Laboratory Services

Cortisol, Free, 24 Hour, Urine

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Updated Test Information:

Test Description
Cortisol, Free, 24 Hour, Urine
Synonym(s)

Cortisol Free Urine; Free Urinary Cortisol; Urinary Free Cortisol

Test ID
CORTU
General Information

Useful for:



  • Preferred screening test for Cushing syndrome

  • Diagnosis of pseudo-hyperaldosteronism due to excessive licorice consumption

  • May not be useful in the evaluation of adrenal insufficiency

Specimen Type

24-Hour Urine

Specimen Requirements

24-Hour Urine Collection

Specimen Collection / Processing Instructions

  • Collect urine for 24 hours

  • Preferred: add 10 g of boric acid as preservative at start of collection

  • Acceptable: refrigerated or frozen

  • Acceptable: 50% Acetic Acid

  • The addition of preservative must occur prior to the start of the collection or application of temperature controls must occur during collection

  • See Collection and Transportation for 24-Hour Urine Specimens for multiple collections

Minimum Sample Volume

3 mL

Required Information

24-Hour volume is required

Stability

  • Refrigerated (preferred):14 days

  • Frozen: 28 days

  • Ambient: 7 days

Unacceptable Specimen Conditions

All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.

Limitations

  • Acute stress (including hospitalization and surgery), alcoholism, depression, and many drugs (eg, exogenous cortisone, anticonvulsants) can obliterate normal diurnal variation, affect response to suppression/stimulation tests, and increase baseline levels

  • This test has limited usefulness in the evaluation of adrenal insufficiency

  • This methodology (liquid chromatography-tandem mass spectrometry) eliminates analytical interferences including carbamazepine (Tegretol) and synthetic corticosteroids

  • Renal disease (decreased excretion) may cause falsely low 24-hour urinary free cortisol values

  • Improper collection may alter results. For example, a missed morning collection may result in false-negative tests; an extra morning collection (ie, >24 hours) may give false-positive results

  • Twenty-four hour urinary free cortisol values may be elevated to twice the upper limit of the normal range during pregnancy

  • Patients with exogenous Cushing syndrome caused by ingestion of hydrocortisone will not have suppressed cortisol values

  • Reference intervals not established for patients < 3 years old

Methodology

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

Estimated TAT

2-5 days

Testing Schedule

Monday-Friday

Retention

14 days

CPT Code(s)

82530

Reference Range
Age (years) Ref Range (mcg/24H)*
3-8  1.4 - 20.0
9-12 2.6 - 37.0
13-17 4.0 - 56.0
≥ 18 3.5 - 45.0

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

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

Performing Lab

Mayo

LOINC Code(s)

14158-0, 13362-9, 3167-4

Additional Information