Hyperadrenocorticism, more commonly known as Cushing’s, is the production of excessive amounts of cortisol. Cortisol is an important hormone that helps to regulate the body’s metabolism. It is also released into the bloodstream at times of stress to prepare the body for a flight or fight response.
Cortisol is produced by the adrenal glands which are two small glands in the abdomen, situated next to each kidney. A hormone called ACTH controls the production and release of cortisol from the adrenal glands. ACTH is produced by the pituitary gland which is a pea sized gland located at the base of the brain.
In healthy animals, the cortisol concentration in their blood varies depending on the body’s demand for it. During illness or stress, it is normal for an increased production of cortisol which then returns to normal once the period of stress has passed.
Dogs who suffer from Cushing’s produce an excessive amount of cortisol over a prolonged period of time. This has a harmful effect on the body’s organs and metabolism. The cause of this overproduction is most commonly a benign tumour of the pituitary gland. This tumour causes large amounts of the ACTH hormone to be produced which then stimulates the adrenal glands to overproduce cortisol.
The other less common cause of Cushing’s is a tumour of the adrenal glands, which produces excessive amounts of cortisol.
- Increased water intake
- Frequent urination and sometimes incontinence
- Ravenous appetite
- A pot- bellied appearance
- Hair loss or recurrent skin diseases
- Thin skin
- Muscle wastage
- Excessive panting
A full clinical examination will be performed by your veterinary surgeon. If your veterinary surgeon suspects Cushing’s they will need to perform several blood tests to confirm the diagnosis. A general health blood test will be performed as Cushing’s has harmful effects on the whole body. This will then be followed by an ACTH Stimulation test and/or a Low Dose Dexamethasone test.
The ACTH test requires bloods to be taken before and after the administration of a synthetic version of the hormone by intravenous injection. This assesses how well your dog’s adrenal glands control the production of cortisol.
The Low Dose Dexamethasone test is a similar procedure but using an injection of steroid. In a healthy dog the dexamethasone should suppress the cortisol levels in the blood. With Cushing’s disease this does not happen.
The tests take several hours and you may be required to leave your dog with your veterinary surgeon for a short while.
Another blood test can be performed if necessary to determine whether the tumour is located in the pituitary or adrenal area if required.
Cushing’s is not a disease which can be cured but it is possible to manage and control it with medication containing a drug called Trilostane. This is a chemical substance that blocks the production of cortisol.
Once your dog has started treatment you should see a gradual improvement in the clinical signs and your veterinary surgeon will need to repeat ACTH blood tests to assess the effectiveness. These are usually carried out 10 days, 4 weeks, 12 weeks and every 3 months thereafter.