Estrogen secretion, biosynthesis and metabolism: Their relationship to the menstrual cycle

Abstract

Estriol production rates and the amount of estriol biosynthesized from estradiol have been determined in normal women by the simultaneous administration of estradiol and estriol bearing different isotopic labels and the examination of the radioactive urinary metabolites. In similar experiments estrone and estradiol secretion rates and interconversions have been measured during normal menstrual cycles. These experiments demonstrate increased estriol production during the luteal phase of the menstrual cycle. The luteal phase increment in estriol production is not accounted for by an increased rate of conversion of estradiol to estriol. On the basis of specific activity data a sizeable portion of luteal phase estriol may come from pathways independent of estrone and estradiol. The estrone and estradiol secretion rate determinations confirm the dual primary secretion of estrone and estradiol and show no qualitative pattern peculiar to either menstrual cycle phase.