Diagnosis | Cushing’s Syndrome

Diagnosis

If a Cushing’s syndrome is suspected, it must first be clarified whether the symptoms are caused by a drug-based cortisol therapy or not. If the patient takes cortisone regularly, an ectopic Cushing’s syndrome is most likely present. Special examinations are carried out if the patient is not treated with cortisol but has typical symptoms of Cushing’s syndrome.

Determination of the amount of cortisol in the blood as well as function tests of the pituitary gland and the adrenal gland can help to confirm the diagnosis. The diagnostic steps are therefore as follows: There are several tests for the diagnosis of Cushing’s syndrome with different areas of application and significance. The dexamethasone test is primarily used at the beginning of the diagnosis.

In this test procedure, a small amount of dexamethasone, an artificially produced substance similar to cortisol, is administered at night, which causes the amount of cortisol in the blood to decrease in healthy individuals. A measurement of the cortisone level in the morning before and in the morning after the administration allows a comparison to be made as to whether the cortisone production changes as a result of the dexamethasone administration. If the blood test on the following day does not show a reduction in the cortisol level, this indicates a Cushing’s syndrome, because in this disease cortisol is produced and released into the blood independently of the normal regulatory processes.

As a consequence of the primary Cushing’s test, further diagnostic tests are required to determine the cause of the disease. With the help of the determination of further hormones, for example “ACTH” and “CRH”, it is possible to decide between the adrenal gland and the pituitary gland as a possible cause. In order to be able to say exactly why the cortisol in the blood is elevated and where the cause of the hypercortisolism lies, a CRH test can be carried out.

Corticotropin Releasing Hormone causes the pituitary gland to secrete ACTH into the blood. In patients, the ACTH level in the blood is measured before and after the administration of CRH. If the formation of ACTH increases or an elevated ACTH level can be determined in the blood, this is called Cushing’s disease: The pituitary gland is the site of the disease.

However, if there is no increase in ACTH in the blood after the administration of CRH, this indicates adrenal or ectopic Cushing’s syndrome. The high-dose dexamethasone test is also used to diagnose Cushing’s syndrome: the patient is given 8 mg dexamethasone. If the value for the cortisol in the blood drops within 2 days, the underlying disease is a central Cushing’s disease.

If the value remains high, either an adrenal gland tumour or an ectopic tumour produces the cortisol. In order to be able to distinguish between an adrenal gland tumour and an ectopic tumour, ultrasound examinations and computed tomography (CT) imaging, possibly also a magnetic resonance imaging (MRI) of the kidney, are arranged. . – Cushing’s test/Dexamethasone test

  • Distinction between the different forms of hypercortisolism
  • Localization Diagnostics

Read next article in this series:

All articles in this series:

  1. Cushing’s Syndrome
  2. What is the Cushing’s threshold?
  3. Diagnosis
  4. Therapy
  5. What is the life expectancy for Cushing’s syndrome?
  6. Cushing’s syndrome in horses