PLASMA-LEVELS OF BETA-ENDORPHIN DURING THE MENSTRUAL-CYCLE

During recent years, many research teams have suggested a possible rol e of endogenous opiates in the control of the menstrual cycle. The lev el of immunoreactive beta-endorphin was measured on different days dur ing the ovulatory cycle of 131 healthy volunteers. The levels of lutei nizing hormone (LH), follicle-stimulating hormone (FSH), 17 beta-estra diol and progesterone were also measured. The graphic representation o f opiate levels during the female menstrual cycle, where day 0 is the day of ovulation, shows that plasmatic beta-endorphin levels are not s table throughout. The levels increase progressively during tile follic ular 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. Dur ing 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 re ached 24 h before the next menses. The beta-endorphin level has a nega tive correlation with the LH level (r = -0.50, p < 0.001) on the preov ulatory days, and during the luteal phase a positive linear correlatio n (r = 0.47, p < 0.001) is found with the progesterone level. It seems that beta-endorphin levers in the plasma are influenced by the ovaria n steroids. However, the influence of the plasmatic opiate on the gona dotropins is currently under discussion.