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Cushing’s syndrome (Hyperadrenocorticism)

Cushing’s syndrome (Hyperadrenocorticism)

What is Cushing’s Syndrome (Hyperadrenocorticism)?

Cushing’s Syndrome, also known as hyperadrenocorticism, is a disease caused by excessive

production of cortisol. Cortisol is a very important hormone that the body needs on a day-to-day

basis, but its levels need to stay within a normal range that the body normally regulates. Cortisol is

produced by the adrenal glands, two small glands located near the kidneys in the tummy (abdomen).

The adrenal glands are stimulated to produce cortisol by another hormone (called ACTH) which is

released by the pituitary gland, a very small gland located in the lower part of the brain.

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Why do dogs get Cushing’s Syndrome?

Cushing’s Syndrome occurs due to excessive amounts of cortisol in

the bloodstream. The condition can be caused by:

• a very small tumour of the pituitary gland (this is the

most common form). These tumours are usually so small

that the tumour itself is not otherwise harmful

• a large tumour of the pituitary gland (this is uncommon)

• tumours or benign enlargement of one or, rarely, both of

the adrenal glands next to the kidneys

• administration of too much of a medication called

corticosteroids e.g. prednisolone or dexamethasone

What are the symptoms (signs) of Cushing’s Syndrome?

• increased thirst

• increased frequency and volume of urination

• increased appetite

• weight gain

• thin skin, and sparse hair coat

• ‘pot belly’

• muscle wastage

• calcification of the skin or ligaments

• excessive panting

• being prone to infections

• uncontrolled diabetes

(see Diabetes mellitus information sheet)

How is Cushing’s Syndrome diagnosed?

Cushing’s Syndrome can be very hard to diagnose. The disease can

have similar symptoms to several other diseases such as diabetes,

hypothyroidism and urinary tract infections. Cushing’s Syndrome

is suspected after we have taken a full history and performed a

detailed physical examination, but further tests are required to

confirm the diagnosis.

Cortisol is normally present in the bloodstream, levels of cortisol

increase whenever the body is ‘stressed’ (i.e. by illness, external

strains or anxiety). A single blood cortisol test does not tell us if a

pet has Cushing’s Syndrome, because numerous situations can lead

to an increase in cortisol. We use the combination of urine tests,

blood tests and ultrasound scans of the abdomen (tummy)

to diagnose Cushing’s Syndrome.

Routine blood screening in pets with Cushing’s Syndrome

often shows:

• raised liver enzyme activities (these are chemicals

produced by the liver)

• increased cholesterol in the blood

• increased white blood cell counts (the blood cells

which fight off infection)

• occasionally, increased calcium levels

These findings are not specific to Cushing’s Syndrome, as they not

uncommonly occur in other diseases. To refine our diagnosis, we

perform what is called ‘dynamic blood testing’ – most commonly an

ACTH stimulation test, or a low-dose dexamethasone suppression

test. These tests help us to assess the function of the adrenal glands,

and their ability to increase or decrease cortisol production. These

tests require your pet to be admitted into hospital for the day. An

initial blood sample is taken to measure the baseline cortisol level.

An injection of ACTH or dexamethasone is then given, and further

blood samples are taken to measure the response of the adrenal

glands to these substances. The procedure is quite simple and

doesn’t hurt your pet. Specialised blood tests (e.g. measuring the

levels of other hormones such as the body’s natural ACTH produced

by the pituitary gland) can also aid in making the diagnosis.

In addition to performing blood tests, diagnostic imaging may be

required in some cases. For example, an ultrasound scan of the

abdomen can show whether one or both of the adrenal glands is

enlarged, and occasionally adrenal tumours can be diagnosed on

the scan. An MRI or CT scan of the brain is occasionally needed to

determine if there is a large pituitary gland tumour present.

How is Cushing’s Syndrome treated?

Cushing’s Syndrome is usually treated medically, or by surgery

in some cases. We most commonly use medication to manage

Cushing’s Syndrome, as modern drug treatment can often

successfully reduce cortisol production. Cushing’s Syndrome is not

curable but can often be successfully managed by using medication

which is given for life.

Medical treatment of Cushing’s Syndrome

The most common medication used in the UK to treat Cushing’s

Syndrome is trilostane (Vetoryl®). This treatment is given once

or twice a day as a capsule. Trilostane reduces the production of

excessive amounts of cortisol. It can have powerful effects, and

it is therefore very important that we regularly measure the

amount of cortisol produced. Too much medication can lead to

inadequate amounts of cortisol in the bloodstream, creating

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a life-threatening-crisis (hypoadrenocorticism or Addison’s

disease). On the other hand, too little medication can lead

to poor control of the disease and ongoing symptoms. Blood

tests need to be performed at intervals to measure the body’s

response to treatment. Your vet will advise you how frequently

blood tests need to be performed. In most patients the dosage

of trilostane needs to be adjusted as time goes by.

Surgical treatment of Cushing’s Syndrome

Surgery to remove the adrenal gland(s) is sometimes required to

control the disease process in certain cases of Cushing’s Syndrome.

This surgery is complicated and is performed by our Specialist team

of anaesthetists and surgeons. If surgery is an option, we will discuss

this in detail with you to ensure that you are fully informed of all

the significant implications of the procedure.

What is the long term outlook for Cushing’s Syndrome?

Although Cushing’s Syndrome is quite a serious disease which can

affect life expectancy, we will do all we can to enable your dog to

enjoy a good quality life, hopefully for a long time to come. In most

cases, the earlier the condition is diagnosed and the more closely the

effects of treatment are monitored, the better the outlook will be.

Can cats get Cushing’s Syndrome?

Cushing’s Syndrome is very rare in cats.

If you have any queries or concerns regarding your pet and

Cushing’s Syndrome, please do not hesitate to contact us.

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