Lifetime cumulative number of menstrual cycles and serum sex hormone levels in postmenopausal women |
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Authors: | Mariana Chavez-MacGregor Carla H van Gils Yvonne T van der Schouw Evelyn Monninkhof Paulus A H van Noord Petra H M Peeters |
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Institution: | (1) Julius Center for Health Sciences and Primary care, University Medical Center, STR 6.131, PO BOX 85500, 3508 GA Utrecht, The Netherlands;(2) Department of Medicine, Washington University School of Medicine, Campus Box 8121, 660 South Euclid, St. Louis, MO 63110, USA |
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Abstract: | Objective Lifetime cumulative number of menstrual cycles is related to breast cancer risk. The aim of this study is to investigate the
relation between this index and serum sex hormone levels in postmenopausal women.
Methods Cross-sectional study including 860 naturally postmenopausal Dutch participants of the European Prospective Investigation
into Cancer and Nutrition. Lifetime cumulative number of menstrual cycles was computed using questionnaire data on ages at
menarche and menopause, number of pregnancies, breastfeeding, oral contraceptive use (OC) and regularity pattern. Measurements
of hormones included estrone (E1), estradiol (E2), andostrenedione, testosterone, sex-hormone binding globulin (SHBG) and
dehydroepiandrostenedione sulfate (DHEAS). The relation between the lifetime cumulative number of menstrual cycles and hormone
levels was assessed using analysis of covariance. Relations between reproductive characteristics and hormone levels were also
studied. Adjustments for characteristics at blood collection included age, years since menopause, BMI, hormone replacement
therapy use, OC use, smoking habits, alcohol intake and physical activity were done.
Results Lifetime cumulative number of cycles was related with SHBG; participants in the lowest category had higher SHBG levels. For
the separate characteristics, DHEAS and androstenedione increased significantly with increasing age at menarche, while androstenedione
and testosterone decreased with increasing age at menopause. For the parity characteristics, SHBG levels increased according
to the number of live births.
Conclusions Lifetime cumulative number menstrual cycles was related only to SHBG. Therefore, free levels of estrogens or androgens may
be related to this number of menstrual cycles estimate, reflecting lifetime exposure to ovarian hormones. |
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Keywords: | Reproductive Characteristics Breast Cancer Sex Hormones Steroids Cumulative number of menstrual cycles Risk Factors |
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