The menstrual cycle: relations of biophysical and hormonal determinations in normal women of reproductive age.

Appropriate relationships between circulating levels of 17 beta-E2 and P are necessary for normal endometrial development and blastocyst implantation. The aim of this study was to relate biophysical and biochemical measurements obtained during the menstrual cycle of six healthy women in 25 menstrual cycles. One hundred eighteen vaginosonographic determinations of the endometrial thickness together with serum E2 and P assays were performed at 5-day intervals. The three parameters studied were standardized by the formula: observation minus mean determination for that parameter divided by the standard deviation of that parameter. Using this common unit, the physiological relations between ultrasonographically determined endometrial thickness, E2, and P were readily seen.