Cushing’s disease

Canine Cushing’s Disease or Cushing’s Syndrome, known medically as hyperadrenocorticism, is a hormonal condition in which a dog’s body produces too much of the stress hormone called cortisol. It was first discovered in 1932 by American neurosurgeon Dr Harvey Cushing. There are three main causes for Cushing’s Disease, and identifying the correct cause is important since each diagnosis is treated differently.

It most commonly happens in dogs aged 6 years and older, when a small and benign pituitary tumour (non-cancerous) stimulates the adrenal gland, accelerating the speed at which cortisol is released.

The role of the cortisol hormone, both in us humans and dogs, is to help regulate our stress response, metabolism, weight, and proper functioning of our immune system. Therefore, too much or too little cortisol can lead to problems.

Symptoms and diagnosis

Diagnosing Cushing’s Disease early in dogs is tricky, as many of the symptoms are mild and are similar to those of other conditions. Some initial symptoms you may notice are:

• Excess urination and thirst
• Increased appetite
• Weight gain
• A ‘pot-bellied’ or bloated appearance, with the belly visibly hanging lower than normal
• Lethargy
• Panting
• Thinning skin and persistent skin infections
• Hair loss

Vets will initially use a urine test and a blood test to diagnose Cushing’s and to find out whether the disease is caused by the pituitary or adrenal gland. An ultrasound scan of the dog’s tummy may also be carried out to locate the tumour on the adrenal gland, although this is a less common occurrence; around only 15% of Cushing’s patients have adrenal tumours.

Cause

The three main causes of Cushing’s Disease are:

• Pituitary gland tumour
• Adrenal gland tumour
• An overproduction of cortisol due to prolonged steroid use

The excessive levels of the cortisol hormone are more commonly caused by a tumour on the pituitary gland, leading to complications in other organs. However, the condition can also be an unfortunate side effect arising from the prolonged use of steroid medications, such as those used to treat allergies or immune disorders.

Prevention

There is currently no known way to prevent Cushing’s Disease. Unfortunately, some breeds of dog are simply more prone to naturally overproduce more cortisol in their bodies than other breeds; including Beagles, Poodles, Dachshunds, Terriers and Boxers. If you own one of these breeds, it is worthwhile asking your vet for a Cushing’s test when they reach 6 years old.

An important part of preventing the problems arising from Cushing’s Disease is knowing the early signs and symptoms because the condition can be life-threatening if left untreated. The disease is not easy to spot, so if you notice any of the above symptoms in your dog – no matter how mild – you should speak to your vet straight away, especially so if your dog is already undergoing steroid treatment.

Treatment and costs

Cushing’s Disease is a lifelong condition and can be costly to manage, however dogs who have this disease can still live a happy life! If the condition was caused by a tumour on the pituitary gland, the dog would need to be treated with regular medication for the rest of his or her life. It’s important that your dog also sees the vet for regular check-ups and blood tests, whilst supplying the medication exactly as directed by your vet.

In the case that it was caused by a tumour on the adrenal gland, and if it hasn’t spread further throughout the dog’s body, surgery may be necessary to remove the tumour. Providing the tumour hasn’t spread further, surgery is successful in most cases.

If the dog has developed the disease as a result of taking long-term steroid treatments to manage other canine health problems, treatment usually involves gradually weaning off the steroids, so speak to your vet to find out if this is the case.