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Cushing's Disease in Dogs

overview

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What is Cushing's Disease?

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Hyperadrenocorticism, more commonly known as "Cushing's disease", is characterised by excessive production of the steroid hormone cortisol. This is usually due to a benign (non-aggressive) tumour of the pituitary gland in the brain or, less commonly, a tumour of one of the small adrenal glands, which sit next to the kidneys. Cushing's disease can sometimes be challenging to diagnose but is generally manageable with medication.

symptoms

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What are the symptoms of Cushing's Disease?

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Dogs with Cushing's disease can show a variety of symptoms. Several of these in combination make the likelihood of Cushing's disease much higher. However, all symptoms can be caused by other conditions as well, so it is important to follow the correct process for diagnosis.

Dogs often experience:

• Increased thirst and urination (90% of cases)
• Increased appetite
• Pot-bellied appearance
• Skin changes (hair loss, spots, thin skin)
• Panting
• Exercise intolerance
• Poor wound healing

diagnosis

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Which tests are used to diagnose Cushing's Disease?

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Since symptoms are not specific, it is important to confirm a diagnosis before treating. Usually several tests are required:

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General blood work

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This doesn't diagnose Cushing's but can be suggestive, and is important to rule out other diseases that could be causing the symptoms.

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Urinalysis

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Dogs with Cushing's often have dilute urine containing a high level of protein. Up to 50% of dogs may have a urinary tract infection at the time of diagnosis.

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Specific blood tests

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Known as either a Low Dose Dexamethasone Suppression Test (LDDST) or an Adrenocorticotropic Hormone Stimulation Test (ACTH), these involve giving an injection and measuring the body's response over several hours. These tests are the only way to confirm a diagnosis, however, they can give an inconclusive (borderline) result. Usually only one of the two is required, but if the test is inconclusive and no other diagnosis is found, it may need repeating a few weeks later.

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Blood pressure

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Affected dogs often have high blood pressure (hypertension). This may resolve when the Cushing's disease is treated, but if it doesn't then medication will be needed to manage and prevent secondary damage.

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Imaging

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Ultrasound can be used to assess the adrenal glands, however, a pituitary mass can only be seen on an MRI scan.

treatment

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How is Cushing's Disease treated?

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Cushing's is not curable, but can be managed with medication given daily. Blood tests are required to monitor response and guide dose adjustments, as not every dog will require the same dose and over-treatment can be dangerous. Bloods are usually checked 10 days after starting treatment, and at least twice a year long-term. Your vet may want to check more often during the first few months while your dog adjusts to treatment.

Dogs with Cushing's are prone to high blood pressure, excessive protein in the urine, and insufficient tear production known as "dry eye". These may need treatment in their own right, so it is recommended to also periodically monitor blood pressure, urinalysis and tear production.

15-20% of dogs have Cushing's due to a mass on the adrenal gland. Sometimes this can be removed surgically, however, it is a complex procedure so specialist referral is advised. CT assessment is usually recommended before surgery as some masses are invasive.

outlook

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What is the outlook for dogs with Cushing's Disease?

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Cushing's disease has a good prognosis, however, treatment is lifelong with the need for regular monitoring, so can be expensive. Occasionally, some dogs do not respond well to medication, in which case this carries a more guarded prognosis for management.<span data-ccp-props='{"201341983":0,"335559739":160,"335559740":259}'> </span>