Cushing’s syndrome occurs when a dog is exposed to high levels of the hormone cortisol for an extended period of time. Cortisol is produced by 2 small glands situated near the kidneys called the adrenal glands. The hormone ACTH controls the production & release of cortisol. ACTH is produced by a small gland beneath the brain called the pituitary. Cortisol is normally released into the bloodstream at times of stress to prepare the body for a “fight or flight” response.
In dogs with Cushing’s syndrome, cortisol release is excessive and so results in a number of possible clinical signs including:
- Increased thirst
- Increased urination
- Increased appetite
- A “pot belly”
- Thinned skin & hair loss
- Development of muscle wastage
There are 2 forms of Cushing’s syndrome:
Pituitary – dependent Cushing’s syndrome
- Most common form
- Due to the development of a slow growing tumour in the pituitary gland which produces large amounts of the hormone ACTH
Adrenal – dependent Cushing’s syndrome
- Development of a tumour in 1 or possibly both of the adrenals producing large amounts of cortisol
Cushing’s syndrome is usually seen in the older dog and therefore the clinical signs may initially attributed to normal ageing.
As the cortisol levels in the blood of all dogs fluctuates greatly throughout the day, diagnosis of Cushing’s
Syndrome involves an “ACTH stimulation test” which measures the ability of a dog’s adrenal glands to produce cortisol when stimulated. An alternative test is the “low dose dexamethasone suppression test” which assesses the ability of the adrenal glands to control the production of cortisol.
The above blood tests require you to leave your dog with us at the surgery for a couple of hours or for the day.
If your dog is diagnosed as having Cushing’s syndrome they will need to start medication in the form of capsules. Unfortunately this is not a cure and your dog will have to take the medication for the rest of their life but by reducing the body’s cortisol production it is efficient at reversing the signs of Cushing’s syndrome.
We will need to monitor your dog’s treatment to ensure they are on the correct dose. Repeat blood samples will need to be taken after 4 weeks and then every 6 months, providing your dog is stable. Your vet may decide a sample is required 10 days after starting treatment.