Cortisol, Urinary Free

CPT: 82530
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Synonyms

  • Urinary Free Cortisol

Special Instructions

State 24-hour volume.


Expected Turnaround Time

3 - 6 days



Related Documents


Specimen Requirements


Specimen

Urine (24-hour)


Volume

100 mL aliquot


Minimum Volume

10 mL aliquot


Container

Plastic urine container


Collection

Instruct the patient to void at 8 AM and discard the specimen. Then collect all urine including the final specimen voided at the end of the 24-hour collection period (ie, 8 AM the next morning) in a plastic bottle. Screw the lid on securely. (It is acceptable to collect cortisol with boric acid or HCl preservative.)


Storage Instructions

Room temperature


Stability Requirements

Temperature

Period

Room temperature

14 days

Refrigerated

14 days

Frozen

14 days

Freeze/thaw cycles

Stable x3


Test Details


Use

The diagnosis of Cushing syndrome (CS) requires evidence of cortisol hypersecretion. While serum cortisol levels fluctuate unpredictably and are strongly dependent on concurrent cortisol-binding globulin (CBG) levels, a 24-hour urine specimen integrates the cortisol production for an entire day and is not affected by CBG. Urinary cortisol reflects the portion of serum-free cortisol filtered by the kidney, and correlates well with cortisol secretion rate.

The most common causes of CS are pituitary adenoma (65% to 70%), adrenal tumor (15% to 20%), and ectopic CS (10% to 15%).


Limitations

Not useful in the evaluation of adrenal insufficiency (AI). Results in AI overlap with normal ranges. Increased in pregnancy and with oral contraceptives. Increased excretion may be found with pseudo-Cushing syndrome, trauma, or infection.2 Tetracyclines may cause false elevation of results.

This test was developed and its performance characteristics determined by LabCorp. It has not been cleared or approved by the Food and Drug Administration.


Methodology

Liquid chromatography/tandem mass spectrometry (LC/MS-MS)


Reference Interval

Age

Male (μg/24h)

Female (μg/24h)

0 days to 1 year

Not established

Not established

2 to 5 years

2 – 16

2 – 16

6 to 11 years

4 – 28

4 – 24

12 years

4 – 36

4 – 36

13 to 17 years

6 – 45

6 – 42

18 to 80 years

5 – 64

6 – 42

>80 years

3 – 49

3 – 49


Additional Information

This test is useful in the initial evaluation of patients with suspected Cushing syndrome (CS).1,2 Patients with CS usually have urine free cortisol >100 μg/24 hours, but there is wide variation and no single cutoff can be used safely. If the 24-hour urine free cortisol is elevated, additional testing is indicated to differentiate among pituitary-dependent CS, pituitary-independent CS, and pseudo-Cushing syndrome.2

Some patients with an elevated 24-hour urine cortisol do not have Cushing syndrome and are often classified as pseudo-Cushing syndrome. Establishing this diagnosis requires additional testing which includes the low-dose dexamethasone suppression test, the CRH stimulation test, or a protocol that combines them both.3

The diagnosis of CS requires a meticulous history and physical examination,2 and these should precede a biochemical evaluation.


Footnotes

1. Watts NB, Keffer JH. Adrenal cortex. Practical Endocrinology. 4th ed. Philadelphia, Pa: Lea & Febiger;1989.
2. Orth DN. Cushing's syndrome. N Engl J Med. 1995 Mar 23; 332(12):791-803. Erratum: 1995 Jun 1; 332(22):1527. 7862184
3. Yanovski JA, Cutler GB Jr, Chrousos GP, Nieman LK. Corticotropin-releasing hormone stimulation following low-dose dexamethasone administration, A new test to distinguish Cushing's syndrome from pseudo-Cushing's states. JAMA. 1993 May 5; 269(17):2232-2238. 8386285

References

Canalis E, Reardon GE, Caldarella AM. A more specific, liquid-chromatographic method for free cortisol in urine. Clin Chem. 1982 Dec; 28(12):2418-2420. 7139923

LOINC® Map

Order Code Order Code Name Order Loinc Result Code Result Code Name UofM Result LOINC
004432 Cortisol, Urinary Free 004433 Cortisol,F,ug/L,U ug/L 11040-3
004432 Cortisol, Urinary Free 004434 Cortisol,F,ug/24hr,U ug/24 hr 2147-7

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The LOINC® codes are copyright © 1994-2019, Regenstrief Institute, Inc. and the Logical Observation Identifiers Names and Codes (LOINC) Committee. Permission is granted in perpetuity, without payment of license fees or royalties, to use, copy, or distribute the LOINC® codes for any commercial or non-commercial purpose, subject to the terms under the license agreement found at https://loinc.org/license/. Additional information regarding LOINC® codes can be found at LOINC.org, including the LOINC Manual, which can be downloaded at LOINC.org/downloads/files/LOINCManual.pdf