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- Title
Exogenous Estrogen as Mediator of Racial Differences in Bioactive Insulin-Like Growth Factor-I Levels Among Postmenopausal Women.
- Authors
Su Yon Jung; Vitolins, Mara Z.; Paskett, Electra D.; Chang, Shine
- 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.
- Subjects
ESTROGEN; SOMATOMEDIN; CANCER risk factors; BIOACTIVE compounds; POSTMENOPAUSE; HYPERTENSION
- Publication
Journals of Gerontology Series A: Biological Sciences & Medical Sciences, 2015, Vol 70, Issue 4, p495
- ISSN
1079-5006
- Publication type
Article
- DOI
10.1093/gerona/glu164