Hum. Reprod. Advance Access originally published online on January 28, 2008
Human Reproduction 2008 23(4):919-927; doi:10.1093/humrep/dem432
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17-β-Estradiol in relation to age at menarche and adult obesity in premenopausal women
1 Department of Oncology, Ullevål University Hospital, 0407 Oslo, Norway 2 Department of Biostatistics, Institute of Basic Medical Sciences, University of Oslo, Oslo, Norway 3 Applied Research Program, Division of Cancer Control and Population Sciences, National Cancer Institute, EPN 4005, 6130 Executive Boulevard, MSC 7344, Bethesda, MD 20892-7344, USA 4 NORM Surveillance Program for Antimicrobial Resistance in Human Pathogens, Department of Microbiology and Infection Control, University Hospital of North Norway, N-9038 Tromsø, Norway 5 Institute of Community Medicine, Faculty of Medicine, University of Tromsø, N-9037 Tromsø, Norway 6 Department of Anthropology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA 7 Department of Epidemiology and Population Studies, Jagiellonian University, Collegium Medicum, Krakow, Poland 8 Institute of Population-Based Cancer Research, Cancer Registry of Norway, Montebello, N-0310 Oslo, Norway 9 The Research Council of Norway, PO Box 2700, St Hanshaugen, N-0131 Oslo, Norway
10 Correspondence address. Tel: +47-95-93-06-82; Fax: +47-23-02-68-31; E-mail: aina.emaus{at}medisin.uio.no
BACKGROUND: We hypothesize that premenopausal endogenous estradiol may be associated with age at menarche and adult overweight and obesity, potentially contributing to breast cancer risk.
METHODS: We assessed age at menarche by questionnaire among 204 healthy Norwegian women, aged 25–35 years. Measures of body composition included body mass index (BMI, kg/m2), waist circumference (WC, cm), waist-to-hip ratio (WHR) and fat percentage dual energy X-ray absorptiometry, (DEXA). Daily salivary 17-β-estradiol (E2) concentrations were collected throughout one entire menstrual cycle and assessed by radioimmunoassay (RIA). Linear regression analyses and linear mixed models for repeated measures were used and potential confounding factors and effect modifiers were tested.
RESULTS: Among women with an early age at menarche (
12 years), the overall mean salivary E2 concentration increased by 3.7 pmol/l (95% confidence interval, 1.8–5.7 pmol/l) with each 9.8 cm (1 SD) increase in WC, which represents a 20.7% change in the mean for the total group. Among the same early maturers, a 1 SD (0.06) change in WHR was directly associated with a 24.0% change in mean E2 concentration for the total group.
CONCLUSIONS: Our findings support the hypothesis that early age at menarche, together with adult overweight and obesity, result in high levels of 17-β-estradiol throughout the menstrual cycle.
Key words: 17-β-estradiol/age at menarche/adult body fatness/breast cancer risk/Norway
Submitted on August 29, 2007; resubmitted on November 28, 2007; accepted on December 20, 2007.