24-hour urinary free cortisol (UFC)

A 24-hour urine sample is needed. The health care provider will instruct you, if necessary, to stop taking drugs that may affect 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 you return it 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. Check the infant frequently and change the bag after the infant has urinated into the bag. Drain the urine into the container for transport to the laboratory.

Deliver the urine to the laboratory or your health care provider as soon as possible.

No special preparation is necessary for this test. If you are taking the collection from an infant, you may need a couple of extra collection bags.

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

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 a.m. to 8 a.m. and lowest levels at about midnight.

Cortisol affects many different body systems. It plays a role in:

• Bone
• Circulatory system
• Immune system
• Metabolism of fats, carbohydrates, and protein
• Nervous system
• Stress responses

Different diseases, such as Cushing's disease and Addison's disease, can lead to either too much or too little 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.

Normal range: 10 - 100 mcg/24 h.

Note: mcg/24 h = micrograms per 24 hours

Normal value ranges may vary slightly among different laboratories. Talk to your doctor about the meaning of your specific test results.

Increased levels of urine cortisol may indicate:

• Cushing syndrome -- pituitary-independent
• Cushing's disease -- pituitary-dependent
• Pseudo-Cushing's
• Tumor that releases ACTH

Decreased levels of urine cortisol may indicate:

• Addison's disease
• Hypopituitarism
• Congenital adrenal hyperplasia

The test may also be done in cases of exogenous Cushing syndrome.

Factors that interfere with this test are:

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

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

Stewart PM. The Adrenal Cortex. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Kronenberg: Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008:chap 14.

Melmed S, Kleinberg D. Anterior Pituitary. In: Kronenberg HM, Melmed S, Polonsky KS, Larsen PR. Kronenberg: Williams Textbook of Endocrinology. 11th ed. Philadelphia, PA: Saunders Elsevier; 2008:chap 8.