Urinary free cortisol increases in adolescent Caucasian females during perimenarche

Urinary free cortisol (UFC) excretion has been thought to be constant during female reproductive maturation when normalized for body surface area. We sought to determine whether there are longitudinal changes in urinary free cortisol excretion during perimenarche in adolescent females. We performed a longitudinal study of 24-h UFC excretion obtained at 6-month intervals over a 4-yr period in a cohort of 112 adolescent non-Hispanic white perimenarchal females from south central Pennsylvania. The overall mean values (mean ± SD) for UFC/24 h for all measurements between ages 12 and 17 yr was 67.4 ± 43.8 μg/24 h (to convert to nanomoles per day, multiply by 2.759). In our model, we found a significant positive association between UFC excretion with both gynecological age (P = 0.002) and chronological age (P = 0.0001). For every incremental increase in Tanner stage, the UFC/BSA increased by 3.0 μg/24 h per square meter. Correcting the UFC values by both creatinine and BSA creates a fairly constant number (6.3 ± 3.1 μg/mg per square meter per 24 h) over the age range 12-17 yr represented in this study. An increase in cortisol excretion may be part of normal reproductive maturation.