Body composition and bone mineral distribution during growth in females.

The total mass of lean tissue, fat and bone mineral was measured in a cross-sectional study by dual-photon absorptiometry in 76 normal, ambulatory females aged 8 to 26 years. These measurements allowed quantification of average total-body bone mineral density and assessment of the mass and the average density of bone mineral in different regions of the body, specifically the head and the legs. Both total-body and regional results are presented as logistic functions of age; the functions were derived by nonlinear regression analysis. Normal ranges, defined as twice the root mean square deviation about the fitted equation, are also expressed as functions of age. As well as providing normal reference values, these data suggest that muscle mass is an important determinant of total-body bone mineral mass and that peak bone mass is achieved at different ages in different regions of the skeleton.