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Free cortisol in the urine
Last reviewed: 23.04.2024
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The reference values (the norm) of the amount of free cortisol in the urine are 55-248 nmol / day (20-90 μg / day) or 15-30 nmol / nmol of creatinine.
Free cortisol (not associated with blood plasma proteins) is filtered in the renal glomeruli and excreted in the urine. Free cortisol in blood plasma is the main biologically active form of the hormone. Its amount in the urine directly reflects the content of free cortisol in the blood. The concentration of the hormone is determined in the daily urine, to avoid the influence of the stress factor on the results of the study, repeated collection of daily urine is recommended. Determination of free cortisol in 24-hour urine is the main test for detecting hyperfunction of the adrenal cortex. When evaluating the results, it is necessary to take into account that, under physical exertion and in patients with obesity, the concentration of the hormone can be increased. If the patient has renal failure, the concentration of free cortisol in the urine decreases and does not reflect its secretion.
In most patients (up to 90%) with Isenko-Cushing's syndrome and disease, the content of free cortisol in urine exceeds 551.8 nmol / l. A very high concentration of free cortisol in the urine indicates adrenal carcinoma.
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