Enzyme immunoassay for the in-vitro-diagnostic quantitative determination of Cortisol in human serum and plasma.
Cortisol (hydrocortisone, compound F) is the main glucocorticoid in humans and is produced in the zona fasciculata of the adrenal cortex. 90 % of the circulating cortisol are bound to corticoid binding globulin (CBG, Transcortin), ca. 7 % are bound to albumin and only 1–3 % are unbound. Only the latter part represents the active form of cortisol.
In humans there is a physiological fluctuation of cortisol achieving the highest level in the morning and the lowest during midnight. This fluctuation of cortisol plasma level is reflected in saliva normally with a peak in the first 90 minutes after wake up.
The cortisol measurement is indicated in diseases with abnormal gluco-corticoid production e.g. Cushing Syndrome and Addison’s Disease. Because of the diurnal fluctuation of cortisol levels it is necessary to take several samples for an individual cortisol profile or during dynamic tests like dexamethasone-suppression- or ACTH-stimulation-test.