Cushing’s Disease in Dogs: Symptoms, Diagnosis & Treatment

Cushing’s Disease in Dogs: Symptoms, Diagnosis, and Management

Cushing’s disease (canine hyperadrenocorticism) is a common condition seen in older dogs, caused by excess production of the hormone cortisol by the adrenal glands. This article provides a comprehensive overview of the signs, diagnostic approaches, treatment options, prognosis, and important questions for pet owners facing Cushing’s disease in their canine companions.

What is Cushing’s Disease?

Cushing’s disease develops when a dog’s adrenal glands produce excessive amounts of cortisol, a hormone responsible for various metabolic and stress-related bodily functions. This condition typically arises from:

• Pituitary-dependent Cushing’s disease: Most cases (over 80%) result from a benign tumor in the pituitary gland that causes overstimulation of the adrenal glands.
• Adrenal-dependent Cushing’s disease: Some cases are due to tumors (benign or malignant) in one or both adrenal glands themselves.
• Iatrogenic Cushing’s disease: Prolonged or excessive administration of corticosteroid medications can also induce similar symptoms.

Symptoms of Cushing’s Disease in Dogs

The clinical signs of Cushing’s disease are related to prolonged exposure to excessive cortisol. These signs often develop gradually, making early detection challenging. Common symptoms include:

• Increased appetite (polyphagia)
• Increased water consumption and excessive urination (polydipsia and polyuria)
• Lethargy or reduced activity levels
• Poor coat quality, hair loss, and thinning skin
• Pot-bellied or distended abdomen due to fat redistribution and weakened abdominal muscles
• Panting and respiratory changes
• Chronic or recurrent skin infections (pyoderma)
• Hyperpigmentation (dark spots on the skin)
• Skin mineralization (22calcinosis cutis22)
• Poor skin healing
• Persistent bladder infections

Not all affected dogs display every symptom, and severity can vary.

Clinical Signs: Table Overview

Diagnostic Procedures for Cushing’s Disease

Diagnosis of Cushing’s disease requires thorough veterinary evaluation, as its signs overlap with other canine health problems. The diagnostic process typically includes:

• Physical examination: The veterinarian checks for characteristic signs such as a pot-bellied abdomen, hair loss, and reduced muscle mass.
• Medical history review: Owners should report behavioral and physical changes, any medications (particularly steroids), and the progression of symptoms.

Laboratory Testing

• Blood tests: Complete blood count (CBC) and biochemistry panel often show a stress leukogram, elevated alkaline phosphatase (ALP), high cholesterol, and increased liver enzymes.
• Urinalysis: Typically reveals low urine concentration and sometimes proteinuria.
• Specialized hormone tests:
  • ACTH stimulation test: Assesses adrenal response to ACTH hormone.
  • Low-dose dexamethasone suppression (LDDS) test: Evaluates how the dog’s body responds to suppression of cortisol production.
  • Urine cortisol:creatinine ratio: Useful for screening but not definitive.
  • High-dose dexamethasone suppression (HDDS) test: May help distinguish between pituitary and adrenal forms.

Imaging

• Abdominal ultrasound: Enables visualization of adrenal glands and identification of tumors or abnormalities.
• Radiography (X-ray): May reveal enlarged liver or changes in abdominal organs.
• Magnetic resonance imaging (MRI): Highly effective for detailed assessment, especially of the pituitary gland, but often costly.

Note: False positives are possible if other diseases mimic Cushing’s symptoms; veterinarians must rule out liver, bladder, or gastrointestinal diseases.

Types of Cushing’s Disease

The treatment strategy depends on the underlying type:

• Pituitary-dependent Cushing’s: Caused by a pituitary gland tumor; most common.
• Adrenal-dependent Cushing’s: Caused by adrenal gland tumor (may be benign or malignant).
• Iatrogenic Cushing’s: Results from prolonged oral or injectable steroid therapy.

How is Cushing’s Disease Treated?

Cushing’s disease management focuses on controlling symptoms, reducing cortisol production, and addressing underlying causes wherever possible. The type of Cushing’s disease largely influences the approach taken:

Pituitary-dependent Cushing’s Disease

• Usually managed with medication to suppress excess cortisol production.
• Trilostane and mitotane are the most commonly prescribed medications. They work by inhibiting steroid production in the adrenal glands.
• Veterinarians closely monitor blood cortisol levels during treatment via ACTH stimulation tests, adjusting dosages over time.

Adrenal-dependent Cushing’s Disease

• Surgical removal of the affected adrenal gland is often recommended, provided the tumor is localized and not malignant.
• If surgery is successful and complete, dogs may return to normal health but require post-operative monitoring.
• If surgery isn’t possible (e.g., due to tumor spread or patient risk), medical management is similar to pituitary-dependent cases.

Iatrogenic Cushing’s Disease

• Treatment involves gradual withdrawal of the corticosteroid medication under veterinary guidance to avoid complications.
• Underlying disease (for which the steroids were originally prescribed) may recur, requiring alternative therapies.

Managing Dogs on Treatment

• Regular monitoring: Frequent veterinary visits for ACTH stimulation tests and bloodwork are essential to check medication effectiveness and adjust dosages.
• Long-term care: Lifelong medication and routine monitoring of blood chemistry are often required. Dose adjustments may be necessary as the dog ages or as the disease progresses.
• Watch for side effects: Over-medication can lead to Addison’s disease (adrenal insufficiency), while under-medication may result in persistent Cushing’s symptoms.

Prognosis and Quality of Life

With proper diagnosis and treatment, many dogs with Cushing’s disease live comfortably for years. Early identification and diligent care are crucial for minimizing complications associated with high cortisol, such as infections and muscle wasting.

• Dogs with pituitary-dependent Cushing’s: Often well-controlled with regular medication and monitoring.
• Dogs with adrenal tumors: Prognosis depends on tumor type; benign tumors removed surgically offer good outcomes, while malignant tumors may shorten lifespan.
• Iatrogenic cases: Prognosis relies on successfully tapering steroids and managing the underlying disease.

Owner vigilance, routine veterinary care, and adherence to prescribed treatment plans are essential for optimizing a dog’s quality of life.

Frequently Asked Questions About Cushing’s Disease in Dogs

Q: Can Cushing’s disease be cured?

A: Surgical removal of an adrenal tumor offers the only potential cure. Most cases, particularly pituitary-dependent, are managed rather than cured with lifelong medication and monitoring.

Q: What is the expected survivability for a dog with Cushing’s disease?

A: With proper treatment, dogs often live for years with a good quality of life. Prognosis varies by type and severity.

Q: How often should my dog be monitored after diagnosis?

A: Initially, dogs require frequent blood tests (every few weeks) to adjust medications. Long-term, they should be seen at least every three to six months for checkups and lab tests.

Q: Are there any complications associated with Cushing’s disease?

A: Yes. Common complications include diabetes mellitus, urinary tract infections, skin infections, muscle wasting, and increased susceptibility to other illnesses due to immune suppression.

Q: What should I expect with medication side effects?

A: Side effects can include gastrointestinal upset, lethargy, poor appetite, or symptoms of adrenal insufficiency. Regular follow-ups are necessary to monitor and manage these issues.

Q: Can diet and lifestyle changes help?

A: Diet and exercise support a dog’s overall health but do not replace medication or veterinary guidance. Consult your veterinarian for advice on nutrition and safe activity for your dog’s condition.

Owner Tips for Living With a Dog Who Has Cushing’s Disease

• Keep a symptom diary: Track appetite, thirst, urination, and behavioral changes.
• Establish a routine: Regular veterinary visits and consistent medication schedules.
• Watch for skin and urinary infections: These require prompt veterinary attention.
• Discuss diagnostic and monitoring costs with your veterinarian: Advanced tests, medications, and long-term care may be expensive.
• Educate yourself: Understanding the disease helps you advocate for your pet’s needs and make informed choices about their care.

Key Takeaways

• Cushing’s disease is most common in middle-aged and older dogs.
• Symptoms are subtle initially but progress over time. Increased drinking, urination, appetite, and abdominal distension are hallmark signs.
• Accurate diagnosis requires specialized testing and often imaging.
• Management usually involves medication, but surgery may be warranted for certain cases.
• Long-term monitoring and owner vigilance are essential to maintain quality of life.

Quick Reference: Cushing’s Disease in Dogs

Final Thoughts

Cushing’s disease, while serious, can be successfully managed with coordinated veterinary care and informed pet ownership. By understanding the signs, pursuing accurate diagnosis, and adhering to treatment plans, owners can ensure the highest possible quality of life for their dogs. Regular monitoring, communication with your veterinary team, and prompt attention to changes are keys to living well with Cushing’s disease.