Liaison: Phyllis Edwards
Email: Phyllis.E.Edwards@gmail.com
Addison’s Disease, also called hypoadrenocorticism or adrenal insufficiency, is a disorder in which the adrenal glands do not produce enough hormones to allow the body to function normally. The adrenal glands, located above the kidneys, are unable to produce sufficient amounts of cortisol and aldosterone hormones. This disease can be life-threatening but can be managed by taking replacement hormones (1).
Addison’s disease affects humans as well as animals. In the United States Addison’s disease affects one in 100,000 people, men and women equally, and all age groups especially the 30-50 year olds (2). This disease was first noticed in humans around the middle of the 19th century and was named after Thomas Addison (3).
Addison’s disease in dogs was first officially recognized in 1953. This disease affects some breeds of dogs more than others, and tends to affect young to middle-aged female dogs (4a).
As mentioned previously, Addison’s disease is a condition where the adrenal glands do not produce enough of the hormones called cortisol and aldosterone. These two hormones are important because bodily functions depend on them to help sustain life. Cortisol is important as it helps the body cope with shock, stress and acts to reduce the amount of pain being experienced (3). It also helps to maintain blood pressure, heart function, the immune system and blood glucose levels (2). Aldosterone is a hormone that regulates the minerals sodium and potassium, which are key in maintaining fluid balance in the body (5).
The opposite condition of Addison’s disease is called Cushing’s Disease where there is an overproduction of cortisol (6).
Signs and Symptoms
The first signs and symptoms of dogs suffering from Addison’s disease are vague, tend to wax and wane, progress slowly and are sometimes overlooked or misdiagnosed (7).
The signs and symptoms may arise from situations that cause tension, distress, strain and nervousness. What is defined as stress varies with each different dog’s temperament. Some examples of overtaxing situations are grooming, having house guests, being left alone or trying to fight an infection (6). Even good stress such as a car ride can be too much for the Addisonian dog.
Healthy adrenal glands will produce enough cortisol to help deal with stressful situations, whereas compromised adrenal glands producing insufficient amounts of cortisol may lead to conditions of:
- Depression
- Lethargy
- Anorexia (lack of appetite)
- Weight loss
- Vomiting
- Diarrhea
- Bloody stools
- Alopecia (hair loss)
- Increased urination
- Increased thirst
- Dehydration
- Shaking
- Weak pulse
- Irregular heart rate
- Low temperature
- Painful abdomen
- Hypoglycemia
- Hyperpigmentation of the skin
In general, these dogs seem overall unwell and weak. Since these symptoms are sometimes not indicative of a particular disease or condition, many vets fail to promptly diagnose Addison’s disease in dogs. Addison’s disease in humans and dogs is known for causing vague symptoms which may mimic the clinical signs associated with other diseases. Addison’s disease is sometimes referred to as “The Great Pretender” (7). For example, during an examination, a vet may see lack of energy, dehydration along with increased drinking and urination, weak pulse and irregular heart rate. Routine blood panels show a low blood sodium and high blood potassium which may be caused by the dehydration due to vomiting and diarrhea. Kidney disease is sometimes wrongly diagnosed instead of Addison’s disease (6).
If your dog’s first signs and symptoms of Addison’s go undiagnosed and come to a critical breaking point, with severe abdominal pain, vomiting and diarrhea, collapse, or shock, this is known as an Addisonian crisis. An Addisonian crisis is a life-threatening event (8).
Causes
Addison’s disease is caused by damage to the adrenal glands. Underlying reasons why the adrenal glands may no longer work may stem from these conditions (3, 4a, 7).
- Autoimmune disorder, immune system mistakenly attacks adrenal glands
- Tumor or defect in the pituitary gland so that it no longer signals the adrenal glands to produce hormones
- Drug used to treat Cushing’s syndrome (e.g., Mitotane, Trilostane) damage too much of the adrenal tissues or hormone production, resulting in a deficiency of cortisol and aldosterone
- Prolonged treatment with corticosteroids, leading to atrophy of the adrenal glands
- Sudden discontinuation of steroid medication
- Infections of the adrenal glands
- Hemorrhage of the adrenal glands
- Infarction (obstruction of blood supply to the adrenal gland causing death of the tissue)
- Granulomatous disease (inherited disorder where white blood cells which help to fight infections do not work properly)
Risk Factors
A predisposing condition or situation that may make your dog more at risk or susceptible to a disease is considered a “risk factor”. Although research has indicated there is a genetic link, especially in certain breeds, the direct cause is unknown. Mostly Addison’s is considered to be an autoimmune disease and there is some indication that Addison’s is becoming more common (4b).
Diagnostic Tests
Since the initial signs and symptoms of Addison’s disease are vague and may mimic the clinical signs associated with other diseases, the correct diagnosis usually occurs during an Addisonian crisis. Once the dog is stabilized, the veterinarian will administer a series of tests that may include an Adrenocorticotropic hormone (ACTH) stimulation test, blood panel, urinalysis, leukogram (looks at white blood cells) and an electrocardiogram (ECG).
The most important test for Addison’s is the ACTH stimulation test. The cortisol level in blood is measured, the adrenals stimulated with a dose of synthetic ACTH, then cortisol levels are measured again. In a healthy dog, the adrenals will respond and the level of cortisol will increase. Lack of increase is indicative of Addison’s. The results of this test help the veterinarian detect diseases that are associated with an excess or deficiency of cortisol in the body (4a).
A blood panel helps to identify if potassium and urea levels are high and whether changes in the levels of sodium, chloride, and calcium in the blood are indicative of Addison’s.
A leukogram may be performed since sick dogs often show a pattern of changes in their white blood cells (WBCs) called a stress leukogram. The changes in the pattern in the WBCs are caused by cortisol. When the test reveals the absence of a stress leukogram in a sick dog, this may be a clue to consider Addison’s disease.
Lastly, the vet may also check for changes in your dog’s heart by running an electrocardiogram (ECG) (6).
Treatment Guidelines
Note: Treatment of animals should only be performed by a licensed veterinarian. Veterinarians should consult the current literature and current pharmacological formularies before initiating any treatment protocol.
There are two stages of treatment for Addison’s disease. During an Addisonian crisis, intensive therapy in a veterinary hospital is typically required to end the crisis. This includes intravenous fluids, cortisol-like drugs, and drugs to counteract the effect of high serum potassium on the heart. Once the dog is out of immediate danger, the long-term treatment involves life-long administration of replacement hormones. Aldosterone may be replaced as either a daily pill (fludrocortisone) or an injection that is given about every 25 days (desoxycorticosterone pivalate, DOCP). Fludrocortisone also has cortisol-like activity. If the aldosterone is replaced by DOCP injection, the cortisol must also be replaced with an oral glucocorticoid, typically prednisone or dexamethasone (6).
There is an ongoing research study at Michigan State University College of Veterinary Medicine on the dosing of the injection. The background information for the study gives a good description of some of the challenges and costs of treatment.
Be prepared to visit the veterinarian frequently for the first month after diagnosis so that your dog’s hormones and electrolyte levels can be measured and medication adjustments made. After the first month, the long term treatment includes regular testing to ensure the correct dosage is given to your pet as his body chemistry may change over time. (4a).
Management
Because dogs with Addison’s disease cannot produce sufficient amounts of cortisol in response to stress, stress should be minimized whenever possible. It may be necessary to increase the amount of hormones given should you foresee any upcoming overtaxing events (e.g. professional grooming away from home, boarding, surgery, travel, etc.) (6).
“Pet owners must be well aware of the subtle signs of illness and committed to daily medication and regular rechecks for the rest of the dog’s life” (9).
Your dog can be expected to live a happy and healthy life after diagnosis and hormone replacement treatment. Many dogs resume being their playful old selves soon after beginning treatment if the disease is diagnosed in time (4b).
“The good news is that, with proper treatment and monitoring, a dog with Addison’s disease has the same life expectancy as one without the disease” (10).
References
- Addison’s Disease. Mayo Clinic.
- Addison’s Disease. Cleveland Clinic.
- A guide to Addison’s Disease in Dogs. PawDiet.
- American Kennel Club. 4a: Burke A. Addison’s Disease in Dogs: Symptoms, Diagnosis, Treatment, and Prevention – American Kennel Club September 2020. 4b: Paddock A. Addison’s Disease in Dogs—Early Recognition Is Critical – American Kennel Club July 2015.
- Ward E and Downing R. Addison’s Disease in Dogs overview. VCA Hospitals.
- Addison’s Disease. Washington State University School of Veterinary Medicine
- Farricelli A. Signs of an Addisonian Crisis in Dogs. Pethelpful July 2019.
- What is Addison’s Disease in Dogs. Facty July 2019.
- Galati P, Lathan P. Diagnosis and Management of Hypoadrenocorticism in Dogs. Today’s Veterinary Practice, July/Aug 2019.
- Clark M. Addison’s Disease In Dogs: Symptoms, Causes, And Treatment. DogTime.
Support Groups
Here are a couple of online support groups for dogs with Addison’s:
CaRe: Canine Addison’s Resource & Education: See “Our Stories” for a collection of experiences shared by clients who have struggled with getting a diagnosis and with prescriptions that were dosed terribly wrong. There is also a link to their Facebook group.
Addison’s Dogs- Canine Addison’s Disease Public Facebook Group
Current Research
Lathan P and Thompson A. 2018. Management of hypoadrenocorticism (Addison’s Disease) in Dogs. Veterinary Medicine (Auckl) 9:1-10. (published paper)
Addison’s Disease Research in Progress – Genetics Study in several breeds (NOT Samoyeds) by College of Veterinary Medicine (Canine Genetics Lab, University of Minnesota)
New Dosage Protocol for Dogs with Addison’s disease: A Randomized Controlled Clinical Trial, College of Veterinary Medicine, Michigan State University. (research in progress)