Measuring free cortisol levels in a 24-hour urine collection reflects the average level of free cortisol in the blood over the collection period. However, this test is mainly used to diagnose hypercortisolaemia, because under normal physiological conditions, only the free fraction of the hormone (not bound to proteins) is filtered by the kidneys. A significant increase in urinary cortisol excretion occurs only when its serum concentration exceeds the binding capacity of plasma proteins.<\/p>\n
Collect urine in a dry, clean container of sufficient capacity (approx. 2 \u2013 2,5 l). The laboratory has graduated containers available. Start the collection in the morning (e.g. 7.00) and finish at the same time the following day:
\n\u2013 discard the first urine passed in the morning (into the toilet),
\n\u2013 collect all subsequent urine in the prepared container, including the first urine passed the following morning,
\n\u2013 keep the urine container in a dark, cool place throughout the collection period,
\n\u2013 once the collection is complete, measure the total amount of urine collected and record the volume (in millilitres),
\n\u2013 mix the urine, pour a 30 \u2013 50 ml sample into a urine specimen container and deliver it to the laboratory.<\/p>\n
If, for any reason, even one portion of urine passed during the collection period is not transferred to the collection container, the test will not be accurate. In this case, repeat the urine collection on another day.<\/p>\n
Results available in: approx. 6 working days<\/p>\n