24-hour urinary free cortisol (UFC)

Definition

A cortisol urine test measures the amount of cortisol in the urine.

Alternative Names

Why the 24-hour urinary free cortisol (UFC) is Performed

The test is used to evaluate for increased or decreased cortisol production.

Cortisol is a steroid hormone released from the adrenal gland in response to ACTH, a hormone from the anterior pituitary gland in the brain. Cortisol levels rise and fall during the day. Highest levels occur at about 6 to 8 a.m. and lowest levels at about midnight.

Cortisol affects many different body systems. It plays a role in lipid, carbohydrate, and protein metabolism. Cortisol also plays a role in the bone, circulatory, nervous, and immune systems. Cortisol is critical for normal stress responses.

Different diseases, such as Cushing's disease and Addison's disease, can lead to either over- or under-production of cortisol. Urinary free cortisol measurements can help to diagnose these conditions.

Urinary free cortisol is a measurement of the cortisol in the urine that is not attached to other substances. Free cortisol represents the active form of the hormone. The urine measurement directly reflects the blood level of cortisol.

How the 24-hour urinary free cortisol (UFC) is Performed

A 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to discontinue drugs that may interfere with the test.

• On day 1, urinate into the toilet when you get up in the morning. Afterwards, collect all urine in a special container for the next 24 hours. Keep the container in a cool place during the test period.
• On day 2, urinate into the container when you get up in the morning.
• Cap the container. Label the container with your name, the date, the time of completion, and return it as instructed. Keep it in the refrigerator or a cool place until returned to the laboratory.

FOR INFANTS

Thoroughly wash the area around the urethra. Open a urine collection bag (a plastic bag with an adhesive paper on one end), and place it on the infant. For boys, the entire penis can be placed in the bag and the adhesive attached to the skin. For girls, the bag is placed over the labia. Diaper as usual over the secured bag.

This procedure may take a couple of attempts -- lively infants can displace the bag. The infant should be checked frequently and the bag changed after the infant has urinated into the bag. The urine is drained into the container for transport to the laboratory.

Deliver it to the laboratory or your health care provider as soon as possible upon completion.

How to Prepare for the 24-hour urinary free cortisol (UFC)

No special preparation is necessary for this test, but if the collection is being taken from an infant, a couple of extra collection bags may be necessary.

How the 24-hour urinary free cortisol (UFC) Will Feel

The test involves only normal urination, and there is no discomfort.

Considerations

Factors that interfere with this test are:

• Severe emotional or physical stress
• Medications, including glucocorticoids, lithium, diuretics, ketoconazole, estrogens and tricyclic antidepressants

Note: Due to these interfering factors, the urine cortisol is often tested on three or more separate occasions to get a truer picture of average cortisol production.

Normal Results

The normal range is 10 to 100 mcg/24 h. Normal value ranges may vary slightly among different laboratories.

Note: mcg/24 h = micrograms per 24 hours

What Abnormal Results Mean

Increased levels of urine cortisol may indicate:

• ACTH-secreting tumor
• Cushing's syndrome -- pituitary-independent
• Cushing's disease -- pituitary-dependent
• Pseudo-Cushing's

Decreased levels of urine cortisol may indicate:

• Addison's disease
• Hypopituitarism
• Congenital adrenal hyperplasia

Additional conditions under which the test may be performed include exogenous Cushing's syndrome.

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