Cortisol, Free, 24 Hour, Urine
Use
Urinary free cortisol measurement over 24 hours by LC‑MS/MS is the preferred screening test for Cushing syndrome, and can assist in diagnosing pseudo‑hyperaldosteronism due to excessive licorice consumption. It is less useful for evaluating adrenal insufficiency. LC‑MS/MS minimizes analytical interferences from carbamazepine and synthetic corticosteroids.
Special Instructions
Requires collection of a 24‑hour urine sample with total volume (mL) recorded. Add 10 g of boric acid preservative at start of collection. Use urine tubes (10 mL, T068) and submit in plastic urine tube. If not ordering electronically, submit Renal Diagnostics Test Request (T830). Refer to “Urine Preservatives‑Collection and Transportation for 24‑Hour Urine Specimens.”
Limitations
Stress, hospitalization, surgery, alcoholism, depression, and various medications (eg, exogenous cortisone, anticonvulsants) can affect cortisol levels. Renal disease may cause falsely low values. Incorrect collection (under‑ or over‑collection) and pregnancy (levels up to twice normal) may alter results. Exogenous hydrocortisone ingestion may not suppress results. Without additional tests, 24‑hour urinary cortisol cannot reliably diagnose hypocorticalism.
New York Approved
Methodology
Mass Spectrometry (LC‑MS/MS)
Biomarkers
LOINC Codes
- 43126-2
- 14158-0
- 13362-9
Result Turnaround Time
2-7 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
5 mL
Minimum Volume
3 mL
Container
Plastic urine tube (10‑mL, T068)
Collection Instructions
Collect urine for 24 hours. Add 10 g of boric acid at start of collection.
Causes for Rejection
All specimens will be evaluated for test suitability.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 7 days |
| Refrigerated | 14 days |
| Frozen | 28 days |