Cortisol, Urinary Free
Also known as: Urinary Free Cortisol
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.
Special Instructions
Patients should state the 24-hour urine volume. The collection should begin at 8 AM and continue for a full 24-hour period, ensuring all urine is collected. Using boric acid or HCl preservative is acceptable.
Limitations
Results should not be used to evaluate adrenal insufficiency (AI) as they may overlap with normal ranges. Increased urinary cortisol excretion can be observed during pregnancy, with oral contraceptives, and in conditions like pseudo-Cushing syndrome, trauma, or infection. Tetracycline antibiotics can falsely elevate cortisol levels.
Methodology
Mass Spectrometry
Biomarkers
LOINC Codes
- 43126-2
- 33346-8
- 2147-7
Result Turnaround Time
4-6 days
Related Documents
For more information, please review the documents below
Specimen
Urine
Volume
100 mL aliquot
Minimum Volume
10 mL aliquot
Container
Plastic urine container
Collection Instructions
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 storage for 14 days.
Stability Requirements
| Temperature | Period |
|---|---|
| Room Temperature | 14 days |
| Refrigerated | 14 days |
| Frozen | 14 days |