Serum sex hormone-binding globulin and testosterone in relation to cardiovascular disease risk factors in young men: a population-based study

Metabolic-Associated Fatty Liver Disease and Insulin Resistance: A Review of Complex Interlinks

Metabolic-associated fatty liver disease (MAFLD) has now surpassed alcohol excess as the most common cause of chronic liver disease globally, affecting one in four people. Given its prevalence, MAFLD is an important cause of cirrhosis, even though only a small proportion of patients with MAFLD ultimately progress to cirrhosis. MAFLD suffers as a clinical entity due to its insidious and often asymptomatic onset, lack of an accurate and reliable non-invasive diagnostic test, and lack of a bespoke therapy that has been designed and approved for use specifically in MAFLD. MAFLD sits at a crossroads between the gut and the periphery. The development of MAFLD (including activation of the inflammatory cascade) is influenced by gut-related factors that include the gut microbiota and intactness of the gut mucosal wall. The gut microbiota may interact directly with the liver parenchyma (through translocation via the portal vein), or indirectly through the release of metabolic metabolites that include secondary bile acids, trimethylamine, and short-chain fatty acids (such as propionate and acetate). In turn, the liver mediates the metabolic status of peripheral tissues (including insulin sensitivity) through a complex interplay of hepatokines, liver-secreted metabolites, and liver-derived micro RNAs. As such, the liver plays a key central role in influencing overall metabolic status. In this concise review, we provide an overview of the complex mechanisms whereby MAFLD influences the development of insulin resistance within the periphery, and gut-related factors impact on the development of MAFLD. We also discuss lifestyle strategies for optimising metabolic liver health.

Age-related decrease in serum dihydrotestosterone concentration is accompanied by impaired vascular status

INTRODUCTION

The effect of androgens on the cardiovascular system in humans is ambiguous. Moreover, still little is known about the effects of the most potent androgen, dihydrotestosterone, on arterial stiffness and endothelial function. The aim of this study was to evaluate whether age-dependent alterations in serum concentration of dihydrotestosterone and its circulating metabolite are accompanied by changes in endothelial function and arterial stiffness.

METHODS

In 12 young and 11 older men, basal serum concentrations of testosterone, dehydroepiandrosterone sulfate (DHAE-S), androstenedione (AE), dihydrotestosterone (DHT) and androstanediol glucuronide (ADG) were analyzed in relation to vascular status including cIMT - carotid intima media thickness, cAI - central augmentation index, crPWV - carotid radial pulse wave velocity, SI - stiffness index, endothelial and inflammatory markers.

RESULTS

Although concentration of testosterone was not different between young and older group, it was demonstrated that DHT, DHEA-S, AE and ADG were significantly lower in older men in comparison to young men (p < 0.01). Interestingly the most surprising difference was found for DHT concentration, that was as much as 61 % lower in aged men that displayed significantly higher values of cIMT, AI, crPWV and SI (p < 10^-4), suggestive of arterial stiffness. Furthermore, DHT was negatively correlated to all arterial wall parameters (cAI, crPWV, SI and cIMT), c-reactive protein (CRP) and hyaluronic acid (HA) concentration, as well as positively correlated to markers of endothelial function (MNA and 6-keto-PGF_1α) in all studied individuals (n = 23).

CONCLUSIONS

We have shown that ageing leads to a significant decrease in DHT concentration that is accompanied by impaired arterial wall characteristics and worsened endothelial function. Therefore more attention should be paid to the DHT, DHEA-S and ADG concentrations as a biomarkers for vascular dysfunction in ageing men.

Association Between Sex Hormone-Binding Globulin, Atherogenic Indices of Plasma Among Young Sedentary Males

Background

Males are more likely than females to suffer from cardiovascular disease (CVD). So, sex hormones may modify these variations and affect the lipid profile. We examined the relationship between sex hormone-binding globulin (SHBG) and CVD risk factors among young males in this study.

Methods

Using a cross-sectional design, we measured total testosterone, SHBG, lipids, glucose, insulin, antioxidant parameters, and anthropometric factors in 48 young males in the age range of 18 to 40 years. Atherogenic indices of plasma were calculated. In this study, a partial correlation analysis was carried out to assess the relationship between SHBG and other variables after adjustment for confounders.

Results

According to the results of multivariable analyses adjusted for age and energy, SHBG had a negative correlation with total cholesterol (r = -.454, P =.010), low-density lipoprotein cholesterol (r = -.496, P =.005), quantitative insulin-sensitivity check index, and positive correlation with high-density lipoprotein cholesterol (r = .463, P =.009). No significant correlation was observed between SHBG and triglycerides (P >.05). Several atherogenic indices of plasma have a negative correlation with SHBG levels. These include Atherogenic Index of Plasma (r = -.474, P = .006), Castelli Risk Index (CRI)1 (r = -.581, P < .001), CRI2 (r = -.564, P = .001), and Atherogenic Coefficient (r = -.581, P < .001).

Conclusion

Among young men, high plasma SHBG was associated with reduced CVD risk factors, modified lipid profile and atherogenic ratios, and better glycemic markers. Therefore, reduced SHBG concentrations could be a prognostic marker of CVD among young sedentary males.

Differential Changes in Circulating Steroid Hormones in Hibernating Brown Bears: Preliminary Conclusions and Caveats

Brown bears are obese when they enter the den, and after 6 mo of hibernation and physical inactivity, bears show none of the adverse consequences of a sedentary lifestyle in humans, such as cardiovascular disease, type 2 diabetes, and kidney failure. The metabolic mechanisms that drive hibernation physiology in bears are poorly defined, but systemic endocrine regulators are likely involved. To investigate the potential role of steroid hormones, we quantified the total levels of 12 steroid hormones, the precursor cholesterol, sex hormone-binding globulin (SHBG), and corticosterone-binding globulin (CBG) in paired serum samples from subadult free-ranging Scandinavian brown bears during the active and hibernation states. During hibernation, androstenedione and testosterone were significantly decreased in subadult female bears (n=13), whereas they increased in all males but one (n=6) and therefore did not reach a significant difference. Despite this difference, SHBG increased more than 20-fold during hibernation for all bears. Compared with SHBG concentrations in humans, bear levels were very low in the active state, but during hibernation, levels equaled high levels in humans. The increased SHBG levels likely maintain a state of relative quiescence of the reproductive hormones in hibernating bears. Interestingly, the combination of SHBG and testosterone levels results in similar free bioavailable testosterone levels of 70-80 pM in both subadult and adult sexually active male bears, suggesting a role for SHBG in controlling androgen action during hibernation in males. Dehydroepiandrosterone sulfate, dihydrotestosterone, and estradiol levels were below the detection limit in all but one animal. The metabolically active glucocorticoids were significantly higher in both sexes during hibernation, whereas the inactive metabolite cortisone was reduced and CBG was low approaching the detection limit. A potential caveat is that the glucocorticoid levels might be affected by the ketamine applied in the anesthetic mixture for hibernating bears. However, increased hibernating cortisol levels have consistently been reported in both black bears and brown bears. Thus, we suggest that high glucocorticoid activity may support the hibernation state, likely serving to promote lipolysis and gluconeogenesis while limiting tissue glucose uptake to maintain a continuous glucose supply to the brain.

Obesity and polycystic ovary syndrome

The increased global prevalence of obesity over the last 40-years has driven a rise in prevalence of obesity-related co-morbidities, including polycystic ovary syndrome (PCOS). On a background of genetic susceptibility, PCOS often becomes clinically manifest following weight gain, commonly during adolescence. A common endocrinopathy affecting between 6%-10% of reproductive-age women, PCOS presents with the cardinal features of hyperandrogenism, reproductive and metabolic dysfunction. PCOS associates with insulin resistance, independently of (but amplified by) obesity. Insulin resistance in PCOS is characterized by abnormal post-receptor signalling within the phosphatidylinositol-kinase (PI3-K) pathway. Multiple factors (including most notably, weight gain) contribute towards the severity of insulin resistance in PCOS. Compensatory hyperinsulinaemia ensues, resulting in over-stimulation of the (intact) post-receptor mitogen-activated protein kinase (MAP-K) insulin pathway, with consequent implications for steroidogenesis and ovarian function. In this concise review, we explore the effects of weight gain and obesity on the pathogenesis of PCOS from the perspective of its three cardinal features of hyperandrogenism, reproductive and metabolic dysfunction, with a focus on the central mediating role of the insulin pathway. We also consider key lifestyle strategies for the effective management of obese and overweight women with PCOS.

Aging, Cardiovascular Risk, and SHBG Levels in Men and Women From the General Population

AIMS

Prior studies have reported inconsistent results for the association between sex hormone-binding globulin (SHBG) and cardiovascular disease among men and women. Although it is suggested that SHBG levels change with aging, the exact trend of SHBG across age and cardiovascular risk and the underlying mechanisms of these changes remain to be elucidated.

METHODS

Using data of 3264 men and women from a large population-based cohort study, we first visualized the distribution of serum SHBG levels across age. Second, we computed a cardiovascular risk factor sum score and investigated the mean SHBG levels across categories of the risk factor sum score and stratified per age-category. Next, linear regression models were used to investigate the associations between serum SHBG levels and age and potential regulators of SHBG, including body mass index (BMI), fasting insulin, sex steroids, thyroxine, and triglycerides.

RESULTS

Among men, a linear increase in SHBG levels with age and among women a U-shaped pattern was observed. Participants with larger number of cardiovascular risk factors had lower SHBG levels. When stratified by age, older participants had higher SHBG levels. A multivariate model including total testosterone and triglyceride levels in men and total testosterone, triglycerides, BMI, and fasting insulin in women explained, respectively, 46.2% and 31.8% of the variance in SHBG levels.

CONCLUSION

We observed a clear sex-specific pattern for SHBG levels with age. Our findings highlight the importance of taking into account the age-related changes in SHBG levels to avoid controversial results in the assessment of the cardiovascular risk associated with SHBG.

Lowered Serum Testosterone Concentration Is Associated With Enhanced Inflammation and Worsened Lipid Profile in Men

The negative relationship between testosterone and inflammatory cytokines has been reported for decades, although the exact mechanisms of their interactions are still not clear. At the same time, little is known about the relation between androgens and acute phase proteins. Therefore, in this investigation, we aimed to study the relationship between androgen status and inflammatory acute phase reactants in a group of men using multi-linear regression analysis. Venous blood samples were taken from 149 men ranging in age from 18 to 77 years. Gonadal androgens [testosterone (T) and free testosterone (fT)], acute phase reactants [C-reactive protein (CRP), ferritin (FER), alpha-1-acid glycoprotein (AAG), and interleukin-6 (IL-6)], cortisol (C), and lipid profile concentrations were determined. It was demonstrated that the markers of T and fT were negatively correlated with all acute phase proteins (CRP, FER, and AAG; p < 0.02) and the blood lipid profile [total cholesterol (TC), low-density lipoprotein (LDL), and triglycerides (TG); p < 0.03]. Multivariate analysis showed that T, fT, and the fT/C ratio were inversely correlated with the CRP, AAG, and FER concentrations independently of age and blood lipids. When adjustment for BMI was made, T, fT, and the fT/C ratio were negatively correlated with the AAG concentrations only. In addition, it was demonstrated that gonadal androgens were positively correlated with physical activity level (p < 0.01). We have concluded that a lowered serum T concentration may promote inflammatory processes independently of adipose tissue and age through a reduced inhibition of inflammatory cytokine synthesis, which leads to enhanced acute phase protein production. Therefore, a low serum T concentration appears to be an independent risk factor in the development of atherosclerosis and cardiovascular diseases. Moreover, the positive correlation between testosterone and physical activity level suggests that exercise training attenuates the age-related decrease in gonadal androgens and, in this way, may reduce the enhancement of systemic low-grade inflammation in aging men.

Cardiac remodeling in patients with childhood-onset craniopharyngioma-results of HIT-Endo and KRANIOPHARYNGEOM 2000/2007

Hypothalamic obesity caused by childhood-onset craniopharyngioma results in long-term cardiovascular morbidity. Knowledge about clinical markers and risk factors for cardiovascular morbidity is scarce. A cross-sectional study on transthoracic echocardiographic parameters was performed to determine the associations with clinical and anthropometric parameters in 36 craniopharyngioma patients. BMI correlated with the thickness of interventricular septum in diastole (IVSd) (r = 0.604, p < 0.001) and left ventricular posterior wall thickness in diastole (LVPWd) (r = 0.460, p = 0.011). In multivariate analyses on risk factors for cardiac remodeling, sex hormone replacement therapy, BMI, and male gender were positively correlated with increased left ventricular internal diameter in diastole (LVIDd), R² = 0.596, F = 10.323, p < 0.001. BMI and insulin resistance were selected as significant independent determinants of IVSd, produced R² = 0.655, F = 29.441, p < 0.001. Due to a wide range of disease duration, 17 pediatric and 19 adult patients were analyzed separately. In the adult subgroup (age at study ≥ 18 years), BMI correlated with IVSd (r = 0.707, p = 0.003), LVPWd (r = 0.592, p = 0.020), and LVIDd (r = 0.571, p = 0.026). In the pediatric subgroup (age at study < 18 years), no correlation between transthoracic echocardiography (TTE) parameters and BMI was observed. Only LVIDd correlated with disease duration (r = 0.645, p < 0.001). All cardiac functions were within the normal range, indicating no association with functional impairments.Conclusion: Cardiac remodeling in patients with craniopharyngioma correlated with the degree of hypothalamic obesity, disease duration, sex hormone replacement therapy, male gender, and insulin resistance. As echocardiography has limited sensitivity in patients with obesity, further research on more sensitive techniques for cardiac diagnostics in craniopharyngioma patients is warranted. What is Known: •Long-term prognosis in survivors of craniopharyngioma is impaired by obesity and cardiovascular disease. •Associations between echocardiographic findings and clinical and anthropometric parameters after craniopharyngioma are not yet analyzed. What is New: •In patients with childhood-onset craniopharyngioma, cardiac remodeling was associated with hypothalamic obesity, duration of disease, male gender sex hormone replacement, and insulin resistance. •Due to reduced echocardiographic sensitivity caused by obesity-related technical limitations, more sensitive cardiac diagnostics should be considered.

The brown bear as a translational model for sedentary lifestyle-related diseases

Sedentary lifestyle accelerates biological ageing, is a major risk factor for developing metabolic syndrome and is associated with cardiovascular disease, diabetes mellitus, kidney failure, sarcopenia and osteoporosis. In contrast to the linear path to worsening health in humans with metabolic syndrome, brown bears have developed a circular metabolic plasticity enabling these animals to tolerate obesity and a 'sedentary lifestyle' during hibernation and exit the den metabolically healthy in spring. Bears are close to humans physiology wise, much closer than rodents, the preferred experimental animals in medical research, and may better serve as translational model to develop treatments for lifestyle-related diseases. In this review, aspects of brown bear hibernation survival strategies are outlined and conceivable experimental strategies to learn from bears are described.

Higher Serum Sex Hormone-Binding Globulin Levels Are Associated With Incident Cardiovascular Disease in Men

CONTEXT

Sex hormone-binding globulin (SHBG) levels are associated with cardiovascular disease (CVD) risk factors. However, prospective data on the association between SHBG levels and CVD events are sparse, with conflicting results.

OBJECTIVES

To examine associations between serum SHBG, total testosterone (TT), and incident CVD and CVD-related mortality in middle-aged to elderly men.

DESIGN AND METHODS

Data on 2563 community-dwelling men (35 to 80 years) were obtained from participants in the Men Androgen Inflammation Lifestyle Environment and Stress cohort. The analytic sample included 1492 men without baseline (2002 to 2007) CVD and with fasted morning serum SHBG and TT available at both baseline and follow-up (2007 to 2010) and without medications affecting TT or SHBG. Associations of baseline SHBG and TT, with incident CVD and CVD mortality, were analyzed using logistic regression for incident CVD and Cox proportional hazard regression for CVD mortality, adjusting for established CVD risk factors.

RESULTS

In multivariable models, elevated baseline SHBG and lower baseline TT were independently associated with incident CVD (SHBG: OR, 1.54; 95% CI, 1.15 to 2.06 per SD increase in SHBG, P = 0.003; TT: OR, 0.71; 95% CI, 0.52 to 0.97 per SD decrease in TT; P = 0.03). A decrease in TT between time points was associated with incident CVD (OR, 0.72; 95% CI, 0.56 to 0.92; P = 0.01). Neither SHBG nor TT was significantly associated with all-age CVD mortality [hazard ratio (HR), 0.69; 95% CI, 0.29 to 1.63; P = 0.40; and HR, 0.60; 95% CI, 0.28 to 1.26; P = 0.18, respectively].

CONCLUSIONS

Among all men and men >65 years, elevated SHBG and lower TT were independently associated with both a greater risk of CVD and an increased CVD mortality risk.

Circulating sex hormone binding globulin: An integrating biomarker for an adverse cardio-metabolic profile in obese pregnant women

Sex hormone-binding globulin (SHBG) negatively associates with pre-gestational body mass index (BMI) and gestational weight gain. The link with other cardio-metabolic risk factors in pregnant women is poorly understood. Our aim was to study the association of SHBG levels with common cardio-metabolic risk parameters in pregnant woman.

Serum SHBG was quantified in 291 Caucasian pregnant women (142 with normal weight, 42 with pregestational obesity, 50 with gestational obesity and 57 with pregestational plus gestational obesity) with uncomplicated pregnancies and parturition. Cardio-metabolic [C-reactive protein (CRP), blood pressure (BP), glycosylated hemoglobin (HbAc1), glucose, C-peptide, insulin, triglycerides and high molecular weight (HMW) adiponectin], and endocrine [testosterone and estradiol] parameters were also assessed.

SHBG was negatively correlated with BMI, but also with CRP, BP, HbAc1, pre and post-load glucose, C-peptide, HOMA-IR, triglycerides; and positively with HMW adiponectin (all p<0.01 to p<0.0001). These associations were more robust in women with pregestational plus gestational obesity, who had lower SHBG, in comparison to normal-weight women (p<0.0001). In multivariate analyses in women with pregestational plus gestational obesity SHBG showed independent associations with CRP (β = −0.352, p = 0.03, R² = 8.0%), DBP (β = −0.353, p = 0.03, R² = 7.0%) and SBP (β = −0.333, p = 0.04, R² = 6.0%) independently of BMI and metabolic and endocrine parameters.

SHBG is decreased in pregnant women with pregestational plus gestational obesity in association with common cardio-metabolic parameters. SHBG could represent an integrating biomarker for an adverse cardio-metabolic profile in pregnant women with pregestational plus gestational obesity.

Cross-sectional and longitudinal determinants of serum sex hormone binding globulin (SHBG) in a cohort of community-dwelling men

Despite its widespread clinical use, there is little data available from population-based studies on the determinants of serum sex hormone binding globulin (SHBG). We aimed to examine multifactorial determinants of circulating SHBG levels in community-dwelling men. Study participants comprised randomly selected 35–80 y.o. men (n = 2563) prospectively-followed for 5 years (n = 2038) in the Men Androgen Inflammation Lifestyle Environment and Stress (MAILES) study. After excluding men with illness or medications known to affect SHBG (n = 172), data from 1786 men were available at baseline, and 1476 at follow-up. The relationship between baseline body composition (DXA), serum glucose, insulin, triglycerides, thyroxine (fT4), sex steroids (total testosterone (TT), oestradiol (E2)), and pro-inflammatory cytokines and serum SHBG level at both baseline & follow-up was determined by linear and penalized logistic regression models adjusting for age, lifestyle & demographic, body composition, metabolic, and hormonal factors. Restricted cubic spline analyses was also conducted to capture possible non-linear relationships. At baseline there were positive cross-sectional associations between age (β = 0.409, p<0.001), TT (β = 0.560, p<0.001), fT4 (β = 0.067, p = 0.019) and SHBG, and negative associations between triglycerides (β = -0.112, p<0.001), abdominal fat mass (β = -0.068, p = 0.032) and E2 (β = -0.058, p = 0.050) and SHBG. In longitudinal analysis the positive determinants of SHBG at 4.9 years were age (β = 0.406, p = <0.001), TT (β = 0.461, p = <0.001), and fT4 (β = 0.040, p = 0.034) and negative determinants were triglycerides (β = -0.065, p = 0.027) and abdominal fat mass (β = -0.078, p = 0.032). Taken together these data suggest low SHBG is a marker of abdominal obesity and increased serum triglycerides, conditions which are known to have been associated with low testosterone and low T4.

Association of central obesity with sex hormonebinding globulin: a cross-sectional study of 1166 Chinese men

Background Both sex hormone-binding globulin and central obesity have been found to be associated with metabolic and cardiovascular diseases. However, the direct relation between sex hormone-binding globulin and central obesity has not been demonstrated.

Methodology We performed a cross-sectional study of 1166 male participants from Zunyi, Guizhou, western China, in 2013. Each participant completed a questionnaire and had a brief clinical exam with a fasting blood sample taken. All blood samples underwent standard laboratory testing for sex hormone-binding globulin. Level of serum sex hormone-binding globulin was compared by demographic characteristics, and multiple linear regression was used to evaluate the independent association of variables and sex hormone-binding globulin level.

Results The mean serum level of sex hormone-binding globulin was increased in old-aged men (older than 40 years; mean 44.68±20.58 nmol/L), low diastolic blood pressure (<90mmHg; 43.76±20.50 nmol/L), waist-to-height ratio <0.5 (48.73±20.59 nmol/L), no education (52.36±22.91 nmol/L), farm occupation (43.58±20.60nmol/L), non-alcohol or former user (44.78±20.94 nmol/L) and long-term medication history (44.79±21.50 nmol/L). Factors independently associated with sex hormone binding globulin level on multiple regression were waist-to-height ratio (β=- 11.84 [95% confidence interval -13.96,-9.72]), age(β=12.40 [9.63,15.17]) and diastolic blood pressure (β=-5.07 [-7.44,-2.71]).

Conclusions Central obesity has an independent inverse relation with serum level of sex hormone binding globulin among western Chinese men

Metabolic phenotype of male obesity-related secondary hypogonadism pre-replacement and post-replacement therapy with intra-muscular testosterone undecanoate therapy

AIM

To explore the metabolic phenotype of obesity-related secondary hypogonadism (SH) in men pre-replacement and post-replacement therapy with long-acting intramuscular (IM) testosterone undecanoate (TU).

METHODS

A prospective observational pilot study on metabolic effects of TU IM in male obesity-related SH (hypogonadal [HG] group, n = 13), including baseline comparisons with controls (eugonadal [EG] group, n = 15). Half the subjects (n = 7 in each group) had type 2 diabetes mellitus (T2D). Baseline metabolic assessment on Human Metabolism Research Unit: fasting blood samples; BodPod (body composition), and; whole-body indirect calorimetry. The HG group was treated with TU IM therapy for 6-29 months (mean 14.8-months [SD 8.7]), and assessment at the Human Metabolism Research Unit repeated. T-test comparisons were performed between baseline and follow-up data (HG group), and between baseline data (HG and EG groups). Data reported as mean (SD).

RESULTS

Overall, TU IM therapy resulted in a statistically significant improvement in HbA1C (9 mmol/mol, P = 0.03), with 52% improvement in HOMA%B. Improvement in glycaemic control was driven by the HG subgroup with T2D, with 18 mmol/mol [P = 0.02] improvement in HbA1C. Following TU IM therapy, there was a statistically significant reduction in fat mass (3.5 Kg, P = 0.03) and increase in lean body mass (2.9 kg, P = 0.03). Lipid profiles and energy expenditure were unchanged following TU IM therapy. Comparisons between baseline data for HG and EG groups were equivalent apart from differences in testosterone, SHBG and basal metabolic rate (BMR).

CONCLUSION

In men with obesity-related SH (including a subgroup with T2D), TU IM therapy improved glycaemic control, beta cell function, and body composition.

Impact of Metabolic Syndrome Factors on Testosterone and SHBG in Type 2 Diabetes Mellitus and Metabolic Syndrome

OBJECTIVE

Several studies have often reported low testosterone and SHBG to be associated with type 2 DM and the metabolic syndrome (MetS). Our objective was to determine the impact of metabolic syndrome and diabetic parameters on testosterone and SHBG in both MetS subjects and type 2 DM patients.

METHODS

In this study, 120 Yemeni male aged 30-70 years old were enrolled, 30 of whom were healthy subjects with BMI < 25 kg/m² that served as control, 30 MetS, 30 type 2 DM without MetS, and 30 type 2 DM with MetS according to IDF criteria.

RESULTS

Testosterone (free and total) and SHBG were significantly lower in MetS subjects and modestly reduced in type 2 DM with and without MetS. Stepwise linear regression showed free and total testosterone to be negatively affected by waist circumference, and univariate analysis shows this significant difference to disappear when adjusted for waist circumference. On the other hand, stepwise linear regression showed SHBG to be positively affected by testosterone and age and negatively affected by FBG and TG. Univariate analysis shows this observed significant difference to disappear when adjusted for testosterone.

CONCLUSION

Abdominal obesity is a major determinant of low testosterone levels irrespective of diabetes status. Thus, supporting evidence suggesting that the causative relationship between the often low testosterone and type 2 DM might be bidirectional or even multidirectional and interrelated with obesity, MetS, and IR.

Associations Between Sleep Deprivation and Salivary Testosterone Levels in Male University Students: A Prospective Cohort Study

Sleep deprivation is a common health problem that is growing rapidly worldwide and it is associated with short- and long-term impacts on health. The aim of this study was to detect potential predictors of salivary testosterone (sT) association with sleep deprivation in Arab male university students. In this prospective cohort study, 77 university male students in the age range of 18 to 26 years were divided into two groups, sleep-deprived (SD) participants and non-sleep-deprived (NSD) participants. Sleep deprivation was defined as sleeping less than 5 hr per night. Blood samples and sT were collected from fasting participants to measure serum levels of glucose, lipid profile, leptin, serotonin, sT, and body mass index (BMI) values. The multiple linear correlation model of high-density lipoprotein cholesterol (HDL-C), BMI, and serotonin was positively correlated with sT (r = .977, p < .05) in the SD group. No correlations were identified with sT in the NSD group. In the SD study group, the multiple linear regression model of HDL-C, BMI, and serotonin was significantly influenced by sT (R² = .955, p < .05). These predictors together explained approximately 96% of the variance in sT levels in the SD study group. No predictive variables for sT were reported in the NSD group. Results indirectly confirmed the presence of a positive association between sT and sleep deprivation in young men. This association is mediated by three factors, HDL-C, BMI, and serum serotonin, which are collectively considered as part of a significant physiological adaptation to sleep deprivation in young men.

The Utility of Sex Hormone-Binding Globulin in Hypogonadism and Infertile Males

PURPOSE

We sought to determine the role of sex hormone-binding globulin in patients with male infertility.

MATERIALS AND METHODS

We retrospectively reviewed the records of 168 males seen at a fertility clinic from 2012 to 2014 to investigate the accuracy of total testosterone in the biochemical diagnosis of hypogonadism using calculated bioavailable testosterone as the reference value. We used multivariable analysis to assess sex hormone-binding globulin as an independent predictor of infertility.

RESULTS

Computations using calculated bioavailable testosterone as a standard in the measurement of definitive biochemical hypogonadism (less than 156 ng/dl) revealed 81% sensitivity, 83% specificity, 81% positive predictive value and 82% negative predictive value for diagnosing hypogonadism with total testosterone alone. Of the 90 men with total testosterone greater than 300 ng/dl, 20% had low bioavailable testosterone less than 156 ng/dl, 52% had borderline low bioavailable testosterone less than 210 ng/dl and only 48% could be considered biochemically eugonadal according to calculated bioavailable testosterone. Of the 80 patients with total testosterone less than 300 ng/dl, 19% had free testosterone levels greater than 6.5 ng/dl and, thus, could be considered to be eugonadal. By a magnitude similar to that of follicle-stimulating hormone, sex hormone-binding globulin independently predicted decreased sperm concentration (p = 0.0027) and motility (p = 0.0447). After excluding men with azoospermia, only sex hormone-binding globulin levels differed significantly in classically hypogonadal men (group 1-total testosterone less than 300 ng/dl) and those missed but hypogonadal (group 2-calculated bioavailable testosterone less than 210 ng/dl) (p = 0.0001). At a more stringent cutoff of calculated bioavailable testosterone less than 156 ng/dl, sperm motility was significantly different for groups 1 and 2 (p = 0.014).

CONCLUSIONS

Adding sex hormone-binding globulin to total testosterone serum testing facilitates more accurate diagnosis with free testosterone and calculated bioavailable testosterone, and clinical implications of decreased semen parameters to a magnitude similar to that of follicle-stimulating hormone. This warrants further study of the role of sex hormone-binding globulin in male infertility.

Low Levels of Sex Hormone-Binding Globulin Constitute an Independent Risk Factor for Arterial Stiffness in Korean Women

The association between sex hormone-binding globulin (SHBG) and arterial stiffness in women is not conclusive. In addition, obesity might also be involved in the relationship between SHBG and atherosclerosis. The aim of this study was to determine the relationship between SHBG and arterial stiffness in association with central obesity in women. This cross-sectional study included 381 women who participated in the health checkup programs in one hospital. The brachial-ankle pulse wave velocity (baPWV) was measured as a marker for arterial stiffness. A negative correlation was observed between SHBG levels and baPWV (rho = -0.281). The relationship was significant even after adjusting for potential confounders (beta = -0.087 in fully adjusted model). After considering the interaction between central obesity and SHBG levels, the significant association was evident only in obese women (P for interaction = 0.025). Adjustment for a 10-year atherosclerotic cardiovascular disease (ASCVD) risk scores, instead of each cardiovascular risk factor individually, did not affect the significance of the relationship between SHBG levels and baPWV. Serum levels of SHBG were negatively associated with arterial stiffness independent of cardiovascular risk factors or 10-year ASCVD risk scores in Korean women. The relationship may be potentiated by central obesity.

Biochemical Foundations of Health and Energy Conservation in Hibernating Free-ranging Subadult Brown Bear Ursus arctos

Brown bears (Ursus arctos) hibernate for 5-7 months without eating, drinking, urinating, and defecating at a metabolic rate of only 25% of the summer activity rate. Nonetheless, they emerge healthy and alert in spring. We quantified the biochemical adaptations for hibernation by comparing the proteome, metabolome, and hematological features of blood from hibernating and active free-ranging subadult brown bears with a focus on conservation of health and energy. We found that total plasma protein concentration increased during hibernation, even though the concentrations of most individual plasma proteins decreased, as did the white blood cell types. Strikingly, antimicrobial defense proteins increased in concentration. Central functions in hibernation involving the coagulation response and protease inhibition, as well as lipid transport and metabolism, were upheld by increased levels of very few key or broad specificity proteins. The changes in coagulation factor levels matched the changes in activity measurements. A dramatic 45-fold increase in sex hormone-binding globulin levels during hibernation draws, for the first time, attention to its significant but unknown role in maintaining hibernation physiology. We propose that energy for the costly protein synthesis is reduced by three mechanisms as follows: (i) dehydration, which increases protein concentration without de novo synthesis; (ii) reduced protein degradation rates due to a 6 °C reduction in body temperature and decreased protease activity; and (iii) a marked redistribution of energy resources only increasing de novo synthesis of a few key proteins. The comprehensive global data identified novel biochemical strategies for bear adaptations to the extreme condition of hibernation and have implications for our understanding of physiology in general.

Current medical management of endocrine-related male infertility

Male factor contributes to 50%-60% of overall infertility but is solely responsible in only 20% of couples. Although most male factor infertility is ascertained from an abnormal semen analysis, other male factors can be contributory especially if the sample returns normal. Male infertility can be due to identifiable hormonal or anatomical etiologies that may be reversible or irreversible. This manuscript will highlight existing guidelines and our recommendations for hormone evaluation for male infertility and empiric therapies including multivitamins, estrogen receptor modulators (clomiphene), estrogen conversion blockers (anastrozole), and hormone replacement.

Adaptation to acute coronary syndrome-induced stress with lowering of testosterone: a possible survival factor

OBJECTIVE

The objective of this study was to explore whether circulating testosterone (T) concentration is associated with the occurrence and risk for acute coronary syndromes (ACS).

METHOD

This case-control study included male patients with acute myocardial infarction (AMI) (n=174) or unstable angina pectoris (UAP) (n=90) and healthy controls (n=238). Patients gave serum samples during the acute (n=264) and recovery (n=132) phases after a median of 10.5 months after the incident event. Secondary events (ACS or cardiovascular death) were registered during the following 6 years.

RESULTS

During the acute phase, AMI and UAP patients had similar significantly reduced concentrations of serum testosterone in comparison to controls. Testosterone associated inversely with weight, the degree of inflammation (i.e. C-reactive protein concentration) and signs of a chronic infection. In a multiadjusted Cox regression, when compared to testosterone concentrations considered high-normal (14.91-34.0  nmol/l), low-normal testosterone (9.26-14.90  nmol/l) in the acute phase predicted better prognosis for cardiovascular death rate with a hazard ratio (HR) of 0.17 (0.04-0.68, P=0.012). The increased testosterone concentrations after the recovery period did not associate with future cardiovascular disease events.

CONCLUSION

Low-normal testosterone levels in the acute phase of ACS predicted better survival. The observation may indicate better adaptation to stress in survivors and warrants further study.

Metformin treatment to reduce central adiposity after prenatal growth restraint: a placebo-controlled pilot study in prepubertal children

BACKGROUND

Children born small-for-gestational-age (SGA) who experience rapid postnatal catch-up in weight are at risk for central adiposity and hyperinsulinemia.

OBJECTIVES

To study the effects of prepubertal metformin intervention over 24 months on the body composition and endocrine-metabolic profile of catch-up SGA children.

METHODS

Double-blind, placebo-controlled, pilot study including 23 post-catch-up non-obese prepubertal SGA children [age, 7.7 yr; body mass index standard deviation score (BMI SDS) >50th and <97th centile for age] with increased visceral fat [by magnetic resonance imaging (MRI) and insulin-like growth factor-I (IGF-I) both p > 75th for age]. Patients were randomized to receive either placebo or metformin (425 mg/d) for 24 months. Clinical, biochemical [IGF-I, glucose, insulin, lipids, androgens, sex-hormone-binding globulin (SHBG) and high-molecular-weight (HMW)-adiponectin] and imaging [body composition (absorptiometry and MRI; carotid intima-media thickness (ultrasonography)] variables were assessed at baseline, and at 6, 12, and 24 months.

RESULTS

After 24 months, metformin-treated children were leaner, had higher SHBG levels, and less total and abdominal fat than placebo-treated children (all p ≤ 0.05). Longitudinal analyses showed that metformin had a significant effect on anthropometric (weight, BMI, and waist) and biochemical variables [glucose, homeostasis model assessment-insulin resistance (HOMA-IR), and triglycerides] (all p ≤ 0.05); and in total and abdominal fat (p = 0.01 and p = 0.02).

CONCLUSIONS

Prepubertal intervention with metformin reduces central adiposity and improves insulin sensitivity in non-obese catch-up SGA children.

Sex hormone-binding globulin associations with circulating lipids and metabolites and the risk for type 2 diabetes: observational and causal effect estimates

BACKGROUND

The causal role of circulating sex hormone-binding globulin (SHBG) for type 2 diabetes is controversial. Information on the relations between SHBG and new biomarkers of cardiometabolic risk is scarce.

METHODS

We applied quantitative nuclear magnetic resonance metabolomics in three Finnish population-based cohorts to comprehensively profile circulating lipids and metabolites and study their associations with SHBG. Mendelian randomization was used to examine potential causality of SHBG on the metabolic measures and insulin resistance. Prospective associations and causal effect estimates of SHBG on type 2 diabetes were assessed via meta-analysis including summary statistics from the DIAGRAM consortium.

RESULTS

In cross-sectional analysis in 6475 young adults (mean age 31, 57% men), higher SHBG was linked with a more favourable cardiometabolic risk profile, including associations with lipoprotein subclasses, fatty acid composition, amino acids, ketone bodies and inflammation-linked glycoproteins. Prospective analysis of 1377 young adults with 6-year follow-up indicated that SHBG is also associated with future insulin resistance. Mendelian randomization suggested only minor, if any, causal effects of SHBG on lipid and metabolite measures and insulin resistance(n = 10,895).Causal effect estimates on type 2 diabetes for 41,439 cases and 103,870 controls indicated a causative protective role of SHBG (OR = 0.83 per 1-SD, 95% CI: 0.76, 0.91); however, effects were considerably weaker than observed in meta-analysis of prospective studies [hazard ratio (HR) = 0.47 per 1-SD, 95% CI: 0.41, 0.53].

CONCLUSION

Circulating SHBG is strongly associated with systemic metabolism and predictive for insulin resistance and diabetes. The weaker causal estimates suggest that the observational associations are partly confounded rather than conferred directly via circulating SHBG.

An update on testosterone, HDL and cardiovascular risk in men

Testosterone prescriptions have risen steadily and sharply in the USA despite a lack of clear understanding of the relationship between androgens and cardiovascular disease. In men with increasing age, testosterone levels decline and cardiovascular disease risk goes up. Ties between hypogonadism and cardiovascular disease are suggested by observational data, yet therapy with testosterone replacement has not been shown to mitigate that risk. To the contrary, recent literature has raised concern for increased cardiovascular disease in certain groups of men receiving testosterone therapy. In this article, we review current literature in an attempt to better understand what it suggests is the true relationship between testosterone and cardiovascular disease. We also take a closer look at effects of testosterone on lipids and HDL in particular, to see if this explains the cardiovascular effects seen in clinical studies.

Association of sex hormones with carotid artery distensibility in men and postmenopausal women: multi-ethnic study of atherosclerosis

The decline in carotid distensibility with age is steeper in women than in men, however, the correlates of this sex difference are not known. We examined the association of bioavailable testosterone, estradiol, dehydroepiandrosterone, and sex hormone-binding globulin, in 2783 postmenopausal women and 2987 men aged 45 to 84 years at the Multi-Ethnic Study of Atherosclerosis baseline examination. Carotid artery lumen diameters by ultrasound and brachial artery blood pressures were measured at systole and diastole. Regression models to determine the association of carotid distensibility coefficient and lumen diameter with sex-specific quartiles of sex hormones were adjusted for age, race, height, weight, diabetes mellitus, current smoking, antihypertensive medication use, total and high-density lipoprotein cholesterol levels, and hormone replacement therapy in women. A higher DC indicates a more distensible vessel. In women, higher dehydroepiandrosterone (P=0.008) and lower sex hormone-binding globulin (P=0.039) were associated with lower distensibility; higher dehydroepiandrosterone and lower estradiol were associated with smaller carotid diameters. In men, higher Bio-T (P=0.009) and lower estradiol (P=0.007) were associated with greater distensibility and also with smaller diameters (P=0.012 and 0.002, respectively). An androgenic internal milieu is associated with lesser carotid distensibility and diameter remodeling in women, but the opposite is true for men. Higher levels of estradiol are associated with smaller carotid diameters in both the sexes. Future longitudinal and experimental studies are needed to reveal the mechanism and clinical consequences of these associations.

Human sex hormone-binding globulin binding affinities of 125 structurally diverse chemicals and comparison with their binding to androgen receptor, estrogen receptor, and α-fetoprotein

One endocrine disruption mechanism is through binding to nuclear receptors such as the androgen receptor (AR) and estrogen receptor (ER) in target cells. The concentration of a chemical in serum is important for its entry into the target cells to bind the receptors, which is regulated by the serum proteins. Human sex hormone-binding globulin (SHBG) is the major transport protein in serum that can bind androgens and estrogens and thus change a chemical's availability to enter the target cells. Sequestration of an androgen or estrogen in the serum can alter the chemical elicited AR- and ER-mediated responses. To better understand the chemical-induced endocrine activity, we developed a competitive binding assay using human pregnancy plasma and measured the binding to the human SHBG for 125 structurally diverse chemicals, most of which were known to bind AR and ER. Eighty seven chemicals were able to bind the human SHBG in the assay, whereas 38 chemicals were nonbinders. Binding data for human SHBG are compared with that for rat α-fetoprotein, ER and AR. Knowing the binding profiles between serum and nuclear receptors will improve assessment of a chemical's potential for endocrine disruption. The SHBG binding data reported here represent the largest data set of structurally diverse chemicals tested for human SHBG binding. Utilization of the SHBG binding data with AR and ER binding data could enable better evaluation of endocrine disrupting potential of chemicals through AR- and ER-mediated responses since sequestration in serum could be considered.