Cortisol, Urinary Free
Code:7010|CPT:82530|LOINC:33346-8, 2147-7
| Includes | Cortisol,F,ug/L,U Cortisol,F,ug/24hr,U |
|---|
Analysis details
Methodology
- Liquid chromatography–tandem mass spectrometry (LC-MS/MS)
- Chemiluminescent immunoassay (CLIA)
Expected Turnaround Time
1 day
Special Instructions
- Record the total urine volume collected over 24 hours and provide this value with the specimen.
- With clinician approval, stop estrogens and androgens 48 hours before starting the collection.
- With clinician approval, withhold diuretics for 48 hours before and throughout the 24-hour urine collection.
- Avoid strenuous exercise and significant emotional stress for the duration of the 24-hour collection.
- Do not smoke during the 24-hour urine collection.
How to use
Cortisol, Urinary Free (urinary free cortisol; urine cortisol) is commonly used as an initial assessment for hypercortisolism because a 24-hour urine collection captures total daily cortisol production and is unaffected by alterations in cortisol‑binding globulin. The assay is also used to follow patients undergoing treatment for Cushing syndrome. When elevated, results may point to endogenous Cushing syndrome due to an ACTH-producing pituitary adenoma, an adrenal neoplasm producing cortisol autonomously, or ectopic ACTH secretion.
Limitations
Pituitary ACTH drives adrenal cortisol secretion through a negative feedback loop. Excess ACTH output (for example, from an ACTH-secreting pituitary adenoma) or autonomous adrenal cortisol production increases urinary free cortisol excretion. Patients with hypercortisolism often present with hypertension, hyperglycemia, central weight gain, thinning of the skin, and violaceous abdominal striae. Urinary free cortisol is not appropriate for assessing adrenal insufficiency because values in affected individuals may overlap the reference range. Elevated UFC can also be observed in pseudo‑Cushing states and during intercurrent illness.
| Unit | mcg/24h |
|---|---|
| Reference interval | — |
| Indications | Clinical suspicion for Cushing syndrome, including features such as central adiposity, proximal muscle weakness, hypertension, and violaceous striae, Hypertension that remains uncontrolled or recurs despite appropriate therapy, Monitoring therapeutic response in individuals treated for Cushing syndrome |
Possible Causes of Abnormal Results
Increased levels
- alcohol
- infection
- nicotine (smoking)
- oral contraceptives
- pregnancy
- pseudo-cushing syndrome
- spironolactone
- stress (surgery, trauma)
- tetracyclines
Decreased levels
- dexamethasone
- prednisolone
Specimen Requirements
| Specimen | Urine |
|---|---|
| Container | 24-Hour Urine Collection Container |
| Volume | 100 mL (min 10 mL) |
| Storage Instructions | Room temperature, Refrigerated, Frozen |
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. PubMed 7139923