Preferred screening test for Cushing syndrome
Diagnosis of pseudo-hyperaldosteronism due to excessive licorice
Test may not be useful in the evaluation of adrenal insufficiency
Liquid Chromatography-Tandem Mass Spectrometry (LC-MS/MS)
Cortisol Free Urine
Free Urinary Cortisol
Urinary Free Cortisol
Urine
24-Hour volume is required.
Question ID | Description | Answers |
---|---|---|
TM93 | Collection Duration | |
VL47 | Urine Volume |
Supplies: Urine Tubes, 10-mL (T068)
Submission Container/Tube: Plastic, urine tube
Specimen Volume: 5 mL
Collection Instructions:
1. Collect urine for 24 hours.
2. Add 10 g of boric acid as preservative at start of collection.
Additional Information: See Urine Preservatives-Collection and Transportation for 24-Hour Urine Specimens for multiple collections.
Note: The addition of preservative must occur prior to the start of the collection or application of temperature controls must occur during collection.
Ambient | No |
Refrigerate | OK |
Frozen | OK |
50% Acetic Acid | OK |
Boric Acid | Preferred |
Diazolidinyl Urea | No |
6M Hydrochloric Acid | No |
6M Nitric Acid | No |
Sodium Carbonate | No |
Thymol | No |
Toluene | No |
3 mL
Specimen Type | Temperature | Time | Special Container |
---|---|---|---|
Urine | Refrigerated (preferred) | 14 days | |
Frozen | 28 days | ||
Ambient | 7 days |
Preferred screening test for Cushing syndrome
Diagnosis of pseudo-hyperaldosteronism due to excessive licorice
Test may not be useful in the evaluation of adrenal insufficiency
Cortisol is a steroid hormone synthesized from cholesterol by a
Only a small percentage of circulating cortisol is biologically active (free),
UFC is a sensitive test for the various
0-2 years: not established
3-8 years: 1.4-20 mcg/24 hours
9-12 years: 2.6-37 mcg/24 hours
13-17 years: 4.0-56 mcg/24 hours
> or =18 years: 3.5-45 mcg/24 hours
Use the factor below to convert from mcg/24 hours
Conversion factor
Cortisol: mcg/24 hours x 2.76=nmol/24 hours (molecular weight=362.5)
For SI unit Reference Values, see https://www.mayocliniclabs.com/order-tests/si-unit-conversion.html
Most patients with Cushing syndrome have increased 24-hour urinary
Values in the normal range may occur in patients with mild Cushing
Patients with Cushing syndrome due to intake of synthetic
Suppressed cortisol values may also be observed in
Acute stress (including hospitalization and surgery),
This test has limited usefulness in the evaluation of adrenal
This methodology (liquid chromatography-tandem mass spectrometry
Renal disease (decreased excretion) may cause falsely low
Improper collection may alter results. For example, a missed morning
Twenty-four hour urinary free cortisol values may be elevated to
Patients with exogenous Cushing syndrome caused by ingestion
In Mayo's reference value study, gender was found to significantly influence cortisol values (P value=0.001). However, while this was statistically significant, gender explained only 6% of the variability in cortisol normal ranges and, therefore, was not considered to have a clinically significant impact on cortisol reference values.
1. Findling JW, Raff H: Diagnosis and differential diagnosis of Cushing's syndrome. Endocrinol Metab Clin North Am 2001;30:729-747
2. Boscaro M, Barzon L, Fallo F, Sonino N: Cushing's syndrome. Lancet 2001;357:783-791
3. Taylor RL, Machacek D, Singh RJ: Validation of a high-throughput liquid chromatography-tandem mass spectrometry method for urinary cortisol and cortisone. Clin Chem 2002;48:1511-1519
4. Eisenhofer G, Grebe S, Cheung N-K V: Chapter 63 Monoamine-Producing Tumors. In Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. Sixth edition. Edited by N Rafai, AR Horvath, CT Wittwer. Elsevier, 2018. pp 1421
5. Luo A, El Gierari ETM, Nally LM, et al: Clinical utility of an ultrasensitive urinary free cortisol assay by tandem mass spectrometry. Steroids. 2019 Jun;146:65-69. doi: 10.1016/j.steroids.2019.03.014
Deuterated cortisol (d3-cortisol) is added to a 0.1-mL urine specimen as an internal standard. Cortisol, cortisone, and d3-cortisol are extracted from the specimens using online turbulent-flow HPLC and analyzed by liquid chromatography-tandem mass spectrometry using multiple-reaction monitoring in positive mode. The following ion pairs are used for analysis: cortisol (363.0/121.1), cortisone (361.0/163.0), d3-cortisol (366.0/121.2). A calibration curve, generated from stripped urine spiked standards, is included with each batch of patient specimens.(Taylor RL, Machacek DA, Singh RJ: Validation of a high-throughput liquid chromatography-tandem mass spectrometry method for urinary cortisol and cortisone. Clin Chem 2002;48:1511-1519)
Monday through Friday
This test was developed, and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. This test has not been cleared or approved by the US Food and Drug Administration.
82530
Test Id | Test Order Name | Order LOINC Value |
---|---|---|
CORTU | Cortisol, Free, U | 43126-2 |
Result Id | Test Result Name |
Result LOINC Value
Applies only to results expressed in units of measure originally reported by the performing laboratory. These values do not apply to results that are converted to other units of measure.
|
---|---|---|
8546 | Cortisol, U | 14158-0 |
TM93 | Collection Duration | 13362-9 |
VL47 | Urine Volume | 3167-4 |