DefinitionCushing syndrome due to adrenal tumor is an endocrine system disorder that occurs when there is a tumor of the adrenal gland releasing excess amounts of the hormone cortisol.Alternative NamesAdrenal tumor - Cushing syndromeCauses, incidence, and risk factorsCushing syndromeis caused by constant, high levels of the steroid hormone cortisol. A tumor on one of the adrenal glands causes about 15% of all cases of Cushing syndrome. Adrenal tumors release cortisol.Adrenal tumors may be noncancerous (benign) or cancerous (malignant).Noncancerous tumors that may cause Cushing syndrome include:Adrenal adenomasMicronodular hyperplasiaCancerous tumors that may cause Cushing syndrome include:Adrenal carcinomasAdrenal tumors are rare. They may develop in anyone at any age, but are much more co