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Cushing's Disease in Dogs

Pearl's Story

"Pearl" was a beautifully groomed eight-year-old, white Poodle. She was brought into the clinic as her owner had noticed that she had recently had a tremendous thirst, and she had a couple of large pee "accidents" in the kitchen, … which was very unlike her.  

After Urine tests and several Blood tests it was revealed that "Pearl" had Cushing's disease.  

Cushing's disease, also known as Cushing’s syndrome, or Hyperadrenocorticism, is a condition in which the adrenal glands overproduce certain hormones.    

The adrenal glands are located near the kidneys, they produce several vital substances that regulate a variety of body functions that are necessary to sustain healthy life. The most widely known of these substances is Cortisol, commonly known as cortisone. Cushing’s Disease is caused by excessive levels of cortisol in the body, normally produced in much more precise amounts by the adrenal glands.  

Cushing’s disease is common in middle aged and older dogs. Although it can affect any dog, it is more common in small breeds, such as Terriers, Poodles, and Dachshunds.   

Signs and symptoms that your dog may have Cushing’s include drinking more and urinating frequently, hair loss, weight gain, panting, changes to the skin’s appearance and an abdominal swelling. However, these can be similar signs of lots of other health conditions, so Blood tests are essential to confirm this diagnosis and advise on any treatment.    

The adrenal glands are sent messages to produce cortisol by the Pituitary gland, which sits at the base of the brain. In a dog with Cushing’s disease, far too much cortisol is produced.    

There are three types of Cushing’s disease, each of which has a different cause. Identifying the cause is important, because each type can be treated differently, and each has a different outcome.   

A Pituitary gland tumour. The most common cause of Cushing's disease, which covers most, 85% - 90%, of all cases, is a tumour of the Pituitary gland, which is located at the base of the brain. These tumours are mainly small and benign. The tumour causes the pituitary gland to overproduce a hormone (ACTH) which then stimulates the adrenal glands to produce Cortisol. Generally, if the activity of the glands can be controlled with medication, many dogs with this form of Cushing's disease can live normal, happy lives for many years. If the pituitary tumour grows however, it can affect the surrounding brain tissues, often resulting in neurological signs, giving the pet a less favourable prognosis.   

Adrenal gland tumours. Cushing's disease may also be the result of benign or malignant tumours of the adrenal glands themselves. An adrenal gland tumour causes the gland to become overactive and produce much more cortisol than normal. If the tumour is benign, specialist surgical removal may be possible. If the tumour is malignant, surgery may help for some time, but the prognosis is much less favourable.   

The third type of the disease is called iatrogenic Cushing's disease. It is caused when there has been a long-term administration of an oral or injectable steroid. Although steroids were given for a legitimate medical reason, in these cases, their prolonged use can eventually become harmful to the patient.   

Regardless of the type, the clinical signs and symptoms of Cushing’s disease are essentially the same. An increased appetite and thirst, urinating more, lethargy and a poor hair coat. Many cases can develop a bloated, “pot-bellied” appearance to their abdomen. Panting more, thin skin with recurrent skin infections, pigmentation and mineralization, and persistent urine infections, are other clinical signs.  

Getting a confirmed final diagnosis of Cushing’s Disease can be challenging. Your vet will need to take blood samples and urine tests, and further tests may also be required to finally confirm the diagnosis. An abdominal ultrasound examination can be a valuable part of the diagnostic process to determine the size of the adrenal glands and any suspicion of the presence of a tumour.   

Once diagnosed, the treatment of Cushing’s Disease depends on which type of the disease is present.  

The most common cause of Cushing’s Disease is a small, benign Pituitary tumour. Treatment of the pituitary-induced form of Cushing’s disease is with lifelong daily medication therapy, and essential regular check-ups and close monitoring of its effects involving regular blood checks.   

Treatment of an adrenal tumour often requires specialist abdominal surgery. The prognosis for patients diagnosed with malignant adrenal tumours is sadly guarded to poor. In cases of benign adrenal tumours, however, specialist surgery may be curative if successful. If surgery is not an option, some of these patients can also be managed with lifelong medication.   

Dogs who have developed iatrogenic Cushing’s disease due to taking steroid medications for other health conditions, will need to be carefully weaned off those long-term steroids. This must be done in a controlled and gradual manner, so that other complications do not occur.  

If a Pituitary tumour is suspected, and lifelong medication is chosen, your pet must be carefully monitored using blood and urine tests and by monitoring clinical signs. Follow-up blood tests are extremely important to be certain your pet is receiving the correct drug dosage and not too little or too much of the advised medication, both of which can cause concerning complications. While Cushing’s disease cannot be cured, if responsive it generally can be managed well with medication. However, if the patient is not responsive to treatment, and the Pituitary tumour is large and this structure begins to affect the surrounding brain tissues, the pet has a much less favourable prognosis. Further advanced imaging CT/MRI scans may be required for a further diagnosis with these cases.  

Thankfully, lovely "Pearl" had a Pituitary lesion which responded very well to her advised daily treatment and monitoring. Her tremendous thirst lessened after her advised treatment, … and there were no further "accidents" on the kitchen floor!  

If you are concerned about similar symptoms with your dog, please do arrange an appointment with your Vet for an initial check-up.  

Alison Laurie-Chalmers
Senior Consultant
Crown Vets. 

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