Kenny A M, Prestwood K M, Marcello K M, Raisz L G
Center on Aging, University of Connecticut Health Center, Farmington 06030-5215, USA.
J Gerontol A Biol Sci Med Sci. 2000 Sep;55(9):M492-7. doi: 10.1093/gerona/55.9.m492.
Osteoporosis is a significant problem in older men, 30% of all hip fractures occur in men and the mortality rate following hip fracture exceeds that of women. Testosterone is thought to be important in the development of peak bone mass hut its role in age-related bone loss is not established. The purpose of this study was to define the predictors of bone mass ill healthy older men with low testosterone levels but without symptomatic osteoporosis.
Eighty-three community-dwelling white men, aged more than 65 years old, selected for low bioavailable testosterone levels (< or = 4.44 nmol/l) participated in a cross-sectional study located at a university general clinical research center. Sex hormone concentrations and markers of bone turnover were assayed in serum and urine. Risk factors for osteoporosis and physical activity were ascertained by physical examination and questionnaire, including the Physical Activity Scale in the Elderly (PASE) questionnaire. Bone mineral densities of the femoral neck (FN BMD), spine, and whole body were measured by dual x-ray absorptiometry. Lower extremity muscle strength (1 repetition maximum) was measured using a leg press machine.
Mean bone mineral density values were 0.93 +/- 0.14 g/cm2 for femoral neck, 1.31 +/- 0.23 g/cm2 for spine, and 1.22 +/- 0.12 g/cm2 for whole body. Thirty-one of the 82 subjects (37%) had t scores < -1 and 12 of 82 subjects (15%) had t scores < -2.5 at the femoral neck. Multiple linear regression analysis demonstrated that bioavailable testosterone, body mass index (BMI), and PASE scores were positively correlated with, and significant predictors of, femoral neck BMD, accounting for 34.4% of the variance in FN BMD (F = 10.10, p = .001). Examining each variable independently, bioavailable testosterone accounted for 20.7%, physical activity score for 9.0%, and BMI for 6.5% of FN BMD. Using analysis of variance, mean values for FN BMD were significantly different between men grouped by tertile of bioavailable testosterone (F = 6.192, p = .003). FN BMD mean values were 0.86 +/- 0.14 g/cm2 for the lowest tertile, 0.94 +/- 0.16 for the middle tertile, and 0.99 +/- 0.14 for the highest tertile. Markers of bone turnover were inversely correlated, and strength directly correlated with BMD, but did not contribute to the multiple regression model.
Fifty-two percent of older men with low bioavailable testosterone levels had BMD levels below the young adult normal range and are likely at an increased risk of fracture. Bioavailable testosterone, BMI, and physical activity scores were significant determinants of FN BMD in these men. These variables are potentially modifiable and, therefore, amenable to intervention. Hence, our results suggest the need for testosterone replacement and physical activity intervention trials in men at risk for osteoporotic fractures.
骨质疏松症在老年男性中是一个重要问题，所有髋部骨折中有30%发生在男性身上，且髋部骨折后的死亡率超过女性。睾酮被认为在峰值骨量的发育中很重要，但其在与年龄相关的骨质流失中的作用尚未明确。本研究的目的是确定睾酮水平低但无症状性骨质疏松症的健康老年男性骨量的预测因素。
83名年龄超过65岁、社区居住的白人男性，因生物可利用睾酮水平低（≤4.44 nmol/l）入选一项位于大学综合临床研究中心的横断面研究。检测血清和尿液中的性激素浓度及骨转换标志物。通过体格检查和问卷确定骨质疏松症的危险因素及身体活动情况，包括老年人身体活动量表（PASE）问卷。采用双能X线吸收法测量股骨颈（FN BMD）、脊柱和全身的骨密度。使用腿部推举机测量下肢肌肉力量（1次重复最大值）。
股骨颈的平均骨密度值为0.93±0.14 g/cm²，脊柱为1.31±0.23 g/cm²，全身为1.22±0.12 g/cm²。82名受试者中有31名（37%）股骨颈的t值＜-1，82名受试者中有12名（15%）股骨颈的t值＜-2.5。多元线性回归分析表明，生物可利用睾酮、体重指数（BMI）和PASE评分与股骨颈骨密度呈正相关，且是其显著预测因素，占FN BMD方差的34.4%（F = 10.10，p = 0.001）。单独检查每个变量时，生物可利用睾酮占FN BMD的20.7%，身体活动评分占9.0%，BMI占6.5%。使用方差分析，按生物可利用睾酮三分位数分组的男性之间，FN BMD的平均值有显著差异（F = 6.192，p = 0.003）。最低三分位数组的FN BMD平均值为0.86±0.14 g/cm²，中间三分位数组为0.94±0.16，最高三分位数组为0.99±0.14。骨转换标志物与骨密度呈负相关，力量与骨密度呈正相关，但对多元回归模型无贡献。
52%生物可利用睾酮水平低的老年男性骨密度水平低于年轻成人正常范围，骨折风险可能增加。生物可利用睾酮、BMI和身体活动评分是这些男性FN BMD的显著决定因素。这些变量可能是可改变的，因此适合进行干预。因此，我们的结果表明需要对有骨质疏松性骨折风险的男性进行睾酮替代和身体活动干预试验。
