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Low-dose and high-dose variations of the test exist. [4] The test is given at low (usually 1–2 mg) and high (8 mg) doses of dexamethasone, and the levels of cortisol are measured to obtain the results. [5] A low dose of dexamethasone suppresses cortisol in individuals with no pathology in endogenous cortisol production.
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 low-dose short test, 1 μg of an ACTH drug is injected into the patient. In the conventional-dose short test, 250 μg of drug are injected. Both of these short tests last for about an hour and provide the same information. Studies have shown the cortisol response of the adrenals is the same for the low-dose and conventional-dose tests ...
Evocative/suppression testing refers to a class of tests performed where one substance is measured both before and after the administration of another substance to determine if the levels are stimulated ("evocative") or suppressed.
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 ...
The ACTH release creating the cortisol awakening response is strongly inhibited after intake of a low-dose dexamethasone. [31] This is a synthetic glucocorticoid and this inhibition allows the detection of the presence of negative feedback from circulating cortisol that controls to ACTH -secreting cells of the pituitary.
The TRH test involves administration of a small amount of TRH intravenously, [1] following which levels of TSH will be measured at several subsequent time points using samples of blood taken from a peripheral vein. [citation needed] The test is used in the differential diagnosis of secondary and tertiary hypothyroidism.
Low doses are insufficient to generate a response, while high doses generate a maximal response. The steepest point of the curve corresponds with an EC 50 of 0.7 molar The dose–response relationship , or exposure–response relationship , describes the magnitude of the response of an organism , as a function of exposure (or doses ) to a ...