What is Hyperadrenocorticism (Cushing’s Disease) in Dogs?

Introduction

For months, Jennifer had been observing some unusual changes in her loyal Boston Terrier, Bella. She noticed that Bella had developed a pot-bellied appearance, was losing hair, and seemed to be constantly hungry and thirsty. Concerned about her canine companion’s well-being, Jennifer scheduled a visit to her veterinarian. After a series of tests, the vet delivered the unexpected news that Bella had Cushing’s Disease, a condition Jennifer had never encountered before.

Cushing’s disease, hyperadrenocorticism, is a serious and complex condition that primarily targets middle-aged and older dogs. This disease is a pivotal catalyst for the overproduction of cortisol, a hormone playing a central role in regulating the body’s responses to stress, upkeeping cardiovascular health, counterbalancing insulin effects, and managing the immune system’s inflammatory response.

Cortisol, integral to a dog’s well-being, is produced and dispensed by the dog’s adrenal glands, strategically located near the kidneys. Dogs suffering from Cushing’s syndrome, especially pituitary-dependent Cushing’s disease, exhibit adrenal glands in overdrive, releasing an excessively high amount of this crucial hormone. Different triggers can spur this overproduction, leading to multiple variations of the disease, which includes pituitary-dependent Cushing’s disease.

Due to the abnormal increase in cortisol levels resulting from pituitary-dependent Cushing’s disease or other forms, the disease can induce systemic changes within a dog’s body, affecting numerous organs. This occurs due to the alteration in the dogs’ adrenal glands’ functioning. Consequently, this disease can seriously impact a dog’s quality of life and instigate severe health complications if left untreated.

The Three Types of Addison’s Disease in Dogs

Addison’s disease, medically referred to as hypoadrenocorticism, is classified into two primary types in dogs: Primary Addison’s Disease and Secondary Addison’s Disease.

1. Primary Addison’s Disease: This is the most common type of Addison’s disease seen in dogs. It is characterized by the inadequate production of cortisol and aldosterone due to the destruction or dysfunction of the adrenal glands’ outer layer, known as the adrenal cortex. Primary Addison’s is often caused by an autoimmune process where the dog’s immune system attacks its adrenal glands. However, it can also be due to other factors, such as infectious diseases, trauma, or certain medications.
2. Secondary Addison’s Disease: This form is less common due to a deficiency in the production of adrenocorticotropic hormone (ACTH) by the pituitary gland. ACTH stimulates the adrenal glands to produce cortisol. If there is insufficient ACTH, the adrenal glands become inactive, and cortisol levels drop. In most cases of secondary Addison’s, aldosterone levels remain normal, but cortisol deficiency can still cause significant clinical signs.

There is also a variant of Addison’s disease known as Atypical Addison’s Disease. In this form, only some layers of the adrenal cortex are affected, resulting in a deficiency in cortisol production but not aldosterone.

Understanding that all forms of Addison’s disease are serious and potentially life-threatening conditions that require immediate veterinary care is crucial. However, dogs with Addison’s disease can usually lead normal, healthy lives with appropriate treatment.

Causes of Cushing’s Disease in Dogs

Cushing’s disease in dogs, known as hyperadrenocorticism, primarily arises from three scenarios. Each causes an overproduction of cortisol, a steroid hormone integral to several processes such as immune response, stress regulation, and metabolism.

Pituitary Gland Tumor: The Culprit Behind Pituitary Dependent Cushing’s

The most common instigator of Cushing’s disease in dogs is a tumor within the pituitary gland at the base of the brain. This tumor, typically benign, produces excessive adrenocorticotropic hormone (ACTH). This overproduction induces the adrenal glands to release an overabundance of cortisol, leading to what’s known as pituitary-dependent Cushing’s disease. This condition often leads to an increased risk of urinary tract infections due to changes in cortisol levels.

Adrenal Gland Tumor: The Underlying Cause of Adrenal Dependent Cushing’s

Another key contributor to Cushing’s disease is an adrenal gland tumor. These tumors can be benign or malignant, resulting in the adrenal glands near the kidneys producing too much cortisol. This adrenal-dependent Cushing’s disease can, over time, cause kidney damage due to excessive cortisol levels.

Prolonged Use of Corticosteroid Medications: The Iatrogenic Cause

In some instances, Cushing’s syndrome can be traced back to the prolonged use of corticosteroid medications prescribed for other health issues, such as gastrointestinal disease, inflammation, or allergies. These medications, used to suppress immune system disorders or chronic inflammatory liver disease, can lead to an iatrogenic form of Cushing’s. This form can be reversed by closely managing and adjusting the medication dosage under a veterinarian’s guidance. This careful control helps regulate the dog’s cortisol level, effectively reducing the symptoms and causes of Cushing’s disease in dogs.

Symptoms of Hyperadrenocorticism in Dogs

Cushing’s disease in dogs often displays symptoms that appear gradually over many years, developing subtly and often unnoticed. However, in some instances, signs of Cushing’s disease can manifest abruptly and unexpectedly. The following list highlights the most commonly observed symptoms in dogs affected by this condition:

• Elevated thirst and subsequent increased urination
• A surge in appetite
• Frequent panting
• Altered skin condition
• A distinctive pot-bellied appearance
• Pronounced muscle weakness and persistent fatigue
• Frequent occurrences of infections

These symptoms, which could lead to adverse reactions such as a blood clot, require prompt attention and possibly emergency care from a veterinarian. Based on the severity of these clinical signs and the extent of organ damage, the vet will suggest a suitable treatment strategy.

Diagnosis of Cushing’s Disease in Dogs

Diagnosing Cushing’s disease in dogs requires a comprehensive process. Internal medicine professionals employ a thorough physical examination and a range of laboratory tests, including a “blood test,” adrenal function tests, and sometimes even imaging studies to determine this disease.

Detailed Physical Examination and Medical History

The initial step in diagnosing Cushing’s disease encompasses an extensive physical examination and a thorough review of the dog’s medical history. Veterinarians typically enquire about the dog’s observable symptoms and the duration these symptoms have persisted. Physical examination may reveal telltale signs, such as a pot-bellied appearance, excessive panting, and skin changes common in dogs diagnosed with Cushing’s disease.

Laboratory Tests: Complete Blood Panel and Urinalysis

The second step involves laboratory tests, including a complete blood panel and urinalysis. Dogs with Cushing’s disease often exhibit changes in their blood cells and chemistry, revealed through abnormalities like high cholesterol, high blood sugar, and elevated liver enzymes that may indicate gallbladder disease. In addition, urinalysis can detect diluted urine, a common marker of Cushing’s disease.

Hormone Tests: ACTH Stimulation Test

Since Cushing’s disease impacts the hormone-producing glands, specific hormone tests are integral in the diagnostic process. For example, the ACTH stimulation test is routinely used to detect elevated cortisol levels in dogs, a definitive indicator of Cushing’s disease.

Imaging Studies

When the previous diagnostic steps indicate Cushing’s disease, imaging studies such as ultrasound are considered. Ultrasounds help visualize the adrenal glands and determine the presence of a tumor in either the adrenal or pituitary gland, confirming the diagnosis and form of Cushing’s disease.

Additional Diagnostic Tests: High Dose Dexamethasone Suppression Test

Additional tests like the high-dose dexamethasone suppression test or endogenous plasma ACTH concentration determination may be required if the diagnosis is still ambiguous. Veterinarians may also recommend specific advanced imaging techniques, such as CT or MRI scans, particularly when a pituitary gland tumor is suspected.

A veterinarian will recommend treatment based on the severity of clinical signs and the extent of organ damage. Treatment options include surgery to remove the affected part of the brain, radiation therapy, and medications. Medications typically consist of drugs called corticosteroids, which reduce inflammation and slow down cell division.

Treatment for Canine Cushing’s Disease

Treating Cushing’s disease in dogs primarily involves managing the hormone imbalance, typically achieved through medications, surgery, or radiation therapy. The best treatment approach depends on several factors, including the specific type of Cushing’s disease (pituitary or adrenal) and the dog’s overall health.

Medication

Medication is often the first line of treatment for dogs with pituitary-dependent Cushing’s disease and is also used when surgery is not an option for adrenal tumors. Two commonly used drugs are Trilostane and Mitotane. Trilostane works by inhibiting the enzyme involved in the production of cortisol, thereby reducing cortisol levels. On the other hand, Mitotane destroys the layers of the adrenal gland that produce cortisol. Both these medications require regular follow-ups and blood tests to ensure the correct dosage and to monitor the dog’s response.

Surgery

Surgery is an option for dogs with an adrenal gland tumor. The procedure involves removing the affected adrenal gland. It’s a more invasive approach, but it can cure the disease if the tumor is benign and hasn’t spread. However, the operation is complex and can have significant risks, so a specialist veterinary surgeon typically performs it.

Radiation Therapy

Radiation therapy can also be considered, especially for pituitary-dependent Cushing’s disease. This therapy targets the pituitary gland tumor with high-energy radiation to kill the tumor cells and reduce the tumor size.

Regardless of the chosen treatment method, dogs with Cushing’s disease need lifelong management and regular check-ups since the disease can’t be entirely cured but can be effectively managed. Pet owners must work closely with their veterinarians to monitor their dog’s condition and adjust the treatment plan. The goal of treatment is to minimize the symptoms and improve the quality of life for the affected dog.

Prevention of Cushing’s Disease in Dogs

Understanding and managing Cushing’s disease in dogs can be complex, but pet owners with adequate knowledge can play a vital role in their pet’s health. Here are some strategies that may help prevent Cushing’s or mitigate its effects:

1. Balanced Diet: Ensuring your dog consumes a well-balanced diet suitable for their age, breed, size, and existing health conditions is crucial for overall wellness. This approach is the first line of defense in fostering a robust immune system, reducing the risk of ‘false positives when another disease’ with similar clinical signs is present.
2. Regular Exercise: Regular physical activity aids in maintaining an ideal weight for your dog and promotes overall health. Given that obesity can lead to a multitude of health issues and potentially exacerbate conditions like Cushing’s disease, exercise is key. Particularly for ‘dogs with adrenal tumors,’ maintaining an active lifestyle can be beneficial.
3. Regular Vet Check-ups: Routine veterinary check-ups help detect potential health issues at an early stage. This early detection is essential as some dogs may exhibit ‘disease with similar clinical signs’ to Cushing’s, requiring different treatment. ‘Adequate monitoring’ can lead to prompt and accurate treatment, improving outcomes.
4. Monitor Medications: ‘Vets explain what causes’ some instances of Cushing’s disease, and one notable factor is the long-term use of specific medications like corticosteroids. Therefore, if your dog is on these medications, managing them under your vet’s guidance is crucial, including using the lowest effective dose and monitoring for side effects.
5. Awareness: ‘Know about Cushing’s disease’ by familiarizing yourself with its signs and symptoms. Early detection is paramount for managing this disease effectively, improving your dog’s prognosis and quality of life, and reducing the chances of ‘the recurrence of the disease.’

While these strategies may not guarantee the prevention of Cushing’s disease, they contribute significantly to your dog’s overall health and vitality, which could lessen the likelihood of numerous health conditions, including Cushing’s. Always consult your vet if you have concerns about your dog’s health.

Frequently Asked Questions