Plasma levels of norepinephrine during the periovulatory period in normal women. Further studies

Eleven normally cycling women in whom laparotomy was indicated for benign gynecologic pathology were studied. Surgery was performed on day 0 (expected day of ovulation). Blood samples were drawn daily from day -8 to day -4, and every 8 hours from day -3 to day +2; estradiol (E2), progesterone (P), norepinephrine (NE), and LH were determined by RIA. Ovulation was certified by ovarian visualization and biopsy during laparotomy. In nine ovulatory patients mean E2 peak was found 48 hours before LH peak. Mean NE levels showed minimal variations until 48 hours before LH peak; 8 hours after E2 peak mean NE values increased significantly, fell 8 hours later, and rose immediately again, reaching maximal levels 24 hours after E2 peak. These values remained high until 16 hours before the LH peak and decreased gradually, thereafter reaching basal levels 32 hours after LH peak. Two anovulatory patients showed an atypical pattern of ovarian steroids and LH secretion and NE showed large variations without any correlation with estradiol or LH levels. This study confirms previous findings in women and experimental work in animals regarding the existence of a noradrenergic trigger mechanism to the LH ovulatory discharge.