CYTOCHROME-P450 3A4 ACTIVITY IN PREMENOPAUSAL AND POSTMENOPAUSAL WOMEN, BASED ON 6-BETA-HYDROXYCORTISOL CORTISOL RATIOS/

Objective. To characterize cytochrome P450 (CYP) 3A4 activity in preme nopausal and postmenopausal women by evaluating the urinary 6-beta-hyd roxycortisol:cortisol ratio. Design. Prospective study. Subjects. Thir teen premenopausal and 13 postmenopausal women who were healthy and no t receiving drugs known to affect CYP3A4 activity. Interventions. Begi nning on day 2 of menses, premenopausal women collected first morning urine samples every other day for a complete menstrual cycle. Postmeno pausal women collected first morning urine every other day for 28 days . Measurements and Main Results. Mean weekly 6-beta-hydroxycortisol:co rtisol ratios did not differ during the phase (week) of the menstrual cycle. Daily ratios did not differ in postmenopausal women. No differe nce between premenopausal and postmenopausal women was found on compar ing overall median ratios. Conclusion. Cytochrome P450 3A4 activity as measured by 6-beta-hydroxy cortisol:cortisol ratio did not differ by week of menstrual cycle, suggesting no menstrual cycle-related changes . Menopause does not appear to be associated with differences in CYP3A 4 activity, compared with premenopause.