performing a physical examination to determine any visual field defect may be necessary if a pituitary lesion is suspected, which may compress the optic chiasm, causing typical bitemporal hemianopia. when any of these tests is positive, ct scanning of the adrenal gland and mri of the pituitary gland are performed to detect the presence of any adrenal or pituitary adenomas or incidentalomas (the incidental discovery of harmless lesions). scintigraphy of the adrenal gland with iodocholesterol scan is occasionally necessary. occasionally, determining the acth levels in various veins in the body by venous catheterization, working towards the pituitary (petrosal sinus sampling) is necessary. in many cases, the tumors causing cushing's disease are less than 2 mm in size and difficult to detect using mri or ct imaging. in one study of 261 patients with confirmed pituitary cushing's disease, only 48% of pituitary lesions were identified using mri prior to surgery. plasma crh levels are inadequate at diagnosis (with the possible exception of tumors secreting crh) because of peripheral dilution and binding to crhbp. diagnosis cushing's syndrome can be ascertained via a variety of tests which include the following: 24-hour urine free cortisol dexamethasone suppression test saliva cortisol level treatment most cases of cushingoid symptoms are caused by corticosteroid medications, such as those used for asthma, arthritis, eczema and other inflammatory conditions. consequently, most patients are effectively treated by carefully tapering off (and eventually stopping) the medication that causes the symptoms. if an adrenal adenoma is identified, it may be removed by surgery. an acth-secreting corticotrophic pituitary adenoma should be removed after diagnosis. regardless of the adenoma's location, most patients require steroid replacement postoperatively at least in the interim, as long-term suppression of pituitary acth and normal adrenal tissue does not recover immediately. clearly, if both adrenals are removed, replacement with hydrocortisone or prednisolone is imperative. in those patients not suited for or unwilling to undergo surgery, several drugs have been found to inhibit cortisol synthesis (e.g. ketoconazole, metyrapone) but they are of limited efficacy. mifepristone is a powerful glucocorticoid type ii receptor antagonist and, since it does not interfere with normal cortisol homeostasis type i receptor transmission, may be especially useful for treating the cognitive effects of cushing's syndrome. however, the medication faces considerable controversy due to its use as an abortifacient. in february 2012, the fda approved mifepristone to control high blood sugar levels (hyperglycemia) in adult patients who are not candidates for surgery, or who did not respond to prior surgery, with the warning that mifepristone should never be used by pregnant women- although pregnancy is extremely rare during the course of cushing's syndrome in march 2020, isturisa (osilodrostat) oral tablets a 11-beta-hydroxylase enzyme inhibitor was approved by fda for treating those patients who cannot undergo pituitary surgery or for patients who underwent surgery but continue to have the disease. removal of the adrenals in the absence of a known tumor is occasionally performed to eliminate the production of excess cortisol. in some occasions, this removes negative feedback from a previously occult pituitary adenoma, which starts growing rapidly and produces extreme levels of acth, leading to hyperpigmentation. this clinical situation is known as nelson's syndrome. epidemiology cushing's syndrome caused by treatment with corticosteroids is the most common form. cushing's disease is rare; a danish study found an incidence of less than one case per million people per year. however, asymptomatic microadenomas (less than 10 mm in size) of the pituitary are found in about one in six individuals. people with cushing's syndrome have increased morbidity and mortality as compared to the general population. the most common cause of mortality in cushing's syndrome is cardiovascular events. people with cushing's syndrome have nearly 4 times increased cardiovascular mortality as compared to the general population. about 0.9 to 1% of those with cushing's syndrome have a tendency to develop venous thrombosis. other factors such as surgery and obesity also increase the chance of getting thrombosis. other animals for more information on the form in horses, see pituitary pars intermedia dysfunction.