Cortisol, Free, 24 Hour, Urine

Cortisol Free Urine; Free Urinary Cortisol; Urinary Free Cortisol

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

24-Hour Urine

24-Hour Urine Collection

• 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

3 mL

24-Hour volume is required

• Refrigerated (preferred):14 days


• Frozen: 28 days


• Ambient: 7 days

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

• 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

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

2-5 days

Monday-Friday

14 days

82530

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

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

Mayo

14158-0, 13362-9, 3167-4

Test Definition: CORTU

Collection and Transportation for 24-Hour Urine Specimens