Submitted to: Cancer Epidemiology Biomarkers and Prevention
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/21/1995
Publication Date: N/A
Interpretive Summary: Pregnancy may induce long term changes in secretion or metabolism of estrogens and androgens which affect breast cancer risk. In a cross- sectional study of 107 premenopausal women, we examined the relation of age, menarcheal age, parity, and age at first live birth with plasma estrogen and androgen levels. Plasma hormones were measured at three points during the menstrual cycle, follicular (early), midcycle (around th time of ovulation), and luteal (late, post ovulatory stage). Age was associated with plasma estrogen levels at certain points in the menstrual cycle. The relationship of age to plasma estrogen was different depending on parity. Plasma androgens decreased with age. The study suggests that pregnancy may lower breast cancer risk by modifying age related changes in plasma estrogen levels. This information is useful to scientist and other professionals concerned with breast cancer risk in relation to hormones and dreproductive history in premenopausal women.
Technical Abstract: We used data from a cross-sectional study of 107 premenopausal women to evaluate the relation of age, menarcheal age, parity, and age at first live birth with plasma estrogen and androgen levels in premenopausal women. Fasting blood specimens were collected on each of days 5-7, 12-15, and 21-23 of every participant's menstrual cycle and pooled to create follicular, midcycle, and luteal phase samples, respectively, for analysis Age was associated significantly and positively with plasma estradiol levels during the follicular phase (% difference/year = 2.6; 95% CI = 1.0 - 4.2) and midcycle (% difference/year = 2.7; 95% CI = 0.9 - 4.7) but not the luteal phase (% difference/year = 0.4; 95% CI = -1.9 - 1.3) of the menstrual cycle. The relation of age to plasma estradiol varied by parity with interactions being significant midcycle and during the luteal phase. Among nulliparous women, plasma estradiol levels increased with age midcycle and during the luteal phase, but among parous women estradiol levels decreased with age during these phases of the menstrual cycle. Plasma estrone increased with age during the follicular phase of the menstrual cycle (% difference/year = 1.5; 95% CI = 0.2 - 2.8). During the luteal phase there was a significant interaction with parity; estrone levels in nulliparous women varied only slightly with age but levels in parous women decreased significantly as age increased. The androgens, androstenedione and dehydroepiandrosterone sulfate, decreased and sex hormone binding globin increased as age increased. The results of this cross-sectional study suggest that pregnancy may influence breast cancer risk by modifying age related changes in plasma estrogen levels.