Cushing’s Disease in Dogs: Symptoms, Causes, and Treatment

Understanding Cushing’s Disease in Dogs

Cushing’s disease, also known as hyperadrenocorticism, is a condition that occurs when a dog’s adrenal glands produce too much cortisol. While cortisol is essential for many bodily functions, including helping dogs respond to stress and regulating the immune system, an excess can lead to a range of health problems.

Cushing’s disease is most commonly seen in older dogs, though it can affect dogs of any age.

If your dog has been diagnosed with Cushing’s disease or you suspect they may be showing signs of it, understanding the symptoms, causes, and treatment options can help you provide the best care. In this blog, we’ll cover all the essential information you need to know about this condition and how to manage it effectively.

What is Cushing’s Disease?

Cushing’s disease in dogs is caused by the excessive production of cortisol, a hormone released by the adrenal glands. There are three types of Cushing’s disease:

• Pituitary-Dependent Cushing’s

• This is the most common form, accounting for approximately 80-90% of cases. It occurs when a benign tumour on the pituitary gland causes the overproduction of adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands to produce cortisol.

• Adrenal-Dependent Cushing’s

• This form results from a tumour on one or both adrenal glands, causing them to produce too much cortisol independently of ACTH levels.

• Iatrogenic Cushing’s

• This occurs when a dog is given too much corticosteroid medication over a long period. Once the medication is reduced or stopped, this form of Cushing’s often resolves.

Symptoms of Cushing’s Disease in Dogs

Cushing’s disease tends to develop slowly, and the symptoms may be subtle at first. However, as cortisol levels continue to rise, the signs become more pronounced. Some of the most common symptoms of Cushing’s disease in dogs include:

• Increased Thirst and Urination

• Excessive cortisol leads to an increase in thirst, which causes dogs to drink more and, consequently, urinate more frequently. If your dog is suddenly having accidents in the house or needing to go outside more often, this could be a sign of Cushing’s.

• Increased Appetite

• Dogs with Cushing’s often have an insatiable appetite. They may beg for food more often or scavenge around the house.

• Pot-Bellied Appearance

• The redistribution of fat and weakening of the abdominal muscles due to Cushing’s can give dogs a pot-bellied appearance.

• Thinning Fur and Hair Loss

• Dogs with Cushing’s may experience thinning fur or noticeable hair loss, particularly on the flanks and tail. Their skin may also become thinner and more prone to infections or slow healing.

• Lethargy and Weakness

• As the disease progresses, dogs may become less active and show signs of muscle weakness.

• Panting

• Dogs with Cushing’s may pant excessively, even when they’re not particularly hot or after minimal exertion.

• Skin Issues

• In addition to thinning skin, dogs with Cushing’s are prone to developing skin infections (pyoderma) and calcinosis cutis, which are hard lumps under the skin caused by calcium deposits.

If you notice any combination of these symptoms in your dog, it’s important to consult your veterinarian for further testing.

Causes of Cushing’s Disease in Dogs

Cushing’s disease is most commonly caused by a tumour on the pituitary gland (pituitary-dependent Cushing’s) or, less frequently, by a tumour on the adrenal glands (adrenal-dependent Cushing’s). There is also an iatrogenic form, which is caused by prolonged use of corticosteroid medications, such as prednisone, used to treat conditions like allergies or autoimmune disorders.

Certain breeds are more prone to developing Cushing’s disease, including:

• Poodles (especially Miniature and Toy Poodles)
• Dachshunds
• Beagles
• Boxers
• Terriers (including Yorkshire Terriers and Boston Terriers)

Additionally, the risk of Cushing’s disease increases with age, and it is most commonly diagnosed in dogs over the age of 6.

Diagnosis of Cushing’s Disease in Dogs

Diagnosing Cushing’s disease can be challenging, as its symptoms often overlap with other common conditions such as diabetes or kidney disease. Your vet will likely perform a series of tests to confirm the diagnosis, including:

• Blood and Urine Tests

• These tests can help identify elevated liver enzymes, increased glucose levels, and dilute urine, which are common in dogs with Cushing’s.

• ACTH Stimulation Test

• This test measures the adrenal glands’ response to adrenocorticotropic hormone (ACTH) and is used to confirm the overproduction of cortisol.

• Low-Dose Dexamethasone Suppression Test (LDDS)

• In this test, your dog is given a low dose of dexamethasone (a synthetic steroid), and cortisol levels are measured over time. In dogs with Cushing’s, cortisol levels will remain elevated despite the administration of dexamethasone.

• Ultrasound

• An ultrasound can help your vet determine if the cause of Cushing’s is related to a tumour on the adrenal glands, which can be treated differently than pituitary-dependent Cushing’s.

Treatment for Cushing’s Disease in Dogs

The treatment for Cushing’s disease depends on the underlying cause of the condition.

• Medications

• In most cases, dogs with Cushing’s disease are treated with medication to control cortisol production. The most commonly prescribed drugs are trilostane (Vetoryl) and mitotane (Lysodren). These medications work by reducing the production of cortisol or destroying some of the adrenal tissue that produces it.

• Surgery

• If the cause of Cushing’s is an adrenal tumour, surgery to remove the tumour may be an option. However, this procedure is complex and carries certain risks, especially in older dogs.

• Discontinuing Steroids

• For dogs with iatrogenic Cushing’s, simply reducing or stopping the corticosteroid medication under veterinary supervision can resolve the symptoms.

• Monitoring and Adjustments

• Dogs with Cushing’s will need regular veterinary check-ups and blood tests to monitor their cortisol levels and adjust medications as necessary. Some dogs can live for years with managed Cushing’s disease, but others may experience complications from the condition or its treatment.

Managing Cushing’s Disease in Dogs

While there is no cure for Cushing’s disease, it can be managed with proper treatment and monitoring. Here are some tips for helping your dog live a comfortable life with Cushing’s:

• Regular Vet Visits

• Frequent check-ups are necessary to monitor your dog’s cortisol levels and ensure that treatment is working effectively.

• Diet and Exercise

• Keeping your dog at a healthy weight can help manage some symptoms of Cushing’s disease. A well-balanced diet, low in fat, and regular exercise can support overall health.

• Medication Compliance

• Ensure that you give your dog their prescribed medications consistently and as directed by your vet. Missing doses can lead to a resurgence of symptoms or other complications.

• Monitoring for Side Effects

• Medications for Cushing’s can have side effects, including vomiting, diarrhoea, and lethargy. Always report any changes in your dog’s behaviour or health to your vet.

• Skin Care

• If your dog develops skin issues, work with your vet to manage infections or irritation. Your dog may need medicated shampoos or topical treatments.

Conclusion: Living with Cushing’s Disease

Cushing’s disease can be a challenging diagnosis for both dogs and their owners, but with the right treatment plan, many dogs can continue to live happy, comfortable lives. Early detection is key to managing the condition and preventing complications. If you suspect your dog may have Cushing’s disease, consult with your veterinarian to discuss testing and treatment options.
By staying informed and proactive, you can help your dog maintain their quality of life and ensure they receive the best care possible for this condition.