Pathophysiologically, Cushing's syndrome can be caused by pituitary adenomas that release unregulated amounts of ACTH hormone (ACTH‐dependent Cushing's syndrome), adrenal adenomas that release unregulated amounts of cortisol directly (ACTH‐independent Cushing's syndrome), and ectopic tumors outside the hypothalamus–pituitary–adrenal axis that produce ACTH 1. This evidence concerns the gene POMC and pituitary gland adenoma.