Making a successful diagnosis of Cushing’s Syndrome can often be challenging especially when the symptoms are mild. This is because Cushing’s syndrome shares similar symptoms with other more common conditions, such as hypertension and underactive thyroid gland.
However there are few ways that we can diagnose Cushing’s syndrome accurately. Firstly, checking the medication history, then test for cortisol and finally determine the underlying cause.
Medication History
Since corticosteroid used is the leading cause of Cushing’s syndrome, the general practitioner will ask if the patient has been on any medication.
Testing for cortisol
There will be several tests which could be done to determine the level of cortisol in your body. For example, urine test, blood test and finally saliva test which is the most accurate method. A medication called dexamethasone may be given before being asked to take urine test. This works in a way if you are healthy, taking dexamethasone should decrease your cortisol level. However if your cortisol level are unchanged it could be due to the Cushing’s syndrome.
Determining the underlying cause
Once a diagnosis of Cushing’s syndrome is established, it would be necessary to find out the underlying cause to decide the course of treatment. Firstly it is required to determine the whether your Cushing’s syndrome is due to high levels of ACTH in your blood. If so, this could suggest that there could be tumour in either your pituitary gland or less commonly in your lungs. On the other hand, there could be a tumour in your adrenal gland if low levels of ACTH are found.
The suspected tumour can usually be confirmed by taking a computer tomography (CT) scan of the location. Sometimes, despite having a CT scan, it may still be difficult to confirm the location of the tumour. In such cases, a further test known as petrosal sinus sampling may be recommended. Samples of blood are taken from the veins of your pituitary glands and your forearm. The levels of ACTH in the blood in both samples are then compared. If the level of ACTH is higher in the pituitary vein, this could mean that the cause is probably a tumour in your pituitary gland. If the levels of ACTH are similar, the cause could probably be a tumour in your lungs. Further x-rays and CT scans of your chest may be performed to investigate the tissues of your lungs. Medication such as metyrapone could be taken simultaneously while waiting for full and complete diagnosis to be made. A special type of X-ray known as DEXA scan can also be used to check the weakening of your bones which is a sign of osteoporosis.
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