Free cortisol (24 hour urine)

General Information

CortisolDetermination in 24-hour urine is the method of choice for the diagnostics of Cushing's syndrome because the rate of cortisol excretion in the urine is not affected by the daily variability of hormone secretion by the adrenal cortex. The test allows for a more accurate differentiation of healthy individuals with Cushing's syndrome.

Urine cortisol reflects the amount of free cortisol in the serum, which is filtered by the kidneys and correlates with the rate of cortisol secretion.

Usually, there is a direct proportional relationship between urinary free cortisol and the biologically active portion of serum cortisol.

When should we take a free cortisol test?

• Assessment of adrenal cortex function (especially in the case of hypercortisolism);
• Examination of patients with obesity, hypertension, hirsutism, stretch marks, low back pain or menstrual disorders or hypertension.

How to prepare for the test?

Avoid stress throughout the urine collection process (24 hours).

Study material / urine collection rule

24-hour urine. At 7 o'clock in the morning the patient urinates and does not store this urine, and during the next urination he collects the whole volume of urine in a plastic container (2-3 liter urine container) until 7 o'clock in the morning of the next day (24 hours); The patient should transfer 100 ml of urine from this container (e.g. with a syringe) to a disposable plastic cup for urine and should be stored at 2-8 ° C before the test (1-1,5 h).

Possible interpretation of the results

Urine free cortisol Increased concentration In a patient who has adequately collected a urine sample, it is sufficient to diagnose Cushing's syndrome; Normal result Will likely rule out this diagnostics.

Diagnostic limitations

Taking low values ​​does not necessarily indicate adrenal insufficiency.

Pregnancy and oral contraceptives are associated with increased cortisol excretion.