What is Cushings Disease?
Cushing’s Disease, or Canine Hyperadrenocorticism, is where an excessive amount of cortisol is released into your dog’s body from the adrenal glands, which are located near the kidneys. Cortisol regulates the body’s metabolism. It is one of the most common hormonal disorders, mostly occurring in middle-aged and older dogs.
What causes Cushings Disease?
In 85-90% of dogs with naturally-occurring Cushings Disease, the problem is caused by a benign tumour in the pituitary gland of the brain, which controls the adrenals. The tumour over-produces ACTH, leading to enlargement and over-production of cortisol by both of the adrenal glands. This is called Pituitary-Dependant Cushings Disease. Occasionally (only 10% of these dogs), the tumour is large enough to compress the brain and neurological signs may be seen. In the remaining 10-15%, the tumour is in one adrenal gland, which is directly over-producing cortisol. The tumour is often large enough to see with ultrasound and may be malignant (can spread to other organs). This type is called Adrenal-Dependant Cushings Disease.
Both types of tumour tend to be slow growing, so the symptoms seen take time to develop. A third, less common, type of Cushings Disease is caused by a prolonged or high-dose course of corticosteroid antiinflammatories, such as Prednisone, given to the dog to treat allergies or immune-mediated disease. Prednisone is a derivative of cortisol and can have the same effects. Consequently, vets try to limit its use and minimise both the dose and duration given. This type of Cushings Disease is called latrogenic Cushings. Iatrogenic just means that it has been caused by medical treatment. This type can often be reversed by stopping or reducing the Prednisone.
Typical signs of Cushings Disease:
Excessive thirst and urination
Excessive hunger
A pot-belly (swollen tummy)
Excessive panting
Bilaterally symmetrical hair thinning
Other skin changes
Lethargy
Poor wound healing
Urinary tract infections
Diagnosis
Diagnosis In most cases, the changes in your dog’s appearance and behaviour caused by Cushing’s Disease occur very gradually, making them easy to overlook.
If your vet is suspicious of Cushing’s Disease, a series of blood tests are likely to be needed to confirm the diagnosis, as well as assess the overall health of your pet, before treatment is considered.
Diagnosis is not always straight forward. Cortisol levels in the blood fluctuate throughout the day, both in healthy dogs and those with Cushing’s. Therefore, a single cortisol measurement can be misleading.
The most commonly-used screening tests for Cushing’s Disease are called:
Low-dose Dexamethasone Suppression Test
ACTH-stimulation Test
Abdominal Ultrasound, often more than one test is needed
Treatment
Fortunately, medication is available, which reduces cortisol production by the adrenal glands. The medication, which comes in capsule form, is given each morning with food. Lifelong treatment will be required.
With treatment: A vast majority of dogs respond well to medication and their symptoms are likely to start improving within a few weeks. Many dogs with well-controlled Cushings live a relatively normal and happy life for many years.
Without treatment: Some dogs with Cushings disease live without treatment for some time but tend to be happier and healthier with medication.
Unfortunately, if your dog has a malignant adrenal tumour (rare), he or she may not respond well to the medication and the prognosis is less favourable.
If the tumour is in one adrenal gland and there is no evidence of further spread to other organs via the blood stream, surgery to remove the affected adrenal may be an option. A CT scan would be used to look for spread.
Monitoring
Your vet will work with you to monitor clinical response. You will be asked to complete short survey forms about your dog’s clinical signs and quality of life before each appointment. Combined with occasional blood test results, your vet can use these surveys to fine-tune your dog’s treatment dose, so that it is most effective. If your dog is due for a blood test, please note that the test is best done just prior to the time the next dose is due to be given.
We understand that treatment and monitoring can be expensive, especially for bigger dogs, so please discuss any concerns with your vet, so that the best option can be found for you and your dog.
Side Effects of Treatment
It is very important that the correct dose is given and at the correct intervals, or the cortisol levels may drop dangerously low.
SYMPTOMS TO WATCH OUT FOR ARE:
Reduced appetite
Lethargy and weakness
Vomiting
If you see any of these signs in your dog with Cushings Disease, please do not give another dose of the medication and contact your vet immediately.
If a dose of medication is inadvertently missed or late, do not give the dose and resume the medication course at the next scheduled time
Please find below some handy downloadable pet owner resources and the 2 survey forms to be completed before each visit.
Cushing’s Clinical Score
Cushing’s Disease Owner Logbook
Owner Booklet
Cushing’s Quality-of-life Questionnaire