Ovarian function influences many areas of concern in women’s health, including breast cancer and other chronic diseases. However, ovarian function has been little studied in healthy, premenopausal women, partly because of cyclical variation.Methods.
We measured biomarkers of ovarian function (daily urinary metabolites of estrogen and progesterone) among 411 women age 18–39 years, who were Kaiser Permanente members in Northern California in 1990–1991. We have summarized the hormone metabolite levels of about 1,500 cycles and examined their associations with demographic and menstrual cycle characteristics.Results.
Cycles with a short follicular phase showed elevations of 10–13% in both baseline (days 1–5) and average follicular-phase estrogen metabolite levels, as well as some elevations in progesterone metabolites. Progesterone metabolite levels were directly related to the length of the luteal phase. Compared with whites, Hispanics had estrogen metabolite levels that were 7–13% higher in the follicular and luteal phases, whereas nonwhite, non-Hispanic women (primarily Asians) had slightly lower levels. Generally, women with a prior pregnancy or those with a later age at menarche had lower estrogen metabolite levels, whereas women with prior induced abortions had higher levels. Luteal-phase progesterone metabolite levels tended to be lower among women who were overweight, were less educated, were older at their first livebirth, or had an induced abortion.Conclusions.
Some menstrual cycle characteristics provide a crude surrogate of the hormonal milieu, particularly luteal-phase length and progesterone levels. Hormone levels varied by reproductive characteristics, potentially explaining their relevance to breast cancer risk.