How to tell the difference between adrenal Cushing syndrome and pituitary?

Cushing’s syndrome is a condition characterized by an excess of the hormone cortisol in the body. This excess can be caused by various factors, but the two most common are adrenal Cushing’s syndrome and pituitary Cushing’s syndrome, also known as Cushing’s disease.

Adrenal Cushing’s syndrome is caused by a tumor in one or both of the adrenal glands, which are small glands located on top of each kidney. These tumors can be either benign or malignant, but they all produce excess cortisol. This form of the syndrome accounts for about 15% of cases.

On the other hand, pituitary Cushing’s syndrome, or Cushing’s disease, is caused by a small, usually benign, tumor in the pituitary gland, which is located at the base of the brain. This tumor produces excess adrenocorticotropic hormone (ACTH), which in turn stimulates the adrenal glands to produce more cortisol. This is the most common form of Cushing’s syndrome, accounting for about 85% of cases.

The symptoms of both forms of Cushing’s syndrome are similar and can include weight gain, fatigue, high blood pressure, high blood sugar, and changes in skin appearance. However, there are some differences in the diagnostic tests and treatments for the two forms.

In terms of diagnosis, the same test used to determine if Cushing’s disease is present can also classify the Cushing’s disease. This test is called the low dose dexamethasone suppression test. If the cortisol level suppresses to a level below 50% of baseline at 4 hours, only a pituitary tumor is possible. While pituitary tumors do not always show this kind of classic suppression at four hours, adrenal tumors never do. If suppression is seen in the 4-hour sample, further testing is not needed.

In terms of treatment, medication protocols are completely different for adrenal tumors versus pituitary tumors. Surgery protocols are also completely different for adrenal tumors versus pituitary tumors. If an adrenal tumor is present, there is a 50% chance that it is a malignant tumor. It is helpful to know if the patient has a condition with this kind of a malignancy rate, especially if surgery is being considered. On the other hand, if the patient is known to have a pituitary tumor, it becomes more relevant to image the brain to look for evidence of pressure on the brain.

In conclusion, while adrenal Cushing’s syndrome and pituitary Cushing’s syndrome can cause similar symptoms, they have different causes and require different diagnostic tests and treatments. Therefore, it’s important to accurately diagnose the type of Cushing’s syndrome in order to provide the most effective treatment.