Bone Abstracts

Objective: To describe changes in the muscle–bone unit, assessed as the ratio of bone mineral content (BMC) to lean body mass (LBM) at skeletal sites during puberty in Indian males and females, after adjusting for age and fat.

Methods: Data on arm, leg and total body (less head) BMC, LBM and fat mass (FM) assessed by DXA for 888 apparently healthy children and adolescents (426 females), 5–17 years of age from a cross-sectional study used to generate bone mineral density reference data were used (Bone 2011 48 (4) 810–819). Tanner staging (TS) was performed. Amount of BMC per unit LBM (arms, legs and total body) was computed. Linear regression was performed to examine change in mean BMC/LBM at various TS (adjustment: age, fat).

Results: Mean total BMC/LBM increased significantly (7.7%) at successive TS from 1 (4.76±0.04) to 4 and by 5% from stage 4 to 5 (adjusted for age) in females (P<0.001). In males, % increase in total BMC/LBM was small (1.8 to 4%) and insignificant from TS 1 (4.89±0.05) to 4 (P>0.1) but increased significantly by 7.4% from 4 to 5 (P<0.001). Similar results were seen for total BMC/LBM adjusted for fat. Significant increase of 6.6–14.7% in mean arm BMC/LBM (age adjusted) was seen in females; in males increase (7.4%) was significant only from stage 1 to 2 and 4 to 5 (4.9%) (P<0.001). BMC/LBM increased significantly by 18.5% from stage 3 to 4 in males (P<0.001); increase in leg BMC/LBM in females was small (P>0.1).

Conclusion: BMC for LBM increased with TS, but was more marked at arms and total body in females; this ‘extra’ BMC may act as a reservoir for later demands of pregnancy and lactation.