Why a 24-hour urine test and not blood or saliva?
Hormones are released in our bodies in a pulsed 24-hour cycle (biological rhythm) so an analysis over the entire 24-hour period is a lot more informative over a single blood sample (which is a fixed point within the 24-hour cycle). Hormones do not float around in the blood freely – they are bound to proteins within the blood which makes them difficult to assess. Saliva is not useful to evaluate the metabolism of hormones and for measuring thyroid levels.
