老年男性骨密度与年龄和性激素关系的研究

目的 探讨老年男性骨密度与年龄和性激素之间的关系.方法 双能X线吸收测定法(DEXA)测定360例老年男性腰椎正位(L1～4)、股骨颈、股骨大转子、ward's三角区和股骨干的骨密度,化学发光法测定血清总睾酮和雌二醇.根据年龄和骨密度进行分值,比较不同骨密度老年男性年龄和性激素的差异.结果 360例中共检出骨质疏松者48例,骨密度减少者72例,非骨质疏松者240例.老年男性股骨颈、股骨大转子、Ward's三角区、股骨干的骨密度随年龄的增长而下降(F值分别为3.038,3.029,3.024,3.021,P<0.05),年龄大于80岁组股骨颈、股骨大转子、Ward's三角区、股骨干骨密度分别为(0.701±0.140)、(0.682±0.185)、(0.629±0.211)、(0.986±0.160)g/cm2;年龄大于70岁组分别为(0.829±0.156)、(0.765±0.170)、(0.698±0.187)、(1.042±0.190)g/cm2;年龄大于60岁组分别为(0.875±0.138)、(0.800±0.130)、(0.731±0.145)、(1.071±0.125)g/cm2,但L1～4的骨密度差异无统计学意义(F=2.988,P>0.05).骨密度正常、骨密度减低和骨质疏松组血清总睾酮水平差异无统计学意义(F=3.032,P>0.05),而血清雌二醇水平在骨密度正常、骨密度减低和骨质疏松组分别为(180.6±62.3)、(130.5±39.9)、(110.5±68.5)ρmol/L,随骨密度减少,血清雌二醇水平降低,且差异有统计学意义(F=3.059,P<0.05).结论 老年男性骨密度随年龄增加而下降,雌激素水平可能影响老年男性骨质疏松的发生.     

Endogenous sex steroid, GH and IGF-I levels in normal elderly men: relationships with bone mineral density and markers of bone turnover.

There are studies concerning the association among endogenous sex steroids, growth hormone (GH), insulin-like growth factor-I (IGF-I) and bone mineral density (BMD) in both men and women. However, little is known concerning the association of these parameters with markers of bone turnover in healthy elderly men. We studied the association of BMD (dual energy X-ray absorptiometry of spine, hip and forearm) and markers of bone turnover (bone-specific alkaline phosphatase, serum C-terminal propeptide of type I collagen, and serum osteocalcin reflecting formation, urine deoxypyridinoline and calcium excretion in relation to creatinine excretion reflecting resorption) with endogenous sex steroids, GH and IGF-I in 14 elderly normal men (age range 60-79 years). There was a negative correlation between age and dehydroepiandrosterone sulphate (DHEAS) (r=-0.60, p=0.022) and a positive correlation between GH and IGF-I (r=0.53, p=0.048). Serum estradiol concentrations correlated with BMD at distal 1/3 radius (r=0.41, p=0.1) and mid-radius (r=0.47, p=0.08), and negatively correlated with age (r=-0.45, p=0.09). There was no correlation of estradiol with bone turnover markers, testosterone, free testosterone, DHEAS, GH and IGF-I. Serum GH and IGF-I levels showed no correlation with BMD (all sites) and bone turnover markers. Serum total testosterone concentrations positively correlated with BMD at distal 1/3 radius (r=0.47, p=0.09), femoral neck (r=0.56, p=0.037) and Ward's triangle (r=0.49, p=0.07). These data suggest that serum estradiol and testosterone levels are associated with BMD in elderly men, possibly indicating their contribution to skeletal maintenance in old age. However, correlations of IGF-I, GH and DHEAS with BMD and bone turnover markers are lacking in the group studied.     

Relationship of leptin and sex hormones to bone mineral density in men

Sex hormones are strongly associated with bone mineral density (BMD) in adult humans. Leptin, a hormonal product of the OB gene, also appears to be associated with BMD, but results from previous studies are conflicting. Most of the studies in this area have been in women and apparently none have simultaneously analyzed the relationship of estradiol, testosterone, and leptin with BMD in healthy men. To address these issues, serum sex hormones, sex-hormone-binding globulin (SHBG), leptin, dehydroepiandrosterone sulfate (DHEAS), and insulin were measured in 50 apparently healthy men, 18-66 years of age. After controlling for age and body mass index (BMI), BMD correlated positively with estradiol ( p=0.007) and testosterone ( p=0.019), but negatively with leptin ( p=0.001). No significant correlations between BMD and SHBG, DHEAS, or insulin were observed. In multiple regression analysis with age, BMI, estradiol, testosterone, and leptin as the independent variables, only age ( p<0.05), BMI ( p<0.001), and leptin ( p=0.004) were significantly related to BMD. These findings suggest that in men, leptin may have an important negative relationship with BMD.     

Relationship of serum leptin levels with body composition and sex steroid and insulin levels in men and women

Whether the higher serum leptin levels in women are due to gender differences in fat mass or to other factors such as sex steroids remains unclear. In addition to sex steroids, serum insulin levels also appear to be related to leptin levels, although whether this effect is independent of the effects of body composition is unclear. The purpose of this study was to identify the major determinants of circulating serum leptin levels. We studied a large, population-based cohort of 345 men (23 to 90 years), 137 premenopausal women (21 to 54 years), and 212 postmenopausal women (34 to 94 years), including 47 women on hormone replacement therapy (HRT). Serum leptin levels were related to body composition as assessed by dual-energy x-ray absorptiometry (DEXA) and to circulating sex steroid and insulin levels. Serum leptin levels remained significantly higher in women versus men even after adjustment for fat mass, and leptin levels were significantly correlated with fat mass independently of age. By univariate analyses, logarithmically transformed serum leptin levels correlated positively with bioavailable estrogen ([E] estradiol plus estrone) in postmenopausal women not on HRT, and negatively with total and bioavailable testosterone (T) levels in men. Serum insulin levels were directly related to leptin levels regardless of gender and age. By multivariate analyses, fat mass, lean mass, and insulin levels were the strongest predictors of leptin levels in all groups. In addition, bioavailable E entered the model in the postmenopausal women not on HRT. These studies indicate that the fat mass, lean mass, and insulin level are the major determinants of the serum leptin level in adults. Moreover, after adjusting for these variables, bioavailable E also explains a significant proportion of the variance in leptin levels among postmenopausal women not on HRT.     

Relationship of volumetric bone density and structural parameters at different skeletal sites to sex steroid levels in women

CONTEXT: Although estrogen clearly plays a central role in regulating bone mass in women, studies in men have suggested that there may be a threshold bioavailable (bio) estradiol (E2) level below which aging men begin to lose bone and that the threshold for estrogen deficiency in cortical bone may be considerably lower than that in trabecular bone. There are no data testing this in women. OBJECTIVE: Our objective was to assess volumetric bone mineral density (vBMD) and bone geometry by quantitative computed tomography and relate these to circulating bio E2 and bio testosterone levels. DESIGN: We studied a cross-sectional, age-stratified population sample of 235 women (age, 21-97 yr). RESULTS: vBMD/structural parameters were not related to sex steroid levels in young premenopausal women (age, 20-39 yr) with a median bio E2 level of 17 pg/ml (63 pmol/liter). By contrast, bio E2 and bio testosterone levels were both significantly associated with trabecular and cortical vBMD and cortical area at multiple sites in late postmenopausal women (age > or = 60 yr) who had a median bio E2 level of 3 pg/ml (11 pmol/liter). Late premenopausal and early postmenopausal women (age, 40-59 yr) with an intermediate median bio E2 level of 11 pg/ml (42 pmol/liter) showed age-adjusted correlations of bio E2 levels with trabecular but not with cortical vBMD. CONCLUSIONS: In women, bio E2 levels are associated with vBMD and some structural bone parameters at low but not high bio E2 levels. Similar to findings in men, the threshold for estrogen deficiency in cortical bone in women appears to be lower than that in trabecular bone.     

血清性激素水平与老年男性骨代谢指标及骨密度的关系

目的：探讨老年男性血清性激素表达水平与骨代谢指标及骨密度之间的关系。方法：收集老年男性患者230例,年龄65～95岁,分别测定雌二醇（E2）、睾酮、游离睾酮（FT）、性激素结合球蛋白（SHBG）、脱氢表雄酮（DHEA）、骨钙素、骨碱性磷酸酶（BALP）、25-羟维生素D3及尿Ⅰ型胶原交联氨基末端肽（NTX）等指标,同时利用双能X线分别测定髋关节及腰椎（L1～L4）的骨密度,分析老年男性骨密度、骨代谢指标与血清性激素以及年龄与骨密度的相关性。结果：血清E2、FT与腰椎及髋关节的骨密度呈正相关,而睾酮、SHBG、DHEA与骨密度无关。血清E2、FT与骨代谢指标NTX、BALP呈负相关,血清E2与25-羟维生素D3呈正相关,而睾酮、SHBG、DHEA与骨代谢指标NTX、BALP无关。年龄与腰椎L1、L2、L4、L1～4及髋部骨密度呈负相关,与腰椎L3骨密度无关。结论：老年男性骨密度的变化受性激素中FT、E2表达水平的影响,而受E2的影响程度超过雄激素。血清FT及血清E2的水平可作为老年男性骨质疏松症的独立观察指标。     

Relationship of sex steroid hormones with bone mineral density (BMD) in a nationally representative sample of men

Objective Sex steroid hormones influence bone mineral density (BMD) in women, but are less well‐studied in men. We evaluated the association of serum total and free sex steroid hormones and SHBG with osteopaenia in a nationally representative sample of men aged 20–90 years. Design BMD and sex steroid hormones were measured among participants in NHANES III, a cross‐sectional study of the US population. Population A total of 1185 adult men in morning examination session of Phase I of NHANES III (1988–91). Measurements Relation of oestradiol (E₂), testosterone, and SHBG concentrations with BMD. Osteopaenia was defined as 1–2·5   SD below the mean for white men aged 20–29 years. Results Men in the lowest quartile of free E₂ had 70% increased odds (OR = 1·69, 95% CI 0·95–2·98) of osteopaenia compared with men in the highest quartile. Men in the lowest quartile of free testosterone had nearly four times the odds of osteopaenia than those in the highest quartile (OR = 3·82, 95% CI 1·87–7·78). Lower concentrations of SHBG appeared protective against osteopaenia (P‐trend = 0·01). Neither total testosterone nor total E₂ was associated with BMD, although men with clinically low E₂ (< 20 ng/l) had lower BMD (0·930 g/cm², 95% CI 0·88–0·98) than men with normal‐range E₂ (1·024 g/cm², 95% CI 1·01–1·04; P = 0·004). Findings for free E₂ were most pronounced among elderly men, while the findings for free testosterone were most pronounced among younger men. Conclusions In this nationally representative study, men with lower free E₂, lower free testosterone, and higher SHBG concentrations in circulation were more likely to have low BMD.     

Polymorphisms of the SHBG gene contribute to the interindividual variation of sex steroid hormone blood levels in young, middle-aged and elderly men

Objective  In men there is a large interindividual variation of SHBG levels and consequently of testosterone (T) and E₂ levels. Family and twin studies suggested a strong genetic contribution, besides metabolic and hormonal influences. The aim of this study was to examine the influence of a missense mutation in exon 8 (Asp327Asn) and a (TAAAA)_n-repeat in the promoter region of the SHBG gene, on SHBG and sex steroid serum concentrations in a population of healthy men.
Design  SHBG and hormone levels were measured in 1485 men, contributed by three independent cohort studies and representing three different age groups (young, middle-aged and elderly men). The number of TAAAA-repeats was determined by fragment-analysis; carriers of the Asn³²⁷-allele were identified using restriction fragment length polymorphism analysis.
Results  In the different age groups, carriers of six TAAAA-repeats presented with higher SHBG (young 19%, middle-aged 20% and elderly 26%; P < 0·001) and T (young 9%, middle-aged 22% and elderly 21%; P < 0·05) levels compared to non-carriers. For free T, a modest increase was found for carriers in the middle-aged group, but not for the young and elderly group. E₂ and free E₂ did not differ between carriers and non-carriers in the different age-groups. The Asn³²⁷-allele was associated with higher mean SHBG (14·20%, P  < 0·001) and T levels (7·33%; P  = 0·01) in the middle-aged group only.
Conclusions  Our findings show that and the (TAAAA)_n-repeat and the Asp327Asn polymorphism contribute to the genetically determined interindividual variation in total serum T levels in healthy men through variation in SHBG concentrations.     

Relationship between leptin levels and bone mineral density in the elderly

OBJECTIVE: To assess the relationship between circulating leptin levels, bone mineral content and density in the elderly. DESIGN: A cross-sectional study. PATIENTS: A cohort of 92 men and 171 women, with ages ranging from 68 to 75 years, selected as a healthy and normal functioning group, in the city centre of Verona. MEASUREMENTS: Plasma leptin levels were determined in each participant. Body composition was evaluated with dual energy X-ray absorptiometry (DXA). Bone mineral content (BMC) and bone mineral density (BMD) were measured at whole-body, hip and femoral neck level in all subjects. RESULTS: In both men and women a significant relationship between fat mass and whole-body BMC or BMD was found. The strength of this association was consistently reduced after adjustment for plasma leptin. A significant association between circulating leptin levels, whole-body, total hip and femoral neck BMC and BMD was found in both sexes. This association retained the statistical significance after adjustment for fat mass percentage, especially in women. In stepwise multiple linear regression analyses, leptin was shown to be a significant predictor of whole-body, total hip and femoral neck BMC and BMD, independently of age and the percentage of body fat in both sexes. The circulating levels of leptin accounted for a variance in whole-body BMC of 8.9% in men and 18.2% in women, and in whole-body BMD of 10.6% in women. CONCLUSION: Our data show a significant relationship between leptin, bone mineral mass and density in healthy elderly men and women.     

Relationship between alcohol consumption and serum lipid levels in elderly Korean men

We evaluated the association between alcohol consumption and blood lipid levels in elderly Korean men. This was a cross-sectional study consisting of men (n=1893) aged 60 years and older from the Korea National Health and Nutrition Examination Survey (KNHANES) 2005-2009. Demographic characteristics and dietary intake were obtained from the participants using a questionnaire, and lipid levels were determined by blood-sample analyses. After adjusting for demographic and dietary factors, alcohol consumption was negatively associated with a risk for low high-density lipoprotein cholesterol (HDL-C) (p for trend<0.001), whereas the risk for high triglycerides increased with increasing alcohol consumption (p for trend=0.014). However, the odds ratios (ORs) of high non-HDL-C and the ratio of high triglycerides to HDL-C were not significantly different with alcohol drinking. These results suggest that light consumption of alcohol decreases the risk for dyslipidemia and that heavy alcohol consumption differentially affects lipid measures according to the amount of alcohol intake in elderly men.     

Longitudinal association between sex hormone levels, bone loss, and bone turnover in elderly men

Male osteoporosis is an increasingly important health problem. It is known that sex steroid hormones play an important role in regulating bone turnover and bone mass in males as well as in females. However, the exact mechanism of bone loss in men remains unknown. In the present study, 200 elderly men (age range, 55-85 yr) were followed for 4 yr to evaluate the relationships between hormone levels, bone turnover markers, bone mineral density, and rates of bone loss. Femoral and lumbar bone mineral density, bone ultrasound parameters at the os calcis, serum testosterone (T), serum estradiol (E(2)), SHBG levels, and bone turnover markers (urinary crosslaps and bone alkaline phosphatase) were evaluated for each man at enrollment and 4 yr afterward. The free androgen index (FAI) and free estrogen index (FEI) as well as measures of the bioavailable sex hormones [calculated bioavailable E(2) (c-bioE(2)) and T (c-bioT)] were calculated from total hormone levels and SHBG. In the total population, T, c-bioT, c-bioE(2), FAI, and FEI, but not E(2), decreased significantly with age, whereas SHBG increased significantly. Subjects with FEI, c-bioE(2), and E(2) levels below the median showed higher rates of bone loss at the lumbar spine and the femoral neck as well as higher speed-of-sounds decrease at the calcaneus with respect to men with FEI, c-bioE(2), and E(2) levels above the median. Serum bone alkaline phosphatase and urinary crosslaps were significantly higher in men with FEI, c-bioE(2), and E(2) in the lower quartile than in men with FEI, c-bioE(2), and E(2) levels in the higher quartile. No statistically significant differences were observed in relation to T, c-bioT, or FAI levels. Finally, the ratio between E(2) and T, an indirect measure for aromatase activity, increased significantly with age and was higher in normal than in osteoporotic subjects. In conclusion, results from the present study indicate an important role of estrogens, and particularly of the ability to aromatize T to E(2), in the regulation of bone loss and bone metabolism in elderly men.     

Genome-wide association studies on serum sex steroid levels

Even though the levels of circulating sex steroid hormones are to a large extent heritable, their genetic determinants are largely unknown. With the advent of genome-wide association studies (GWAS), much progress has been made and several genetic loci have been identified to be associated with serum levels of dehydroepiandrosterone sulfate, testosterone and sex hormone-binding globulin. The variants identified so far only explain a small amount of the overall heritability, but may help to elucidate the role of sex steroid hormones in common disorders such as hypogonadism, type 2 diabetes and hormone-sensitive cancers. This review provides an overview of the current state of knowledge of the genetic determinants of sex steroid hormones, with a focus on recent GWAS and brief directions for elucidating the remaining heritability.     

Growth hormone and sex steroid effects on bone metabolism and bone mineral density in healthy aged women and men.

BACKGROUND: Aging is associated with concomitant declines in activity of the growth hormone (GH) and gonadal steroid axes, and in bone mineral density (BMD), in both sexes. Long-term estrogen replacement slows bone loss and prevents fractures in postmenopausal women, whereas the effects of supplementation of GH or testosterone on bone metabolism and BMD in aged individuals remains uncertain. METHODS: Using a randomized, placebo-controlled, double-blind study design, we investigated the separate and interactive effects of 6 months of administration of recombinant human GH and/or gonadal steroids on bone biochemical markers and BMD in 125 healthy, older (>65 years) women (n = 53) and men (n = 72) with age-related reductions in GH and gonadal steroids. RESULTS: In women, administration of GH, but not GH + hormone replacement therapy (HRT), increased serum levels of osteocalcin and procollagen peptide (PICP) and increased urinary excretion of deoxypyridinoline (DPD) crosslinks. Urinary calcium excretion decreased after HRT. In men, GH, and to a greater extent GH + T, increased osteocalcin. GH increased serum PICP, and GH + T increased urinary DPD. Urinary calcium excretion was unaffected by hormone treatment in men. In women, administration of HRT and GH + HRT, but not GH, increased BMD at the lumbar spine, femoral neck, and distal radius. In men, GH + T led to a small decrease in BMD at the proximal radius; there were no other significant effects of hormone administration on BMD. CONCLUSIONS: These data suggest that short-term administration of HRT exerts beneficial effects on bone metabolism and BMD in postmenopausal women, which are not significantly altered by the coadministration of GH. In andropausal men, T administration to achieve physiologic levels did not result in significant effects on bone metabolism or BMD, whereas GH + T increased one marker of bone formation and decreased one marker of bone resorption. Given the known biphasic actions of GH on bone and the apparent favorable biochemical effects of GH + T in men, the longer-term effects of GH + T on BMD in aged men remain to be clarified.     

中老年男性血清性激素水平与动脉粥样硬化关系的探讨

目的：探讨中老年男性血清性激素水平变化及其与动脉粥样硬化发病间的关系。方法：中老年男性分为有和无颈动脉粥样硬化两组,年轻男性构成对照组,测定血浆总睾酮、雌二醇、促卵泡激素、促黄体生成素水平。结果：与对照组比较,中老年男性血睾酮水平显著降低,促卵泡素、促黄体生成素显著升高（P均〈0.05）,雌二醇水平无差异,但中老年男性动脉硬化组血睾酮与雌二醇之比值较无动脉硬化组显著降低（P〈0.05）。结论：中老年男性动脉硬化发病与血雄激素水平降低有关。     

不同骨量老年男性血清vaspin水平变化及意义

目的观察不同骨量老年男性血清内脏脂肪特异性丝氨酸酶抑制剂(vaspin)水平变化,并探讨其意义。方法选择在日照市人民医院健康查体的60~80岁的老年男性210例为研究对象,根据骨密度(BMD)将其分为正常组、骨量减少组、骨质疏松组。收集其基础资料(年龄、身高、体质量),测定血清学指标[血清Ca、血清P、血脂(TG、TC、LDL、HDL)、空腹葡萄糖(Glu)]及骨代谢五项,后者包括甲状腺旁腺素(PTH)、25羟维生素D[25(OH)D]、骨钙素(OC)、血清1型胶原C末端肽(CTX)、1型胶原N端前肽(P1NP);应用ELISA试剂盒检测血清vaspin水平;应用双能X线骨密度仪(DXA)检测股骨颈(FN)和腰椎(LS)两个部位的BMD;应用生物电阻抗法(BIA)测定人体成分组成,计算骨骼肌指数(SMI)。采用Spearman相关分析不同骨量老年男性血清vaspin水平与上述各指标的关系。将单因素分析中有统计学意义的因素纳入多因素logistic回归,分析其与老年男性骨质疏松症的关系。结果骨量减少组及骨质疏松组血清vaspin水平显著低于正常组,其中以骨质疏松组水平最低(P均<0.05)。在老年男性骨质疏松组,血清vaspin水平与HDL、P1NP、FNBMD及SMI呈正相关(r=0.676,P=0.007;r=0.548,P=0.016;r=0.683,P=0.003;r=0.510,P=0.025),与CTX呈负相关(r=-0.645,P=0.008)。在骨量减少组,血清vaspin水平与HDL、P1NP、FN BMD及SMI呈正相关(r=0.349,P=0.041;r=0.339,P=0.045;r=0.483,P=0.035;r=0.450,P=0.039),与CTX呈负相关(r=-0.441,P=0.040)。logistic回归分析结果表明,血清vaspin水平(OR=0.774,95%CI:0.655~0.856,P=0.002)是老年男性骨质疏松症的保护因素。结论骨量减少及骨质疏松老年男性血清vaspin水平降低,高水平血清vaspin可能是老年男性骨质疏松症的保护因素。     

中老年男性血脂水平与腰椎骨密度的相关性研究

目的 探讨中老年男性血脂水平与腰椎骨密度（BMD）的关系.方法 根据BMD将232名中老年男性分为3组：骨量正常组、骨量减少组和骨质疏松组.单因素方差分析比较3组间血脂谱的差异,对其BMD和胆固醇（TC）、低密度脂蛋白胆固醇（LDL-C）、有氧运动等变量之间的关系进行有序Logistic回归分析.结果 骨质疏松组TC和LDL-C显著高于骨量正常组（P＜0.05）.有序Logistic回归分析发现,影响BMD情况的独立因素有TC和有氧运动,其中前者为危险因素,后者为保护因素.结论 血脂异常促进骨质疏松的发展,而有氧运动能减缓骨量丢失.预防中老年男性骨质疏松应采用综合干预的方法.     

Usefulness of sex steroid hormone levels in predicting coronary artery disease in men

The relation between sex hormone levels and subsequent risk of a major coronary event was studied in a nested case-control study among 163 men in the Multiple Risk Factor Intervention Trial who later had a major coronary event and in 163 controls. Cases and controls were matched for age, serum cholesterol level, randomization group, randomization date and clinic. Blood samples were collected at baseline before randomization and frozen at -70 degrees C. Follow-up extended over 6 to 8 years. Sixty-one patients had a nonfatal acute myocardial infarction and 102 fatal infarction. Total and free testosterone, total and free estradiol, androstenedione and estrone concentrations were measured. There were no significant differences between cases and controls for any sex hormone level. There was also no difference in the ratio of testosterone to estradiol. Controlling for other cardiovascular risk factors did not change these results. These results do not support previous case-control studies of a relation between sex hormone levels and risk of heart attack among men.     

Lifestyle factors and forearm bone density in young Greek men

OBJECTIVE: The aim of this study was to evaluate the effects of dietary factors (calcium, proteins, alcohol, coffee and tea intake), exercise, sunlight exposure and immobilization on bone mineral content (BMC) and bone mineral density (BMD) in young men. PATIENTS AND MEASUREMENTS: We examined a group of 300 healthy men, aged 18-30. Mean weight was 80-81 kg (53-125 kg range) and height 179 cm (160-195 cm range). Distal BMC (dBMC), distal BMD (dBMD) and ultradistal BMD (udBMD) at the radius were measured by single X-ray absorptiometry (Osteometer DTX). The data concerning lifestyle factors were obtained through a questionnaire. The 300 men were divided in four groups according to calcium intake, four groups taking into account protein and three groups alcohol intake. There also were five groups of exercise level, six groups of sun exposure and two groups of duration of immobilization. RESULTS: In the group with the lowest levels of calcium intake (< 400 mg/day), dBMD and udBMD were lower than in the other groups of calcium intake (P = 0.002). dBMC and udBMD were lower (P = 0.043 and 0.015, respectively) in subjects with low physical activity (< 2 h/week), whereas dBMC and udBMD were higher (P < 0.0005) in subjects with frequent sun exposure (group labelled 'very often'). Multiple regression analysis on bone mineral density of the forearm showed that, calcium intake, exercise and sunlight were also independent predictors of bone mass. No significant correlation between the other examined factors and BMD or BMC was detected. CONCLUSIONS: Calcium intake, exercise level and sun exposure showed a statistically significant correlation with distal BMD and BMC in young adult men.     

Lack of influence of the androgen receptor gene CAG-repeat polymorphism on sex steroid status and bone metabolism in elderly men

OBJECTIVE: Population means for serum testosterone (T) levels in healthy men decrease with ageing but there is considerable interindividual variability of serum T in elderly men. Ultimate androgen action is mediated through the androgen receptor. Subtle differences in androgen sensitivity might contribute to serum T variability through the T negative feedback regulation. The androgen receptor gene (AR) contains in exon 1 a polymorphic trinucleotide CAG-repeat, whose length modulates androgen receptor action. The aims of the study were to assess the potential contribution of the AR CAG-repeat polymorphism in the interindividual variability of serum T and in the determination of bone metabolism in ambulatory elderly men. DESIGN AND PATIENTS: We used cross-sectional baseline data of a longitudinal study investigating the process of ageing, in particular the changes in hormonal status and bone metabolism, in a cohort of 273 community-dwelling healthy men, between age 71 and 86 years. MEASUREMENTS: AR CAG-repeat length was determined by automated DNA sequencing of exon 1 of the AR gene. Serum T, sex hormone binding globulin, LH and oestradiol were measured by specific immunoassays. Bone mineral density (BMD) was determined by dual energy X-ray absorptiometry. Bone turnover was assessed by measurement of serum bone-specific alkaline phosphatase, serum osteocalcin, serum C-terminal type I procollagen peptide, serum and urinary C-terminal telopeptides of type I collagen and urinary deoxypyridinoline levels, with use of immunoassays. RESULTS: No significant association was found between the AR CAG-repeat length and either total or free T, LH or the androgen sensitivity index (LHxT). BMD measurements at the hip and the forearm were not associated with AR CAG-repeat length and there was no association of this AR polymorphism with any of the biochemical markers of bone turnover. Results were not different after adjustments for age and body mass index. CONCLUSIONS: The findings of the present study do not support the view that in community-dwelling, healthy elderly men the androgen receptor gene CAG-repeat polymorphism has a substantial impact on interindividual variability of serum testosterone levels or on the determination of bone turnover and bone mineral density.     

Effects of experimentally induced mild hyperthyroidism on growth hormone and insulin secretion and sex steroid levels in healthy young men

Although triiodothyronine (T₃) exerts major regulatory actions in both animals and humans, most clinical studies of T₃ administration have been relatively short-term. The present study examined the effects of more than 2 months (63 days) of low-dose T₃ treatment on overnight pulsatile growth hormone (GH) secretion, short-term insulin secretion, and of sex steroid levels in seven healthy, lean men studied at an inpatient metabolic unit. At baseline, there were strong correlations between sex hormone—binding globulin (SHBG) and several measures of GH production, including total GH production (r = .99), GH interburst interval (r = −.75, and GH mass (r = .82). SHGB was also inversely correlated with basal insulin secretion (r = −.74). There was a 42% increase in serum levels of total testosterone (18.5 ± 1.3 to 26.3 ± 1.8 nmol/L, P = .005) and a 150% increase in SHBG (18.0 ± 2.2 to 44.9 ± 7.0 nmol/L, P = .008) following T₃ treatment. Estradiol and free testosterone levels were unchanged by treatment, although free testosterone decreased from 142.8 ± 18.4 to 137.3 ± 19.5 pmol/L. T₃ treatment significantly reduced the GH interburst interval (P < .05) and produced slight increases in the measures of GH secretion. There were no statistically significant effects of T₃ treatment on insulin secretion, although insulin peak amplitude, mass secreted per burst, and total production all decreased. We conclude that experimentally induced T₃ excess in healthy men produces significant and sustained changes in sex hormone levels and GH secretion. Furthermore, there are strong associations between SHBG and both GH and insulin secretion independent of thyroid hormone excess that require additional study.