[Interaction of plasma beta-endorphin and progesterone in the luteal phase]

Recent research indicates that opioid peptides may be participants in the coordination and control of the menstrual cycle. The peripheral ovarian steroids (progesterone and estradiol) seem to modulate endogenous opioid activity and thereby hypothalamic LH-RH-secretion. This mechanism works during the luteal-phase under the influence of progesterone. The purpose of this study is to investigate the interaction of endogenous opioid peptides and peripheral ovarian steroids in 24 women by comparing progesterone and beta-endorphin levels of unstimulated and HMG-stimulated cycles. The women with stimulated cycles showed significantly higher progesterone and beta-endorphin levels. The interaction of progesterone und beta-endorphin may partly be explained by the fact that progesterone acts on progesterone receptors in the central nervous system. This leads to activity of opioid neurons in the brain and finally influences LH-RH- and LH-release. Beta-endorphin production is also discussed to come from the ovary. Beta-endorphin is involved maintaining normal luteal phase and therefore plays an important role in reproduction.