Specialist Referral Service Willows Information Sheets Cushing’s syndrome (Hyperadrenocorticism)
Specialist Referral Service
Willows Information Sheets
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.
© WILLOWS VETERINARY CENTRE AND REFERRAL SERVICE
Willows Information Sheets www.willows.uk.netT: 0121 712 7070
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
© WILLOWS VETERINARY CENTRE AND REFERRAL SERVICE
Willows Information Sheets www.willows.uk.netT: 0121 712 7070
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.
© WILLOWS VETERINARY CENTRE AND REFERRAL SERVICE
Willows Information Sheets www.willows.uk.netT: 0121 712 7070
Specialist Referral Service
www.willows.uk.net