TOTAL-BODY BONE-MINERAL MEASUREMENTS IN CHILDREN WITH PRADER-WILLI-SYNDROME - THE INFLUENCE OF THE SKULLS BONE-MINERAL CONTENT PER AREA (BMA) AND OF HEIGHT

Background. The aim of this study was to investigate the influence of body height and growth on total body measurements with dual energy X-r ay absorptiometry (DEXA) in children. Material and methods. Seventeen children with Prader-Willi syndrome were studied as part of a clinical investigation ion of the effect of growth hormone (Genotropin) treatm ent. Bone mineral areal mass (BMA), in g/cm(2), was studied with DEXA at 0, 12, 24 and 30 months after the start of the study, The effect of increased bone volume on BMA was studied by making a rough estimate o f bone width, which was correlated with BMA. Results. There was a weak correlation between total body BMA and body height (r = 0.58), which increased after exclusion of the head (r = 0.84). The BMA of the head was more than twice as high as that of the rest of the body. In the sh ortest children more than 50 % of the total bone mineral was contained in the skull, which decreased with height to below 20 % in the talles t children. The correlation between the so-called bone width and BMA ( total body, head excluded) was 0.97. Conclusion. The results indicate that (a) the bone mineral content (BMC) of the head and (b) the bone v olume and body height have a major influence on BMA measurements with DEXA in children. A theoretical method for evaluating the relative bon e density (g/cm(3))has also been described.