Bone Abstracts

Objectives: AIS is associated with both low bone mass and elevated serum bone alkaline phosphatase. The greater the latitude of the geographical region, the higher is the prevalence of AIS. These specific features were compatible with the presence of either Vit-D insufficiency or abnormal physiology with Vit-D. It is important to evaluate these potentially treatable conditions regarding their roles in the etiopathogenesis of AIS. The objectives of this case-control study were to evaluate Vit-D status and its correlation with areal bone mineral density (aBMD) in AIS subjects and normal controls.

Methods: 215 AIS girls and 186 gender-matched non-AIS healthy controls (mean age 12.9±0.6 and 12.9±0.5 yeas old respectively, P=0.449) were recruited in the summer and winter season. aBMD at bilateral femoral necks was measured with dual energy X-ray absorptiometry (DXA) and serum 25(OH)Vit-D was measured with liquid chromatography–tandem mass spectroscopy.

Results: The mean aBMD at the right and left side for AIS subjects were 0.752±0.109 and 0.745±0.107, and that for controls were 0.785±0.114 and 0.785±0.117 g/cm² respectively. The mean 25(OH)Vit-D levels for AIS and controls were 41.6±14.4 and 39.5±11.5 nmol/l respectively(P=0.103). With multivariate linear regression analysis using aBMD as the dependent variable and after adjustment for age, body weight, armspan, season, physical activity and dietary calcium intake levels, the P value of the regression coefficient for 25(OH)Vit-D level for the right and left side for controls were 0.055 and 0.047, while that for AIS were 0.804 and 0.466 respectively.

Conclusion: Both the AIS and control group had mean 25(OH)Vit-D levels at the insufficiency range. The positive correlation between Vit-D level and aBMD that was seen in normal controls was not present in AIS subjects, thus spelling out the possibility of certain degree of Vit-D resistance being present in AIS. Whether the lack of correlation is responsible for low bone mass that characterizes AIS and how this is related to the etiopathogenesis of AIS warrant further studies.

Funding: Research Grants Council of the Hong Kong S.A.R., China (project nos: 468809 and 468411).