Determinants of early follicular phase gonadotrophin and estradiol concentrations in women of late reproductive age

Abstract

Background: FSH and estradiol measured during the menstrual (basal) phase of cycles predict the success of infertility treatment; but the role of these hormones as markers for ovarian reserve in normal populations needs further study. Methods and results: From a cohort study of depressed and non-depressed women, a subset of 406 non-depressed women between the ages of 36 and 45 years with spontaneous periods were selected and their concentrations and determinants of basal hormones measured at study entry, 6 and 12 months later were described. FSH and LH increased significantly over the 12 months of observation (P ≤ 0.001), but considerable variation was noted in FSH and estradiol in some women monitored over the three cycles. Concentrations often varied between a pattern of low FSH, high estradiol in one cycle and high FSH, low estradiol in another. In multivariate models focusing on the maximum observed hormone concentration, significant predictors included: increasing age (P < 0.0001), smoking (P = 0.04), and shorter cycle length (P < 0.0001) during adolescence (P < 0.0001) associated with higher FSH; increasing age (P < 0.0266) and lower body mass index (P < 0.0289) associated with higher LH; and a greater number of estimated ovulatory cycles associated with higher estradiol (P < 0.0425). Conclusions: Early reproductive landmarks, smoking, body weight, and factors that determine number of ovulatory cycles impact on ovarian/pituitary physiology in late reproductive life.