Effect of oral contraceptives or dexamethasone on plasma beta-endorphin during the menstrual cycle.

Several studies have showed a significant increase of plasma beta-endorphin levels during the periovulatory days of the menstrual cycle. The aim of the present study was to investigate the origin of the periovulatory changes of plasma beta-endorphin, trying to discriminate between a possible ovarian and/or pituitary origin. Daily plasma beta-endorphin, luteinizing hormone (LH), and cortisol levels were measured from the 8th to the 20th day of the menstrual cycle in healthy normal-cycling women (10 cases) before and during dexamethasone (DEX; 6 cases) or estroprogestinic treatment with monophasic (5 cases) or triphasic (5 cases) pill. In the control menstrual cycle, during the preovulatory days, a significant increase of plasma beta-endorphin was found. While oral contraceptives abolished the midcycle increase of plasma beta-endorphin, the periovulatory plasma beta-endorphin peak was present during DEX treatment. Plasma cortisol levels did not show any significant change throughout the control menstrual cycle, while they were significantly lowered by the DEX administration and significantly increased during estroprogestinic treatment. These results suggest that the increase of plasma beta-endorphin during the periovulatory days is related to the ovulatory function, and suggest a possible ovarian origin.