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Alison Laurie-Chalmers: Pearl’s story and types of Cushing’s disease in dogs

By Alison Laurie-Chalmers

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Young veterinarian examining dog in clinic
Young veterinarian examining dog in clinic

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 per cent - 90 per cent, 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 over-active 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. Thankfully, lovely “Pearl” had a Pituitary lesion which responded very well to her advised daily treatment and monitoring.

  • Alison Laurie-Chalmers is a senior consultant at Crown Vets in Inverness.

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