Plasma levels of norepinephrine (NE) during the periovulatory period and after LH-RH stimulation in women

In three normally cycling women studied daily from day 10 to day 17 of the menstrual cycle, the levels of circulating norepinephrine showed a sharp rise preceding or concomitantly with the ovulatory LH surge. In two patients the norepinephrine peak took place 24 hr. previously to the LH rise and in the third one it occurred simultaneously. The simultaneous determination of ovarian hormones and norepinephrine showed no temporal correlation between this catecholamine and either estradiol or progesterone. On the other hand, after a single intravenous 100 μg dose of LH-RH, a significant rise in plasma norepinephrine, preceding the LH peak, was found in the four patients studied. The determination of norepinephrine at 3 minute intervals beginning one minute after LH-RH injection showed a significant rise in the amine levels ranging from 5 to 10 times in respect to basal values between 1 and 6 minutes after LH-RH stimulation. In these patients a second peak of norepinephrine occurred simultaneously with the maximal response of LH, which rose to peak levels after 18 minutes in one patients and after 24 minutes in the other. These findings are discussed with respect to the origin and role of increased amounts of plasma norepinephrine related to the LH surge.