Endocrine Abstracts

Objectives: This study aimed at determining the age of PBM and the age-specific relationships between calcium intake or serum 25(OH) D and bone mineral density (BMD) in Iranian adolescents.

Design and Methods: A group of 187 healthy individuals of age 10-20 years was recruited. Using dual x-ray absorptiometry, areal BMD at femoral neck (aNBMD) and lumbar vertebrae (L2-L4) (aLBMD) were measured. Bone mineral apparent (volumetric) density (gram per cm ³) of the vertebral cube (L2-L4) (LBMAD) and femoral neck (NBMAD) were also determined. Stage of puberty was determined and food frequency questionnaires were filled out to estimate daily calcium intake. Serum level of 25(OH) D was determined.

Results: The aLBMD and LBMAD nearly reached their peak at age 17.8 and 17 yr in girls; while neither reached their peak in boys. Both aNBMD and NBMAD increased with age until they plateaued around the ages of 15yr and 16yr in girls and 18.5yr and 19yr in boys. In subjects who were going through puberty (tanner: II, III, IV) serum 25(OH) D status along with age and weight predict 61% of aNBMD variations (p<0.0001). Among these participants (from whom 52% were vitamin D deficient), age and serum 25(OH) D status were predictors (25%, p<0.0001) of NBMAD. Mean of daily calcium intake was 846.7±382.5 milligram per day and again in participants who were going through puberty, NBMAD correlated with calcium intake (spearman rho=0.228, p<0.05) even when age was taken into account.

Conclusion: We conclude that PBM is mainly achieved by late adolescence in Iranians as in Caucasians. Calcium intake and vitamin D play crucial roles in accumulation of bone mass during critical years of pubertal maturation. These findings may be prerequisite of preventive programs aim at maximizing PBM.