Although some studies have reported a relationship between several candidate polymorphic genes and bone mineral density (BMD), little is known concerning the genetic factors influencing BMD in children. This study examined this relationship in healthy Japanese girls (n=125; age, 13.4 +/- 0.89 years; range, 12-15 years). We investigated allelic variants of the vitamin D receptor (VDR) gene, the estrogen receptor (ER) gene, the parathyroid hormone (PTH) gene, the Ca-sensing receptor (CaSR) gene, and the beta3-adrenergic receptor (beta3-AR) gene. The genotype of the VDR gene (Fok I) correlated with lumbar spine, and femoral neck BMD. The PTH polymorphisms (BstB I, Dra II) were also associated with lumbar spine BMD. No relationship was found between genotypes of the ER gene, CaSR gene, or beta3-AR gene and BMD. The age, height, weight, and body mass index did not differ significantly among girls with different VDR and PTH genotypes. These results suggest that the Fok I polymorphism of the VDR gene and the Dra II polymorphism of the PTH gene are risk factors for low bone density in Japanese girls.

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Both genetic and environmental factors have been shown to contribute to the determination of bone density. To clarify the interaction between genetic and environmental factors affecting peak bone mass, we investigated the correlation between bone mineral density (BMD) and physical constitution, vitamin D receptor (VDR) genotype, age, age of menarche, history of menstrual dysfunction, and exercise in 157 healthy young Japanese women. History of exercise and menstrual dysfunction were significant independent predictors of BMD. The VDR genotype also affects peak bone density. Exercise has been shown to increase BMD in a similar way for each VDR genotype including those women who have the particular genotype associated with low bone density. This data indicate that there are complex gene-environmental interactions particularly in relation to menstrual history, exercise, and genetic factors during childhood/adolescence that may have implications for the development of adult BMD in women.

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