Studies on ovarian and adrenal steroids at different phases of the menstrual cycle. 1. Dynamic changes during the periovulatory period.

In order to assess the periovulatory interrelationships between the plasma levels of estradiol, estrone, 17-hydroxyprogesterone, progesterone, cortisol and biologically active lutropin (LH), peripheral blood samples withdrawn from 12 normally menstruating women at 07.00, 15.00 and 23.00 h. during seven days of the midcycle period were analyzed. The estradiol peak varied between 0.86 and 1.50 nmol/l; it preceded the LH peak in 11 subjects and occurred simultaneously with it in 1 case. Although the peak levels of estradiol were significantly higher than those associated with the LH peak, there was no significant difference between the estradiol levels at the LH peak and those found during the 32-hour period prior to the LH peak. Calculation of the estradiol to estrone ratios revealed the existence of two groups of subjects with significantly different ratios. In one group the estradiol levels were significantly lower and those of estrone significantly higher than in the other group. No difference was found between these two groups concerning the other hormonal indices measured. No significant variation was found in the estradiol, estrone and LH levels during the day; however, there was a significant overnight increase in their levels during 3 to 4 days preceding the day of the LH peak. A significant rise in 17-hydroxyprogesterone levels occurred 8 h. before the earliest rise in LH and progesterone levels; on the other hand, in none of the subjects did the first rise in progesterone levels precede the first significant elevation of LH levels.