Cushing’s disease, or hyper-adrenocorticism, is a chronic excess of steroids produced in the body by the adrenal gland. The types of steroids in question are glucocorticoids, which are produced by the adrenal gland in response to stimulation by the pituitary gland. Thus, Cushing’s disease can occur as a result of over-activity of either of these glands.
The disease occurs mainly in middle-aged to older dogs of any breed. It can occur in cats but is extremely rare, so in this article we will focus on dogs. Glucocorticoids have a number of functions in the body, but an excess of these steroids can have a number of adverse effects. Common signs of Cushing’s disease include:
- Increased drinking and urination
- Increased appetite
- Abdominal enlargement, or ‘Pot Belly’
- Hair loss and thinning skin
- Delayed wound healing and infections
Some dogs present with the classic signs of drinking and urinating more, abdominal enlargement and skin changes. However, this disease is slowly progressive and as a vet, I have even seen early cases who display subtle signs such as restlessness or hair loss that even the owners had not yet noticed.
Testing for Cushing’s disease initially involves blood sampling. To start with, the vet may take blood and urine for general tests. The next step will probably be more specific blood tests for Cushing’s disease, called Dexamethasone Suppression Tests or ACTH Stimulation Test. An ultrasound may also be necessary to assess the adrenal glands.
Treatment for Cushing’s disease depends on whether the primary problem is with the adrenal gland or with the pituitary gland. If the adrenal gland is the primary problem, it usually contains a functional, benign tumor, and should be removed surgically. If the tumor is in the pituitary gland, it is also usually benign, but cannot be removed as this gland is in the brain. This applies to the majority of cases, and this condition, called pituitary-dependent hyperadrenocorticism (PDH) is treated using medication. If your dog requires daily medication for this problem, frequent monitoring using blood tests will also be necessary to ensure that the disease is well controlled. Lack of treatment will eventually lead to severe muscle weakness and a very sick doggy!