The Relation of Circulating Progesterone and Oestradiol Concentrations to the Onset of Menstruation

Abstract

Summary Forty patients have been studied over 96 menstrual cycles during which a blood sample was obtained within five days of the next menstrual period. Two features emerged: circulating concentrations of progesterone and oestradiol could be elevated on the day bleeding began and conversely the levels of these hormones could be low for some days without menstruation occurring. These data suggest there may not be any direct relation between circulating ovarian hormone levels and the onset of menstrual bleeding.