Is opioidergic activity responsible for the circadian variation observed in the gonadotrophin responsiveness of early follicular phase women?

Abstract

Opioidergic blockade imposed by naloxone did not noticeably change GnRH-stimulated gonadotrophin release at any of the study times. We therefore infer that mechanisms other than a nocturnal increase of opioidergic inhibition may account for eventual circadian changes in the gonadotrophin responsiveness of early follicular phase women.