Adrenocorticotropic hormone stimulates the release of cortisol and androgens from the adrenals. Cortisol has negative feedback control on the release of CRH and ACTH. When cortisol levels increase, it suppresses the release of CRH and ACTH. Hypercortisolic states like midnight serum cortisol and plasma ACTH, nighttime salivary cortisol and 24 hour urinary free cortisol etc., are discussed here. Various suppression tests such as overnight 1-mg-dexamethasone suppression test, LDD suppression test, combined low-dose dexamethasone and CRH test used to check ACTH levels. Investigating of the cause of Cushing’s syndrome such as adrenocorticotropic hormone measurement, high-dose dexamethasone suppression test, CRH stimulation test and the desmopressin test have their complete detail. Computerized tomography gives the best resolution of adrenal anatomy. Treatment measures of ACTH-secreting pituitary adenomas include transsphenoidal radical excision, resurgery, radiation therapy, and bilateral adrenalectomy. Medical management is required for the pre-operative preparation of the patients. Neuromodulatory, Metyrapone and Ketoconazole, Temozolomide etc., are used for treating patients with aggressive pituitary tumors. In addition Transsphenoidal Pituitary Surgery, Radiation Therapy, Corticotroph Pituitary Carcinoma etc., also thoroughly described here.