Association between estrogen receptor-β dinucleotide repeat polymorphism and incidence of femoral fracture

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Estrogens are thought to play an important role in bone metabolism through estrogen receptors (ER). Dinucleotide (cytosine-adenine, CA) repeat polymorphism in the human ER-β gene (ESR2) has been reported to be associated with bone mineral density. We aimed to further elucidate the importance of this polymorphism in the pathogenesis of osteoporosis by examining its association with the incidence of femoral fracture. Deoxyribonucleic acids extracted from the renal cortex of 1489 consecutive Japanese autopsies (799 male, mean age 79years, 690 female, mean age 82years) with complete clinical/pathological data were enrolled in the study. ESR2 CA repeat polymorphism was determined by polymerase chain reaction using fluorescein-labeled primers. The presence or absence of femoral fracture during each subject's lifetime was determined by thorough examination of the clinical record. Incidence of femoral fracture in subjects bearing at least one allele of 20 CA repeats (4/132, 3.0%) was significantly lower than in those without this allele (127/1357, 9.4%, P=0.0098). After adjustments for age and sex, logistic regression analysis revealed that having no allele of 20 CA repeats was an independent risk factor of femoral fracture [adjusted odds ratio (OR) 3.875, 95% confidence interval (CI) 1.392-10.788, P=0.0095], which was emphasized among women (adjusted OR 6.360, 95% CI 1.520-26.618, P=0.0133). Japanese subjects, especially women, bearing at least one allele of 20 CA repeats in the ESR2 may have a lower risk of femoral fracture than those without it, suggesting this polymorphism plays a role in bone metabolism.