Pulsatile Secretion of Ovarian Steroids in the Mid-luteal Phase of the Menstrual Cycle

Abstract

The possibility of the pulsatile secretion of pituitary gonadotropins (LH and FSH) and ovarian steroids (estradiol and progesterone) was studied. In addition, an evaluation was made of the regulatory factors for steroid secretion of corpus luteum in view of the response behavior of the secretion of LH, FSH, estradiol and progesterone when loaded with hCG and gonadotropin releasing hormone (Gn-RH). The study was performed on 9 cases of infertile women in the mid-luteal phase of a normal menstrual cycle. In 5 cases, blood was collected every 30 minutes and over 24 hours. Thereafter, 2,500 iu of hCG was given twice to another subject at 8 hour intervals, and blood was collected every 30 minutes from immediately after the 1st administration over 16 hours. In the other 3 cases, 15 micrograms of Gn-RH was given at an interval of 90 minutes, and blood was collected every 20 minutes for 16-24 hours. Then, the frequency and amplitude of each pulse for LH, FSH, estradiol and progesterone were calculated under the modified Santen's rule in situ and when loaded with Gn-RH, and the relationship between pulses of gonadotropins and those of estradiol and progesterone was analysed by determining the number of concomitant pulses. The hormone dynamics when loaded with hCG were also assessed. The pulse frequency and amplitude in situ of each hormone were 10.6 +/- 0.8 times/24 h and 4.9 +/- 0.6 miu/ml for LH, 9.9 +/- 9.9 times/24h and 1.3 +/- 0.1 miu/ml for FSH, 9.2 +/- 0.9 times/24h and 34.3 +/- 2.7 pg/ml for estradiol, 7.4 +/- 0.5 times/24 and 3.7 +/- 0.4 ng/ml for progesterone. The coincidence of estradiol pulses and LH pulses was 37 times, and the concomitant ratio of LH pulse to estradiol pulse was 81%. The coincidence of progesterone pulses and LH pulses was 31 times, and the concomitant ratio of LH pulse to progesterone pulse was 84%. Furthermore, the concomitant ratio of FSH pulse to estradiol pulse or progesterone pulse was 61% or 70%, respectively. The mean plasma concentration of LH, estradiol and progesterone during 8 hours after the 1st administration and 2nd administration of hCG changed from 29.9 +/- 2.3 to 41.8 +/- 1.6 miu/ml, from 140.3 +/- 3.0 to 160.6 +/- 3.6 pg/ml and from 19.2 +/- 1.0 to 25.7 +/- 0.6 ng/ml, respectively. These values increased significantly after the second injection (P less than 0.001).(ABSTRACT TRUNCATED AT 400 WORDS)