Abstract: Objective To study the relationship between lumbar and proximal femoral bone mineral density (BMD) with gender, age and body mass index (BMI) in adolescents ranged from 12 to 19 years of age in Tianjin city, and provide preliminary reference to understand the bone health status of adolescent in the city. Methods The BMD values of lumbar spine (L1-L4), femoral neck and total hip were detected by the dual-energy X-ray absorptiometry (DXA) in 221 adolescents from Tianjin Hospital, and the Z value was used for clinical diagnosis standard. Simultaneously the height and weight of adolescents were measured, and BMI was calculated. The differences of BMD values in the lumbar, femoral neck and total hip were compared between different age, gender and BMI groups. Results The BMD values of femoral neck and total hip were significantly higher in males than those in females (P < 0.01). The BMD values of lumbar spine, femoral neck and total hip were gradually increased with age. The BMD was correspondingly increased in adolescents with higher BMI in the lumbar spine, femoral neck and total hip. Conclusion There is a close relationship between BMD with age, gender and BMI in adolescents. We should pay more attention to the nutrition health and the level of BMI in adolescents.

Key words: bone density, osteoporosis, adolescent, body mass index, Z value