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Cushing's Syndrome & Disease - Causes

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What Causes Cushing’s Syndrome and Cushing’s Disease?

Cushing’s syndrome can be caused by medication or by a tumor. Sometimes, there is a tumor of the adrenal gland that makes too much cortisol. It may also be caused by a tumor in the pituitary gland (a small gland under the brain that produces hormones that in turn regulate the body’s other hormone glands).

Some pituitary tumors produce a hormone called adrenocorticotropic hormone (ACTH), which stimulates the adrenal glands and causes them to make too much cortisol. This is termed Cushing’s disease. ACTH-producing tumors can also originate elsewhere in the body and these are referred to as ectopic tumors.

See below for an illustration of the differences between these three situations. It is important to note that pituitary tumors are almost never cancerous.

The Various Causes of Cushing’s Syndrome

Scenario 1

In Cushing’s disease a pituitary tumor makes ACTH, which stimulates adrenal gland production of cortisol. High cortisol levels inhibit CRH secretion and ACTH secretion from normal pituitary cells.

Scenario 2

In ectopic ACTH secretion, a non-pituitary tumor makes ACTH, which stimulates adrenal gland production of cortisol. High cortisol levels inhibit CRH secretion and ACTH secretion from normal pituitary cells.

Scenario 3

In primary adrenal disease, the adrenal glands independently make too much cortisol. High cortisol levels inhibit CRH secretion and ACTH secretion from normal pituitary cells.