title: Bone mass in young adults: relationship with gender, weight and genetic factors.
abstract: OBJECTIVE
  To determine the relationship of the bone mass attained in young adults with anthropometric and genetic factors.
  
  
  METHODS
  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)-alpha and -beta, 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-beta showed a significant association with BMD in women (P = 0.03 at the spine, and 0.008 at the hip). The relationship between ER-beta 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-beta are associated with BMD in young adults.
authors.affiliation: Department of Internal Medicine, Hospital U.M. Valdecilla, Santander, Spain.
authors.forename: C
authors.initials: C
authors.lastname: Valero
authors.forename: M T
authors.initials: MT
authors.lastname: Zarrabeitia
authors.forename: J L
authors.initials: JL
authors.lastname: Hernández
authors.forename: A
authors.initials: A
authors.lastname: Zarrabeitia
authors.forename: J
authors.initials: J
authors.lastname: González-Macías
authors.forename: J A
authors.initials: JA
authors.lastname: Riancho
mesh_terms: D015502:Absorptiometry, Photon / Q000379:methods; D000328:Adult; D001141:Aromatase / Q000235:genetics; D001827:Body Height / Q000502:physiology; D001835:Body Weight / Q000502:physiology*; D015519:Bone Density / Q000235:genetics / Q000502:physiology*; D005260:Female; D005787:Gene Frequency; D006801:Humans; D008019:Life Style; D008297:Male; D008875:Middle Aged; D010088:Oxidoreductases / Q000235:genetics; D011110:Polymorphism, Genetic / Q000235:genetics*; D011944:Receptors, Androgen / Q000235:genetics; D011960:Receptors, Estrogen / Q000235:genetics; D012737:Sex Factors; D013254:Steroid 17-alpha-Hydroxylase / Q000235:genetics
chemical_list: D011944:Receptors, Androgen; D011960:Receptors, Estrogen; D010088:Oxidoreductases; D001141:Aromatase; D013254:Steroid 17-alpha-Hydroxylase