Cushing's Disease in Dogs

What Is Cushing's Disease in Dogs？

Cushing's disease, also known as hyperadrenocorticism, is a common endocrine disorder that affects dogs. It occurs when the adrenal glands produce an excess of cortisol, a hormone that plays a crucial role in various bodily functions. Cushing's disease can have a significant impact on a dog's health and overall well-being. In this article, we will explore the causes, symptoms, and treatment options for Cushing's disease in dogs.

What Are the Three Stages of Cushing's Disease in Dogs?

Cushing's disease in dogs, also known as hyperadrenocorticism, is a condition caused by an overproduction of cortisol, a hormone produced by the adrenal glands. This condition typically progresses through three stages:

Preclinical Stage

In this initial stage, the dog may not exhibit any noticeable clinical signs, and the disease can be challenging to diagnose. However, there may be subtle biochemical changes in the dog's bloodwork that indicate elevated cortisol levels. Some dogs may develop increased thirst and urination during this stage.

Symptomatic Stage

As Cushing's disease progresses, the dog will start to exhibit more noticeable clinical signs. Common symptoms in this stage include:

• Increased thirst and urination (polydipsia and polyuria)
• Increased appetite
• Weight gain, often with a pot-bellied appearance
• Muscle weakness and wasting
• Thinning of the skin, leading to easy bruising
• Hair loss (alopecia), particularly on the trunk
• Recurrent skin infections and slow wound healing
• Panting and excessive panting (polyphagia)
• Changes in behavior, such as increased restlessness or lethargy
• Enlarged abdomen due to an enlarged liver (hepatomegaly)

Complicated Stage

If left untreated, Cushing's disease can progress to a complicated stage where more severe health issues can arise. These complications can include:

• Diabetes mellitus: Elevated cortisol levels can interfere with insulin function, leading to diabetes in some cases.
• Hypertension (high blood pressure): Cushing's disease can cause an increase in blood pressure, which can lead to cardiovascular problems.
• Infections: Weakened immune function can make dogs more susceptible to infections.
• Blood clotting disorders: Cushing's disease can lead to changes in blood clotting mechanisms.
• Neurological signs: In some advanced cases, neurological symptoms may develop.

Causes of Cushing's Disease in Dogs

Cushing's disease in dogs can be caused by three primary factors:

• Pituitary-Dependent Cushing's Disease: This is the most common form of the condition, accounting for about 80-85% of cases. It occurs when a tumor in the pituitary gland (located at the base of the brain) overstimulates the adrenal glands, leading to excess cortisol production.
• Adrenal-Dependent Cushing's Disease: In around 15% of cases, a tumor develops in one or both of the adrenal glands, causing them to produce excessive cortisol independently. These tumors can be benign or malignant.
• Iatrogenic Cushing's Disease: Sometimes, Cushing's disease can be a side effect of long-term steroid medication usage. This is known as iatrogenic Cushing's disease and is usually reversible by tapering off the medication.

What Dog Breeds Are More at Risk for Cushing's Disease?

The most commonly affected breeds include:

• Poodle: Miniature and toy poodles, in particular, have a higher risk.
• Dachshund: Especially the miniature and standard varieties.
• Terrier Breeds: Yorkshire terriers and Boston terriers are among those at increased risk.
• Beagle: Beagles are also prone to Cushing's disease.
• Boxer: This breed can be predisposed to the condition.
• German Shepherd: Though less common than in some other breeds, German Shepherds can still develop Cushing's disease.

It's essential for owners of these breeds and any dog, in general, to be vigilant about regular checkups and monitoring for symptoms of Cushing's disease. 

How to Diagnose Cushing's Disease in Dogs?

Veterinarians often start by evaluating the dog's clinical signs and medical history. Common clinical signs of Cushing's disease in dogs include:

• Increased thirst and urination
• Increased appetite
• Weight gain, often with a pot-bellied appearance
• Muscle wasting
• Hair loss and thinning coat
• Skin problems like thinning, bruising, or slow wound healing
• Panting excessively
• Restlessness and behavior changes
• Physical Examination:
• A thorough physical examination by a veterinarian may reveal specific signs associated with Cushing's disease, such as abdominal distention or skin changes.

Blood Tests

Blood tests are essential for diagnosing Cushing's disease. Two primary blood tests are typically performed:

a. ACTH Stimulation Test (LDDS Test): This is considered the gold standard for diagnosing Cushing's disease. It involves injecting the dog with a synthetic form of ACTH (adrenocorticotropic hormone) and then measuring cortisol levels before and after the injection. In dogs with Cushing's disease, cortisol levels will remain elevated after the injection.

b. Low-Dose Dexamethasone Suppression Test (LDDST): In this test, the dog is given a small dose of dexamethasone, a synthetic corticosteroid, and cortisol levels are measured before and after the administration. In Cushing's disease, cortisol levels remain elevated after the dexamethasone injection.

Urine Tests:

Urine tests can help confirm the diagnosis and determine the type of Cushing's disease (pituitary-dependent or adrenal-dependent). The urine cortisol-to-creatinine ratio (UC:Cr) can be measured. Elevated levels may suggest Cushing's disease.

Imaging:

In some cases, imaging studies may be performed to identify the underlying cause of Cushing's disease or to rule out other conditions. Abdominal ultrasound is commonly used to visualize the adrenal glands and look for any abnormalities.

Once Cushing's disease is diagnosed, your veterinarian will work with you to develop a treatment plan tailored to your dog's specific needs. 

Treatment for Cushing Disease in Dogs

There are two main forms of Cushing's disease in dogs: pituitary-dependent and adrenal-dependent. Treatment options may vary depending on the underlying cause, but here are the general approaches to treating Cushing's disease in dogs:

Pituitary-Dependent Cushing's Disease Treatment:

• Medication: The most common treatment for pituitary-dependent Cushing's disease is the use of medication. This usually involves drugs like trilostane (Vetoryl) or mitotane (Lysodren). These medications help to suppress the overproduction of cortisol.

Adrenal-Dependent Cushing's Disease Treatment:

• Surgery: If a tumor is identified on one of the adrenal glands, surgical removal of the affected gland may be necessary.
• Medication: In some cases, medication like trilostane or mitotane may also be used to manage adrenal-dependent Cushing's disease if surgery is not an option.

Managing Symptoms

Cushing's disease can cause a range of symptoms, including increased thirst and urination, skin issues, and muscle weakness. 

Skin Issues

Skin problems are common in dogs with Cushing's disease. These can include thinning skin, hair loss, skin infections, and slow wound healing.

Treatment: Addressing skin issues often involves treating secondary skin infections with antibiotics or antifungal medications. Additionally, providing good skin care, such as regular baths with a gentle, hypoallergenic shampoo, can help improve skin and coat quality. Controlling the underlying Cushing's disease with medication can also lead to improvement in skin conditions over time.

Muscle Weakness

Dogs with Cushing's disease may experience muscle weakness and loss of muscle mass. This can result in reduced physical activity and mobility.

Treatment: Adequate exercise and a balanced diet can help maintain muscle mass and prevent further weakness. In some cases, your veterinarian may recommend supplements like omega-3 fatty acids or joint supplements to support overall muscle and joint health.

It's important to note that Cushing's disease is a chronic condition that requires ongoing management. Treatment aims to control the symptoms and improve the dog's quality of life. 

How to Prevent Cushing's Disease in Dogs?

Preventing Cushing's disease in dogs is not always possible, as it can be caused by various underlying factors, including genetics and aging. However, there are some steps you can take to reduce the risk or manage the condition if it does develop. Here are some preventive measures and management strategies:

Maintain a Healthy Weight

Obesity is a risk factor for Cushing's disease. Keep your dog at a healthy weight through portion control, regular exercise, and a balanced diet. Consult your vet for guidance on an appropriate weight management plan.

Diet for Dogs With Cushing's Disease

Dogs with Cushing's disease are often prone to weight gain and obesity. A low-fat diet can help prevent excess weight gain, which can exacerbate the condition. Look for dog foods with lower fat content or consider preparing homemade meals with lean proteins and limited fat sources, like lean meats (chicken, turkey, lean beef), fish, and eggs can help maintain muscle mass and support overall health. 

Reduce Stress

High-stress levels can potentially contribute to the development or exacerbation of Cushing's disease. Provide your dog with a calm and stable environment, regular exercise, and plenty of mental stimulation.

Regular Exercise

Exercise is crucial for overall health and can help manage weight. Ensure your dog gets daily physical activity appropriate for their age, breed, and fitness level.

Monitor Symptoms

Be vigilant for common signs of Cushing's disease, such as increased thirst, urination, appetite, and lethargy. If you notice any concerning symptoms, consult your veterinarian promptly for a proper diagnosis.

Genetic Considerations

Some breeds are more predisposed to developing Cushing's disease. If you have a breed with a higher risk, be especially vigilant about regular checkups and monitoring for symptoms.

Conclusion

Cushing's disease is a manageable condition in dogs with proper veterinary care. Early diagnosis and appropriate treatment can significantly improve a dog's quality of life and help them lead a happy, healthy life. If you notice any of the symptoms mentioned above or suspect that your dog may have Cushing's disease, don't hesitate to consult your veterinarian for a thorough evaluation and guidance on the best course of action.