JCEM：肥胖青少年有更强壮的骨骼

肥胖对青春期骨发育的影响存在争议。为了确定在骨成熟、肌肉体积和力量发育、以及循环性类固醇激素和IGF–1部分重叠的男性肥胖青少年（ObAs），体积骨密度（vBMD）和骨几何学的差异，假设骨参数变化在承重点更明显，而且血清雌二醇的变化最突出，来自比利时根特大学医院内分泌科的Sara Vandewalle教授及其团队进行了一项研究，该研究发现ObAs在前臂和小腿有更大和更强壮的骨骼。骨骼参数的差异可以被骨成熟增加、更多的雌激素暴露、以及由更高的肌肉体积和强度导致的更重的机械负荷联合解释。该研究结果在线发表在2013年5月10日的美国《临床内分泌代谢杂志》（The journal of endocrinology & metabolism）上。

该研究中，在居民减肥计划项目中招募了51例ObAs（10-19岁）和51例健康的年龄相匹配对照者及51例骨骼、年龄相匹配的对照者。通过外周定量CT研究前臂和小腿的vBMD和骨几何学参数，以及肌肉和脂肪面积。通过跳跃试验研究肌力。

该研究结果表明，除了骨成熟增加外，在不同的青春期阶段，在ObAs的桡骨和胫骨也观察到了骨小梁参数（更高的vBMD和更大的骨小梁面积）和皮质骨几何参数（更大的皮质面积和骨外膜及骨内膜周径）的差异。在匹配骨龄后，所有在胫骨的差异仍有意义，但在桡骨仅有骨小梁vBMD的差异仍有意义。与对照组相比，在ObAs发现更多的肌肉面积和更高的最大肌力，以及更高的循环游离雌激素，但游离睾酮和IGF–1水平与对照组相似。

该研究发现，ObAs在前臂和小腿有更大和更强壮的骨骼。骨骼参数的差异可以被骨成熟增加、更多的雌激素暴露、以及由更高的肌肉体积和强度导致的更重的机械负荷联合解释。

Bone Size and Bone Strength Are Increased in Obese Male Adolescents.
Abstract
Context:Controversy exists on the effect of obesity on bone development during puberty.Objective:Our objective was to determine differences in volumetric bone mineral density (vBMD) and bone geometry in male obese adolescents (ObAs) in overlap with changes in bone maturation, muscle mass and force development, and circulating sex steroids and IGF-I. We hypothesized that changes in bone parameters are more evident at the weight-bearing site and that changes in serum estradiol are most prominent.Design, Setting, and Participants:We recruited 51 male ObAs (10-19 years) at the entry of a residential weight-loss program and 51 healthy age-matched and 51 bone-age-matched controls.Main Outcome Measures:vBMD and geometric bone parameters, as well as muscle and fat area were studied at the forearm and lower leg by peripheral quantitative computed tomography. Muscle force was studied by jumping mechanography.Results:In addition to an advanced bone maturation, differences in trabecular bone parameters (higher vBMD and larger trabecular area) and cortical bone geometry (larger cortical area and periosteal and endosteal circumference) were observed in ObAs both at the radius and tibia at different pubertal stages. After matching for bone age, all differences at the tibia, but only the difference in trabecular vBMD at the radius, remained significant. Larger muscle area and higher maximal force were found in ObAs compared with controls, as well as higher circulating free estrogen, but similar free testosterone and IGF-I levels.Conclusions:ObAs have larger and stronger bones at both the forearm and lower leg. The observed differences in bone parameters can be explained by a combination of advanced bone maturation, higher estrogen exposure, and greater mechanical loading resulting from a higher muscle mass and strength.