Bone mineral density acquisition in peripubertal female rhythmic gymnasts is directly associated with plasma IGF1/IGF-binding protein 3 ratio.
Résumé
OBJECTIVES: Intense physical activity in peripubertal girls may delay menarche and cause menstrual disorders and estrogen deficiency, particularly in sport disciplines that require strict weight control. It may also have a deleterious effect on bone mass acquisition. The aim of this study was to determine the time-course of bone mass accretion in peripubertal elite female rhythmic gymnasts (FRGs) over a 1-year period, as well as the anthropometric and hormone parameters that could be helpful for predicting bone mineral density (BMD) gain. METHODS AND DESIGN: We conducted a 1-year follow-up study in 29 FRGs (10.7-16.1 years old). Whole body composition and BMD of the whole body, proximal femur, lumbar spine, mid-radius, and skull were measured by dual energy X-ray absorptiometry (DXA). Moreover, baseline growth- and bone metabolism-related hormones such as IGF1, IGF-binding protein 3 (IGFBP3), leptin, and bone markers were measured. RESULTS: BMD increased significantly at all bone sites throughout puberty, particularly between Tanner stages II and IV-V (P=0.025 to P<0.001). The IGF1 level, IGF1/IGFBP3 ratio, and leptin level were higher in late pubertal stages (i.e. IV-V) compared with early stage (i.e. I). In simple and multivariate analyses, only the IGF1/IGFBP3 ratio was strongly correlated with the BMD change at all bone sites (r=0.49, P=0.02 to r=0.77, P<0.0001). CONCLUSION: This 1-year follow-up study of peripubertal FRGs showed that BMD gain was maximal around Tanner stage III. The plasma IGF1/IGFBP3 ratio was associated with bone mass acquisition in this period, and it may thus serve as a surrogate marker of bone mass gain in this population.