Progressive Temporal Change in Serum SHBG, But Not in Serum Testosterone or Estradiol, Is Associated With Bone Loss and Incident Fractures in Older Men: The Concord Health and Ageing in Men Project

Gender-Specific effects of L-arginine supplementation on bone mineral density and trabecular bone volume in Sprague-Dawley rats; stereological study

BACKGROUND

L-arginine (Arg) is a semi-essential amino acid that can be used as a key mediator for the release of growth hormone (GH), insulin-like growth factor-1(IGF-1), and other growth factors. In this study, we comprehensively evaluated the effect of Arg intake on bone growth and associated markers.

METHODS

The study involved 24 Sprague-Dawley rats (12 males, 12 females) divided into two groups (Age = 24 days). One group received a standard diet, while the other was injected with 10 mg/kg of Arg daily for 90 days. Serum bone markers like calcium (Ca), phosphorous(P), and alkaline phosphatase (ALP) were analyzed via colorimetric assays. stereological study and bone mineral density (BMD) were conducted via dissector method and Hologic Dual-energy x-ray absorptiometry (DXA) system; respectively.

RESULTS

Biochemical assays showed no significant differences in Ca, P, and ALP levels between groups. Male rats in the case group exhibited lower testosterone levels (p.value = 0.009). Stereological and bone mineral density (BMD) analyses revealed contrasting gender-specific outcomes. Female rats in the case group had higher BMD (p.value = 0.001), while males had lower BMD compared to controls (p.value = 0.018). Arg consumption affects trabecula volume values differently in females compared to males (p.value = 0.022). Furthermore, the study observed decreased osteocytes and osteoblasts in male case rats. The gender-based differences in BMD were attributed to Arg's paradoxical impact on testosterone levels in males.

CONCLUSION

Overall, Arg supplementation was found to influence BMD and trabecular bone volume, with outcomes varying depending on gender. The study highlights the intricate interplay between Arg, sex hormones, and bone health, offering insights into these complex relationships.

Inverted U-shaped association between total testosterone with bone mineral density in men over 60 years old

BACKGROUND

Aging often leads to changes in hormone levels, particularly testosterone, which is thought to significantly affect bone health in older males.

OBJECTIVE

This study aimed to explore the link between testosterone levels and bone mineral density in men aged 60 and above.

METHODS

Data from the National Health and Nutrition Examination Survey 2013-2014 were used. Weighted multivariable linear regression models were employed to study the association between testosterone and bone mineral density. Furthermore, a weighted generalized additive model and smooth curve fitting were used to address potential nonlinear patterns in the data.

RESULTS

The analysis included 621 elderly men. After accounting for various factors, the study uncovered a Inverted U-shaped correlation between testosterone levels and femoral neck density. Notably, a turning point was identified at the testosterone level of 406.4 ng/dL. Further examination, using different models, showed that testosterone levels in the third quartile (group Q3) were positively linked to bone density. However, contrasting trends were observed in the first (group Q1) and fourth quartiles (group Q4), where testosterone levels displayed a negative relationship with bone density.

CONCLUSION

The results indicate a complex interplay between testosterone levels and bone mineral density in elderly men. The U-shaped trend suggests that both low and high testosterone levels could negatively impact bone health. These findings highlight the importance of maintaining testosterone levels within an optimal range to preserve bone health in aging men.

Assessing the causal relationship between frailty and sex hormone-binding globulin or insulin-like growth factor-1 levels: A sex-stratified bidirectional Mendelian Randomization study

BACKGROUND

The association between frailty and sex hormone-binding globulin (SHBG) or insulin-like growth factor-1(IGF-1) levels demonstrates sex differences with inconsistent conclusions. This study aims to explore the causal relationship between frailty and SHBG or IGF-1 levels through bidirectional Mendelian randomization (MR).

METHODS

We conducted two-sample bidirectional sex-stratified MR analyses using summary-level data from genome-wide association studies (GWASs) to examine the causal relationship between frailty and IGF-1 or SHBG levels, as measured by frailty index (FI) and frailty phenotype (FP). We use the random-effects inverse-variance weighted (IVW), weighted median, MR-Egger, MR-Egger intercept, and leave-one-out approaches.

RESULT

The relationship between frailty and SHBG or IGF-1 levels is inversely related, with a significant decrease in SHBG levels in females. Specifically, SHBG levels significantly decrease with FI (β = -5.49; 95 % CI: -9.67 to -1.32; FDR = 0.02) and more pronounced with FP (β = -10.14; 95 % CI: -16.16 to -4.13; FDR = 0.01), as determined by the IVW approach. However, reverse analysis shows no significant effect of IGF-1 or SHBG levels on either FI or FP (p > 0.05).

CONCLUSION

Our study indicates a negative correlation between frailty and the levels of SHBG and IGF-1. It is suggested that further research is required to establish cut-off values for SHBG and IGF-1 levels in the frailty population. This is particularly important for females at higher risk, such as those undergoing menopause, to enable comprehensive assessment and early prevention efforts. While the findings imply that reduced IGF-1 and SHBG levels may not directly contribute to frailty, it is important not to overlook the underlying mechanisms through which they may indirectly influence frailty.

Causal relationship between gut microbiome and sex hormone-binding globulin: A bidirectional two-sample Mendelian randomization study

PROBLEM

Currently, there is a variety of evidence linking the gut microbiota to changes in sex hormones. In contrast, the causal relationship between SHBG, a carrier of sex hormones, and the gut microbiota is unclear.

METHOD OF STUDY

Bidirectional two-sample Mendelian randomization (MR) analysis was used to detect the causal effect between SHBG and the gut microbiome. Summary statistics of genome-wide association studies (GWASs) for the gut microbiome and SHBG were obtained from public datasets. Inverse-variance weighting (IVW), weighted median, weighted mode, MR-Egger and simple mode methods were used to operate the MR analysis. F-statistics and sensitivity analyses performed to evaluate bias and reliability.

RESULTS

When we set gut microbiome as exposure and SHBG as outcome, we identified nine causal relationships. In males, Coprobacter (PIVW = 2.01 × 10-6 ), Ruminococcus2 (PIVW = 3.40 × 10-5 ), Barnesiella (PIVW = 2.79 × 10-2 ), Actinobacteria (PIVW = 3.25 × 10-2 ) and Eubacterium fissicatena groups (PIVW = 3.64 × 10-2 ) were associated with lower SHBG levels; Alphaproteobacteria (PIVW = 1.61 × 10-2 ) is associated with higher SHBG levels. In females, Lachnoclostridium (PIVW = 9.75 × 10-3 ) and Defluviitaleaceae UCG011 (PIVW = 3.67 × 10-2 ) were associated with higher SHBG levels; Victivallaceae (PIVW = 2.23 × 10-2 ) was associated with lower SHBG levels. According to the results of reverse MR analysis, three significant causal effect of SHBG was found on gut microbiota. In males, Dorea (PIVW = 4.17 × 10-2 ) and Clostridiales (PIVW = 4.36 × 10-2 ) were associated with higher SHBG levels. In females, Lachnoclostridium (PIVW = 7.44 × 10-4 ) was associated with higherr SHBG levels. No signifcant heterogeneity of instrumental variables or horizontal pleiotropy was found in bidirectional two-sample MR analysis.

CONCLUSIONS

This study may provide new insights into the causal relationship between the gut microbiome and sex hormone-binding protein levels, as well as new treatment and prevention strategies for diseases such as abnormal changes in sex hormones.

Assessing the Casual Association between Sex Hormone Levels and Fracture Risk: A Two-Sample Mendelian Randomization Study

OBJECTIVE

Prior observational studies have reported that levels of sex hormones constitute a risk factor for the fracture. The aim of this study was to ascertain whether there is a causal relationship between the levels of sex hormones and the risk of fracture through Mendelian randomization (MR).

METHODS

Single-nucleotide polymorphisms (SNPs) associated with two indicators of sex hormone levels, circulating sex hormone-binding globulin (SHBG) and bioavailable testosterone levels, as exposures were selected from a large genome-wide association study (GWAS) from UK Biobank. The summary statistics for 11 different types of fracture as outcomes from the FinnGen consortium. This study employed the two-sample MR approach. For the main analysis, the inverse-variance-weighted (IVW) method was utilized. To assess the heterogeneity of MR results, the IVW method and MR-Egger method were utilized. To evaluate potential pleiotropy, MR-Egger regression was conducted. Additionally, a leave-one-SNP-out test was performed to assess the robustness of MR results to the exclusion of any individual SNP.

RESULTS

The MR analyses demonstrated a conspicuous impact of SHBG on the risk of pathological fracture with osteoporosis (OP). We found that an increase of one standard deviation (SD) in SHBG correspondingly increased the risk of pathological fracture with OP [odds ratio (OR) 2.42, 95% confidence interval (CI), 1.52-3.85; p = 1.93 × 10-4 ]. The bioavailable testosterone showed the negative casual genetic associations with fractures of foot and forearm. An increase of one SD in the genetically predetermined bioavailable testosterone was associated with a reduction of 37% in the risk of fracture of foot (OR 0.63, 95% Cl 0.49 to 0.81; p = 3.37 × 10-4 ), as well as a 39% decrease in the risk of fracture of forearm (OR 0.61, 95% Cl 0.50 to 0.76; p = 5.40 × 10-6 ).

CONCLUSIONS

Our study confirms that individuals experiencing elevated SHBG concentrations showed a major causal effect on pathological fracture with OP. High bioavailable testosterone levels play an important role in preventing the fractures of foot and forearm. Although increasing bioavailable testosterone and decreasing SHBG levels had no casual effect on most fractures in the general population, they are likely to have the most clinically relevant effect on certain fracture risk reduction.

Endocrine sequelae of hematopoietic stem cell transplantation: Effects on mineral homeostasis and bone metabolism

Hematopoietic stem cell transplantation (HSCT) is an established therapeutic strategy for the treatment of malignant (leukemia and lymphoma) and non-malignant (thalassemia, anemia, and immunodeficiency) hematopoietic diseases. Thanks to the improvement in patient care and the development of more tolerable conditioning treatments, which has extended the applicability of therapy to the elderly, a growing number of patients have successfully benefited from HSCT therapy and, more importantly, HSCT transplant-related mortality has consistently reduced in recent years. However, concomitantly to long term patient survival, a growing incidence of late HSCT-related sequelae has been reported, being variably associated with negative effects on quality of life of patients and having a non-negligible impact on healthcare systems. The most predominantly observed HSCT-caused complications are chronic alterations of the endocrine system and metabolism, which endanger post-operative quality of life and increase morbidity and mortality of transplanted patients. Here, we specifically review the current knowledge on HSCT-derived side-effects on the perturbation of mineral metabolism; in particular, the homeostasis of calcium, focusing on current reports regarding osteoporosis and recurrent renal dysfunctions that have been observed in a percentage of HSC-transplanted patients. Possible secondary implications of conditioning treatments for HSCT on the physiology of the parathyroid glands and calcium homeostasis, alone or in association with HSCT-caused renal and bone defects, are critically discussed as well.

Genetically predicted sex hormone levels and health outcomes: phenome-wide Mendelian randomization investigation

BACKGROUND

Sex hormone-binding globulin (SHBG), testosterone and oestradiol have been associated with many diseases in observational studies; however, the causality of associations remains unestablished.

METHODS

A phenome-wide Mendelian randomization (MR) association study was performed to explore disease outcomes associated with genetically proxied circulating SHBG, testosterone and oestradiol levels by using updated genetic instruments in 339 197 unrelated White British individuals (54% female) in the UK Biobank. Two-sample MR analyses with data from large genetic studies were conducted to replicate identified associations in phenome-wide MR analyses. Multivariable MR analyses were performed to investigate mediation effects of hormone-related biomarkers in observed associations with diseases.

RESULTS

Phenome-wide MR analyses examined associations of genetically predicted SHBG, testosterone and oestradiol levels with 1211 disease outcomes, and identified 28 and 13 distinct phenotypes associated with genetically predicted SHBG and testosterone, respectively; 22 out of 28 associations for SHBG and 10 out of 13 associations for testosterone were replicated in two-sample MR analyses. Higher genetically predicted SHBG levels were associated with a reduced risk of hypertension, type 2 diabetes, diabetic complications, coronary atherosclerotic outcomes, gout and benign and malignant neoplasm of uterus, but an increased risk of varicose veins and fracture (mainly in females). Higher genetically predicted testosterone levels were associated with a lower risk of type 2 diabetes, coronary atherosclerotic outcomes, gout and coeliac disease mainly in males, but an increased risk of cholelithiasis in females.

CONCLUSIONS

These findings suggest that sex hormones may causally affect risk of several health outcomes.

Bone health in ageing men

Osteoporosis does not only affect postmenopausal women, but also ageing men. The burden of disease is projected to increase with higher life expectancy both in females and males. Importantly, osteoporotic men remain more often undiagnosed and untreated compared to women. Sex steroid deficiency is associated with bone loss and increased fracture risk, and circulating sex steroid levels have been shown to be associated both with bone mineral density and fracture risk in elderly men. However, in contrast to postmenopausal osteoporosis, the contribution of relatively small decrease of circulating sex steroid concentrations in the ageing male to the development of osteoporosis and related fractures, is probably only minor. In this review we provide several clinical and preclinical arguments in favor of a 'bone threshold' for occurrence of hypogonadal osteoporosis, corresponding to a grade of sex steroid deficiency that in general will not occur in many elderly men. Testosterone replacement therapy has been shown to increase bone mineral density in men, however data in osteoporotic ageing males are scarce, and evidence on fracture risk reduction is lacking. We conclude that testosterone replacement therapy should not be used as a sole bone-specific treatment in osteoporotic elderly men.

Sex-specific differences in bone mineral density loss after sleeve gastrectomy

Background

Sleeve gastrectomy is an effective bariatric procedure; however, sleeve gastrectomy-related adverse skeletal outcomes have been increasingly reported. High levels of sex hormone-binding globulin (SHBG) have been documented to be a risk factor of bone mineral density (BMD) loss with different effects observed between sexes. The aim of this study was to identify sex-specific changes in BMD following sleeve gastrectomy and to evaluate the role of SHBG in this process.

Methods

This retrospective study included 19 middle-aged men and 30 non-menopausal women with obesity who underwent sleeve gastrectomy in China. Anthropometrics, bone turnover markers, calciotropic hormones, BMD, SHBG, and gonadal steroids were measured preoperatively and at 6 and 12 months postoperatively. Longitudinal changes in BMD, bone turnover markers and SHBG were compared between sexes by linear mixed models. Multiple stepwise regression analysis was used to identify the predictors of BMD loss at the investigated bone sites.

Results

Over the 12-month study period, total hip and femoral neck BMD decreased, while lumbar spine BMD remained largely unchanged in both sexes. Linear mixed models revealed significant sex × time interaction effects in total hip BMD and SHBG, showing that men had a significantly greater reduction in total hip BMD and less increase in SHBG after sleeve gastrectomy than women. In the multivariate model, SHBG was significantly associated with total hip BMD loss in men (adjusted β = −0.533, P = 0.019) but not women while total estrogen was significantly associated with total hip BMD loss in women (adjusted β = 0.508, P = 0.01) but not men.

Conclusion

Significant sex-specific BMD changes were observed after sleeve gastrectomy in the current study. Sleeve gastrectomy-related increase in SHBG may be a specific risk factor for total hip BMD loss in men. Our results indicate that sex-specific screening may be warranted to facilitate personalized postoperative bone care in this population.

Thyroid Hormone Abuse in Elite Sports: The Regulatory Challenge

Abuse of androgens and erythropoietin has led to hormones being the most effective and frequent class of ergogenic substances prohibited in elite sports by the World Anti-Doping Agency (WADA). At present, thyroid hormone (TH) abuse is not prohibited, but its prevalence among elite athletes and nonprohibited status remains controversial. A corollary of prohibiting hormones for elite sports is that endocrinologists must be aware of a professional athlete's risk of disqualification for using prohibited hormones and/or to certify Therapeutic Use Exemptions, which allow individual athletes to use prohibited substances for valid medical indications. This narrative review considers the status of TH within the framework of the WADA Code criteria for prohibiting substances, which requires meeting 2 of 3 equally important criteria of potential performance enhancement, harmfulness to health, and violation of the spirit of sport. In considering the valid clinical uses of TH, the prevalence of TH use among young adults, the reason why some athletes seek to use TH, and the pathophysiology of sought-after and adverse effects of TH abuse, together with the challenges of detecting TH abuse, it can be concluded that, on the basis of present data, prohibition of TH in elite sport is neither justified nor feasible.

Secondary Osteoporosis

Osteoporosis is a global public health problem, with fractures contributing to significant morbidity and mortality. Although postmenopausal osteoporosis is most common, up to 30% of postmenopausal women, > 50% of premenopausal women, and between 50% and 80% of men have secondary osteoporosis. Exclusion of secondary causes is important, as treatment of such patients often commences by treating the underlying condition. These are varied but often neglected, ranging from endocrine to chronic inflammatory and genetic conditions. General screening is recommended for all patients with osteoporosis, with advanced investigations reserved for premenopausal women and men aged < 50 years, for older patients in whom classical risk factors for osteoporosis are absent, and for all patients with the lowest bone mass (Z-score ≤ -2). The response of secondary osteoporosis to conventional anti-osteoporosis therapy may be inadequate if the underlying condition is unrecognized and untreated. Bone densitometry, using dual-energy x-ray absorptiometry, may underestimate fracture risk in some chronic diseases, including glucocorticoid-induced osteoporosis, type 2 diabetes, and obesity, and may overestimate fracture risk in others (eg, Turner syndrome). FRAX and trabecular bone score may provide additional information regarding fracture risk in secondary osteoporosis, but their use is limited to adults aged ≥ 40 years and ≥ 50 years, respectively. In addition, FRAX requires adjustment in some chronic conditions, such as glucocorticoid use, type 2 diabetes, and HIV. In most conditions, evidence for antiresorptive or anabolic therapy is limited to increases in bone mass. Current osteoporosis management guidelines also neglect secondary osteoporosis and these existing evidence gaps are discussed.

The Role of Sex Hormones on Bone Mineral Density, Marrow Adiposity, and Muscle Adiposity in Middle-Aged and Older Men

PURPOSE

The etiology of age-related bone loss is less clear in men. This study is aimed to observe the variations of endogenous sex hormone concentrations with increasing of age in men, and investigate their relations to bone mass, marrow adiposity, and muscle adiposity.

METHODS

A total of 199 community-dwelling Chinese men (aged 41 to 82 years) were included and measured of serum total estradiol, total testosterone, and follicle-stimulating hormone (FSH) concentrations by enzyme-linked immunosorbent assay (ELISA). Vertebral trabecular volumetric bone mineral density (vBMD) was measured by quantitative computed tomography for all participants, and vertebral marrow fat content and erector muscle fat content were quantified by Chemistry-shift-encoding magnetic resonance imaging in 62 participants.

RESULTS

In this population, FSH concentration increased (p < 0.001) gradually with aging. Lower vBMD was independently associated with higher FSH concentration (β = -0.216, p < 0.001), but not with total estradiol or total testosterone. For each standard deviation increase in FSH there was a 50% higher risk of an individual having osteopenia or osteoporosis (vBMD < 120 mg/cm³). Marrow fat content and erector muscle fat content were greater in osteopenic and osteoporotic men, but there were no associations with sex hormones concentrations.

CONCLUSION

In summary, FSH but not total estradiol or total testosterone is related to vertebral trabecular vBMD in middle-aged and older Chinese men. Neither marrow adiposity nor muscle adiposity is associated with sex hormones.

Association between Serum Total Testosterone Level and Bone Mineral Density in Middle-Aged Postmenopausal Women

BACKGROUND

Hormone status strongly affects women's health and quality of life. To date, studies investigating the association between total testosterone (T) level and bone mineral density (BMD) in women are limited and have yielded contradictory conclusions. The aim of our study was to examine the association between serum total T level and lumbar BMD in postmenopausal women aged 40-59 years.

METHODS

The study group included 1,058 women from the 2011-2016 National Health and Nutrition Examination Survey. Multiple regression analyses were used to evaluate the association between serum total T level and lumbar BMD.

RESULTS

After adjusting for covariates, there was a positive association between the serum total T level and lumbar BMD (β, 1.07; 95% confidence interval, 0.17-1.97). A non-linearity in this association was identified, with a point of inflection at 30 ng/dL.

CONCLUSIONS

Serum total T level was positively associated with lumbar BMD in middle-aged postmenopausal women up to a T level >30 ng/dL. Therefore, increasing T level in women with a low serum total T level may have beneficial outcomes on bone health.

Association between serum estradiol level, sex hormone binding globulin level, and bone mineral density in middle-aged postmenopausal women

Background

Changes in sex hormones are thought to play an important role in bone health in postmenopausal women. Our aim in this study was to evaluate the association between levels of estradiol (E2), which is the most potent endogenous estrogen, and sex hormone binding globulin (SHBG) and bone mineral density (BMD) among postmenopausal women, 40–59 years of age.

Methods

Using data from the National Health and Nutrition Examination Survey 2013–2016, we performed weighted multivariable linear regression models to evaluate the associations between serum levels of E2 and SHBG and lumbar BMD. A weighted generalized additive model and smooth curve fitting were used to address potential nonlinearity.

Results

A total of 608 postmenopausal women were included in the analysis. The serum E2 level was positively associated with lumbar BMD, after adjusting for other covariates (β 0.65; 95% confidence interval (CI) 0.38–0.93). An inverted U-shaped association between the serum E2 level and lumbar BMD was further identified, with the point of inflection at an E2 level of 70 pg/mL. There was no significant association between the SHBG level and lumbar BMD (β 0.01; 95% CI − 0.30 to 0.31). However, the association between these two variables was U-shaped, with the point of inflection at an SHBG level of 65 nmol/L.

Conclusions

Based on our findings, it may be beneficial to appropriately increase serum E2 levels to promote bone health in postmenopausal women with low estrogen levels. Considering the inverted U-shaped association, an excessive E2 level may be harmful to BMD. In addition, increasing the SHBG level to within the normal range (65–144 nmol/L) may be considered.

FSH Level and Changes in Bone Mass and Body Composition in Older Women and Men

CONTEXT

FSH may have independent actions on bone remodeling and body fat regulation. Cross-sectionally, we have shown that serum FSH is associated with bone mineral density (BMD) and body fat in older postmenopausal women, but it remains unknown whether FSH predicts bone and fat changes.

OBJECTIVE

We examined whether baseline FSH level is associated with subsequent bone loss or body composition changes in older adults.

SETTING, DESIGN, PARTICIPANTS

We studied 162 women and 158 men (mean age 82 ± 4 years) from the Age, Gene/Environment Susceptibility (AGES)-Bone Marrow Adiposity cohort, a substudy of the AGES-Reykjavik Study of community-dwelling older adults. Skeletal health and body composition were characterized at baseline and 3 years later.

MAIN OUTCOMES

Annualized change in BMD and body composition by dual-energy X-ray absorptiometry (DXA) and quantitative computed tomography (QCT). Models were adjusted for serum estradiol and testosterone levels.

RESULTS

There was no evidence for an association between baseline FSH level and change in BMD or body composition by DXA or QCT. For femoral neck areal BMD, adjusted mean difference (95% CI) per SD increase in FSH was 1.3 (-0.7 to 3.3) mg/cm2/y in women, and -0.2 (-2.6 to 2.2) mg/cm2/y in men. For visceral fat, adjusted mean difference (95% CI) per SD increase in FSH was 1.80 (-0.03 to 3.62) cm2/y in women, and -0.33 (-3.73 to 3.06) cm2/y in men.

CONCLUSIONS

Although cross-sectional studies and studies in perimenopausal women have demonstrated associations between FSH and BMD and body composition, in older adults, FSH level is not associated with bone mass or body composition changes.

Impact of sex hormone-binding globulin on the human phenome

Background: Sex hormone-binding globulin (SHBG) is a circulating glycoprotein and a regulator of sex hormone levels, which has been shown to influence various traits and diseases. The molecular nature of SHBG makes it a feasible target for preventative or therapeutic interventions. A systematic study of its effects across the human phenome may uncover novel associations. Methods: We used a Mendelian randomization phenome-wide association study (MR-pheWAS) approach to systematically appraise the potential functions of SHBG while reducing potential biases such as confounding and reverse causation common to the literature. We searched for potential causal effects of SHBG in UK Biobank (N = 334 977) and followed-up our top findings using two-sample MR analyses to evaluate whether estimates may be biased due to horizontal pleiotropy. Results: Results of the MR-pheWAS across over 21 000 outcome phenotypes identified 12 phenotypes associated with genetically elevated SHBG after Bonferroni correction for multiple testing. Follow-up analysis using two-sample MR indicated the associations of increased natural log SHBG with higher impedance of the arms and whole body, lower pulse rate, lower bone density, higher odds of hip replacement, lower odds of high cholesterol or cholesterol medication use and higher odds of gallbladder removal. Conclusions: Our systematic MR-pheWAS of SHBG, which was comprehensive to the range of phenotypes available in UK Biobank, suggested that higher circulating SHBG affects the body impedance, bone density and cholesterol levels, among others. These phenotypes should be prioritized in future studies aiming to investigate the biological effects of SHBG or develop targets for therapeutic intervention.

Genetically Predicted Sex Hormone-Binding Globulin and Bone Mineral Density: A Mendelian Randomization Study

Previous observational studies have identified various risk factors associated with the development of osteoporosis, including sex hormone-binding globulin (SHBG). The aim of this study was to determine the potential causal effects of circulating SHBG concentrations on bone mineral density (BMD). Two-sample Mendelian randomization (MR) approach was applied in analyses. From summary-level data of genome-wide association studies (GWAS), we selected 11 single-nucleotide polymorphisms (SNPs) associated with SHBG levels as instrumental variable, and used summary statistics for BMD at forearm (FA) (n = 8143), femoral neck (FN) (n = 32,735), lumbar spine (LS) (n = 28,498) and heel (HL) (n = 394,929), and total-body BMD of different age-stages (15 or less, 15-30, 30-45, 45-60, 60 or more years old) (n = 67,358). Inverse causal associations was observed between SHBG levels and FA BMD (Effect = - 0.26; 95% CI - 0.49 to - 0.04; P = 0.022), HL eBMD (Effect = - 0.09; 95% CI - 0.12 to - 0.06; P = 3.19 × 10^-9), and total-body BMD in people aged 45-60 years (Effect = - 0.16; 95% CI - 0.31 to - 2.4 × 10^-3; P = 0.047) and over 60 years (Effect = - 0.19; 95% CI - 0.33 to - 0.05; P = 0.006). Our study demonstrates that circulating SHBG concentrations are inversely associated with FA and HL eBMD, and total-body BMD in people aged over 45 years, suggesting that the role of SHBG in the development of osteoporosis might be affected by chronological age of patients and skeletal sites.

Testosterone and Bone Health in Men: A Narrative Review

Bone fracture due to osteoporosis is an important issue in decreasing the quality of life for elderly men in the current aging society. Thus, osteoporosis and bone fracture prevention is a clinical concern for many clinicians. Moreover, testosterone has an important role in maintaining bone mineral density (BMD) among men. Some testosterone molecular mechanisms on bone metabolism have been currently established by many experimental data. Concurrent with a decrease in testosterone with age, various clinical symptoms and signs associated with testosterone decline, including decreased BMD, are known to occur in elderly men. However, the relationship between testosterone levels and osteoporosis development has been conflicting in human epidemiological studies. Thus, testosterone replacement therapy (TRT) is a useful tool for managing clinical symptoms caused by hypogonadism. Many recent studies support the benefit of TRT on BMD, especially in hypogonadal men with osteopenia and osteoporosis, although a few studies failed to demonstrate its effects. However, no evidence supporting the hypothesis that TRT can prevent the incidence of bone fracture exists. Currently, TRT should be considered as one of the treatment options to improve hypogonadal symptoms and BMD simultaneously in symptomatic hypogonadal men with osteopenia.

Associations of Sex Steroids With Changes in Calcaneal Quantitative Ultrasound Measurements: A Longitudinal Study in Chinese Male Adolescents

This 2-year longitudinal study aimed to detect the associations of sex steroids, sex hormone-binding globulin with bone parameters and the changes thereof in Chinese male adolescents. A total of 642 male students aged 12-16 years from a secondary school in Jiangmen, China, were included. Total testosterone (T), total oestradiol (E2), and sex hormone-binding globulin were measured by chemiluminescence immunoassay. The bioavailable T (BioT) and E2 (BioE2) were calculated. The speed of sound, broadband ultrasound attenuation, and stiffness index of the right heel were measured by Sahara Clinical Bone Sonometer at both baseline and 2-year follow-up. The confounding effects of age, height, weight, pubertal stage, physical activity, energy-adjusted dietary calcium intake, and dietary vitamin D intake were adjusted. The baseline value of each bone parameter was also adjusted in the longitudinal analysis. Results showed that total T and BioT were positively associated with bone parameters and changes in them (β = 0.076-0.115, p < 0.05). A threshold effect of BioT on broadband ultrasound attenuation, stiffness index and their changes were also observed. Positive associations between BioT and bone mass gain were observed only in individuals with BioT levels <240.0 ng/dl (β = 0.088-0.131, p < 0.05). Moreover, total E2 or BioE2 were found to be inversely associated with speed of sound and its change (β = -0.109 to -0.077, p < 0.05). This study supported that in Chinese male adolescents, serum T was a positive predictor for bone formation with a threshold effect, and E2 could have influence on the changes in bone architecture during puberty. These findings may improve the understanding of the effects of sex steroids on the acceleration of bone formation in male adolescents and provide useful information for the prediction model establishment of peak bone mass.

Late-onset Hypogonadism: Bone health

BACKGROUND

Bone health is underdiagnosed and undermanaged in men. Bone loss occurs in men with hypogonadism and in aging men. Thus, patients with a diagnosis of late-onset hypogonadism (LOH) are at risk of osteoporosis and osteoporotic fractures.

OBJECTIVES

To provide an update on research data and clinical implications regarding bone health in men with LOH by reviewing literature articles on this issue.

MATERIALS AND METHODS

A thorough search of listed publications in PubMed on bone health in older men with hypogonadism was performed, and other articles derived from these publications were further identified.

RESULTS

Late-onset Hypogonadism may be associated with reduced bone mineral density (BMD). In a pathophysiological perspective, the detrimental effects of testosterone (T) deficiency on BMD are partly ascribed to relative estrogen deficiency and both serum T and serum estradiol (E2) need to be above 200 ng/dL and 20 pg/mL to prevent bone loss. The effects of exogenous T on BMD are controversial, but most of the studies confirm that testosterone replacement therapy (TRT) increases BMD and prevents further bone loss in men with hypogonadism. No data are available on TRT and the prevention of fractures.

DISCUSSION AND CONCLUSION

In men with documented LOH, a specific clinical workup should be addressed to the diagnosis of osteoporosis in order to program subsequent follow-up and consider specific bone active therapy. TRT should be started according to guidelines of male hypogonadism while keeping in mind that it may also have positive effects also on bone health in men with LOH.

Follicle-stimulating hormone and estradiol are associated with bone mineral density and risk of fractures in men with type 2 diabetes mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is associated with a higher fracture risk. Sex hormones are important for maintaining skeletal health. It is not clear which sex hormone(s) contribute(s) to bone mineral density (BMD) and fracture risk in males with T2DM. This study investigated the relationships of these parameters in males with T2DM.

METHODS

This study involved 482 men with T2DM. BMDs at the lumbar spine (L2-4), femoral neck (FN), and total hip (TH) were measured by dual-energy X-ray absorptiometry (DXA). The 10-year probability of fractures was assessed using the modified Fracture Risk Algorithm (FRAX) tool. Serum levels of sex hormones were measured.

RESULTS

Follicle-stimulating hormone (FSH) and estradiol (E2) were associated with BMDs at L2-4 (FSH, β = -.162, P < .05; E2, β = .176, P < .001), and E2 was associated with BMD at FN (β = .137, P < .05) and TH (β = .140, P < .05). FSH was associated with major osteoporotic fractures (β = .288, P < .001) and hip fractures (β = .235, P < .001). Higher FSH was a risk factor for osteoporosis/osteopenia (odds ratios [OR] = 2.92, 95% CI = 1.66-5.14, P < .001), whereas higher E2 was a protective factor (OR = 0.37, 95% CI = 0.22-0.60, P < .001). Patients in the higher tertile of FSH and lower tertile of E2 had an increased risk of osteoporosis/osteopenia (OR = 5.05, 95% CI = 1.37-18.65, P < .05).

CONCLUSIONS

For males with T2DM, FSH and E2 are significantly associated with BMD, osteoporosis/osteopenia, and fracture risk.

U-Shaped Association of Plasma Testosterone, and no Association of Plasma Estradiol, with Incidence of Fractures in Men

PURPOSE

Whether androgens, distinct from estrogen, maintain bone health during male aging has implications for understanding osteoporosis. We assessed associations of different sex hormones with incidence of any bone fracture or hip fracture in older men.

PARTICIPANTS AND METHODS

Analysis of 3307 community-dwelling men aged 76.8 ± 3.5 years, median follow-up period of 10.6 years. Plasma testosterone (T), dihydrotestosterone (DHT), and estradiol (E2) assayed by mass spectrometry, sex hormone-binding globulin (SHBG), and luteinizing hormone (LH) using immunoassay. Incident fractures determined via data linkage. We analyzed probability of fracture and performed Cox regression adjusted for age, medical comorbidities, and frailty.

RESULTS

Incident fractures occurred in 330 men, including 144 hip fractures. Probability plots suggested nonlinear relationships between hormones and risk of any fracture and hip fracture, with higher risk at lower and higher plasma T, lower E2, higher SHBG, and higher LH. In fully adjusted models, there was a U-shaped association of plasma T with incidence of any fracture (Quartile 2 [Q2] versus Q1: fully adjusted hazard ratio [HR] = 0.69, 95% confidence interval [CI] 0.51-0.94, P = .020; Q3: HR 0.59, 95% CI 0.42-0.83, P = .002) and hip fracture (Q2 versus Q1: HR 0.60, 95% CI 0.37-0.93, P = .043; Q3: HR 0.52, 95% CI 0.31-0.88, P = .015). DHT, E2, and LH were not associated with fracture. Higher SHBG was associated with hip fracture (Q4 versus Q1: HR 1.76, 95% CI 1.05-2.96, P = .033).

CONCLUSIONS

Midrange plasma T was associated with lower incidence of any fracture and hip fracture, and higher SHBG with increased risk of hip fracture. Circulating androgen rather than estrogen represents a biomarker for hormone effects on bone driving fracture risk.

New Biomarkers to Evaluate Hyperandrogenemic Women and Hypogonadal Men

Androgens can have variable effects on men and women. Women may be evaluated for androgen excess for several reasons. Typically, young premenopausal women present with clinical symptoms of hirsutism, alopecia, irregular menses, and/or infertility. The most common cause of these symptoms is polycystic ovary syndrome. After menopause, even though ovaries stop producing estrogen, they continue to produce androgen, and women can have new onset of hirsutism and alopecia. Laboratory evaluation involves measurement of the major ovarian and adrenal androgens. In women, age, phase of the menstrual cycle, menopausal status, obesity, metabolic health, and sex hormone-binding proteins significantly affect total-androgen levels and complicate interpretation. This review will summarize the clinically relevant evaluation of hyperandrogenemia at different life stages in women and highlight pitfalls associated with interpretation of commonly used hormone measurements. Hypogonadism in men is a clinical syndrome characterized by low testosterone and/or low sperm count. Symptoms of hypogonadism include decreased libido, erectile dysfunction, decreased vitality, decreased muscle mass, increased adiposity, depressed mood, osteopenia, and osteoporosis. Hypogonadism is a common disorder in aging men. Hypogonadism is observed rarely in young boys and adolescent men. Based on the defects in testes, hypothalamus, and/or pituitary glands, hypogonadism can be broadly classified as primary, secondary, and mixed hypogonadism. Diagnosis of hypogonadism in men is based on symptoms and laboratory measurement. Biomarkers in use/development for hypogonadism are classified as hormonal, Leydig and Sertoli cell function, semen, genetic/RNA, metabolic, microbiome, and muscle mass-related. These biomarkers are useful for diagnosis of hypogonadism, determination of the type of hypogonadism, identification of the underlying causes, and therapeutic assessment. Measurement of serum testosterone is usually the most important single diagnostic test for male hypogonadism. Patients with primary hypogonadism have low testosterone and increased luteinizing hormone (LH) and follicle-stimulating hormone (FSH). Patients with secondary hypogonadism have low testosterone and low or inappropriately normal LH and FSH. This review provides an overview of hypogonadism in men and a detailed discussion of biomarkers currently in use and in development for diagnosis thereof.

Age-related changes in estradiol and longitudinal associations with fat mass in men

Context

In men, circulating 17β-estradiol originates primarily from peripheral aromatization of testosterone particularly in adipose tissue. The effect of ageing and obesity on circulating estradiol remains unclear.

Objective

Determine five-year changes in serum estradiol and the association with testosterone and fat mass in Australian men.

Design

Longitudinal cohort study. At baseline and five-year follow-up, socio-demographic and health-related data including behaviors, chronic conditions, and medication use were collected by questionnaire. Estradiol and testosterone were assayed by liquid chromatography-tandem mass spectrometry and sex hormone-binding globulin by immunochemiluminescent assay. Fat mass was assessed by dual-energy X-ray absorptiometry.

Participants

Community-dwelling men aged 35 years and older at enrollment, resident in the northern and western suburbs of Adelaide without established disease of, or medications affecting, the hypothalamus-pituitary-gonadal axis (n = 725).

Main outcome measures

The dependence of change in serum estradiol over five years on age, testosterone and fat mass after adjustment for multiple confounders.

Results

At baseline, mean age was 53.0 ± 10.8 years. Mean serum estradiol levels at baseline and five-year follow-up were 94.9 ± 34.8 and 89.4 ± 30.4 pmol/L respectively (-1.1 pmol/L/year). On multivariable analyses, estradiol change was associated with changes in testosterone (B-estimate = 2.719, standard error = 0.369, p˂0.001), but not age or total fat mass. Change in testosterone/estradiol ratio was inversely associated with change in fat mass (B = -1.450, SE = 0.575, p = 0.012), and this was consistent across quartiles of fat mass change.

Conclusions

In healthy men, circulating estradiol is primarily dependent on testosterone. With increasing fat mass, estradiol decreases less than testosterone. From a clinical standpoint these data indicate that obesity is associated with a change in the testosterone to estradiol ratio, but a change in estradiol does not occur unless some other pathology is present.

Sex hormone-binding globulin is a biomarker associated with nonvertebral fracture in men on dialysis therapy

Gonadal hormones impact bone health and higher values of sex hormone-binding globulin (SHBG) have been independently associated with fracture risk in men without chronic kidney disease. People with chronic kidney disease have a greatly increased fracture risk, and gonadal dysfunction is common in men receiving dialysis treatment. Nevertheless, in these men the effect of gonadal steroids and SHBG on bone mineral density (BMD) and fracture risk is unknown. Here we investigate relationships between gonadal steroids, SHBG, BMD and fracture in men on long-term dialysis therapy, awaiting kidney or simultaneous pancreas kidney transplantation. Results of serum biochemistry, SHBG, gonadal steroids (total testosterone, calculated free testosterone and estradiol), BMD by dual-energy X-ray absorptiometry and thoracolumbar X-rays were obtained. Multivariable regression models were used to examine associations between SHBG, gonadal steroids, BMD and fracture of 321 men with a mean age of 47 years. Diabetes mellitus was present in 45% and their median dialysis vintage was 24 months. Prior fractures occurred in 42%, 18% had vertebral fracture on lateral spine X-ray, 17% had non-vertebral fragility fracture within 10 years and 7% had both. After adjustment for age, body mass index and dialysis vintage, higher SHBG levels were significantly associated with nonvertebral fractures [odds ratio 1.81 (1.30-2.53)] and remained significant after adjustment for BMD. Calculated free testosterone and estradiol values were not associated with fracture. Prevalent fracture rates were high in relatively young men on dialysis awaiting transplantation. Thus, SHBG is a novel biomarker associated with fracture, which warrants investigation in prospective studies.

Serum follicle stimulating hormone is associated with reduced risk of diabetes in postmenopausal women: The Hong Kong osteoporosis study

Menopause is an important transition of reproductive stage in a woman's life. It is associated with diabetes, but the role of follicle stimulating hormone (FSH), a menopause-related hormone, in the risk of diabetes is largely unknown. We evaluated the relationship between serum FSH and diabetes in 1274 participants from the Hong Kong Osteoporosis Study aged≥55 at baseline. We also searched relevant databases for studies on serum FSH and incident diabetes and conducted a meta-analysis using fixed-effect modeling. Cases of incident diabetes (N = 60) were ascertained during a median follow-up of 10.7 years. Serum FSH was significantly associated with reduced risk of diabetes in both a crude model (hazard ratio [HR] per SD increase: 0.66; 95% CI: 0.48-0.89; P = 0.007) and a full model with adjustment for age, sex, body mass index, factors related to risk of diabetes, and reproductive health (HR per SD increase: 0.70; 95% CI: 0.51-0.97; P = 0.030); a similar result was observed when FSH was analysed in quintiles. In a fixed-effect meta-analysis of two studies, including the current study, serum FSH > 50 IU/L was associated with reduced risk of diabetes (HR = 0.56; 95% CI: 0.36-0.85; P = 0.006; I² = 0). In conclusion, serum FSH levels were independently associated with diabetes.

Identification of Hip BMD Loss and Fracture Risk Markers Through Population-Based Serum Proteomics

Serum proteomics analysis may lead to the discovery of novel osteoporosis biomarkers. The Osteoporotic Fractures in Men (MrOS) study comprises men ≥65 years old in the US who have had repeated BMD measures and have been followed for incident fracture. High-throughput quantitative proteomic analysis was performed on baseline fasting serum samples from non-Hispanic white men using a multidimensional approach coupling liquid chromatography, ion-mobility separation, and mass spectrometry (LC-IMS-MS). We followed the participants for a mean of 4.6 years for changes in femoral neck bone mineral density (BMD) and for incident hip fracture. Change in BMD was determined from mixed effects regression models taking age and weight into account. Participants were categorized into three groups: BMD maintenance (no decline; estimated change ≥0 g/cm2 , n = 453); expected loss (estimated change 0 to 1 SD below the estimated mean change, -0.034 g/cm2 for femoral neck, n = 1184); and accelerated loss (estimated change ≥1 SD below mean change, n = 237). Differential abundance values of 3946 peptides were summarized by meta-analysis to determine differential abundance of each of 339 corresponding proteins for accelerated BMD loss versus maintenance. Using this meta-analytic standardized fold change at cutoffs of ≥1.1 or ≤0.9 (p < 0.10), 20 proteins were associated with accelerated BMD loss. Associations of those 20 proteins with incident hip fracture were tested using Cox proportional hazards models with age and BMI adjustment in 2473 men. Five proteins were associated with incident hip fracture (HR between 1.29 and 1.41 per SD increase in estimated protein abundance). Some proteins have been previously associated with fracture risk (eg, CD14 and SHBG), whereas others have roles in cellular senescence and aging (B2MG and TIMP1) and complement activation and innate immunity (CO7, CO9, CFAD). These findings may inform development of biomarkers for future research in bone biology and fracture prediction. © 2017 American Society for Bone and Mineral Research.

Male Hypogonadism and Osteoporosis: The Effects, Clinical Consequences, and Treatment of Testosterone Deficiency in Bone Health

It is well recognized that bone loss accelerates in hypogonadal states, with female menopause being the classic example of sex hormones affecting the regulation of bone metabolism. Underrepresented is our knowledge of the clinical and metabolic consequences of overt male hypogonadism, as well as the more subtle age-related decline in testosterone on bone quality. While menopause and estrogen deficiency are well-known risk factors for osteoporosis in women, the effects of age-related testosterone decline in men on bone health are less well known. Much of our knowledge comes from observational studies and retrospective analysis on small groups of men with variable causes of primary or secondary hypogonadism and mild to overt testosterone deficiencies. This review aims to present the current knowledge of the consequences of adult male hypogonadism on bone metabolism. The direct and indirect effects of testosterone on bone cells will be explored as well as the important differences in male osteoporosis and assessment as compared to that in females. The clinical consequence of both primary and secondary hypogonadism, as well as testosterone decline in older males, on bone density and fracture risk in men will be summarized. Finally, the therapeutic options and their efficacy in male osteoporosis and hypogonadism will be discussed.