Cushing syndrome refers the manifestations induced by chronic glucocorticoid excess and may arise from various causes. Iatrogenic Cushing syndrome accounts for most patients, when they are given exogenous glucocorticoid treatment. In contrast, spontaneous Cushing syndrome results from endogenous glucocorticoid over-secretion. Although Cushing disease is rare, it is the most common cause of spontaneous Cushing syndrome. The patient with Cushing disease has a pituitary corticotroph adenoma, which overproduces adrenocorticotropic hormone (ACTH). ACTH then stimulates adrenal gland to over-secret glucocorticoid. Patients with untreated Cushing disease were shown to have poor prognosis, estimated a 5-year survival rate of 50%. The first line treatment is tumor resection. Other managements include radiotherapy, medication and bilateral adrenalectomy. The initial remission rate is high (66-90%). However, some patients encounter with disease recurrence during follow-up.