What causes Cushing syndrome?

Cushing syndrome can develop for two reasons:

  • Medication containing a cortisol-like synthetic compound called glucocorticoid 1,2


Medication is responsible for most cases of Cushing syndrome. It is called an exogenous (pronounced ek-SOJ-uh-nuhs) cause because it originates outside the body. Cortisol-like steroid drugs, or glucocorticoids, are by far the main medications linked to Cushing syndrome. These medications are used to treat inflammation caused by one of several sources:

  • Allergies
  • Asthma
  • Organ transplantation, to help avoid organ rejection


Medroxyprogesterone (pronounced mi-drok-see-proh-JES-tuh-rohn) is another drug that occasionally causes Cushing syndrome. This progestin medication is taken to treat abnormal menstruation or irregular vaginal bleeding, or to prevent unusual growth of the uterine (womb) lining.


A tumor is an endogenous (en-DOJ-uh-nuhs) cause of Cushing syndrome, meaning one that originates within the body. Tumors are a much less common cause of Cushing syndrome than are medicines.

The tumors that cause Cushing symptoms can be either cancerous or noncancerous.2

Noncancerous (or Benign, pronounced bih-NAHYN)

  • Adrenal adenoma

Cancerous (or Malignant, pronounced muh-LIG-nuhnt)

  • Adrenal cancer

How Tumors Can Cause Cushing Syndrome


  • A benign pituitary tumor secretes ACTH. This tumor, called a pituitary adenoma, is by far the most common tumor linked to Cushing syndrome. As a result, the condition it causes has been given its own name, Cushing disease. Pituitary adenomas account for 70% (in adults) to more than 90% (in children) of endogenous (non-medicine-related) Cushing syndrome cases.1
  • Some tumors not in the pituitary or adrenal glands can produce ACTH and force more cortisol production. This condition is sometimes called ectopic (pronounced ek-TOP-ik) Cushing disease and accounts for about 15% of non-medicine-related Cushing syndrome cases.1 The tumors, either benign or cancerous, are mostly found in the lungs, pancreas, thyroid, and thymus.

Familial Cushing Syndrome

Individuals with some rare genetic disorders are more vulnerable to tumors in one or more glands that influence cortisol levels. As a result, these people are more likely to develop Cushing syndrome.2 Two such conditions are called multiple endocrine neoplasia type 1 and primary pigmented micronodular adrenal disease.

Pseudo-Cushing Syndrome

In rare instances, a person may have symptoms and test results that point to Cushing syndrome, but further testing reveals that he or she does not have the syndrome. This condition is termed "pseudo-Cushing syndrome." Factors that can cause this syndrome are alcohol dependence, depression or other psychiatric disorders, extreme obesity, pregnancy, and poorly controlled diabetes.3,4

  2. Mayo Clinic. (n.d.). Case detection of Cushing’s syndrome in adults. Retrieved April 8, 2012, from http://www.mayoclinic.org/medicalprofs/cushing-syndrome.html. External Web Site Policy [top]
  4. Nieman, L. K., Biller, B. M. K., Findling, J. W., Newell-Price, J., Savage, M. O., et al. (2008). The diagnosis of Cushing’s syndrome: An Endocrine Society clinical practice guideline. Retrieved April 8, 2012, from http://press.endocrine.org/doi/abs/10.1210/jc.2008-0125 External Web Site Policy. [top]

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