Bone mineral accretion and its relationship to growth, sexual maturation and body composition during childhood and adolescence.

Bone mineral accretion during childhood and adolescence is subject to a number of influences, including body composition changes, sexual maturation and growth. Bone mass and density increase with age and vary by sex, so bone health must be evaluated like other growth outcomes, i.e. in relation to age- and sex-specific reference ranges. Peak bone mass, the amount of bone acquired at the end of skeletal development is an important determinant of lifelong skeletal health. The timing of puberty is inversely related to peak bone mass, such that individuals who experience puberty at older ages have lower bone mass in young adulthood. Height, an indicator of skeletal size, is correlated with bone mineral content and density. Even more importantly, children who are tall for their age have greater bone mass and density than children of average or short stature. Body composition, particularly lean body mass, has a positive effect on bone accretion because of the mechanical strains of muscle mass on bone accretion. The effect of height growth is positively associated with bone accretion, but the magnitude of the effect is not the same at all pubertal stages; in Tanner stage 5, height growth has a more pronounced effect on bone accretion than at the beginning of puberty. Understanding these complex relationships is essential to understanding bone metabolism during this part of the life cycle and the challenges of assessing bone health in children with medical conditions that threaten bone health.