease in their pet but are aware that their pet is ‘not quite right’. You should be suspicious if your pet suffers from recurrent illness (particularly vomiting or diarrhea) but recovers rapidly when treated with intravenous fluids.
How will my vet diagnose the disease?
In its early stages, Addison’s disease can be difficult to diagnose. A review of your dog’s medical history may make your vet suspect Addison’s disease. Although Addison’s disease can be difficult to recognize it is very easy to diagnose. Your vet may suspect the disease based on simple blood tests but specific blood tests are needed to confirm the disease. These tests measure the level of cortisol in the blood. However, because the levels of this hormone vary from hour to hour in the normal animal, the disease cannot be diagnosed on the basis of one blood test. Your vet will need to take a number of blood samples (before and after an injection of a hormone which mimics the action of the pituitary to stimulate your dog’s adrenal glands to produce cortisol). These blood samples will need to be sent away to a veterinary laboratory for analysis. If your dog is unable to increase the amount of cortisol in the blood after the injection then it is clear that its adrenal glands are not working properly.
An abdominal ultrasound and x-rays are also often required to rule out other causes of gastrointestinal upset and can help with the Addison’s diagnosis if small adrenal glands are seen.
How can the disease be treated and is it worth it?
Addison’s disease is caused by there being too little cortisol and/or aldosterone in the blood. Treatment of Addison’s disease involves replacing, or substituting, the hormones that the adrenal glands are not making. Oral steroid tablets (prednisone, prednisolone, dexamethasone) are given to replace cortisol, and DOCP injections or Florinef tablets to replace aldosterone. Tablets are given daily to supplement the missing hormones. The doses of each of these medications are adjusted to meet the needs of individual patients.
During an Addisonian crisis, low blood pressure, low blood sugar and high levels of potassium can be life-threatening. Standard therapy involves intravenous injections of hydrocortisone and a saline (salt water) drip. This treatment usually brings rapid improvement. When the patient can take fluids and medications by mouth, the intravenous treatment is decreased until and maintenance therapy is begun. In fact, once stabilized, many dogs require only Florinef tablets on a daily basis. If your vet is using injectable DOCP to replace aldosterone, your pet will likely also require supplemental oral replacement steroid tablets. Often the steroid dose will need to be increased around times of stress (illness, surgery, changes at home) to help mimic the body’s normal production of cortisol.
Most dogs with Addison’s disease are relatively young and the signs of disease will get worse at they get older. Even if you haven’t really noticed a particular problem with your dog you may see dramatic improvement when treatment starts. Many dogs will go on to live a normal lifespan. Without treatment the complications can be significant and will seriously affect the quality of your pet’s life.
What ongoing monitoring is needed?
Frequent monitoring is needed, especially in the early stages of treating Addison’s disease to find the correct dose of medication. Repeat monitoring of the cortisol levels are not required as these will continue to be low in your pet despite treatment. However, monitoring of your pet’s electrolyte levels (potassium and sodium) will help determine the correct medication dose. Initially a recheck blood test will be done after 1-2 weeks. Once the correct dose is found another blood test is needed after 1 month, then 3 months. Once your pet is on a stable dose, they will need less frequent monitoring but will still require 6 monthly consultations with your Veterinarian to continue to dispense the medications and closely monitor your pet. After the initial tests your Veterinarian will advise when repeat testing is required depending on how your dog has responded, in general this will involve:
General Blood test + Urine Monitoring – every 6 months (to monitor electrolytes and organ function)
Repeat Abdominal Ultrasound – every 12 months
Blood Pressure check – 6-12 monthly
If you have any concerns or notice any changes in your pet’s condition please contact your Veterinarian immediately to make a recheck appointment.
