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HelpTest Code CRANR Cortisol, Free, Random, Urine
Ordering Guidance
The preferred screening test for Cushing syndrome is a measurement of free cortisol in a 24-hour urine collection by liquid chromatography tandem mass spectrometry (LC-MS/MS); order CORTU / Cortisol, Free, 24 Hour, Urine.
The optimal specimen type for evaluation of primary adrenal insufficiency and hypopituitarism is serum; order CORT / Cortisol, Serum.
Specimen Required
Supplies: Urine tube, 10 mL (T068)
Collection Container/Tube: Clean, plastic urine container with no metal cap or glued insert
Submission Container/Tube: Plastic, 10-mL urine tube or clean, plastic aliquot container with no metal cap or glued insert
Specimen Volume: 10 mL
Collection Instructions: Collect a random urine specimen.
Useful For
Investigating suspected hypercortisolism when a 24-hour collection is prohibitive (ie, pediatric patients)
Profile Information
| Test ID | Reporting Name | Available Separately | Always Performed |
|---|---|---|---|
| CRAN | Cortisol, Random, U | No | Yes |
| CRETR | Creatinine, Random, U | Yes, (order RCTUR ) | Yes |
Method Name
CRAN: Liquid Chromatography Tandem Mass Spectrometry (LC-MS/MS)
CRETR: Enzymatic Colorimetric Assay
Reporting Name
Cortisol, Free, Random, USpecimen Type
UrineSpecimen Minimum Volume
3 mL
Specimen Stability Information
| Specimen Type | Temperature | Time | Special Container |
|---|---|---|---|
| Urine | Refrigerated (preferred) | 14 days | |
| Frozen | 28 days | ||
| Ambient | 7 days |
Reject Due To
All specimens will be evaluated at Mayo Clinic Laboratories for test suitability.Clinical Information
Cortisol is a steroid hormone synthesized from cholesterol by a multienzyme cascade in the adrenal glands. It is the main glucocorticoid in humans and acts as a gene transcription factor influencing a multitude of cellular responses in virtually all tissues. Cortisol plays a critical role in glucose metabolism, maintenance of vascular tone, immune response regulation, and in the body's response to stress. Its production is under hypothalamic-pituitary feedback control.
Only a small percentage of circulating cortisol is biologically active (free), with the majority of cortisol inactive (protein bound). As plasma cortisol values increase, free cortisol (ie, unconjugated cortisol or hydrocortisone) increases and is filtered through the glomerulus. Urinary free cortisol (UFC) correlates well with the concentration of plasma free cortisol. UFC represents excretion of the circulating, biologically active, free cortisol that is responsible for the signs and symptoms of hypercortisolism.
The UFC assay is a sensitive test for the various types of adrenocortical dysfunction, particularly hypercortisolism (Cushing syndrome). A measurement of 24-hour UFC excretion by liquid chromatography tandem mass spectrometry (LC-MS/MS) is the preferred screening test for Cushing syndrome. LC-MS/MS methodology eliminates analytical interferences including carbamazepine (Tegretol) and synthetic corticosteroids, which can affect immunoassay-based cortisol results.
Reference Values
Males
0-2 years: 3.0-120 mcg/g creatinine
3-8 years: 2.2-89 mcg/g creatinine
9-12 years: 1.4-56 mcg/g creatinine
13-17 years: 1.0-42 mcg/g creatinine
≥18 years: 1.0-119 mcg/g creatinine
Females
0-2 years: 3.0-120 mcg/g creatinine
3-8 years: 2.2-89 mcg/g creatinine
9-12 years: 1.4-56 mcg/g creatinine
13-17 years: 1.0-42 mcg/g creatinine
≥18 years: 0.7-85 mcg/g creatinine
Use the conversion factors below to convert each analyte from mcg/g creatinine to nmol/mol creatinine.
Conversion factor
Cortisol: mcg/g creatinine x 312=nmol/mol creatinine
Cortisol molecular weight=362.5
Creatinine molecular weight=113.12
Day(s) Performed
Monday through Friday
Report Available
2 to 6 daysPerforming Laboratory
Mayo Clinic Laboratories in Rochester
Test Classification
This test was developed and its performance characteristics determined by Mayo Clinic in a manner consistent with CLIA requirements. It has not been cleared or approved by the US Food and Drug Administration.CPT Code Information
82530
82570