What is Cushing's disease in dogs?
Dogs with Cushing’s syndrome produce excessive amounts of cortisol. This can have harmful effects on other organs and on the ability of the body to regulate itself.
Cushing’s occurs in dogs who are producing excessive amounts of cortisol, an important hormone that helps to regulate the body’s metabolism.
How cortisol plays a role in your dog’s health
Cortisol plays a vital role in protein, carbohydrate and fat metabolism and is released into the bloodstream at times of stress to prepare the body for a flight or fight response. Cortisol is produced by the adrenal glands - two small glands located in the abdomen, next to each kidney.
A hormone called ACTH controls the production and release of cortisol from the adrenal glands. ACTH itself is produced by the pituitary gland, a pea-sized gland, located at the base of the brain.
The concentration of cortisol in the blood of healthy animals varies greatly as the body’s demand for cortisol fluctuates. For example, during a period of anxiety or illness, it is normal for the adrenal glands to increase their production of cortisol. Once this period of stress has passed, the cortisol concentration in the blood returns to normal.
Why dogs get Cushing’s disease
There is a chronic overproduction of cortisol over weeks and months. Although the concentration of cortisol in the blood of a dog with Cushing’s also fluctuates greatly, it tends to be, on average, much higher than in healthy dogs. The excessive amount of cortisol released into the bloodstream has a harmful effect on the function of many organs and the body’s metabolism.
The most noticeable signs of Cushing’s syndrome include:
- large water intake
- frequent urination and incontinence
- ravenous appetite
- potbelly
- thin skin
- hair loss or recurrent skin diseases
- muscle wastage
- lethargy
- excessive panting
Not all dogs will react to the disease in the same way and your dog may not necessarily display all these signs.
If you become concerned with your dog’s welfare, you should contact us immediately.
What causes Cushing's Syndrome?
Cushing’s will usually occur because of a tumour - often benign - of either the pituitary gland (most common) or adrenal glands (less common). Regardless of its cause, over time a dog suffering from Cushing’s will develop a combination of clinical signs which may initially be associated with the ageing process.
Most dogs with Cushing’s disease (approximately 85% of cases) have a benign tumour of the pituitary gland. The tumour cells produce large amounts of the hormone ACTH, which in turn stimulates the adrenal glands to overproduce cortisol.
Cushing’s disease and tumours
The other cause of Cushing’s (approximately 15% of cases) is a tumour of one (or very rarely both) of the adrenal glands, which produces excessive amounts of cortisol.
Irrespective of the cause of Cushing’s syndrome in your dog, the result is always the same - more cortisol is produced than is needed by the body. This results in the slow development of a combination of clinical signs that are classically associated with Cushing’s.
Untreated Cushing’s disease
If left untreated, your dog may develop other serious conditions which will weaken their body and require further costly treatment. Aside from the impact on your dog’s quality of life, if left untreated Cushing’s syndrome increases your dog’s risk of developing several serious conditions such as diabetes mellitus (a deficiency of insulin resulting in high blood sugar), blood clots in the lungs/brain/legs, kidney infection, urinary tract infection and inflammation of the pancreas.
Book a health check for your pet
Diagnosis of Cushing's disease
Initial signs might alert your vet surgeon to Cushing’s syndrome when you bring your dog in for a health check. Diagnosis is not always straightforward. Your dog will need to undergo a series of blood tests.
Cushing’s is usually seen in older dogs (10-15 years old). Small-breed dogs are more likely to develop the disease.
The most common signs of the disease are very similar to those associated with the normal ageing process. This can make it difficult to diagnose and later monitor. It is always a good idea wherever possible to keep a note of the changes you see in your dog’s habits, behaviour and appearance.
Examining your dog for Cushing’s disease
Your vet surgeon will initially suspect Cushing’s syndrome based on the clinical signs your dog is showing.
At Maven Vets, we will examine your dog to notice any change in their appearance, such as a prominent “pot belly.” Sometimes, the results of a routine blood test may lead us to suspect this condition. 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 we suspect your dog has Cushing’s disease, we will need to perform blood tests to confirm the diagnosis. A blood test to assess your dog’s general health is also recommended. You might remember that the concentration of cortisol in the blood of both healthy dogs and dogs with Cushing’s disease fluctuates throughout the day. It is for this reason that a diagnosis cannot be confirmed by just one measurement of cortisol. The two tests that are used to confirm a diagnosis of Cushing’s are called the ACTH stimulation test and the low-dose dexamethasone suppression test. It may be necessary to perform both tests.
In the ACTH stimulation test, blood is taken to measure cortisol before and after your dog is given a synthetic version of the hormone, ACTH. This test assesses how well your dog’s adrenal glands control the production of cortisol.
Managing Cushing's Syndrome
Cushing’s syndrome is not curable but with medication (Vetoryl®) it can be very effectively controlled; maintaining quality of life for your dog for years to come. Vetoryl®, which is the only licensed treatment for use in dogs, contains the active ingredient trilostane, a drug that rapidly reduces the production of cortisol by the adrenal glands. Your dog will need to be carefully monitored and return for follow-up appointments with us at Maven Vets.
Once we are happy that your dog is stable, you will normally need to visit every three months to make sure nothing is affecting your dog’s condition. At some stage during therapy, it might become necessary to adjust the dose of Vetoryl® prescribed. Your dog will begin Vetoryl® at the recommended starting dose dependent on their body weight. You should then make an appointment for your dog to see us after 10 days. Your dog should be regularly examined and monitored using blood tests. We will assess your dog’s response to Vetoryl® treatment by:
Looking for an improvement in clinical signs:
In most cases, you can expect to see a decrease in your dog’s appetite and the amount they drink within the first couple of weeks on treatment. Other clinical signs may take three to six months to improve.
Performing blood tests:
The results of routine blood tests and an ACTH stimulation test are used to assess the effectiveness of Vetoryl® treatment at 10 days, 4 weeks, 12 weeks, and every 3 months after starting treatment, depending on your vet’s recommendations.
Your dog should be closely monitored during early stages of therapy so that the dose of Vetoryl® can be adjusted to meet its specific needs. This also helps to minimise the risk of side effects or complications that could be harmful to your dog.
Once we are happy with your dog’s progress, it is strongly recommended that you visit the vets every three months for regular monitoring so that dose adjustments can be made as required.
