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Free cortisol in urine
Last reviewed: 05.07.2025
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Reference values (norm) for the amount of free cortisol in urine are 55-248 nmol/day (20-90 mcg/day) or 15-30 nmol/nmol creatinine.
Free cortisol (not bound to plasma proteins) is filtered in the renal glomeruli and excreted in the urine. Free cortisol in the 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 daily urine; to exclude the influence of the stress factor on the results of the study, repeated collection of daily urine is recommended. Determination of free cortisol in daily urine is the main test for detecting hyperfunction of the adrenal cortex. When evaluating the results, it is necessary to take into account that during physical exertion and in obese patients, the concentration of the hormone may be elevated. 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 Itsenko-Cushing syndrome and disease, the content of free cortisol in the urine exceeds 551.8 nmol/l. A very high concentration of free cortisol in the urine indicates adrenal carcinoma.
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