Cushing's disease is brought on by excessive amounts of cortisone circulating around the body.
Dogs with Cushing's disease can show a wide variety of symptoms, the most common ones being:
- Excessive drinking
- Excessive hunger
- Pot bellied
- Chronic skin problems
- Hair loss (alopecia) along the abdomen and chest
Affected pets may display some or all of these symptoms.
- Excess amounts of cortisone therapy e.g. in long running skin problems.
- Malignant tumour of the adrenal glands- tumours made up of the cortisone producing cells of the adrenal glands make excessive cortisone.
- Benign tumour of the pituitary gland in the base of the brain (most common cause).
The pituitary gland is the master gland of the body. Pituitary tumours can make hormones which tell the adrenal glands to make excessive amounts of cortisone
Left untreated, complications can occur e.g. diabetes, poor wound healing, infections, poor skin, pot bellied, fatty liver.
Dogs with pituitary gland tumours can go on to live comfortably for some time until the tumour gets too big and starts to place pressure on adjacent parts of the brain.At this stage, we might see symptoms such as blindness and other hormone imbalances.
Unfortunately, adrenal gland tumours are often malignant and can spread to other parts of the body. Referral to a specialist may be an option if the tumour is in just one adrenal galnd and not adhered to any vital structures e.g. the major vein returning blood to the heart (caudal vena cava) which runs adjacent to the adrenal glands.
Suspected cases have blood tests done to try and find out where the excess cortisone is coming from.
Until recently, most cases were treated with a drug called Lysodren which destroys the parts of the adrenal glands that make cortisone.
A relatively new drug called Trilostane, is the current treatment of choice. It has a much higher success rate and less side effects than Lysodren. Trilostane is used in human medicine for treatment of Cushing's disease.
Trilostane is an expensive drug to supply.
Many cases on Trilostane can have the dose lowered after a few months, which helps with the budget. Regular blood tests pick up if this situation has arisen.
Unexpected Side Effects of Treament
Cortisone has powerful anti-inflammatory actions in the body. Symptoms of arthritis or itchiness (pruritis) may be hidden in dogs suffering from Cushing's disease. Once treated for Cushing's disease, these signs may become obvious to the owner and require other medications to soothe them.
Diabetes is commonly seen in Cushing's cases, probably as a result of cortisone interfering with the action of insulin. Because of this interference, the treatment dose of insulin is much higher than in a diabetic none-cushingoid dog. Once treatment for Cushing's starts, the vet has to closely monitor the diabetes to ensure there is no overdosing of insulin which now has no cortisone to interfere with its action.
Cushing's cases have to be regularly monitored to make sure the medication is working properly and also to ensure that not all the body's cortisone production has been stopped. In other words, we don't want the dogs to have the opposite problem of not enough cortisone (Addison's Disease).
Dogs in treatment are usually given some cortisone tablets (e.g. Cortate) to have on hand just in case their dog's cortisone levels drop to zero during the course of treatment and it starts to show symptoms of Addison's disease.
Expense of Treatment
Before embarking on treatment, owners need to be very aware of the expensive nature of treament. They must be fully committed and prepared to put up with regular blood tests and expensive drug bills. In a very old patient, no treatment may be a more preferable propositon especially if the owners are on a budget.
In human medicine, pituitary gland tumous can be removed by specialist surgeons operating through the nose or roof of the mouth.