Hormonal and biochemical parameters in the determination of osteoporosis in elderly men

Role of sex hormone-binding globulin in the free hormone hypothesis and the relevance of free testosterone in androgen physiology

According to the free hormone hypothesis, biological activity of a certain hormone is best reflected by free rather than total hormone concentrations. A crucial element in this theory is the presence of binding proteins, which function as gatekeepers for steroid action. For testosterone, tissue exposure is governed by a delicate equilibrium between free and total testosterone which is determined through interaction with the binding proteins sex hormone-binding globulin and albumin. Ageing, genetics and various pathological conditions influence this equilibrium, hereby possibly modulating hormonal exposure to the target tissues. Despite ongoing controversy on the subject, strong evidence from recent in vitro, in vivo and human experiments emphasizes the relevance of free testosterone. Currently, however, clinical possibilities for free hormone diagnostics are limited. Direct immunoassays are inaccurate, while gold standard liquid chromatography with tandem mass spectrometry (LC-MS/MS) coupled equilibrium dialysis is not available for clinical routine. Calculation models for free testosterone, despite intrinsic limitations, provide a suitable alternative, of which the Vermeulen calculator is currently the preferred method. Calculated free testosterone is indeed associated with bone health, frailty and other clinical endpoints. Moreover, the added value of free testosterone in the clinical diagnosis of male hypogonadism is clearly evident. In suspected hypogonadal men in whom borderline low total testosterone and/or altered sex hormone-binding globulin levels are detected, the determination of free testosterone avoids under- and overdiagnosis, facilitating adequate prescription of hormonal replacement therapy. As such, free testosterone should be integrated as a standard biochemical parameter, on top of total testosterone, in the diagnostic workflow of male hypogonadism.

Sex-specific associations of serum insulin-like growth factor-1 with bone density and risk of fractures in Chinese patients with type 2 diabetes

We evaluated the associations of serum insulin-like growth factor-1 (IGF-1) with bone mineral density (BMD) and risk of fractures in Chinese patients with type 2 diabetes (T2D). We found positive associations between IGF-I and BMD and negative associations between IGF-I and all three modified 10-year probabilities of MOFs and HFs in men, but not in women.

INTRODUCTION

The objective was to investigate the associations of serum insulin-like growth factor-1 (IGF-1) with bone mineral density (BMD) and risk of fractures in Chinese patients with type 2 diabetes (T2D) in each gender.

METHODS

This was a cross-sectional, retrospective study that included men over 50 years and postmenopausal women with T2D without medical conditions or medications known to significantly affect BMD or serum IGF-I levels. Data of IGF-1, bone metabolism markers, lumbar spine (LS), femoral neck (FN), and total hip (TH) BMD were obtained; 10-year probability of major osteoporotic fractures (MOFs) and hip fractures (HFs) was calculated and modified with rheumatoid arthritis, femoral neck T-score, and age. Correlations of IGF-1 levels with bone metabolism and risk of fractures were statistically analyzed in men and women, respectively.

RESULTS

A total of 391 patients, including 226 men and 165 women, were included. The age, serum fasting C-peptide, glycosylated hemoglobin (HbA1c), bone formation marker, and all three modified 10-year probabilities of MOFs and HFs were higher in women than those in men (all p < 0.05). The levels of 25 hydroxyvitamin D (25OHD), IGF-1, and BMD were lower in women than those in men (all p < 0.05). In men, IGF-1 was positively correlated with FN and TH BMD (FN BMD: r = 0.267, p < 0.001; TH BMD: r = 0.235, p < 0.001) and negatively correlated with all three modified 10-year probabilities of MOFs (RA-modified MOFs: r = - 0.289, p < 0.001; age-modified MOFs: r = - 0.237, p < 0.001; FN T-score-modified MOFs: r = - 0.280, p < 0.001) and HFs (RA-modified HFs: r = - 0.291, p < 0.001; age-modified HFs: r = - 0.271, p < 0.001; FN T-score-modified HFs: r = - 0.270, p < 0.001), while no significant correlations were found between serum IGF-I and BMD and three modified 10-year probability in women.

CONCLUSIONS

According to this study, we found sex differences in the associations of serum IGF-1 with BMD and risk of fractures in Chinese patients with T2D. These results suggested that increasing serum IGF-1 might be a clinical target for protecting fractures in T2D, especially in men.

Osteoporosis in Men: A Review of an Underestimated Bone Condition

Osteoporosis is called the 'silent disease' because, although it does not give significant symptoms when it is not complicated, can cause fragility fractures, with serious consequences and death. Furthermore, the consequences of osteoporosis have been calculated to weigh heavily on the costs of health systems in all the countries. Osteoporosis is considered a female disease. Actually, the hormonal changes that occur after menopause certainly determine a significant increase in osteoporosis and the risk of fractures in women. However, while there is no doubt that women are more exposed to osteoporosis and fragility fractures, the literature clearly indicates that physicians tend to underestimate the osteoporosis in men. The review of the literature done by the authors shows that osteoporosis and fragility fractures have a high incidence also in men; and, furthermore, the risk of fatal complications in hip fractured men is higher than that for women. The authors report the evidence of the literature on male osteoporosis, dwelling on epidemiology, causes of osteoporosis in men, diagnosis, and treatment. The analysis of the literature shows that male osteoporosis is underscreened, underdiagnosed, and undertreated, both in primary and secondary prevention of fragility fractures.

Gender Disparities in Osteoporosis

Osteoporosis is a growing health concern worldwide and its complications are as prevalent as other common chronic disease complications such as hypertension and diabetes. In this review, we will discuss the role of gender in osteoporosis, especially related to peak bone mass and maturation, rate of annual bone loss, screening, prevalence of osteoporosis and its related fractures, mortality after osteoporosis-related fracture, fracture risk predication using different technologies and the impact of gender on osteoporosis management.

Bone turnover predicts change in volumetric bone density and bone geometry at the radius in men

Peripheral quantitative computed tomography scans of the distal and midshaft radius were performed in 514 European men aged 40-79 years at baseline and a median of 4.3 years later. Age-related changes in volumetric bone mineral density (vBMD) and bone geometry were greater in men with higher biochemical markers of bone turnover at baseline.

INTRODUCTION

This study aimed to determine prospective change in bone density and geometry at the radius in men and examine the influence of bone turnover markers and sex hormones on that change.

METHODS

Men aged 40-79 years were recruited from population registers in Manchester (UK) and Leuven (Belgium). At baseline, markers of bone formation (P1NP and osteocalcin) and resorption (β-cTX and ICTP) were assessed. Total and bioavailable testosterone and oestradiol were also measured. Peripheral quantitative computed tomography (pQCT) was used to scan the radius at distal and midshaft sites at the baseline assessment and a median of 4.3 years later.

RESULTS

Five hundred fourteen men, mean (SD) age of 59.6 (10.5) years, contributed to the data. At the midshaft site, there was a significant decrease in mean cortical vBMD (-0.04 %/year), bone mineral content (BMC) (-0.1 %/year) and cortical thickness (-0.4 %/year), while total and medullary area increased (+0.5 and +2.4 %/year respectively). At the distal radius, total vBMD declined (-0.5 %/year) and radial area increased (+0.6 %/year). Greater plasma concentrations of bone resorption and formation markers were associated with greater decline in BMC and cortical area at the midshaft and total vBMD at the distal site. Increased bone resorption was linked with an increase in total and medullary area and decrease in cortical thickness at the midshaft. Sex hormone levels were unrelated to change in pQCT parameters.

CONCLUSIONS

Age-related changes in vBMD and bone geometry are greater in men with higher biochemical markers of bone turnover at baseline. Sex hormones have little influence on change in pQCT parameters.

Off label therapies for testosterone replacement

The incidence of hypogonadism has been steadily increasing over the last few years. Exogenous testosterone has been the standard treatment for hypogonadal men, but is associated with suppression of spermatogenesis as well as other possible adverse effects. There are other medications, currently considered “off label” for androgen replenishment, that exert their effect through modulation of the hypothalamic-gonadal axis. These medications increase endogenous testosterone levels and offer a different therapeutic approach. This review will focus on these alternative (off-label) therapies for androgen replacement in men.

Genetic influence on the association between bone mineral density and testosterone in Korean men

Low bone mineral density (BMD) leads to an increased risk of osteoporotic fracture. Total testosterone and free testosterone were positively associated with BMD, which was significantly influenced by the additive genetic effects.

INTRODUCTION

This cross-sectional study aimed to evaluate an association between testosterone and BMD and the influence of genetic factors on the association.

METHODS

Study subjects were 1070 Korean men including 144 pairs of monozygotic twins and their family members. Levels of serum total testosterone and sex hormone binding globulin (SHBG) were measured by chemiluminescence immunoassay. Calculated free testosterone (cFT) was then determined using Vermeulen's method. BMDs of the whole body and specific regions were measured using dual-energy X-ray absorptiometry.

RESULTS

Linear mixed regression analyses showed that total testosterone and cFT were positively associated with BMD at most regions, after considering intra-familial relationship and covariates including fat mass, lean mass, and SHBG. SHBG had an inverse association with BMD at the pelvis but not with the BMD at other regions after adjusting for all covariates and cFT. Co-twin control analysis in monozygotic twins found no association between pairwise difference of testosterone and pairwise difference of BMD. Bivariate variance component analysis showed that both total testosterone and cFT had a significant positive additive genetic correlation with BMD at rib, spine, and arm, whereas SHBG had no significant genetic correlation with BMD. Inverse environmental correlations were seen between total testosterone and BMDs at the lumbar spine and arm.

CONCLUSIONS

This Korean twin and family study showed that both total testosterone and free testosterone were positively associated with BMD and that genetic effects were significant on the association between testosterone and BMD.

Quantification of the relative contribution of estrogen to bone mineral density in men and women

Background

The study quantified the relative contributions of estrogen (E2) and total testosterone (TT) to variation in bone mineral density in men and women.

Methods

This was a cross-sectional study which involved 200 men and 415 women aged 18 to 89 years. BMD at the lumbar spine (LS) and femoral neck (FN) was measured by DXA. Serum levels of E2 and TT were measured by electrochemiluminescence immunoassays. The association between E2, TT, and BMD was analyzed by the multiple linear regression model, adjusting for age and BMI. The contribution of each hormone to the variation in BMD was quantified by the bootstrap method.

Results

In women, higher serum levels of E2, but not TT, were significantly associated with greater BMD at the FN (P = 0.001) and LS (P < 0.0001). In men, higher serum levels of E2 were independently associated with greater FNBMD (P = 0.008) and LSBMD (P = 0.086). In the multiple linear regression model, age, body weight and E2 accounted for 50-55% variance in FNBMD, and 25% (in men) and 48% (in women) variance in LSBMD. Variation in E2 accounted for 2.5% (95% CI 0.4 - 7.8%) and 11.3% (95% CI 8.1 - 15.3%) variation in FNBMD in men and women, respectively. Moreover, E2 contributed 1.2% (95% CI 0.1 - 5.8%) and 11.7% (95% CI 8.5 - 15.9%) variation in LSBMD in men and women, respectively.

Conclusions

Estrogen is more important than testosterone in the determination of age-related bone mineral density men and women of Vietnamese background. However, the relative contributions of estrogen to bone mineral density in men are likely modest.

The pathogenesis, treatment and prevention of osteoporosis in men

Testosterone stimulates longitudinal and appositional growth during childhood, whereas estrogen induces epiphysial closure. During adulthood, testosterone continues to stimulate periosteal growth, whereas estrogen is important for the maintenance of trabecular bone mass and structure. In males, testosterone is aromatized to estradiol. Both free and bioavailable plasma levels of testosterone and estradiol decrease with age in males, and fracture risk is associated with low estradiol levels. Testosterone may increase muscle mass and prevent fractures related to falls. Younger hypogonadal males should be treated with testosterone to attain peak bone mass and increase bone mineral density (BMD). Older hypogonadal males should be treated in cases of osteoporosis, reduced muscle strength and increased risk of falling. Secondary hyperparathyroidism caused by calcium and vitamin D insufficiency may reduce bone mass and strength and increase fracture risk and should be avoided. Since calcium supplementation has been associated with an increased risk of cardiovascular complications and renal stones, the dose should be tailored to the habitual daily calcium intake. Lifestyle-related risk factors (smoking, alcohol consumption, lack of physical activity and low body weight) should be addressed. The antifracture efficacy of antiresorptive and anabolic treatment for osteoporosis has not been documented in larger randomized controlled studies. However, changes in BMD and bone markers suggest similar effects in males and females of bisphosphonates (alendronate, risedronate, ibandronate, zoledronic acid), nasal calcitonin, denosumab and teriparatide (parathyroid hormone [1-34]). The antiresorptive drugs should be used in males with BMD T-score less than -2.5 and one or more risk factors, or with hip and vertebral fractures. It seems appropriate to recommend a higher cut-off T-score (e.g. less than -1.0 standard deviation [SD]) in glucocorticoid-induced osteoporosis and in patients receiving androgen deprivation therapy because of the fast initial bone loss. Anabolic treatment should be used in more severe spinal fracture cases, including glucocorticoid-induced osteoporosis.

Genetic profiling and individualized assessment of fracture risk

Osteoporosis and its consequence of fragility fracture impose a considerable demand on health-care services because fracture is associated with a series of adverse events, including re-fracture and mortality. One of the major priorities in osteoporosis care is the development of predictive models to identify individuals at high risk of fracture for early intervention and management. Existing predictive models include clinical factors and anthropometric characteristics but have not considered genetic variants in the prediction. Genome-wide association studies conducted in the past decade have identified several genetic variants relevant to fracture risk. These genetic variants are common in frequency but have very modest effect sizes. A remaining challenge is to use these genetic data to individualize fracture risk assessment on the basis of an individual's genetic risk profile. Empirical and simulation studies have shown that the usefulness of a single genetic variant for fracture risk assessment is very limited, but a profile of 50 genetic variants, each with odds ratio ranging from 1.02 to 1.15, could improve the accuracy of fracture prediction beyond that obtained by use of existing clinical risk factors. Thus, genetic profiling when integrated with existing risk assessment models could inform a more accurate prediction of fracture risk in an individual.

The association of concurrent vitamin D and sex hormone deficiency with bone loss and fracture risk in older men: the osteoporotic fractures in men (MrOS) study

Low 25-hydroxyvitamin D (VitD), low sex hormones (SH), and high sex hormone binding globulin (SHBG) levels are common in older men. We tested the hypothesis that combinations of low VitD, low SH, and high SHBG would have a synergistic effect on bone mineral density (BMD), bone loss, and fracture risk in older men. Participants were a random subsample of 1468 men (mean age 74 years) from the Osteoporotic Fractures in Men Study (MrOS) plus 278 MrOS men with incident nonspine fractures studied in a case-cohort design. "Abnormal" was defined as lowest quartile for VitD (<20 ng/mL), bioavailable testosterone (BioT, <163 ng/dL), and bioavailable estradiol (BioE, <11 pg/mL); and highest quartile for SHBG (>59 nM). Overall, 10% had isolated VitD deficiency; 40% had only low SH or high SHBG; 15% had both SH/SHBG and VitD abnormality; and 35% had no abnormality. Compared to men with all normal levels, those with both SH/SHBG and VitD abnormality tended to be older, more obese, and to report less physical activity. Isolated VitD deficiency, and low BioT with or without low VitD, was not significantly related to skeletal measures. The combination of VitD deficiency with low BioE and/or high SHBG was associated with significantly lower baseline BMD and higher annualized rates of hip bone loss than SH abnormalities alone or no abnormality. Compared to men with all normal levels, the multivariate-adjusted hazard ratio (95% confidence interval [CI]) for incident nonspine fracture during 4.6-year median follow-up was 1.2 (0.8-1.8) for low VitD alone; 1.3 (0.9-1.9) for low BioE and/or high SHBG alone; and 1.6 (1.1-2.5) for low BioE/high SHBG plus low VitD. In summary, adverse skeletal effects of low sex steroid levels were more pronounced in older men with low VitD levels. The presence of low VitD in the presence of low BioE/high SHBG may contribute substantially to poor skeletal health.

Genetics and the individualized prediction of fracture

Recent genome-wide association studies have identified many genetic variants associated with fracture risk. These genetic variants are common in the general population but have very modest effect sizes. A remaining challenge is to translate these genetic variant discoveries to better predict the risk of fracture based on an individual's genetic profile (ie, individualized risk assessment). Empirical and simulation studies have shown that 1) the utility of a single genetic variant for fracture risk assessment is very limited; but 2) a profile of 50 genetic variants, each with odds ratio ranging from 1.02 to 1.15, can improve the accuracy of fracture prediction and classification beyond that obtained by conventional clinical risk factors. These results are consistent with the view that genetic profiling, when integrated in existing risk assessment models, can inform a more accurate prediction of fracture risk in an individual.

Male osteoporosis

Osteoporosis is now recognized as a major threat to health in aging men. Morbidity and mortality, particularly following hip fracture, are substantial. Although trabecular bone loss starts in early adulthood, loss of cortical bone only seems to occur from midlife onwards. Declining bioavailable estradiol levels plays an integral role in male age-associated bone loss. Both pharmacologic and supportive care interventions are important for optimal care in men at an increased fracture risk.

Pathogenesis of age-related bone loss in humans

BACKGROUND

Although data from rodent systems are extremely useful in providing insights into possible mechanisms of age-related bone loss, concepts evolving from animal models need to ultimately be tested in humans.

METHODS

This review provides an update on mechanisms of age-related bone loss in humans based on the author's knowledge of the field and focused literature reviews.

RESULTS

Novel imaging, experimental models, biomarkers, and analytic techniques applied directly to human studies are providing new insights into the patterns of bone mass acquisition and loss as well as the role of sex steroids, in particular estrogen, on bone metabolism and bone loss with aging in women and men. These studies have identified the onset of trabecular bone loss at multiple sites that begins in young adulthood and remains unexplained, at least based on current paradigms of the mechanisms of bone loss. In addition, estrogen appears to be a major regulator of bone metabolism not only in women but also in men. Studies assessing mechanisms of estrogen action on bone in humans have identified effects of estrogen on RANKL expression by several different cell types in the bone microenvironment, a role for TNF-α and IL-1β in mediating effects of estrogen deficiency on bone, and possible regulation of the Wnt inhibitor, sclerostin, by estrogen.

CONCLUSIONS

There have been considerable advances in our understanding of age-related bone loss in humans. However, there are also significant gaps in knowledge, particularly in defining cell autonomous changes in bone in human studies to test or validate concepts emerging from studies in rodents. Decision Editor: Luigi Ferrucci, MD, PhD.

Sex steroids and bone health in men

The influence of sex steroids on bone in both men and women has long been recognized. In men, however, the relative contribution of androgens versus estrogens in the regulation of bone metabolism remains uncertain. Animal studies demonstrate that both estradiol (E2), via activation of estrogen receptor-α, and testosterone (T), via activation of the androgen receptor, regulate bone mass in male rodents. The main focus of this review is to summarize and discuss recent findings from the osteoporotic fractures in men (MrOS) cohorts regarding the impact of serum sex steroids on bone health in elderly men. Collectively, these data demonstrate that serum E2 is directly associated with bone mineral density (BMD) and that low serum E2 associates with higher rates of bone loss and fracture. In addition, they substantiate the concept of a threshold E2 level that determines fracture risk in elderly men. We propose that the effect of E2 on fracture risk is at least partly mediated by its effect on BMD, whereas the more modest effect of T on fracture risk mainly is mediated by effects on muscle strength and risk of falls. Findings from the MrOS cohorts also demonstrate that racial and genetic variations in aromatase activity influence serum E2 levels in men. In conclusion, there is compelling evidence that not only androgens, but also estrogens, are important regulators of bone health in men. Consequently, E2 should not exclusively be regarded as the 'female hormone' but as a sex steroid that is necessary for maintenance of bone health in men.

The role of IGF-1 for fracture risk in men

Growth hormone and insulin-like growth factor-1 (IGF-1) are essential for the achievement of normal longitudinal bone growth and bone mass. Preclinical studies using various knockout models have shown that both endocrine (mostly liver-derived) IGF-1 and bone-derived IGF-1 contribute to normal longitudinal skeletal growth and cortical bone size. Since bone size is an important determinant of bone strength, and hence fracture risk, we evaluated the predictive role of serum IGF-1 for fracture risk. The population-based Osteoporotic Fractures in Men Sweden cohort recently showed for the first time that older men with low serum IGF-1 levels have an increased fracture risk, especially for the two most important fracture types, hip and vertebral fractures. This association between serum IGF-1 and incident fracture risk is partly mediated via bone mineral density. Future studies are required to identify the mechanisms by which endocrine and local IGF-1 regulate skeletal growth and bone size. In addition, possible mediators affecting the impact of IGF-1 on fractures in men remain to be elucidated.

Aromatase activity and bone loss in men

Aromatase is a specific component of the cytochrome P450 enzyme system responsible for the transformation of androgen precursors into estrogens. This enzyme is encoded by the CYP19A1 gene located at chromosome 15q21.2, that is, expressed in ovary and testis, but also in many extraglandular sites such as the placenta, brain, adipose tissue, and bone. The activity of aromatase regulates the concentrations of estrogens with endocrine, paracrine, and autocrine effects on target issues including bone. Importantly, extraglandular aromatization of circulating androgen precursors is the major source of estrogen in men. Clinical and experimental evidences clearly indicate that aromatase activity and estrogen production are necessary for longitudinal bone growth, the attainment of peak bone mass, pubertal growth spurt, epiphyseal closure, and normal bone remodeling in young individuals. Moreover, with aging, individual differences in aromatase activity may significantly affect bone loss and fracture risk in men.

Influence of age and sex steroids on bone density and geometry in middle-aged and elderly European men

SUMMARY

The influence of age and sex steroids on bone density and geometry of the radius was examined in two European Caucasian populations. Age-related change in bone density and geometry was observed. In older men, bioavailable oestradiol may play a role in the maintenance of cortical and trabecular bone mineral density (BMD).

INTRODUCTION

To examine the effect of age and sex steroids on bone density and geometry of the radius in two European Caucasian populations.

METHODS

European Caucasian men aged 40-79 years were recruited from population registers in two centres: Manchester (UK) and Leuven (Belgium), for participation in the European Male Ageing Study. Total testosterone (T) and oestradiol (E(2)) were measured by mass spectrometry and the free and bioavailable fractions calculated. Peripheral quantitative computed tomography was used to scan the radius at distal (4%) and midshaft (50%) sites.

RESULTS

Three hundred thirty-nine men from Manchester and 389 from Leuven, mean ages 60.2 and 60.0 years, respectively, participated. At the 50% radius site, there was a significant decrease with age in cortical BMD, bone mineral content (BMC), cortical thickness, and muscle area, whilst medullary area increased. At the 4% radius site, trabecular and total volumetric BMD declined with age. Increasing bioavailable E(2) (bioE(2)) was associated with increased cortical BMD (50% radius site) and trabecular BMD (4% radius site) in Leuven, but not Manchester, men. This effect was predominantly in those aged 60 years and over. In older Leuven men, bioavailable testosterone (Bio T) was linked with increased cortical BMC, muscle area and SSI (50% radius site) and total area (4% radius site).

CONCLUSIONS

There is age-related change in bone density and geometry at the midshaft radius in middle-aged and elderly European men. In older men bioE(2) may maintain cortical and trabecular BMD. BioT may influence bone health through associations with muscle mass and bone area.

The unitary model for estrogen deficiency and the pathogenesis of osteoporosis: is a revision needed?

Over a decade ago, we proposed a "unitary" model for the pathogenesis of osteoporosis that identified estrogen deficiency as the predominant cause of both the early, accelerated, and late slow phases of bone loss in postmenopausal women and as a contributing cause of the continuous phase of bone loss in aging men. While this was a plausible model then, new data over the intervening years suggest a need to modify these concepts. Indeed, based largely on rodent studies, a "revisionist" view of the pathogenesis of osteoporosis has been proposed recently that attempts a paradigm shift from the estrogen-centric model to one in which bone loss is largely independent of estrogen deficiency and is driven instead by cell-autonomous age-related factors. However, detailed clinical investigative studies using quantitative computed tomography demonstrate that the onset of cortical bone loss in humans is closely tied to estrogen deficiency; thus the estrogen-centric view is likely correct for cortical bone, which comprises over 80% of the skeleton and is the major structural determinant of fracture risk at most skeletal sites. By contrast, these same studies also demonstrate that trabecular bone loss begins in sex hormone-replete young adults of both sexes. This suggests that a significant proportion of trabecular bone loss is either estrogen-independent or, as suggested by some studies, requires higher levels for its regulation. In this perspective, we critically review these and other findings, leading us to conclude that our original model requires modification but not revision.

Sex steroid hormones in older men: longitudinal associations with 4.5-year change in hip bone mineral density--the osteoporotic fractures in men study

CONTEXT

There is limited information on the association between sex hormones and bone loss in older men.

OBJECTIVE

Our objective was to determine the longitudinal association between sex steroid hormones and bone mineral density (BMD).

DESIGN AND SETTING

We conducted a prospective study of 5995 men aged at least 65 yr old at six U.S. clinical centers.

PARTICIPANTS

Sex steroid hormones were measured in a random sample of 1602 men. After exclusions, 1238 men were included in cross-sectional analyses and 969 in longitudinal analyses. Baseline sex hormones were measured using liquid chromatography-mass spectrometry. Bioavailable (Bio) estradiol (BioE2) and testosterone (BioT) were calculated from mass action equations. SHBG was measured using chemiluminescent substrate.

MAIN OUTCOME MEASURES

BMD of the total hip, measured at baseline and once or twice afterward over 4.6 yr of follow-up, was evaluated.

RESULTS

The annualized percent change in hip BMD increased with decreasing BioE2 (P trend = 0.03). Men with the lowest BioE2 (<39.7 pmol/liter) compared with the highest BioE2 (> or =66.0 pmol/liter) experienced 38% faster rate of BMD loss (P < 0.05). There was no association between BioT and hip BMD loss. Men with lowest BioE2, lowest BioT, and highest SHBG experienced a 3-fold faster rate of BMD loss compared with men with higher levels (P = 0.02). A threshold effect of SHBG was observed; the rate of hip BMD loss increased in men with SHBG of 49-60 nM.

CONCLUSIONS

Low BioE2 and high SHBG levels were associated with lower BMD and faster hip BMD loss. The combination of low BioE2, low BioT, and high SHBG was associated with significantly faster rates of BMD loss.

Physiology of bone loss

The physiology of bone loss in aging women and men is largely explained by the effects of gonadal sex steroid deficiency on the skeleton. In women, estrogen deficiency is the main cause of early rapid postmenopausal bone loss, whereas hyperparathyroidism and vitamin D deficiency are thought to explain age-related bone loss later in life. Surprisingly, estrogen deficiency also plays a dominant role in the physiology of bone loss in aging men. Many other factors contribute to bone loss in aging women and men, including defective bone formation by aging osteoblasts, impairment of the growth hormone/insulin-like growth factor axis, reduced peak bone mass, age-associated sarcopenia, leptin secreted by adipocytes, serotonin secreted by the intestine, and a long list of sporadic secondary causes. Further elucidation of the relative importance of each of these factors will lead to improved preventive and therapeutic approaches for osteoporosis.

The differences of femoral neck geometric parameters: effects of age, gender and race

This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter, cross-sectional area, cortical thickness, sectional modulus, and buckling ratio and found that the three factors would influence the FNGPs.

INTRODUCTION

Bone geometry is one of the most important predictors of bone strength and osteoporotic fractures. This study aims at investigating the effects of age, sex, and ethnicity on five femoral neck geometric parameters (FNGPs): femoral neck periosteal diameter (W), cross-sectional area (CSA), cortical thickness (CT), sectional modulus (Z), and buckling ratio (BR).

METHODS

In the studied 861 Caucasian subjects and 3,021 Chinese individuals, CSA, CT, and Z displayed trends of decrease with age, but W and BR showed increasing trends with age in both Chinese and Caucasian females and males (p < 0.05). W, CSA, CT, and Z were significantly higher (p <or= 0.001) in Caucasians than in Chinese and higher in males than in females except for BR between Chinese males and Chinese females.

CONCLUSION

In conclusion, the differences of FNGPs according to gender and ethnicity provide important implications in the different prevalence of osteoporotic fracture among different gender and ethnic groups.

Pathogenesis of Osteoporosis

As for most multifactorial disorders, the pathogenesis of osteoporosis is complex, and a different set of mechanisms may be operative in any given individual. However, there are certain common causes of bone loss and increased fracture risk with aging in most people. These include genetic factors contributing to the acquisition of peak bone mass, illnesses affecting skeletal growth and development, sex steroid deficiency following the menopause in women and with aging in men, and intrinsic, age-related changes in bone metabolism. Superimposed on these factors are specific secondary causes of bone loss, such as corticosteroid use or other illnesses affecting bone metabolism that may contribute to fracture risk in individuals exposed to these factors. The past decade has witnessed tremendous advances in our understanding of each of these various causes of bone loss, leading to the development of novel, mechanism-based therapeutic approaches to prevent and treat this important public health disorder.

Androgens and male aging: Current evidence of safety and efficacy

Many signs of aging, such as sexual dysfunction, visceral obesity, impaired bone and muscle strength, bear a close resemblance to features of hypogonadism in younger men. The statistical decline of serum testosterone in aging men is solidly documented. It has been presumed that the above features of aging are related to the concurrent decline of androgens, and that correction of the lower-than-normal circulating levels of testosterone will lead to improvement of symptoms of aging. But in essence, the pivotal question whether the age-related decline of testosterone must be viewed as hypogonadism, in the best case reversed by testosterone treatment, has not been definitively resolved. Studies in elderly men with lower-than-normal testosterone report improvement of features of the metabolic syndrome, bone mineral density, of mood and of sexual functioning. But as yet there is no definitive proof of the beneficial effects of restoring testosterone levels to normal in elderly men on clinical parameters. Few of these studies meet as yet rigorous standards of scientific enquiry: double-blind, placebo-controlled design of the study. The above applies also to the assessment of safety of testosterone administration to elderly men. There is so far no convincing evidence that testosterone is a main factor in the development of prostate cancer in elderly men and guidelines for monitoring the development of prostate disease have been developed. It is of note that there are presently no long-term safety data with regard to the prostate. Polycythemia is another potential complication of testosterone treatment. It is dose dependent and can be managed with dose adjustment.

Effects of aromatase inhibition on bone mineral density and bone turnover in older men with low testosterone levels

CONTEXT

Aging is associated with declining gonadal steroid production, low bone mineral density (BMD), and fragility fractures. The efficacy and safety of testosterone replacement in older men remains uncertain.

OBJECTIVE

The objective of the study was to assess the effects of aromatase inhibition on BMD in older men with low testosterone levels.

DESIGN AND SETTING

This was a 1-yr, double-blind, randomized, placebo-controlled trial that was conducted at a tertiary care academic center in Boston, MA.

PARTICIPANTS

Participants included 69 men aged 60+ yr with borderline or low testosterone levels and hypogonadal symptoms.

INTERVENTION

Intervention included 1 mg anastrozole daily or placebo.

MAIN OUTCOME MEASURES

Changes in gonadal steroid hormone levels, BMD, and bone turnover markers were measured.

RESULTS

Mean serum testosterone increased from 319 +/- 93 ng/dl at baseline to 524+/-139 ng/dl at month 3 (P < 0.0001) and declined slightly to 474 +/- 145 ng/dl by 1 yr. Estradiol levels decreased from 15 +/- 4 pg/ml at baseline to 12 +/- 4 pg/ml at month 3 and then remained stable (P < 0.0001). Posterior-anterior (PA) spine BMD decreased in the anastrozole group as compared with placebo (P = 0.0014). In the anastrozole group, PA spine BMD decreased from 1.121 +/- 0.141 g/cm(2) to 1.102 +/- 0.138 g/cm(2), whereas in the placebo group, PA spine BMD increased from 1.180 +/- 0.145 g/cm(2) to 1.189 +/- 0.146 g/cm(2). Qualitatively similar, but not statistically significant, changes occurred at the other sites. Bone turnover markers were not affected by anastrozole therapy.

CONCLUSIONS

In older men, aromatase inhibition increases testosterone levels, decreases estradiol levels, and appears to decrease BMD. Aromatase inhibition does not improve skeletal health in aging men with low or low normal testosterone levels.

Estrogens as regulators of bone health in men

Bone metabolism is influenced by sex steroids during growth and adulthood in both men and women. Although this influence is well described in women, the relative importance of androgens and estrogens in the regulation of the male skeleton remains uncertain. Even though estradiol has been considered the 'female hormone', levels of serum estradiol in elderly men are higher than those in postmenopausal women. Estradiol levels are more strongly associated with BMD, bone turnover and bone loss than testosterone levels are in adult men. Case reports of young men with estrogen resistance or aromatase deficiency also suggest a crucial role for estradiol in regulation of skeletal growth in men. Moreover, serum levels of both estrogens and androgens are inversely associated with the risk of fracture in aging men. A large, prospective, population-based study showed that levels of serum estradiol predict the risk of fracture, independently of serum testosterone. Evidence suggests that a threshold level of estradiol exists below which the male skeleton is impaired; rates of bone loss and fracture seem to be increased and bone maturation delayed in men with estradiol levels below this threshold. On the basis of these findings, we propose that not only androgens, but also estrogens, are important regulators of bone health in men.

Low body mass index and declining sex steroids explain most age-related bone loss in Brazilian men

SUMMARY

Osteoporosis in men is underestimated, but our data point to an increasing prevalence rate in those over 70 years old with body mass index (BMI) <25 kg/m(2), bioavailable testosterone <2.7 nmol/L, bioavailable estradiol <40 pmol/L, and high bone turnover, defined in this study as serum carboxyterminal cross-linked telopeptide of type I collagen (ICTP) >4.3 microg/L.

INTRODUCTION

The association of sex steroids and osteoporosis was evaluated in 104 men, aged 50-93 years old.

METHODS

Bone mineral density (BMD), bone turnover (ICTP), testosterone (T), and estradiol (E(2)) were measured; free and bioavailable hormones (free testosterone index [FTI], BioT, free estradiol index [FEI], and BioE(2)) were calculated from T, E(2), sex hormone-binding globulin (SHBG), and albumin. Nonparametric analysis and Poisson regression models were used.

RESULTS

Significant increases in SHBG and ICTP and decreases in femoral neck BMD, FTI, FEI, BioT, and BioE(2) were observed with each additional decade of age. Femoral neck BMD was inversely correlated with ICTP, and both were significantly associated with SHBG, FTI, BioT, FEI, and BioE. There was a direct and graded association between age and osteoporosis prevalence rate (OP PR; p = 0.028). Compared to participants less than 70 years old, the crude OP PR of those 80 years and older was 3.2 (95%CI = 1.4-7.3). Adjusting sequentially for BMI and bioavailable sex hormones attenuated the association between age and osteoporosis prevalence by 55% and 77%, respectively.

CONCLUSION

Our data support the view that low BMI and declining sex steroids explain most of the association between aging, increased bone turnover, and osteoporosis in men.

The benefits and risks of testosterone replacement therapy: a review

Increased longevity and population aging will increase the number of men with late onset hypogonadism. It is a common condition, but often underdiagnosed and undertreated. The indication of testosterone-replacement therapy (TRT) treatment requires the presence of low testosterone level, and symptoms and signs of hypogonadism. Although controversy remains regarding indications for testosterone supplementation in aging men due to lack of large-scale, long-term studies assessing the benefits and risks of testosterone-replacement therapy in men, reports indicate that TRT may produce a wide range of benefits for men with hypogonadism that include improvement in libido and sexual function, bone density, muscle mass, body composition, mood, erythropoiesis, cognition, quality of life and cardiovascular disease. Perhaps the most controversial area is the issue of risk, especially possible stimulation of prostate cancer by testosterone, even though no evidence to support this risk exists. Other possible risks include worsening symptoms of benign prostatic hypertrophy, liver toxicity, hyperviscosity, erythrocytosis, worsening untreated sleep apnea or severe heart failure. Despite this controversy, testosterone supplementation in the United States has increased substantially over the past several years. The physician should discuss with the patient the potential benefits and risks of TRT. The purpose of this review is to discuss what is known and not known regarding the benefits and risks of TRT.

Relation between serum testosterone, serum estradiol, sex hormone-binding globulin, and geometrical measures of adult male proximal femur strength

CONTEXT

Although previous studies have indicated associations between circulating testosterone (T) or estradiol (E2) concentrations and bone mineral density, the relationship between gonadal steroids and skeletal geometry is not well defined.

OBJECTIVE

Our objective was to uncover the relation between circulating T or E2 and proximal femur geometry in a diverse sample of men.

DESIGN

We used data on 808 men enrolled in the Boston Area Community Health/Bone Study. Serum concentrations of total and calculated free T and E2 were obtained via early-morning blood sampling. The geometry of the proximal femur at three sites (the narrow neck, intertrochanter, and shaft) was obtained using the Hip Structural Analysis technology. Analyses adjusted for subjects' age, height, total body lean mass and fat mass, and level of physical activity were performed.

SETTING

In-home interviews accompanied by subject visits to the General Clinical Research Center at Boston University School of Medicine were performed.

STUDY PARTICIPANTS

A randomly selected cohort of men living in Boston, MA (ages 30-79 yr) was included in the study.

INTERVENTIONS

These were not applicable.

MAIN OUTCOME MEASURES

Bone mineral density and bone outer diameter, cross-sectional area (measuring bone material), and section modulus (an index of bending strength) were calculated.

RESULTS

In age-adjusted models, E2 was positively associated with hip strength parameters, whereas T was not. Adjustment for age and other parameters resulted in substantial reductions in, but not complete elimination of, associations between E2 and hip strength parameters.

CONCLUSION

Circulating E2 is strongly associated with proximal femur strength, an association that is partially mediated by body composition.

Estrogen and bone: insights from estrogen-resistant, aromatase-deficient, and normal men

Findings from estrogen-resistant and aromatase-deficient men have provided important insights into the role of estrogen in the male skeleton during growth. Importantly, as reported elsewhere in this issue, these data also suggested dose-response relationships between estrogen and bone turnover. In addition, studies in these unusual patients have stimulated research on defining the role of estrogen in regulating bone metabolism in normal adult and aging men, providing further insights into estrogen regulation of bone metabolism not only in men, but also in women.

Osteoporosis in men

With the aging of the population, there is a growing recognition that osteoporosis and fractures in men are a significant public health problem, and both hip and vertebral fractures are associated with increased morbidity and mortality in men. Osteoporosis in men is a heterogeneous clinical entity: whereas most men experience bone loss with aging, some men develop osteoporosis at a relatively young age, often for unexplained reasons (idiopathic osteoporosis). Declining sex steroid levels and other hormonal changes likely contribute to age-related bone loss, as do impairments in osteoblast number and/or activity. Secondary causes of osteoporosis also play a significant role in pathogenesis. Although there is ongoing controversy regarding whether osteoporosis in men should be diagnosed based on female- or male-specific reference ranges (because some evidence indicates that the risk of fracture is similar in women and men for a given level of bone mineral density), a diagnosis of osteoporosis in men is generally made based on male-specific reference ranges. Treatment consists both of nonpharmacological (lifestyle factors, calcium and vitamin D supplementation) and pharmacological (most commonly bisphosphonates or PTH) approaches, with efficacy similar to that seen in women. Increasing awareness of osteoporosis in men among physicians and the lay public is critical for the prevention of fractures in our aging male population.

Correlations between serum testosterone, estradiol, and sex hormone-binding globulin and bone mineral density in a diverse sample of men

CONTEXT

The relationship between hormones and bone mineral density (BMD) in men has received considerable attention. However, most studies have been conducted in homogenous populations, and it is not known whether differences in hormones impact racial and ethnic differences in BMD.

OBJECTIVE

Our objective was to examine associations of testosterone, estradiol, and sex hormone-binding globulin (SHBG) with BMD in a racially and ethnically diverse population.

DESIGN

This was a population-based, observational survey.

PARTICIPANTS

A total of 976 Black, Hispanic, and white randomly selected men ages 30-79 yr from the Boston Area Community Health/Bone Survey were included.

OUTCOME

BMD at the hip, wrist, and spine were calculated.

RESULTS

The mean age of the sample was 46.7 +/- 12.4 yr. BMD levels were highest in black men, followed by Hispanic and then white men. Associations between hormones and BMD were consistent across racial and ethnic groups. Total and free testosterone was not correlated with BMD in age- or multivariate-adjusted models. SHBG was inversely correlated with total hip and ultradistal radius BMD after age adjustment, but not with multivariate adjustment for age, lean mass, fat mass, physical activity, self-rated health, and smoking. Total and free estradiol levels were positively and significantly correlated with femoral neck and total hip BMD, even with multivariate adjustment (partial correlations ranged between 0.11 and 0.16). However, estradiol levels failed to account for racial and ethnic differences in hip BMD.

CONCLUSIONS

In our diverse population, neither serum total nor free testosterone levels were associated with BMD. Correlations between BMD and estradiol were significant but did not appear to account for any of the observed racial and ethnic differences in BMD. These findings suggest that differences in hormone levels are not a major contributor to the observed differences in BMD between Black, Hispanic, and white men.

Predictors of serum testosterone and DHEAS in African-American men

There are few reported data on biochemical and functional correlates of androgen levels in African-American men. This study aimed at reporting physical and biochemical correlates of serum total testosterone (total T), bioavailable testosterone (BT) and dehydroepiandrosterone-sulphate (DHEAS) levels in community-dwelling, African-American men aged 50-65 years. Home-based physical examinations and health status questionnaires were administered to randomly sampled men. Body composition (dual-energy X-ray absorptiometry), lower limb and hand-grip muscle strength, and neuropsychological functions were assessed. Levels of serum total T, BT, DHEAS, oestradiol (E2), adiponectin, leptin, triglycerides and glucose were measured. Multiple linear regression models were constructed to identify factors independently associated with androgen levels. DHEAS levels declined from age 50 to 65 years (p < 0.0001), but total T and BT levels remained constant. Independent of other associated factors, higher total T levels were associated with lower serum triglyceride levels (beta = -0.142, p = 0.049); higher BT was associated with better performance on the trail-making tests (TMT-B:TMT-A ratio: beta = -0.118, p = 0.024) and higher DHEAS levels were associated with lower adiponectin (beta = -0.293, p = 0.047) and higher mini-mental state examination (MMSE) score (beta = 0.098, p = 0.008). Multiple regression models predicted 21, 18 and 29% of variance in total T, BT and DHEAS, respectively. Higher total T levels were associated with serum metabolic markers, particularly lower triglycerides, whereas higher BT was associated with better cognitive and muscle function and DHEAS with lower adiponectin and higher MMSE scores.

Prevention and management of osteoporosis in women with breast cancer and men with prostate cancer

Advances in cancer treatment have resulted in improved life expectancies for survivors of breast and prostate cancer. As the number of cancer survivors grows, the long-term side effects of treatment play an increasingly prominent role in the routine care of these patients. Due to similar management approaches, survivors of breast and prostate cancer are at increased risk for osteoporosis. This review summarizes the prevention and management of osteoporosis and osteopenia resulting from cancer treatment in survivors of breast and prostate cancer.

The relation of the XbaI and PvuII polymorphisms of the estrogen receptor gene and the CAG repeat polymorphism of the androgen receptor gene to peak bone mass and bone turnover rate among young healthy men

The genes coding for estrogen receptor-alpha (ER-alpha) and androgen receptors (AR) are potential candidates for the regulation of bone mass and turnover, which may contribute to both the achievement of peak bone mass and bone loss after completion of growth. The present study was aimed at elucidating the role of two restriction fragment lengths (XbaI and PvuII) polymorphisms of the ER gene and the CAG repeat polymorphism of the AR gene as determinants of peak bone mass in men; special attention was paid to the interaction between serum free estradiol (E2) levels and the XbaI and PvuII genotypes. A cross-sectional study, with data on lifestyle factors collected retrospectively, was performed in 234 young men, aged 18.3 to 20.6 years. Of the men, 184 were recruits of the Finnish Army and 50 were men of similar age who had postponed their military service for reasons not related to health. Bone mineral content (BMC), density (BMD) and scan area were measured in the lumbar spine and upper femur by dual-energy X-ray absorptiometry (DXA). The bone turnover rate was assessed by measuring serum type I procollagen aminoterminal propeptide (PINP) and tartrate-resistant acid phosphatase 5b (TRACP5b) as well as urinary excretion of type I collagen aminoterminal telopeptide (NTX). After adjusting for age, height, weight, exercise, smoking, calcium and alcohol intake, BMC, scan area and BMD at all measurement sites were similar for the different XbaI and PvuII genotypes of the ER and independent of the number of the CAG repeats of the AR gene. No association was found between free E2 levels and bone parameters among any genotype group of the XbaI and PvuII polymorphisms. Except for urinary NTX, which showed a tendency to higher values for the xx (P=0.08) and pp (P=0.10) genotypes of the ER, bone turnover markers were not related to the genotypes studied. Our study does not support the view that the XbaI and PvuII polymorphisms of the ER gene and the CAG polymorphism of the AR gene would have a substantial impact on the development of peak bone mass in young Finnish men.

Determinants of bone mineral density in Chinese men

Osteoporotic fractures are increasing among Asian populations in both genders, but the risk factors for low bone mineral density (BMD) in Asian men is unclear. To determine the hormonal and lifestyle risk factors for low BMD in Asian men, we studied 407 community-dwelling southern Chinese men aged 50 years and above. Medical history and lifestyle habits were obtained with a structured questionnaire. Dietary calcium and phytoestrogen intake were assessed by a semi-quantitative questionnaire. BMD at the spine and hip were measured by dual-energy X-ray absorptiometry (DXA). Fasting blood was analyzed for 25(OH)D, parathyroid hormone (PTH), total and bioavailable estradiol (bio-E) and testosterone (bio-T). The mean age of the cohort was 68.42+/-10.4 (50-96) years. In the linear regression model, weight, age, body mass index (BMI), bio-E, PTH, cigarette smoking and weight-bearing exercise were significant determinants of total hip BMD. Together they explained 55% of the total variance of hip BMD, with body weight being the most important determining factor. With age and weight adjustment, height, bio-T and flavonoid intake were identified as additional determinants of total hip BMD. Strategies to prevent bone loss and osteoporosis in Asian men should include lifestyle modification and maintenance of hormonal sufficiency.

Effect of aromatase inhibition on bone metabolism in elderly hypogonadal men

Both estrogens and androgens play important roles in skeletal development and maintenance in men. The relative importance of estrogens and androgens in male bone metabolism, however, remains undefined. Anastrozole is an oral aromatase inhibitor that decreases estrogen production and increases androgen production in men. Currently, anastrozole is being investigated as a potential agent for the treatment of hypogonadism in aging men. Because anastrozole lowers estrogen levels and raises androgen levels, its effect on bone metabolism is difficult to predict. To assess the effects of anastrozole on bone turnover, we randomized 37 elderly (ages 62-74) mildly hypogonadal men (serum testosterone <350 ng/dl) to receive either anastrozole 1 mg daily (n=12), anastrozole 1 mg twice weekly (n=11), or daily placebo (n=14) for 12 weeks. Serum gonadal steroid levels, serum and urine biochemical markers of bone turnover, serum osteoprotegerin, and total body bone mineral density were measured at baseline and week 12. Mean serum levels of total and bioavailable testosterone increased substantially in both treated groups. Specifically, mean +/- SD bioavailable testosterone levels increased from 99+/-31 ng/dl to 207+/-65 ng/dl in the group receiving 1 mg of anastrozole daily and from 115+/-37 ng/dl to 178+/-55 ng/dl in the subjects receiving 1 mg of anastrozole twice weekly ( p <0.001 vs placebo for both groups). Serum estradiol levels decreased modestly in both treated groups (from 26+/-8 pg/ml to 17+/-6 pg/ml in the daily treatment group and from 27+/-8 pg/ml to 17+/-5 pg/ml in the twice-weekly treatment group, p <0.001 vs placebo for both groups). Despite these hormonal changes, no increases in biochemical markers of bone resorption were observed. Specifically, mean serum N-telopeptide and urinary deoxypyridinoline concentrations remained stable in both treated groups over the 12-week treatment period. Similarly, serum biochemical markers of bone formation (osteocalcin and amino-terminal propeptide of type 1 collagen), serum osteoprotegerin, and total body bone mineral density did not change. These data demonstrate that although short-term administration of anastrozole decreases serum estradiol levels in elderly men with mild hypogonadism, this intervention does not adversely affect bone metabolism over a 12-week period. This lack of an effect may be due to the concomitant increase in testosterone production, the relative modest effect on estradiol production, or a combination of both factors. These results suggest that anastrozole therapy is unlikely to have an adverse effect on bone metabolism when taken over extended periods and may prove to be a valuable method of normalizing testosterone production in older men.

Sex-hormone-binding globulin is negatively correlated with femoral bone-mineral density in male cardiac-transplant recipients

BACKGROUND

Osteoporosis and the subsequent increase in incidence of fractures are a common problem after cardiac transplantation.

DESIGN

We performed a cross-sectional evaluation of male cardiac-transplant recipients in a late post-transplantation period (4.2 +/- 2.6 years after cardiac transplantation, n = 21). Bone-mineral density was measured by dual-energy X-ray absorptiometry and by quantitative heel ultrasound, and the endocrine characteristics of cardiac-transplant recipients with and without vertebral fractures were investigated.

RESULTS

A significant negative correlation was observed between sex-hormone-binding globulin and femoral-neck bone-mineral density (rs = -0.699; p value = 0.001). Linear regression analysis controlling for age and body-mass index proved sex-hormone-binding globulin to be an independent negative predictor for femoral-neck bone-mineral density (r = -0.474; p value = 0.035). Patients with vertebral fractures had significantly lower femoral-neck bone-mineral density (pvalue = 0.035). However, sex-hormone-binding globulin, total and free testosterone, and estradiol did not exhibit significant associations with vertebral fractures in our patients.

CONCLUSION

This investigation demonstrates for the first time an association between high sex-hormone-binding globulin levels and low femoral-neck bone-mineral density in a cohort of male cardiac-transplant recipients. Our data support the important role of sex-hormone-binding globulin in the pathogenesis of post-transplantation bone disease, although--possibly because of the small number of patients--we could not prove an interrelation of sex-hormone-binding globulin with vertebral fractures.

Relative contributions of testosterone and estrogen in regulating bone resorption and formation in normal elderly men

Young adult males who cannot produce or respond to estrogen (E) are osteopenic, suggesting that E may regulate bone turnover in men, as well as in women. Both bioavailable E and testosterone (T) decrease substantially in aging men, but it is unclear which deficiency is the more important factor contributing to the increased bone resorption and impaired bone formation that leads to their bone loss. Thus, we addressed this issue directly by eliminating endogenous T and E production in 59 elderly men (mean age 68 years), studying them first under conditions of physiologic T and E replacement and then assessing the impact on bone turnover of withdrawing both T and E, withdrawing only T, or only E, or continuing both. Bone resorption markers increased significantly in the absence of both hormones and were unchanged in men receiving both hormones. By two-factor ANOVA, E played the major role in preventing the increase in the bone resorption markers, whereas T had no significant effect. By contrast, serum osteocalcin, a bone formation marker, decreased in the absence of both hormones, and both E and T maintained osteocalcin levels. We conclude that in aging men, E is the dominant sex steroid regulating bone resorption, whereas both E and T are important in maintaining bone formation.