OBJECTIVE: Our purpose was to test the hypothesis that endogenous catecholamines may interact with endogenous opioid peptides to influence gonadotropin secretion during the midluteal phase in normal women. STUDY DESIGN: Normal cycling women studied during the midluteal phase were randomized to one of four treatment groups: (1) α-methyl-para-tyrosine, (2) naloxone, (3) α-methyl-para-tyrosine and naloxone, and (4) control. Mean treatment luteinizing hormone levels were compared by analysis of variance. Pulse frequency, amplitude, and integrated area under the curve were assessed by CLUSTER analysis and compared by means of nonparametric analyses. RESULTS: Mean luteinizing hormone levels were significantly higher in the naloxone and α-methyl-para-tyrosine plus naloxone groups compared with α-methyl-para-tyrosine or placebo. Coadministration of α-methyl-para-tyrosine and naloxone caused a significant increase in large-burst luteinizing hormone pulses compared with the group receiving naloxone only. CONCLUSION: Endogenous catecholamines augment the inhibitory effect of opioids on luteinizing hormone secretion during the midluteal phase in normal cycling women.
- Endogenous catecholamines
- luteinizing hormone secretion
- midluteal phase