Cortisol in Urine
A cortisol test is done to measure the level of the hormone cortisol in a 24-hour sample of urine. The cortisol level may show problems with the adrenal glands or the pituitary gland. Cortisol is made by the adrenal glands. Cortisol levels get higher when the pituitary gland releases another hormone called adrenocorticotropic hormone (ACTH).
Cortisol has many functions. It helps the body use sugar (glucose) and fat for energy (metabolism), and it helps the body manage stress. Cortisol levels can be affected by many conditions, such as physical or emotional stress, strenuous activity, infection, or injury.
Normally, cortisol levels rise during the early morning hours and are highest about 7 a.m. They drop very low in the evening and during the early phase of sleep. But if you sleep during the day and are up at night, this pattern may be reversed. If you do not have this daily change (diurnal rhythm) in cortisol levels, you may have overactive adrenal glands. This condition is called Cushing's syndrome.
Cortisol in urine is measured from all of the urine collected over 24 hours because of the wide variation in cortisol levels that occurs throughout the day.
Why It Is Done
A cortisol test is done to find problems of the pituitary gland or adrenal glands, such as making too much hormone, which happens in Cushing's syndrome.
How To Prepare
You may be asked to avoid strenuous physical activity the day before a cortisol test.
Be sure to drink enough fluids during the 24-hour urine test to prevent dehydration.
Many medicines may change the results of this test. Be sure to tell your doctor about all the nonprescription and prescription medicines you take.
Talk to your doctor about any concerns you have regarding the need for the test, its risks, how it will be done, or what the results will mean. To help you understand the importance of this test, fill out the medical test information form(What is a PDF document?).