Bone Abstracts

Puberty is a time for the development of sexual dimorphism in bone and muscle. The aim of this study was to compare sex differences in bone and muscle variables using high-resolution peripheral QCT (HR-pQCT) and jumping mechanography (JM) in children and adolescents. We hypothesised that sex differences to muscle force and power (Fmax and Pmax) may explain differences in bone strength.

Total cross-sectional area and density (Tt.CSA and D100), cortical bone mineral and tissue density (Ct.BMD and Ct.TMD), area and porosity (Ct.Ar and Ct.Po), trabecular density, number and thickness (BV/TV, Tb.N, and Tb.Th) were measured by HR-pQCT at the 8% distal tibia. Fmax and Pmax were measured using JM. Sex differences were tested using multiple regression, adjusting for: sex, age, age², puberty, height, weight, Fmax and Pmax. Sex-by-puberty and sex-by-Fmax or Pmax interactions were tested. Data are presented as beta-coefficient (%) and P-value.

151 children (76 Females) aged 8–16 years were recruited. Fmax was associated with Ct.Ar, D100, BV/TV, Ct.Po, Tb.N and Tb.Th. Females had higher D100 (17%, P<0.01), Ct.BMD (11%, P<0.001), and Ct.TMD (5%, P<0.05) compared to males for a given Pmax, a difference that was greater at higher Pmax. Ct.Po (56%, P<0.001) and Tb.N (12%, p<0.01) were positively associated with Pmax in males, but not in females. Conversely, Tb.Th (17%, P<0.01) was positively associated with Pmax in females but not in males.

Our data suggest that sex differences in bone adaptation to Pmax during puberty exist. For a given Pmax, females accrue more bone than males. Pmax was positively associated with bone microarchitecture in males but not in females. This could be due to effects of oestrogen on mechano-sensitivity in the bones of females and testosterone-related increases in muscle function in males. These sex differences in bone adaptation may contribute to differences in bone phenotype and strength in adulthood.

Disclosure: The authors declared no competing interests.