title: Plasma levels of beta-endorphin during the menstrual cycle.
abstract: During recent years, many research teams have suggested a possible role of endogenous opiates in the control of the menstrual cycle. The level of immunoreactive beta-endorphin was measured on different days during the ovulatory cycle of 131 healthy volunteers. The levels of luteinizing hormone (LH), follicle-stimulating hormone (FSH), 17 beta-estradiol and progesterone were also measured. The graphic representation of opiate levels during the female menstrual cycle, where day O is the day of ovulation, shows that plasmatic beta-endorphin levels are not stable throughout. The levels increase progressively during the follicular phase, reaching a maximum (mean 139.49 pg/ml, SD 42.23 pg/ml, 95% confidence interval 121.22-157.75 pg/ml) 4 days before ovulation. During the periovulatory period (days-3 to +3) levels of beta-endorphin are very stable (mean day 0, 27.8 pg/ml, SD 6.36 pg/ml, 95% confidence interval 19.29-27.83 pg/ml) and low (p < 0.05), followed by a renewed increase during the luteal phase (mean day + 5, 87.86 pg/ml, SD 36.49 pg/ml) where a maximum level (mean 102.78 pg/ml, SD 30.35 pg/ml) is reached 24 h before the next menses. The beta-endorphin level has a negative correlation with the LH level (r = -0.50, p < 0.001) on the preovulatory days, and during the luteal phase a positive linear correlation (r = 0.47, p < 0.001) is found with the progesterone level. It seems that beta-endorphin levels in the plasma are influenced by the ovarian steroids. However, the influence of the plasmatic opiate on the gonadotropins is currently under discussion.
authors.affiliation: Obstetrics and Gynecology Service, Hospital Central of Asturias, University of Oviedo, Spain.
authors.forename: J
authors.initials: J
authors.lastname: Ferrer
authors.forename: J
authors.initials: J
authors.lastname: Mtnez-Guisasola
authors.forename: F
authors.initials: F
authors.lastname: Díaz
authors.forename: F
authors.initials: F
authors.lastname: Alonso
authors.forename: M
authors.initials: M
authors.lastname: Guerrero
authors.forename: B
authors.initials: B
authors.lastname: Marín
mesh_terms: D000293:Adolescent; D000328:Adult; D004958:Estradiol / Q000097:blood; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D006801:Humans; D007986:Luteinizing Hormone / Q000097:blood; D008597:Menstrual Cycle / Q000097:blood*; D010060:Ovulation / Q000502:physiology; D011374:Progesterone / Q000097:blood; D001615:beta-Endorphin / Q000097:blood*
chemical_list: D011374:Progesterone; D004958:Estradiol; D001615:beta-Endorphin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone