Predictors of ovarian steroid secretion in reproductive-age women.

During the baseline period (1985-1988) of a prospective study, midcycle and luteal-phase estrogens and progestins were measured in 175 healthy women aged 21-36 years with spontaneous, cyclic menses in Brooklyn, New York. Subjects contributed daily first-morning urine specimens and three blood specimens during a single menstrual cycle monitored by basal body temperature. Hormone levels were compared according to age, race, and levels of known or suspected breast cancer risk factors. Late age at menarche was associated with increased urinary and serum progestin levels. Increased body weight was associated with decreased progestin levels, even in ovulatory women. Neither weight nor age at menarche was related to estrogen levels. Cigarette smoking was associated with decreased midcycle and luteal-phase estradiol levels. No other factors were associated with differences in any of the hormones measured either midcycle or during the luteal phase, despite good statistical power to detect moderate differences. Sources of individual variability in ovarian steroid levels remain unexplained. These data do not support hypotheses that breast cancer risk factors act through an effect on ovarian hormones during the middle reproductive years.