Su Yon Jung1, Mara Z Vitolins2, Electra D Paskett3, Shine Chang4. 1. Department of Epidemiology, Division of Cancer Prevention and Population Sciences, The University of Texas MD Anderson Cancer Center, Houston. sjung@mdanderson.org. 2. Department of Epidemiology and Prevention, Division of Public Health Sciences, Wake Forest School of Medicine, Winston-Salem, North Carolina. 3. Division of Cancer Prevention and Control, College of Medicine, Ohio State University, Columbus. 4. Department of Epidemiology, Division of Cancer Prevention and Population Sciences, The University of Texas MD Anderson Cancer Center, Houston.
Abstract
BACKGROUND: The role of exogenous estrogen use in racial differences in insulin-like growth factor-I (IGF-I) levels which affect cancer risk is unclear. We investigated whether the relationship between race and circulating bioactive IGF-I proteins was mediated by exogenous estrogen and the extent to which exogenous estrogen influenced the race-IGF-I relationship in postmenopausal women. METHODS: This cross-sectional study included 636 white and 133 African American postmenopausal women enrolled in an ancillary study of the Women's Health Initiative Observational Study. To assess exogenous estrogen use (nonusers [n = 262] vs users [n = 507]) as a mediator of the race-IGF-I relationship, we used the Baron-Kenny method and an estimation of the proportional change in the odd ratios for IGF-I levels on race plus a bootstrapping test for the significance of the mediation effect. RESULTS: Compared with white women, African American women were more likely to have high IGF-I levels and less likely to use exogenous estrogen. After accounting for race, estrogen nonusers had higher IGF-I levels than estrogen users did. Among oral contraceptive ever users, exogenous estrogen had a strong mediation effect (67%; p = .018) in the race-IGF-I relationship. In the women with a history of hypertension, exogenous estrogen explained racial differences in IGF-I levels to a modest degree (23%; p = .029). CONCLUSIONS: Exogenous estrogen use has a potentially important role in disparities in IGF-I bioactivity between postmenopausal African American and white women. A history of oral contraceptive use and hypertension may be part of the interconnected hormonal pathways related to racial differences in IGF-I levels.
BACKGROUND: The role of exogenous estrogen use in racial differences in insulin-like growth factor-I (IGF-I) levels which affect cancer risk is unclear. We investigated whether the relationship between race and circulating bioactive IGF-I proteins was mediated by exogenous estrogen and the extent to which exogenous estrogen influenced the race-IGF-I relationship in postmenopausal women. METHODS: This cross-sectional study included 636 white and 133 African American postmenopausal women enrolled in an ancillary study of the Women's Health Initiative Observational Study. To assess exogenous estrogen use (nonusers [n = 262] vs users [n = 507]) as a mediator of the race-IGF-I relationship, we used the Baron-Kenny method and an estimation of the proportional change in the odd ratios for IGF-I levels on race plus a bootstrapping test for the significance of the mediation effect. RESULTS: Compared with white women, African American women were more likely to have high IGF-I levels and less likely to use exogenous estrogen. After accounting for race, estrogen nonusers had higher IGF-I levels than estrogen users did. Among oral contraceptive ever users, exogenous estrogen had a strong mediation effect (67%; p = .018) in the race-IGF-I relationship. In the women with a history of hypertension, exogenous estrogen explained racial differences in IGF-I levels to a modest degree (23%; p = .029). CONCLUSIONS: Exogenous estrogen use has a potentially important role in disparities in IGF-I bioactivity between postmenopausal African American and white women. A history of oral contraceptive use and hypertension may be part of the interconnected hormonal pathways related to racial differences in IGF-I levels.
Authors: Erin J Aiello; Shelley S Tworoger; Yutaka Yasui; Frank Z Stanczyk; John Potter; Cornelia M Ulrich; Melinda Irwin; Anne McTiernan Journal: Cancer Epidemiol Biomarkers Prev Date: 2005-06 Impact factor: 4.254
Authors: William L Haskell; I-Min Lee; Russell R Pate; Kenneth E Powell; Steven N Blair; Barry A Franklin; Caroline A Macera; Gregory W Heath; Paul D Thompson; Adrian Bauman Journal: Med Sci Sports Exerc Date: 2007-08 Impact factor: 5.411
Authors: A Lukanova; E Lundin; A Zeleniuch-Jacquotte; P Muti; A Mure; S Rinaldi; L Dossus; A Micheli; A Arslan; P Lenner; R E Shore; V Krogh; K L Koenig; E Riboli; F Berrino; G Hallmans; P Stattin; P Toniolo; R Kaaks Journal: Eur J Endocrinol Date: 2004-02 Impact factor: 6.664
Authors: Valerie A McCormack; Mitch Dowsett; Elizabeth Folkerd; Nichola Johnson; Claire Palles; Ben Coupland; Jeff M Holly; Sarah J Vinnicombe; Nicholas M Perry; Isabel dos Santos Silva Journal: Breast Cancer Res Date: 2009-06-22 Impact factor: 6.466