Bone mass in young adults: Relationship with gender, weight and genetic factors

Abstract

Objectives. To determine the relationship of the bone mass attained in young adults with anthropometric and genetic factors. Design. Cross-sectional study of normal individuals. Methods. We studied 341 healthy subjects between 22 and 45 years of age. Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DXA) and correlated with body weight, height and nine polymorphisms in six genes involved in sex steroid metabolism (17-hydroxylase, aromatase and 5-reductase) and activity (oestrogen receptors (ER)-α and -β, and androgen receptor). Results. The BMD was higher in men than in women (spine: 1.048 ± 0.120 vs. 1.034 ± 0.112; hip: 0.907 ± 0.131 vs. 0.822 ± 0.104 g cm-2, P < 0.001). However, the difference was due, at least in part, to the larger body size in men and diminished markedly after height adjustment. There was a negative correlation between age and hip BMD. Body weight was the single most influential factor on spine and hip BMD in both sexes, explaining 8-9% of BMD variance. Amongst the genetic factors studied, a common CA repeat polymorphism in ER-β showed a significant association with BMD in women (P = 0.03 at the spine, and 0.008 at the hip). The relationship between ER-β genotype and BMD persisted after adjustment by body weight and age, explaining a further 2-3% of BMD variance. Allelic variants of other genes studied were not related with BMD. Conclusions. Body weight and allelic variants of ER-β are associated with BMD in young adults. © 2005 Blackwell Publishing Ltd.