Rapid radioimmunoassays of plasma LH and estradiol-17β for the prediction of ovulation

Abstract

It is generally accepted that accurate prediction of ovulation can be based on the detection of the estrogen or LH peaks measured either in urine or plasma. A systematic comparison between plasma estradiol-17β (E 2) and urinary total estrogens levels as well as between plasma and urinary LH levels was performed in normally cycling women and during induced follicular maturation. The best correlations were found between urinary total estrogens and plasma E 2 levels, when the latter were measured 48 h before the end of the urine collection ( r = 0.83, P < 0.001) and between urinary LH and plasma LH, when the latter was measured 36 h before the end of the urine collection ( r = 0.55, P < 0.02). Peaks and nadirs of the individual profiles of urinary estrogens and LH were always delayed by at least 1 day and often 2 days with respect to the corresponding plasma profiles. These data confirmed that a permanent shift exists between plasma and urine levels, and this is more clear-cut as far as estrogens are concerned. Consequently, rapid radioimmunoassays for plasma E 2 and LH were set up for monitoring follicular maturation and for detecting LH preovulatory surge. By means of these assays, precise and accurate results were obtained within 8 h after blood sampling. They were applied according to different procedures for predicting ovulation in artificial insemination and oocyte harvesting programs. In view of these preliminary results, it appears that the most efficient way of predicting ovulation will consist of simultaneous determinations of E 2 and LH at 12 h intervals. When LH and E 2 levels are simultaneously high, the positive feedback of E 2 upon LH secretion is achieved and ovulation should occur after a delay of at least 24 h.