Definition of Ectopic Cushing syndrome:

Ectopic Cushing syndrome is a condition in which a tumor outside the pituitary or adrenal glands produces a hormone called adrenocorticotropic hormone (ACTH).

Causes, incidence, and risk factors:

Cushing syndrome is the result of too much glucocorticoid hormones being released over a long period of time. About 15% of Cushing syndrome cases are due to ectopic Cushing syndrome.

Ectopic Cushing syndrome is caused by tumors that release adrenocorticotropic hormone (ACTH). Other causes of Cushing syndrome are:

• Excess release of ACTH by the pituitary gland
• Long-term use of corticosteroid drugs (commonly used to treat conditions such as rheumatoid arthritis and asthma)
• Tumor of the adrenal gland

Tumors that can, in rare cases, release ACTH include:

• Islet cell tumors of the pancreas
• Medullary carcinoma of the thyroid
• Small cell tumors of the lung
• Tumors of the thymus gland