[Simultaneous study of plasma gonadotropins, estrogens, progesterone and 17-hydroxyprogesterone during the ovulatory...

Plasma levels of gonadotrophins, estrone, estradiol, 17-hydroxyprogesterone and progesterone were studied throughout an ovulatory cycle in 11 normal women. For each of these hormones, the initiation of a secretory cycle occured at a different time: on the 10th day after mid-cycle surge for gonadotrophins, on the 3 rd day of menses for estradiol and somewhat later for estrone, on the 8th day of cycle for 17-hydroxyprogesterone and on the day of the LH surge for progesterone. Mean plasma levels and range were reported for every studied hormone. The mid-cycle surges of LH and FSH were found always coincident, after which their concentration decreased simultaneously; during the late follicular phase the increasing LH curve intersected the decreasing FSH curve. A peak of estradiol occured in every subject except one on the day before the mid-cycle surge of LH; a peak of plasma estrone occured either on the day of the LH peak or on the day before. For these two hormones the luteal phase range is always below the peak level. A peak of 17-hydroxyprogesterone occured in every subject on the same day than the mid-cycle LH peak, but the plasma level increased during the luteal phase up to higher levels. Progesterone concentration increased on the day of the LH surge, indicating the initiation of luteinization prior to ovulation.