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Overnight DST or ONDST - An oral dose of dexamethasone is given between 11pm and midnight, and the cortisol level is measured at 8 - 9am the next morning; Two-day DST - This involves giving an oral dose of dexamethasone at six-hourly intervals for 2 days, with the cortisol level measured 6 hours after the final dose was given; Intravenous DST
In the high-dose 48-h DST, 2 mg of dexamethasone is given every 6 hours for 48 hours or a single dose of 8 mg is given. [8] This test is not needed if the 48-h low-dose DST has shown suppression of cortisol by over 30%. [8] These tests are based on the glucocorticoid sensitivity of pituitary adenomas compared to non-pituitary tumors. [8]
In the alcoholic patient with pseudo-Cushing's, admission to hospital (and avoidance of alcohol) will result in normal midnight cortisol levels within five days, excluding Cushing's [6] Another cause for Cushing's syndrome is adrenocortical carcinoma. This is a rare form of cancer with an incidence of 1-2 per million people annually.
Cushing's syndrome is a collection of signs and symptoms due to prolonged exposure to glucocorticoids such as cortisol. [4] [9] [10] Signs and symptoms may include high blood pressure, abdominal obesity but with thin arms and legs, reddish stretch marks, a round red face due to facial plethora, [11] a fat lump between the shoulders, weak muscles, weak bones, acne, and fragile skin that heals ...
Sometimes measuring blood levels of ADH (a synonym for vasopressin) during this test is also necessary. [ citation needed ] If there is no change in the water loss despite fluid deprivation, desmopressin may be administered to distinguish between the two types of diabetes insipidus which are central & nephrogenic diabetes insipidus.
Dexamethasone – a synthetic glucocorticoid binds more powerfully to the glucocorticoid receptor than cortisol does. Dexamethasone is based on the cortisol structure but differs at three positions (extra double bond in the A-ring between carbons 1 and 2 and addition of a 9-α-fluoro group and a 16-α-methyl substituent).
In pharmacologic (supraphysiologic) doses, glucocorticoids, such as prednisone, dexamethasone, and hydrocortisone are used to suppress various allergic, inflammatory, and autoimmune disorders. They are also administered as posttransplantory immunosuppressants to prevent the acute transplant rejection and graft-versus-host disease .
[2] [3] Dexamethasone should be used as the corticosteroid of choice in these cases as it is the only corticosteroid that will not affect diagnostic test results. [ 2 ] [ 29 ] To confirm inappropriately low cortisol secretion, testing can include baseline morning cortisol level in the blood or morning cortisol level in the saliva. [ 2 ]