PROLONGED OPIOID BLOCKADE DOES NOT INFLUENCE LUTEINIZING-HORMONE MODIFICATIONS OF THE FOLLICULAR AND LUTEAL MENSTRUAL PHASES

Although an acute opioid withdrawal markedly modifies LH secretion in the different phases of the menstrual cycle, whether a sustained opioi d blockade imbalances spontaneous LH modifications associated with the progression of the follicular or luteal menstrual phases is presently unknown. Accordingly, normal cycling women during either the follicul ar (n = 14) or luteal(n = 14) menstrual phase, randomly and in double blind fashion, received either placebo (n = 7 for each phase) or 50 mg /day of the oral opioid antagonist naltrexone (n = 7 for each phase). In each subject, LH pulsatility (10-min blood drawing for 8 h) and the pituitary LH response to a 10-mu g GnRH stimulus were investigated at baseline and on the fifth day of placebo/naltrexone administration. I n the follicular phase, after placebo treatment, the number and amplit ude of LH pulses did not significantly vary, whereas mean LH levels (P < 0.01) and the LH response to GnRH (P < 0.05) were significantly inc reased. The same occurred after naltrexone treatment, when significant increases in both mean LH levels (P < 0.02) and LH response to GnRH ( P < 0.025) were observed. In the luteal phase, after placebo administr ation, the frequency of LH pulses and mean LH levels were not modified , but both the amplitude of LH pulses (P < 0.025) and the LH response to GnRH were reduced (P < 0.02). The same occurred after naltrexone tr eatment, when significant decreases in both the amplitude of LH pulses (P < 0.05) and the LH response to GnRH (P < 0.05) were observed. Duri ng both phases of the menstrual cycle, the modifications observed duri ng naltrexone treatment were similar and not significantly different f rom those observed during placebo. The present data do not support imp ortant modulatory functions for endogenous opioid peptides on spontane ous LH modifications occurring with the progression of the follicular or the luteal menstrual phases.