Diurnal Variation in the Excretion of 6β-Hydroxycortisol and Estriol at 32 Weeks Gestation

We have previously shown a marked diurnal variation in the excretion of cortisol and 6 beta-hydroxycortisol at 36-38 weeks pregnancy with no variation in estrogen excretion. Since others have shown a reciprocal relationship between plasma levels of estriol and cortisol at 30-35 weeks of pregnancy, we decided to determine whether a similar relationship was present in urinary concentrations of cortisol, 6 beta-hydroxycortisol and estriol at this gestational age. A significant variation in excretion of both cortisol and 6 beta-hydroxycortisol was found. The variation in urinary levels of estriol was less than that of the corticosteroids but followed the same pattern.