Cushing’s syndrome is a group of clinical syndromes caused by various causes, mainly increased cortisol in the blood. The main causes of Cushing’s syndrome are as follows: a. Pituitary tumor, when the pituitary tumor secretes mainly ACTH (adrenocorticotropic hormone), it can promote the secretion of cortisol by the adrenal glands and cause Cushing’s syndrome. Adrenal adenoma or adenocarcinoma can increase the secretion of cortisol and cause Cushing’s syndrome. Adrenal hyperplasia, unilateral or bilateral adrenal hyperplasia can cause increased secretion of cortisol, resulting in Cushing’s syndrome. Ectopic ACTH syndrome, when ACTH is secreted by tumors other than pituitary and adrenal glands, can also lead to increased secretion of ectopic ACTH, resulting in increased secretion of cortisol and causing Cushing’s syndrome. V. The use of exogenous hormones is common in patients who use a lot of prednisone, methylprednisolone and other drugs.