What Is Addison’s Disease in Dogs?
Canine Addison’s disease, also known as hypoadrenocorticism, arises when a dog’s adrenal glands fail to generate sufficient corticosteroid hormones. With proper diagnosis and treatment, afflicted dogs can lead fulfilling, lengthy lives.
The adrenal glands, situated adjacent to the kidneys, play a crucial role in synthesizing corticosteroid hormones, including the renowned “stress” hormones. These hormones encompass:
- Glucocorticoids (like cortisol): Regulate protein, sugar, and fat metabolism, storing metabolites for utilization during “fight or flight” scenarios.
- Mineralocorticoids (such as aldosterone): Facilitate sodium and potassium regulation.
During times of stress, whether in animals or humans, the adrenal glands are prompted to release stress hormones, precipitating a variety of physiological and behavioral responses. Stress responses in dogs may manifest as:
- Compulsive climbing of stairs
- Restless pacing and visible anxiety
- Altered interactions with other dogs
- Exhibiting excitement upon your return home from work
In dogs affected by Addison’s disease, the adrenal glands fail to produce adequate hormones to sustain normal stress levels. In the absence of corticosteroid hormones to aid in adapting to stress, even minor stressors can provoke severe complications, and in extreme cases, mortality.
Symptoms
Detecting Addison’s disease based solely on signs can be challenging. Often, the diagnosis of Addison’s disease occurs incidentally during routine annual blood work when electrolyte imbalances are detected by your veterinarian. Suspicion may arise if your dog displays fluctuating symptoms of lethargy, reduced appetite, vomiting, and diarrhea.
About 30% of dogs with Addison’s disease receive a diagnosis following an Addisonian crisis. Such a crisis happens when a dog collapses into shock due to an inability to cope with internal or external stressors. This can result in significantly elevated potassium levels, leading to irregular heart rhythms and a markedly slow heart rate. Addison’s disease can also induce severe hypoglycemia, characterized by dangerously low blood sugar levels.
An Addisonian crisis can only occur when approximately 90% of the adrenal cortex (the outer layer of the adrenal gland) ceases to function. If not promptly, aggressively, and appropriately treated, this crisis can be fatal due to shock.
Causes
Hypoadrenocorticism manifests in two primary forms:
- Primary hypoadrenocorticism: This occurs when the immune system of your dog attacks the adrenal glands. Drug-induced necrosis, leading to the death of the adrenal gland, can also result from medications like ketoconazole, trilostane, and lysodren.
- Secondary hypoadrenocorticism: This may arise when the production of releasing hormones in the brain diminishes. Potential causes include inflammation, cancer, brain trauma, or congenital abnormalities.
Dogs afflicted with Addison’s disease are typically young, with the most common age range being around three to six years old; however, the condition can affect dogs of any age. Female dogs tend to be affected more frequently than males. The breeds most commonly associated with Addison’s disease include:
- West Highland White Terriers
- Great Danes
- Basset Hounds
- Portuguese Water Dogs
- Airedale Terriers
- Standard Poodles
- Bearded Collies
It’s important to note that dogs of any breed or age can be affected by Addison’s disease.
Diagnosis
Veterinarians employ various methods to diagnose Addison’s disease, which typically include obtaining a detailed medical history, conducting a comprehensive physical examination, and performing thorough blood work, including an ACTH stimulation blood test to assess cortisol levels. If a dog responds positively to shock treatment with intravenous fluids and steroid administration, veterinarians may suspect Addison’s disease as an underlying cause of the shock.
Full blood work often reveals elevated potassium and low sodium levels, indicative of typical Addison’s disease. However, atypical cases may not exhibit these electrolyte changes, representing a different subtype of the disease. In some instances, azotemia (elevated kidney enzymes) can mimic kidney disease, while low blood sugar levels may mimic a pancreatic tumor known as an insulinoma.
The primary diagnostic test for Addison’s disease is the ACTH test, which involves measuring baseline cortisol levels before administering intravenous ACTH. One hour later, another blood sample is drawn to evaluate the dog’s response to ACTH. A low baseline cortisol level coupled with minimal response to the stress hormone may indicate Addison’s disease.
Baseline cortisol levels may also be assessed in emergency situations, with a full ACTH stimulation blood test administered when the dog is stable. Additionally, abdominal ultrasound may be conducted to identify small adrenal glands.
Other blood tests, such as urine cortisol creatinine ratio, endogenous plasma ACTH levels, and plasma renin levels, may be performed to further assess the dog’s condition. Typically, non-Addison’s disease patients exhibit normal ACTH stimulation test results.
Certain dog breeds originating from the Pacific Rim, like Shiba Inus and Akitas, may display elevated potassium levels in blood work. It’s important to note that whipworm infection can artificially raise potassium levels and lower sodium levels, potentially complicating the diagnosis of Addison’s disease.
Treatment
During an Addisonian crisis, treatment revolves around administering aggressive intravenous fluid therapy and injectable steroids. Addressing hypoglycemia (low blood sugar) and abnormal heart rhythms may also be necessary. Fortunately, most dogs respond promptly to treatment and tend to achieve full recovery.
The cornerstone of Addison’s treatment lies in replacing mineralocorticoids, such as aldosterone, the steroid hormone. This can be accomplished through oral medication (fludrocortisone) given twice daily or by administering an injection of DOCP (desoxycorticosterone pivalate) approximately every 25-30 days. Your veterinarian will collaborate with you to establish an appropriate treatment plan based on your pet’s diagnosis.
Fludrocortisone, if prescribed, possesses both glucocorticoid and mineralocorticoid activity. Conversely, dogs receiving injectable DOCP require supplementary glucocorticoid supplementation, like oral prednisone, as DOCP solely exhibits mineralocorticoid activity.
Some experts advocate for DOCP due to its purported superior electrolyte regulation compared to oral fludrocortisone. However, the choice between formulations often depends on each veterinarian’s preference and the dog’s individual needs. Some dogs may struggle with injections, while others may find oral medication challenging. Your veterinarian will assess what works best for your dog based on their specific diagnosis.
Following the initiation of therapy, electrolyte blood testing and ACTH stimulation testing are typically conducted at various intervals, such as on day 10, day 30, and day 90. Adjustments to mineralocorticoid medication are made once electrolyte levels stabilize, with periodic monitoring throughout the year to ensure appropriate dosage.
During times of heightened stress, glucocorticoid dosing may need adjustment. Veterinary visits, car rides, or changes in routine can induce stress in dogs with Addison’s disease. Temporary increases in steroid dosage can mitigate symptoms like lethargy, vomiting, diarrhea, and prevent Addisonian crises.
Living and Management
During an Addisonian crisis, dogs typically undergo treatment involving intravenous fluid therapy to rectify electrolyte imbalances, along with administration of steroids and medications to address abnormal heart rhythms. This comprehensive approach often yields a favorable prognosis, with dogs showing rapid improvement.
Managing Addison’s disease is a lifelong commitment. Initially, blood work monitoring may be frequent, especially during the early stages of treatment and throughout the first three to six months as your veterinarian determines the optimal medication dosing intervals. However, as the treatment plan stabilizes, monitoring becomes less intensive.
Most dogs diagnosed with Addison’s disease respond well to treatment and go on to lead fulfilling, lengthy lives. With proper management and veterinary care, they can enjoy a good quality of life and remain happy companions for years to come.
Addison’s Disease in Dogs FAQs
Can Addison’s disease in dogs disappear on its own?
No, Addison’s disease does not resolve spontaneously; dogs diagnosed with this condition require medication to stabilize their health.
Is Addison’s disease common in dogs?
Addison’s disease is relatively common in dogs, although it is not as prevalent as Cushing’s disease, which involves excessive production of steroids and cortisol, essentially the opposite of Addison’s disease.
How long can dogs live with Addison’s disease?
With proper diagnosis and treatment using appropriate medications, dogs can live out their natural lifespan despite being diagnosed with Addison’s disease. However, if an Addisonian crisis occurs and remains untreated, it can prove fatal.
What triggers Addison’s disease in dogs?
In many cases, the exact cause of Addison’s disease in dogs is unknown. It is primarily considered an immune-mediated condition, but it can also d
evelop secondary to specific medications, infections, trauma, or adrenal gland cancers.
What causes atypical Addison’s disease in dogs?
The underlying cause of atypical Addison’s disease in dogs is not fully understood. This condition allows dogs to regulate their electrolyte imbalances through other hormones, with only glucocorticoids requiring supplementation. While exhibiting similar symptoms to typical Addisonian dogs, those with atypical Addison’s disease do not experience shock crises. Monitoring electrolytes every three to six months is recommended, as many of these dogs eventually progress to the typical form of the disease.
Is there a test for Addison’s disease in dogs?
The ACTH stimulation test is typically employed to diagnose Addison’s disease in dogs. This test can be conducted at most veterinary clinics, as well as at specialty and emergency facilities. Blood samples are sent to a laboratory for analysis, and results are subsequently relayed to the veterinarian’s office.