Urine free cortisol

Hour urinary Collect urine over 24 Urinary free cortisol greater Easy to perform but should not be used... 

The presence of hypercortisolism can be established with a midnight plasma cortisol, late-night (11 PM) salivary cortisol, 24-hour urine free cortisol, and/or low-dose dexamethasone suppression test. 

In patients in whom the diagnosis of Cushing s syndrome has been established clinically and confirmed by a finding of elevated free cortisol in the urine, suppression with large doses of dexamethasone will help to distinguish patients with Cushing s disease from those with steroid-... 

Concentrations of Drug XYZ, 6-fS-hydroxy-cortisol and free cortisol in urine collected over the profiling period were measured. Volumes of urine collected over each profiling period were recorded. 

Urinary b-p-hydroxy-cortisol and free cortisol The following pharmacokinetic variables were derived from urine concentration data for 6-P-hydroxy-cortisol and free cortisol on Days 1 and 10 using SAS for Windows protocols amount excreted during each collection interval for 6- 3-hydroxy-cortisol and free... 

No abnormalities were found in Brian s urine and his blood cell count was normal. However, his blood glucose was 8.1 mmol l-1 (normal value 3.5-6.7 mmol l-1) and a glucose tolerance test later indicated impaired glucose tolerance. Tests for plasma insulin and thyroid hormones (T3, T4 and TSH) showed normal levels. Two further tests were then performed. A 24-hour urine sample was collected and Brian s free cortisol excretion was found to be considerably higher than normal. A second test, the dexamethasone suppression test, was also carried out. In this test, the patient is given a dose of dexamethasone at 11 -12 p.m. and plasma cortisol is measured early next morning. 

The free component of plasma cortisol is biologically active and is filtered and excreted in the urine, where it can be measured. It would appear that urinary free cortisol estimations may give a more accurate picture of glucocorticoid activity at a tissue level than most other measurements. 

The different methods of assessing hypothalamic-pituitary-adrenal axis activity in patients using inhaled glucocorticoids have been compared (35). The AUC of serum cortisol concentrations was the most reliable method. There were significant positive correlations between AUC and the 8 a.m. serum and salivary cortisol concentrations. The authors favored the non-invasive method of salivary concentration measurement. However, 24-hour urine collection is not recommended, as it correlated only moderately well. This finding is consistent with the results of other studies. Urinary free-cortisol estimation based on immunoassay after inhaled glucocorticoids may be an unreliable surrogate marker of... 

Urinary free cortisol obtained from a 24-hour urine collection is an integrated measure of plasma free cortisol and eliminates the circadian influence on cortisol secretion. Urine free cortisol measurements are therefore considered to be the best screening test for hyperadrenocorticism. The urinary free cortisol excretion rate in normal subjects falls between 20 and 80[lg/day (Figure 51-9), The measurement of urinary 17-hydroxycorticosteroid excretion rates for determining adrenocortical hyperfunction is no longer recommended because of problems with method sensitivity and specificity. 

Procedure Twenty-four-hour urine samples are collected daily for 4 consecutive days. Dexamethasone, 0.5 mg, is given orally every 6 hours starting at 0800 hours on day 2 (for a total of 8 doses). Free cortisol, 17-hydroxycorticosteroids, and creatinine are measured in each 24-hour urine sample. Other measurements include serum cortisol determinations on day 1 (at 0800 hours and 2000 hours) to look for diurnal variation and on day 5 (at 0800 hours). 

Altliough methods involving organic solvent extraction or protein precipitation wfil estimate both free and protein-bound cortisol in tlie circulation, immunoassay-based methods that determine cortisol directly from serum have essentially replaced all extraction-based methods for routine cortisol measurements save for urine free cortisol methods. Flistorically four general methods have been used for the quantitative estimation of total blood cortisol concentrations in the clinical laboratory. These are the Porter-Silber color reaction method modified for plasma,the use of sulfuric acid-induced fluorescence, HPLC methods, or immunoassay. In general, HPLC and immunoassay are now used in both clinical laboratories and reference laboratories for the quantitative determination of cortisol in serum or urine. 

Serum or plasma (with heparin as an anticoagulant) can be used. No special handling procedures are necessary, and specimens may be stored refrigerated overnight at 2 °C to 8 °C. Freezing is preferred for long-term stability. Urinary free cortisol is determined on a 24-hour urine collection with or without boric acid preservative. If collected without preservative, the specimen should be refrigerated between collections and an aliquot frozen immediately after completion of the 24-hour collection. 

Measurement of Free Cortisol in Blood, Urine, and Saliva... 

Free or unbound cortisol represents the biologically active form of the circulating hormone, and its concentration is practically independent of alterations of its transport proteins. Various methods have been developed for estimating the free fraction in serum, but these assays are technically demanding, expensive, and not in general use. The measurement of urine free cortisol comes closest to providing an estimate of the free hormone concentration. As mentioned previously, approximately 2% of cortisol is excreted into the urine in a free form, and its measurement has been shown to be of use as a screening test for cortisol hypersecretion. However, P-hydroxycortisol has been reported to interfere with the immunoassay of free cortisol in urine. ... 

Urine Specimens. A complete 24-hour urine specimen is collected with 10 g of boric acid to maintain the urine pH below 7.5. Urine should be refrigerated during the collection period. After measuring the total volume, a thoroughly mixed aliquot ( 10mL) is stored frozen at -20 °C. Care should be taken to ensure an appropriately timed, complete 24-hour collection because an incorrectly timed sample is the largest source of error with this method. Free cortisol determinations on randomly collected urines are discouraged because of the variation and pulsatile characteristic of cortisol secretion. 

The following are representative values for free cortisol excreted per 24 hours in urine ... 

Canalis E, Reardon G, Caldarella A. A more specific, liquid-chromatographic method for free cortisol in urine, Clin Chem 1982 28 2418-20. 

Elevated urinary free cortisol concentrations are highly suggestive of Cushing s syndrome. Normal reference values for urinary free cortisol are 20 to 90 meg per 24-hour period. It is not unusual to detect a twofold or threefold increase in urine cortisol in the patient with hyperfunction of the adrenal gland. Starvation, topical steroid application, hydration from water loading, and acute stress aU are capable of elevating the urine cortisol concentrations. Because other pathologic conditions can increase the amount of free cortisol, additional... 

Lykkesfeldt, J. Loft, S. Poulsen, H.E. Simultaneous determination of urinary free cortisol and 6fl-hydrojgrcortisol by high-performance liquid chromatography to measure human CYP3A activity. J.Chromatogr.B, 1994, 660, 23—29 [urine extracted 6p-hydroxycortisol dexamethasone (IS) SPE gradient LOQ 1 ng/mL]... 

Li, Y.-M. Chen, L.-R. Qu, Y. Use of micellar mobile phases and an HPLC column switching system for direct injection determination of urinary free cortisol. J.Liq.Chromatogr., 1993,16, 2583—2594 [column-switching direct injection urine LOD 1.2 ng/mL]... 

Nozaki, O. Ohata, T. Ohba, Y Moriyama, H. Kato, Y. Determination of urinary free cortisol by high performance liquid chromatography with sulphuric acid-ethanol derivatization and column switching. Biomed.Chromatogr, 1992, 6, 109—114 [column-switchingK urine derivatization]... 

McCann, S.J. Gillingwater, S. Keevil, B.G. Measurement of urinary free cortisol using liquid chromatography-tandem mass spectrometry Comparison with the urine adapted ACS 180 serum cortisol chemiluminescent immunoassay and development of a new reference range. Ann. Clin. Biochem. 2005, 42 (2), 112-118. 

In conclusion, only obesity and hypertension are consistent findings. Among the clinical findings, the most reliable seems to be that of free cortisol excreted in the urine. The results of the administration of dexa-methasone (which suppresses urinary 17-ketogenetic steroid excretion) may be suggestive, but not always conclusive. Measurements of 17-ketosteroid excretion or of 11-hydroxycorticosteroid excretion are of little or limited value. 

A Comparison of Urine Free Cortisol (RIA) with Cortisol Metabolites (GLC) for Detecting Increased Cortisol Secretion Ann. Clin. Biochem. 17(5) 233-236 (1980) CA 94 79817u... 

The majority of the plasma cortisol is protein bound, only a small proportion being in the free state. This free cortisol is filtered at the glomerulus and passes into the urine where it can be measured, for example by radioimmunoassay. Urinary free cortisol determinations therefore correlate with the plasma free cortisol and the cortisol secretion rate. Increased urinary free cortisol levels are found in cases of Cushing s syndrome. 

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