Addison’s disease, also known as hypoadrenocorticism, is a rare but serious condition affecting dogs’ adrenal glands. The adrenal glands are small organs near the kidneys that produce hormones that regulate many vital functions, such as blood pressure, electrolyte balance, stress response, and metabolism. When the adrenal glands fail to produce enough of these hormones, especially cortisol and aldosterone, the dog can develop Addison’s disease.
What Causes Addison’s Disease in Dogs?
There are two main types of Addison’s disease in dogs: primary and secondary. Primary hypoadrenocorticism is the most common type and occurs when the adrenal cortex (the outer layer of the adrenal gland) is damaged or destroyed by an immune-mediated process, infection, trauma, or cancer. This results in a deficiency of both mineralocorticoids (such as aldosterone) and glucocorticoids (such as cortisol).
Secondary hypoadrenocorticism is less common and occurs when the pituitary gland (a small gland at the base of the brain) fails to produce enough adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to produce cortisol. This results in a deficiency of only glucocorticoids. Secondary hypoadrenocorticism can be caused by tumors, infections, trauma, or drugs that affect the pituitary gland.
What Are the Symptoms of Addison’s Disease in Dogs?
The symptoms of Addison’s disease in dogs can vary depending on the type and severity of the condition. Some dogs may show no signs at all until they experience an acute crisis, which can be life-threatening. Other dogs may show chronic signs that are vague and nonspecific, such as:
- Weight loss
- Lack of appetite
The symptoms of Addison’s disease can also mimic those of other conditions, such as kidney failure, diabetes, or gastrointestinal disorders. Therefore, it is important to consult a veterinarian if you notice any changes in your dog’s health or behavior.
How Is Addison’s Disease in Dogs Diagnosed?
The diagnosis of Addison’s disease in dogs can be challenging because the symptoms are often intermittent and variable. However, there are some laboratory tests that can help confirm the condition. These include:
- Blood tests: A complete blood count (CBC) can reveal anemia (low red blood cell count), lymphocytosis (high white blood cell count), and eosinophilia (high eosinophil count), which are common findings in dogs with Addison’s disease. A serum chemistry panel can reveal low sodium levels, high potassium levels, low blood glucose levels, and high blood urea nitrogen (BUN) and creatinine levels, which indicate electrolyte imbalances and kidney dysfunction. A baseline cortisol test can measure the amount of cortisol in the blood before and after an injection of ACTH. A low or normal baseline cortisol level that does not increase after ACTH stimulation indicates Addison’s disease.
- Urine tests: A urinalysis can reveal low urine specific gravity (USG), which indicates diluted urine due to poor kidney function. A urine cortisol:creatinine ratio (UCCR) test can measure the amount of cortisol in the urine relative to creatinine. A low UCCR indicates low cortisol production by the adrenal glands.
- Imaging tests: An abdominal ultrasound or X-ray can show the size and shape of the adrenal glands and rule out other causes of adrenal dysfunction, such as tumors or hemorrhage.
How Is Addison’s Disease in Dogs Treated?
The treatment of Addison’s disease in dogs depends on the type and severity of the condition. The main goals are to restore normal hormone levels and electrolyte balance and prevent future crises.
Dogs with primary hypoadrenocorticism require lifelong replacement therapy with both mineralocorticoids and glucocorticoids. Mineralocorticoids can be given as oral medication (such as fludrocortisone) or as injectable implants (such as desoxycorticosterone pivalate). Glucocorticoids can be given as oral medication (such as prednisone) or as injections (such as dexamethasone). The dosage and frequency of these medications may need to be adjusted over time based on regular blood tests and clinical signs.
Dogs with primary hypoadrenocorticism also need to receive extra glucocorticoids during times of stress, such as illness, surgery, or travel. This is because their adrenal glands cannot produce enough cortisol to cope with increased demand. Failure to do so can result in an Addisonian crisis, which is a medical emergency that requires immediate intravenous fluids, steroids, and electrolytes.
Dogs with secondary hypoadrenocorticism only require replacement therapy with glucocorticoids, since their mineralocorticoid production is usually normal. They also need to receive extra glucocorticoids during times of stress for the same reason as dogs with primary hypoadrenocorticism.
What Is the Prognosis for Dogs with Addison’s Disease?
The prognosis for dogs with Addison’s disease is generally good if they receive appropriate treatment and regular monitoring. Most dogs can live normal lives with minimal complications if their hormone levels and electrolyte balance are maintained within normal ranges. However, some dogs may experience recurrent crises or side effects from medication that can affect their quality of life and survival.
Which Breeds Are More Prone to Addison’s Disease in Dogs?
Addison’s disease can affect any breed of dog, but some breeds are more prone than others. According to a study by Famula et al., published in 2003 in the Journal of Veterinary Internal Medicine, the most common breeds affected by Addison’s disease are:
- Standard poodles
- West Highland white terriers
- Portuguese water dogs
- Bearded collies
- Great Danes
- Soft-coated wheaten terriers
- Nova Scotia duck tolling retrievers
Other breeds that have been reported to have a higher incidence of Addison’s disease include:
The reason why some breeds are more susceptible to Addison’s disease is not fully understood, but it may be related to genetic factors that affect the immune system or the adrenal glands.
How Can I Prevent Addison’s Disease in Dogs?
There is no definitive way to prevent Addison’s disease in dogs since it is mostly caused by unknown factors that damage or destroy the adrenal glands. However, some possible ways to reduce the risk or severity of the condition include:
- Avoiding drugs that can suppress or interfere with adrenal function, such as mitotane, trilostane, ketoconazole, or prednisone.
- Avoiding infections or parasites that can affect the adrenal glands, such as leishmaniasis or heartworms.
- Avoiding trauma or surgery that can damage or remove the adrenal glands.
- Avoiding stress or anxiety that can trigger an Addisonian crisis.
- Seeking veterinary attention promptly if you notice any signs of illness or abnormality in your dog.
Addison’s disease is a rare but serious condition that affects the adrenal glands of dogs. It causes a deficiency of hormones that regulate many vital functions in the body. The symptoms can vary depending on the type and severity of the condition and can mimic those of other diseases. The diagnosis requires laboratory tests that measure hormone levels and electrolyte balance. The treatment involves lifelong replacement therapy with synthetic hormones and extra doses during times of stress. The prognosis is generally good if appropriate treatment and monitoring are provided. Genetic factors make Some breeds more prone to Addison’s disease than others.
If you suspect your dog has Addison’s disease or if you have any questions about this condition, please consult your veterinarian for advice and guidance.