Cervicovaginal peroxidases: sex hormone control and potential clinical uses

Thirty-one normal women were studied daily in 41 cycles. Venous blood samples were taken for measurements of luteinizing hormone (LH), estradiol (E2), and progesterone (P), and vaginal examinations were done to obtain cervical mucus and vaginal fluid. The specific activity of guaiacol peroxidase (GP), extracted from cervicovaginal secretions with 0.5 M CaCl2, was determined in the vaginal samples. In the follicular phase, from day -7 to day 0 (the LH +1 day, when ovulation presumably occurred), there was a strong negative correlation between GP and the rising E2 (r = -0.94). On days 1 to 10 after ovulation, there was a strong positive correlation between GP and P (r = 0.84). In nine ovulatory cycles in which P levels did not exceed 8 ng/ml on any day, indicating possible luteal phase inadequacy, there were significantly lower GP levels than in another 32 ovulatory cycles with higher P (P = 0.04). These results suggest that (1) at midcycle, E2 seems to "down-regulate" the GP specific activity; and (2) in the luteal phase, serum P levels parallel those of GP activity, even in the presence of high luteal E2. GP activity profiles during the menstrual cycle can be used to define the fertile period, may prove useful in diagnosing pregnancy, and may be a simple, convenient test for an inadequate corpus luteum.