Lactate dehydrogenase in human cervical mucus: correlation with ovulation, influence of ovarian steroid hormones, and isozyme pattern.

The glycolytic enzymes, lactate dehydrogenase (LDH), glucose-6-phosphate dehydrogenase, and hexokinase in cervical mucus of 96 ovulatory women were serially measured daily during the menstrual cycle. Among all of the enzymes, the cyclic changes in LDH activity were the most significant, being high during the proliferative phase, gradually decreasing to the lowest level around ovulation, and then increasing markedly again. Estrogen inhibited cervical mucus LDH activity; progestrone accelerated it. Examination of the LDH isozyme pattern showed that H-LDH (H-subunit of LDH), being predominant throughout the cycle, apparently carries some responsibility for the cyclic change in LDH activity. In a comparison of LDH activity with the serum luteinizing hormone (LH) peak, the activity level nadir of LDH usually appeared between 1 day before and 1 day after the serum LH peak, pointing to the advantage of daily measurement of cervical mucus LDH activity for predicting the potential day of conception.