title: Within-person variability of urinary 6beta-hydroxycortisol to urinaryl ratios in Caucasian women.
abstract: Cortisol is metabolized to 6beta-hydroxycortisol by human cytochrome p450-3A4 (CYP3A4), an important enzyme involved in the metabolism of a variety of exogenous and endogenous compounds. Both cortisol and 6beta-hydroxycortisol are excreted in urine, and the ratio of these steroids has been proposed as an indicator of CYP3A4 activity. We evaluated within-person variability of this biomarker in 10 healthy Caucasian women, aged 23-58 years. Each study participant was asked to provide a fasting morning urine sample once a week consecutively for 8 weeks. Urinary cortisol and 6beta-hydroxycortisol were determined by immunoassay kits purchased from the DiaSorin (Stillwater, MN) and the Stabiligen (Nancy, France), respectively. The coefficients of variation (CV) of urinary 6beta-hydroxycortisol to cortisol ratios from study participants ranged from 16.7 to 51.4% (mean, 31.1%) over the study period. The level of the ratio measured in any single urine sample was correlated reasonably well with the average of the ratios over the 8-week study period from the same woman, with the mean correlation coefficient of 0.79. These results indicated that urinary 6beta-hydroxycortisol to cortisol ratios measured in a spot urine sample may reflect the level of this biomarker over a relatively longer time period in Caucasian women, and thus, it can be used in epidemiologic studies as a biomarker to evaluate the association between CYP3A4 activity and disease risk.
authors.affiliation: Department of Medicine and Vanderbilt-Ingram Cancer Centre, Vanderbilt University, Nashville, IN 37232-8300, USA.
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Lisa A
authors.initials: LA
authors.lastname: Dunning
authors.forename: Kristin E
authors.initials: KE
authors.lastname: Anderson
authors.forename: Jordan L
authors.initials: JL
authors.lastname: Holtzman
authors.forename: Wei
authors.initials: W
authors.lastname: Zheng
mesh_terms: D000328:Adult; D015415:Biomarkers / Q000652:urine; D051544:Cytochrome P-450 CYP3A; D003577:Cytochrome P-450 Enzyme System / Q000235:genetics; D005260:Female; D014644:Genetic Variation; D006801:Humans; D006854:Hydrocortisone / Q000031:analogs & derivatives* / Q000235:genetics / Q000378:metabolism / Q000652:urine*; D008875:Middle Aged; D044465:White People
chemical_list: D015415:Biomarkers; C001380:6 beta-hydroxycortisol; D003577:Cytochrome P-450 Enzyme System; C104464:CYP3A protein, human; D051544:Cytochrome P-450 CYP3A; C510163:CYP3A4 protein, human; D006854:Hydrocortisone