Cushing's disease, also known as hyperadrenocorticism, is a hormonal disorder in dogs characterized by the excessive production of cortisol, a steroid hormone. This overproduction can stem from tumors on the pituitary or adrenal glands, leading to a variety of symptoms and health problems. Early diagnosis and comprehensive treatment are essential for a favorable outcome, allowing dogs to live full and long lives despite the condition. While there is no way to predict or prevent Cushing’s disease, understanding the condition and implementing appropriate management strategies can significantly improve a dog's quality of life.
Understanding Cushing's Disease
Cushing's disease occurs when the body produces excess amounts of cortisone. This can result from hormone-producing glands near the kidney (adrenal glands) or in the brain (pituitary gland) producing too much cortisone. The vast majority of dogs with Cushing's (80-85%) have it due to a tumor in their pituitary gland. A smaller percentage of dogs (15-20%) have adrenal tumors that cause Cushing's. Cortisol-producing tumors in the adrenal or pituitary gland can be either cancerous or benign. In very rare cases, meal- or food-induced Cushing’s can happen.
Types of Cushing’s Disease
There are primarily two types of Cushing’s disease in dogs:
- Pituitary-Dependent Cushing's Disease (PDC): This accounts for 80-90% of cases. It involves a tumor on the pituitary gland, which causes excessive production of adrenocorticotrophic hormone (ACTH). ACTH stimulates the adrenal glands to produce cortisol.
- Adrenal-Dependent Cushing’s (ADC): This type is caused by a tumor on one of the adrenal glands, leading to excess cortisol production. The tumor can be either cancerous or non-cancerous.
Common Symptoms
The most common symptoms of Cushing's disease include:
- Increased thirst and urination
- Increased appetite
- Thinning hair coat
- Pot-bellied appearance
- Excessive panting
- Muscle weakness
Not all dogs demonstrate all these symptoms, and the severity can vary.
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Diagnosis of Cushing's Disease
Diagnosing Cushing's disease involves a thorough physical examination, a detailed medical history, and specific diagnostic tests. Veterinarians typically perform the following tests:
- Blood and Urine Tests: These tests look for signs that could point to Cushing’s, such as dilute urine (high water content) due to excessive water intake.
- ACTH Stimulation Test: This test measures cortisol levels before and after an injection of synthetic ACTH. A significant increase in cortisol levels after the injection suggests Cushing's disease.
- Low-Dose Dexamethasone Suppression (LDDS) Test: Considered accurate for diagnosing Cushing’s, this test involves measuring cortisol levels before and after administering a small dose of dexamethasone. In dogs without Cushing’s, cortisol levels will drop after eight hours.
- High-Dose Dexamethasone Suppression Test: This test helps determine whether the Cushing’s is pituitary-dependent or adrenal-dependent.
- Urine Cortisol: Creatinine Ratio: This test determines if your dog has unusually high levels of cortisol in his system. A negative result rules out Cushing’s.
- Ultrasound or X-ray: These imaging techniques can detect enlarged liver or adrenal glands, which may indicate Cushing’s disease.
Treatment Options
There are several medical and surgical treatments available to manage Cushing’s disease in dogs.
- Surgery: Adrenal tumors can be surgically removed, especially if malignant. Pituitary tumors are less commonly treated surgically due to the complexity of brain surgery.
- Medications:
- Trilostane (Vetoryl): This medication decreases cortisol production by the adrenal gland without affecting the pituitary or adrenal tumor. It is a safer alternative to older medications.
- Mitotane (Lysodren): This drug reduces cortisol production by destroying part of the adrenal cortex. It requires careful monitoring to avoid causing Addison’s disease (too little cortisol production).
- Selegiline Hydrochloride (Anipryl): This medication is less commonly recommended and works by preventing dopamine breakdown in the brain, affecting cortisol production.
The Role of Diet in Managing Cushing's Disease
While diet alone cannot cure Cushing’s disease, it plays a crucial role in managing symptoms and improving a dog’s quality of life. A well-managed diet can help alleviate symptoms, manage weight, improve muscle health, and support organ function. There is no single diet appropriate for all dogs with Cushing’s disease, but there are some general characteristics to look for. The food should meet the Association of American Feed Control Officials’ (AAFCO) recommendations for adult maintenance (ideally one that is not formulated for all life stages).
General Dietary Recommendations
- Low-Fat Content: Some dogs with Cushing’s disease have excess levels of body fat. A food that’s lower in fat (less than 12% on a dry matter basis, or DM) can help combat this.
- Moderate Fiber: A moderate amount of crude fiber (8-17% DM) is reasonable.
- High-Quality Protein: The protein in the food should be highly digestible.
- Limited Sodium: Your veterinarian will recommend avoiding foods that are higher in salt (sodium) if hypertension is present.
- Adult Maintenance Formula: For many dogs who have Cushing’s disease and are a little overweight, a high-quality adult dog food that’s designed to help prevent weight gain is appropriate.
- Avoid Restricting Water: Dogs with Cushing’s disease tend to experience increased thirst, and an adequate source of clean water should always be available to them.
Foods to Avoid
Certain foods and ingredients can worsen symptoms or interfere with treatments. It’s essential to avoid the following:
- High-Fat Foods: Dogs with Cushing's disease may already be prone to weight gain and fat accumulation.
- Sugary Treats: Excessive sugar consumption can affect blood sugar levels, which may already be elevated in dogs with Cushing's disease due to hormonal imbalances.
- Processed Foods: Highly processed commercial dog foods often contain artificial preservatives, fillers, and additives that may not be beneficial for dogs with Cushing's disease.
- High-Sodium Foods: Cushing's disease can lead to increased water consumption and urinary output.
- High-Carb Foods: Carbohydrates can lead to blood sugar spikes.
The Chi Dog Fire Diet
The Fire Diet, developed by Chi Dog, is designed using veterinary science and traditional Chinese medicine principles. It aims to address imbalances caused by Cushing's disease. This diet is high in protein and low in carbs, with anti-inflammatory properties derived from omega-3 fatty acids found in fish, flaxseeds, and certain fruits and vegetables.
Read also: Managing Canine Lymphoma with Diet
Traditional Chinese Veterinary Medicine (TCVM) Perspective
From a TCVM perspective, diets that are rich in carbohydrates and dairy would be more "dampening," meaning more "inflammatory." Diets that are highly processed or something other than kibble-type and foods containing milk, cheese, or other dairy could be more pro-inflammatory and lead to symptoms of "bloating." Given that Cushing's Syndrome can cause similar symptoms, one could use a TCVM approach and avoid these types of foods in an effort to reduce these symptoms. Diets that are more "damp draining" are preferred.
Supplements for Dogs with Cushing's Disease
As long as you are feeding a nutritionally complete and balanced dog food, nutritional supplements for dogs with Cushing’s disease are usually not necessary. However, some supplements can be beneficial in certain cases:
- Flax Hull Lignans: For atypical Cushing’s (normal cortisol levels but abnormal sex hormone secretion), flax hull lignans can be useful. Lignans have natural phytoestrogen activity.
- Melatonin: Can be helpful, especially if hair loss is a symptom.
- Omega-3 Fatty Acids: Fish oil can help manage inflammation.
- Glucosamine: Supports joint health.
- Vitamin E: Provides antioxidant support.
- Calcium supplement: 50mg/kg of body weight (22mg/lb of body weight) per day.
- Medicinal Mushrooms: Can be a beneficial supplement.
- Digestive Enzymes and Probiotics: PET | TAO’s Harmonize Gi boosts gut health, which in turn helps your dog better process all food nutrients.
Herbal Remedies
Certain herbs are believed to support dogs with Cushing’s disease. Prana Pets offers a formula of carefully selected herbs approved by veterinarians called Prana Pets Adrenal Support. It contains dandelion root, horsetail, cleavers, burdock root, turmeric root, ashwagandha root, panax ginseng root, and astragalus root.
- Dandelion Root: A highly nutritional food.
- Horsetail: Contains minerals like magnesium and manganese, supporting the nervous system and balancing hormones.
- Cleavers: Helps the dog’s kidneys expel extra water, benefiting the adrenal glands and relieving the pot belly.
- Burdock Root: Nourishes the dog’s liver, helping to filter the blood.
Prana Pets Cushing’s Support for the Immune System contains alfalfa leaf, which regulates appetite, normalizes digestion, and builds strength.
Home Cooking for Dogs with Cushing's Disease
Homemade meals allow precise control over ingredients. If you choose to feed your dog a homemade diet, you must understand and meet your dog’s needs to stay healthy. Even though pet food recalls and the poor quality of some pet foods are a concern, many veterinarians voice concerns over homemade diets. Some vets feel that when fed exclusively, homemade diets may result in vitamin/mineral deficiencies that can adversely affect a pet’s health. Consult with your veterinarian and use personal judgment when cooking at home for your dog.
Read also: Diet for Seizures in Dogs
Tips for Home Cooking
- Share Recipes with Your Veterinarian: Your veterinarian can advise you on supplements for your pet’s individual situation.
- Monitor Your Dog’s Health: Observe his/her temperament, skin, coat, and waste.
- Transition Gradually: When introducing a new diet, transition gradually over 7-10 days to prevent digestive upset.
Additional Management Tips
- Monitor Your Pet’s Weight: Regular check-ins with your veterinarian are vital to ensure your dog’s diet supports their health.
- Regular Veterinary Check-Ups: Schedule regular veterinary check-ups to monitor weight, cholesterol, and cortisol levels.
- Stress Management: Dogs with Cushing's are often more susceptible to stress.
Prognosis and Quality of Life
Dogs treated for Cushing’s can have a high quality of life for a few years - sometimes more - beyond their diagnosis. According to the American Kennel Club (AKC), the average survival time after diagnosis is two years, with about 10 percent living beyond four years.
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