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Test Code CORTU Cortisol, Free, 24 Hour, Urine

Reporting Name

Cortisol, Free, U

Useful For

Preferred screening test for Cushing syndrome

 

Diagnosis of pseudo-hyperaldosteronism due to excessive licorice consumption

 

Test may not be useful in the evaluation of adrenal insufficiency.

Performing Laboratory

Mayo Clinic Laboratories in Rochester

Specimen Type

Urine


Necessary Information


24-Hour volume (in milliliters) is required.



Specimen Required


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.


Specimen Minimum Volume

3 mL

Specimen Stability Information

Specimen Type Temperature Time Special Container
Urine Refrigerated (preferred) 14 days
  Frozen  28 days
  Ambient  7 days

Reference Values

0-2 years: Not established

3-8 years: 1.4-20 mcg/24 h

9-12 years: 2.6-37 mcg/24 h

13-17 years: 4.0-56 mcg/24 h

≥18 years: 3.5-45 mcg/24 h

 

Use the factor below to convert from mcg/24 hr to nmol/24 hr:

 

Conversion factor

Cortisol: mcg/24 h x 2.76=nmol/24 hr (molecular weight=362.5)

 

For International System of Units (SI) conversion for Reference Values, see www.mayocliniclabs.com/order-tests/si-unit-conversion.html.

Day(s) Performed

Monday through Friday

Test Classification

This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.

CPT Code Information

82530

LOINC Code Information

Test ID Test Order Name Order LOINC Value
CORTU Cortisol, Free, U 43126-2

 

Result ID Test Result Name Result LOINC Value
8546 Cortisol, U 14158-0
TM93 Collection Duration (h) 13362-9
VL47 Volume (mL) 3167-4

Interpretation

Most patients with Cushing syndrome have increased 24-hour urinary excretion of cortisol. Further studies, including suppression or stimulation tests, measurement of serum corticotropin concentrations, and imaging are usually necessary to confirm the diagnosis and determine the etiology.

 

Values in the normal range may occur in patients with mild Cushing syndrome or with periodic hormonogenesis. In these cases, continuing follow-up and repeat testing are necessary to confirm the diagnosis.

 

Patients with Cushing syndrome due to intake of synthetic glucocorticoids should have suppressed cortisol. In these circumstances a synthetic glucocorticoid screen might be ordered (SGSU / Synthetic Glucocorticoid Screen, Random, Urine).

 

Suppressed cortisol values may also be observed in primary adrenal insufficiency and hypopituitarism. However, many normal individuals may also exhibit a very low 24-hour urinary cortisol excretion with considerable overlap with the values observed in pathological hypocorticalism. Therefore, without other tests, 24-hour urinary cortisol measurements cannot be relied upon for the diagnosis of hypocorticalism.

Clinical Reference

1. Eisenhofer G, Grebe S, Cheung N-K V.Monoamine-Producing Tumors. In: Rafai N, Horvath AR, Witter CT, eds. Tietz Textbook of Clinical Chemistry and Molecular Diagnostics. 6th ed. Elsevier, 2018: 1421

2. Lin CL, Wu TJ, Machacek DA, Jiang NS, Kao PC. Urinary free cortisol and cortisone determined by high performance liquid chromatography in the diagnosis of Cushing's syndrome. J Clin Endocrinol Metab. 1997;82(1):151-155

3. Dodds HM, Taylor PJ, Cannell GR, Pond SM. A high-performance liquid chromatography-electrospray-tandem mass spectrometry analysis of cortisol and metabolites in placental perfusate. Anal Biochem. 1997;247(2):342-347. doi:10.1006/abio.1997.2074

Report Available

2 to 6 days

Method Name

Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)