Testosterone Associations with Erectile Dysfunction, Diabetes, and the Metabolic Syndrome

Percent body fat was negatively correlated with Testosterone levels in male

BACKGROUND

Lower testosterone levels in men have been consistently associated with metabolic abnormalities, particularly obesity. This study aims to investigate the relationship between testosterone and obesity by analyzing the correlation between testosterone levels and body fat percentage using data from the NHANES (National Health and Nutrition Examination Survey) database.

METHODS

The study included a total of 5959 participants from the NHANES 2011-2016. Multivariable linear regression models were used to assess the association between testosterone levels and body composition parameters, including total percent fat (TPF), android percent fat (APF), gynoid percent fat (GPF), android to gynoid ratio (A/G), and lean mass percent (LMP). Subgroup analyses stratified by sex were conducted using multivariable linear regression. To account for potential non-linear relationships, fitted smoothing curves and generalized additive models were utilized. A separate analysis of participants with a BMI ≥ 30 kg/m2 was conducted to validate the conclusions.

RESULT

Among males, testosterone levels showed a significant negative correlation with TPF (β = -11.97, P <0.0001), APF (β = -9.36, P<0.0001), GPF (β = -10.29, P <0.0001), and A/G (β = -320.93, P<0.0001), while a positive correlation was observed between LMP and testosterone levels (β = 12.62, P<0.0001). In females, a contrasting pattern emerged in the relationship between testosterone and body fat, but no significant correlation was found between testosterone and body composition in obese women.

CONCLUSIONS

The findings of this study support a negative association between body fat and testosterone levels in males.

Chlorpyrifos Induces Metabolic Disruption by Altering Levels of Reproductive Hormones

Chlorpyrifos (CPF) is a widely used organophosphorus pesticide and detected frequently in fruits, vegetables, as well as in urine and blood in humans. Studies have suggested that CPF can induce metabolic disruption, such as type-2 diabetes mellitus and changed body weight. The main mechanisms are based on oxidative damage, fatty-acid synthesis, and lipid peroxidation. Studies have also shown that CPF can change reproductive hormone (RH) levels. CPF might result in metabolic disorders through altered RH levels. Here, we review the studies showing that CFP causes metabolic disruption. Then, we present the studies showing that CFP changes RH levels. Finally, we discuss a potential pathway of how CPF elicits metabolic disruption.

Serum testosterone levels may influence body composition and cardiometabolic health in men with spinal cord injury

Study Design:

Cross-sectional study

Objective

To establish the association between serum testosterone (T) levels, biomarkers of cardiometabolic health and regional body composition variables after spinal cord injury (SCI).

Setting:

Medical research center

Methods

Metabolic and body composition measurements were collected from thirty-six men with chronic motor complete SCI. Serum T, carbohydrate and lipid profiles were measured after an overnight fast. Body composition was measured using anthropometrics, dual energy x-ray absorptiometry and magnetic resonance imaging. Participants were evenly classified into tertiles based on their serum T levels into low, mid-normal and normal ranges.

Results

Low, mid-normal and normal range serum T were 288.8 ± 84.9ng/dL, 461.0 ± 52.5ng/dL and 648.0 ± 53.5ng/dL, respectively. Low range serum T group had greater total (9.6%, P= 0.04) percentage fat mass and visceral adipose tissue (VAT) area (72%, P= 0.01) compared to normal range serum T group. Serum T was related to the absolute whole thigh muscle area (r= 0.40, P< 0.05) after controlling for body mass index. Serum T was negatively related to fasting plasma glucose (r= −0.46, P= 0.006) and insulin (r= −0.42, P= 0.01), HbA1c (r= −0.39, P= 0.02) and triglycerides (r= −0.36, P= 0.03).

Conclusion

Men with low serum T have more unfavorable body composition and cardiometabolic health outcomes after SCI. Testosterone replacement therapy may serve as a potential strategy in preventing cardiometabolic disorders after SCI.

The Relation Between Metabolic Syndrome and Testosterone Level

Metabolic syndrome is a group of conditions that increases the risk of developing diabetes and cardiovascular diseases. The most important pathogenic factors for metabolic syndrome are insulin resistance and obesity. The clinical presentation of this syndrome results from its influence on glucose and fat metabolism. Testosterone deficiency has a prevalence of up to 50% in men with metabolic syndrome and type 2 diabetes mellitus. A low level of testosterone is a factor for cardiovascular diseases and predictor of metabolic syndrome and, on the other hand, the components of metabolic syndrome can lead to low testosterone. This article reveals the bidirectional link between low testosterone level or hypogonadism and metabolic syndrome.

MECHANISMS IN ENDOCRINOLOGY: The sexually dimorphic role of androgens in human metabolic disease

Female androgen excess and male androgen deficiency manifest with an overlapping adverse metabolic phenotype, including abdominal obesity, insulin resistance, type 2 diabetes mellitus, non-alcoholic fatty liver disease and an increased risk of cardiovascular disease. Here, we review the impact of androgens on metabolic target tissues in an attempt to unravel the complex mechanistic links with metabolic dysfunction; we also evaluate clinical studies examining the associations between metabolic disease and disorders of androgen metabolism in men and women. We conceptualise that an equilibrium between androgen effects on adipose tissue and skeletal muscle underpins the metabolic phenotype observed in female androgen excess and male androgen deficiency. Androgens induce adipose tissue dysfunction, with effects on lipid metabolism, insulin resistance and fat mass expansion, while anabolic effects on skeletal muscle may confer metabolic benefits. We hypothesise that serum androgen concentrations observed in female androgen excess and male hypogonadism are metabolically disadvantageous, promoting adipose and liver lipid accumulation, central fat mass expansion and insulin resistance.

The inter-relational effect of metabolic syndrome and sexual dysfunction on hypogonadism in type II diabetic men

We sought to establish the interplay of metabolic syndrome (MetS) and/or sexual dysfunction (SD) on hypogonadism. Sexual functioning was assessed using Golombok Rust Inventory of Sexual Satisfaction in 274 consecutive diabetic men visiting the diabetic clinic of the Tema General Hospital between November 2010 and March 2011. MetS was assessed employing the criteria of World Health Organization, International Diabetic Federation and the National Cholesterol Education Program Adult Treatment Panel III while testosterone levels were estimated. The mean ages and duration of diabetes from this study were 59.9±11.3 and 6.8±5.9 years, respectively. The prevalence of hypogonadism was 7.3%, with the -SD/+MetS subjects showing the highest prevalence of hypogonadism, irrespective of the criteria used. Additionally, subjects with MetS and its components had a significantly lower level of testosterone compared with those without MetS and its components. Using standard nine-point scale, it was observed that subjects who avoided sexual act had significantly (P=0.0410) lower testosterone values (5.8±2.3 ng ml^-1) than subjects who did not avoid sexual act (6.4±2.6 ng ml^-1). MetS alone impacted more on hypogonadism than SD alone or both conditions altogether.

Interaction of sex steroid hormones and obesity on insulin resistance and type 2 diabetes in men: the Third National Health and Nutrition Examination Survey

AIMS

We examined interaction of sex steroid hormones and obesity with regard to insulin resistance (IR) and type 2 diabetes (T2D) by using nationally representative data from the US.

METHODS

Data of 1461 men aged ≥20years who participated in the Third National Health and Nutrition Examination Survey were analyzed. Multiplicative interaction was calculated by cross-product interaction terms in multivariable logistic regression models. Additive interaction was assessed by the relative excess risk due to interaction (RERI).

RESULTS

After adjusting for demographic and lifestyle covariates, the odds of IR were greatest among obese men with low free testosterone and high androstanediol glucuronide. Multiplicative interactions for total testosterone, free testosterone, and free estradiol index (FEI) were statistically significant with central obesity but not with overweight and obesity regarding to T2D (P<0.05). Significant additive interactions with obesity or central obesity were detected for total testosterone (RERI=2.75, 95% CI=0.92,4.59), SHBG (RERI=5.71, 95% CI=0.77,10.64), and FEI (RERI=-9.96, 95% CI=-19.18,-0.74) with regard to IR, beta-cell dysfunction, and T2D.

CONCLUSIONS

Our findings add to the evidence suggesting that low testosterone and high estradiol may be associated greater risks of IR and T2D by interacting with overall and central obesity in adult men.

Obesity and Hypogonadism

The relationship between obesity and hypogonadism is complicated. The relationship is bidirectional and there are numerous causative and correlative factors on both sides of the equation. Obesity is increasing in prevalence in epidemic proportions. Likewise, we are beginning to see the rapid increase in the incidence of male hypogonadism. It is only recently that we are learning the ways in which these 2 conditions exacerbate each other, and we are only beginning to understand how by treating one of these conditions, we can help to treat the other as well.

Molecular mechanisms associated with diabetic endothelial-erectile dysfunction

Erectile dysfunction (ED) is a common complication of diabetes, affecting up to 75% of all diabetic men. Although the aetiology of diabetic ED is multifactorial, endothelial dysfunction is recognized as a mainstay in the pathophysiology of the disease. Endothelial dysfunction is induced by the detrimental actions of high glucose levels and increased oxidative stress on endothelial cells that make up the vascular lining. Besides directly injuring the endothelium, diabetes might also hamper vascular repair mechanisms of angiogenesis and vasculogenesis. These states exacerbate and maintain endothelial dysfunction, impairing vasorelaxation events and cavernosal blood perfusion, which are crucial for normal erectile function.

The complex and multifactorial relationship between testosterone deficiency (TD), obesity and vascular disease

Testosterone deficiency (TD) is a well-established and recognized medical condition that contributes to several co-morbidities, including metabolic syndrome, visceral obesity and cardiovascular disease (CVD). More importantly, obesity is thought to contribute to TD. This complex bidirectional interplay between TD and obesity promotes a vicious cycle, which further contributes to the adverse effects of TD and obesity and may increase the risk of CVD. Testosterone (T) therapy for men with TD has been shown to be safe and effective in ameliorating the components of the metabolic syndrome (Met S) and in contributiong to increased lean body mass and reduced fat mass and therefore contributes to weight loss. We believe that appropriate T therapy in obese men with TD is a novel medical approach to manage obesity in men with TD. Indeed, other measures of lifestyle and behavioral changes can be used to augment but not fully replace this effective therapeutic approach. It should be noted that concerns regarding the safety of T therapy remain widely unsubstantiated and considerable evidence exists supporting the benefits of T therapy. Thus, it is paramount that clinicians managing obese men with TD be made aware of this novel approach to treatment of obesity. In this review, we discuss the relationship between TD and obesity and highlight the contemporary advancement in management of obesity with pharmacological and surgical approaches, as well as utilization of T therapy and how this intervention may evolve as a novel approach to treatment of obesity in men with TD .

Testosterone and obesity

Testosterone is a key hormone in the pathology of metabolic diseases such as obesity. Low testosterone levels are associated with increased fat mass (particularly central adiposity) and reduced lean mass in males. These morphological features are linked to metabolic dysfunction, and testosterone deficiency is associated with energy imbalance, impaired glucose control, reduced insulin sensitivity and dyslipidaemia. A bidirectional relationship between testosterone and obesity underpins this association indicated by the hypogonadal-obesity cycle and evidence weight loss can lead to increased testosterone levels. Androgenic effects on enzymatic pathways of fatty acid metabolism, glucose control and energy utilization are apparent and often tissue specific with differential effects noted in different regional fat depots, muscle and liver to potentially explain the mechanisms of testosterone action. Testosterone replacement therapy demonstrates beneficial effects on measures of obesity that are partially explained by both direct metabolic actions on adipose and muscle and also potentially by increasing motivation, vigour and energy allowing obese individuals to engage in more active lifestyles. The degree of these beneficial effects may be dependent on the treatment modality with longer term administration often achieving greater improvements. Testosterone replacement may therefore potentially be an effective adjunctive treatment for weight management in obese men with concomitant hypogonadism.

Energy restriction ameliorates metabolic syndrome-induced cavernous tissue structural modifications in aged rats

High-fat (HF) diet regular intake along life highly contributes to vascular dysfunction and to an increment in prevalence of metabolic syndrome (MetS) and erectile dysfunction (ED), a surrogate symptom of occult vascular disease, in the elderly. However, little is known about the effects of energy restriction (ER) alone/or after an HF-feeding period. We show here that in male Sprague-Dawley rats, 16 months of HF-diet consumption led to an increase in body adiposity, blood pressure, lipidemia, C-reactive protein, and insulin resistance and to hypoadiponectinemia, conditions that cluster in MetS. In addition, this treatment strongly favored collagen deposition in cavernous tissue and myocardium. Conversely, for the same time period, the ingestion of 75 % of ad libitum energy intake by controls (ER) extensively counteracted these outcomes. The impact of 6-month ER after 10-month HF period was also analyzed, and despite the decrease in body weight, adiposity, blood pressure, lipidemia, and C-reactive protein and improvement of insulin sensitivity, no differences were observed either in adiponectin blood levels or in retroperitoneal fat pad mass. Moreover, this treatment led to a reduction in cavernous tissue collagen deposition, but not in the myocardium, and evidenced differential mobilization of adipose tissue accretions. The data show the ability of HF diet to cause MetS and produce unwanted effects on myocardium and corpora vascular structure. They also indicate that these consequences are preventable upon ER diet starting early, but not later, in life.

Testosterone and insulin resistance in the metabolic syndrome and T2DM in men

Obesity, type 2 diabetes mellitus and the metabolic syndrome are major risk factors for cardiovascular disease. Studies have demonstrated an association between low levels of testosterone and the above insulin-resistant states, with a prevalence of hypogonadism of up to 50% in men with type 2 diabetes mellitus. Low levels of testosterone are also associated with an increased risk of all-cause and cardiovascular mortality. Hypogonadism and obesity share a bidirectional relationship as a result of the complex interplay between adipocytokines, proinflammatory cytokines and hypothalamic hormones that control the pituitary-testicular axis. Interventional studies have shown beneficial effects of testosterone on components of the metabolic syndrome, type 2 diabetes mellitus and other cardiovascular risk factors, including insulin resistance and high levels of cholesterol. Biochemical evidence indicates that testosterone is involved in promoting glucose utilization by stimulating glucose uptake, glycolysis and mitochondrial oxidative phosphorylation. Testosterone is also involved in lipid homeostasis in major insulin-responsive target tissues, such as liver, adipose tissue and skeletal muscle.

Effect of Testosterone on Inflammatory Markers in the Development of Early Atherogenesis in the Testicular-Feminized Mouse Model

BACKGROUND

Low levels of serum testosterone in men are associated with cardiovascular disease. Clinical studies show that testosterone replacement therapy (TRT) can improve symptoms of cardiovascular disease and reduce the inflammatory burden evident in atherosclerosis.

AIM

We used an in vivo animal model to determine whether testosterone influences mediators of vascular inflammation as part of its beneficial effects on atherogenesis.

METHODS

Testicular-feminized (Tfm) mice, which express low endogenous testosterone and a non-functional androgen receptor (AR), were used to assess the effect of androgen status on atheroma formation, serum lipids, and inflammatory mediators. Tfm mice were fed a high-cholesterol diet, received saline or physiological (TRT), and were compared to saline-treated XY littermates.

RESULTS

A total of 28 weeks of high-cholesterol diet caused fatty streak formation in the aortic root of XY littermates and Tfm mice, an effect significantly amplified in Tfm mice. Tfm mice on normal diet showed elevated serum tumor necrosis factor-α (TFN-α) and interleukin-6 compared to XY littermates. High-cholesterol diet induced increased monocyte chemoattractant protein-1 (MCP-1) in Tfm mice, and TFN-α and MCP-1 in XY littermates. TRT reduced fatty streak formation and serum interleukin-6 in Tfm mice but had no significant effects on lipid profiles. Monocyte/macrophage staining indicated local inflammation in aortic root fatty streak areas of all mice, with TRT reducing local inflammation through plaque reduction in Tfm mice. Fractalkine (CX₃CL1) and its receptor (CX₃CR1) were present in fatty streaks of all mice fed a high-cholesterol diet, independent of androgen status.

CONCLUSION

These results are consistent with AR-dependent and AR-independent anti-inflammatory actions of testosterone in atheroprotection, although the local anti-inflammatory mechanisms via which testosterone acts remain unknown.

Testosterone: a metabolic hormone in health and disease

Testosterone is a hormone that plays a key role in carbohydrate, fat and protein metabolism. It has been known for some time that testosterone has a major influence on body fat composition and muscle mass in the male. Testosterone deficiency is associated with an increased fat mass (in particular central adiposity), reduced insulin sensitivity, impaired glucose tolerance, elevated triglycerides and cholesterol and low HDL-cholesterol. All these factors are found in the metabolic syndrome (MetS) and type 2 diabetes, contributing to cardiovascular risk. Clinical trials demonstrate that testosterone replacement therapy improves the insulin resistance found in these conditions as well as glycaemic control and also reduces body fat mass, in particular truncal adiposity, cholesterol and triglycerides. The mechanisms by which testosterone acts on pathways to control metabolism are not fully clear. There is, however, an increasing body of evidence from animal, cell and clinical studies that testosterone at the molecular level controls the expression of important regulatory proteins involved in glycolysis, glycogen synthesis and lipid and cholesterol metabolism. The effects of testosterone differ in the major tissues involved in insulin action, which include liver, muscle and fat, suggesting a complex regulatory influence on metabolism. The cumulative effects of testosterone on these biochemical pathways would account for the overall benefit on insulin sensitivity observed in clinical trials. This review discusses the current knowledge of the metabolic actions of testosterone and how testosterone deficiency contributes to the clinical disease states of obesity, MetS and type 2 diabetes and the role of testosterone replacement.

Testosterone replacement therapy improves erythrocyte membrane lipid composition in hypogonadal men

AIM

The aim of this study was to investigate the effects of testosterone replacement therapy (TRT) on erythrocyte membrane (EM) lipid composition and physico-chemical properties in hypogonadal men.

METHODS

EM isolated from three patients before and after TRT with injectable testosterone undecanoate or testosterone gel were used for analysis of the phospholipid and fatty acid composition, cholesterol/phospholipid ratio, membrane fluidity, ceramide level and enzyme activities responsible for sphingomyelin metabolism.

RESULTS

TRT induced increase of phosphatidylethanolamine (PE) in the EMs and sphingomyelin. Reduction of the relative content of the saturated palmitic and stearic fatty acids and a slight increase of different unsaturated fatty acids was observed in phosphatidylcholine (PC). TRT also induced decrease of the cholesterol/total phospholipids ratio and fluidization of the EM.

DISCUSSION

The TRT induced increase of PE content and the reduction of saturation in the PC acyl chains induced alterations in the structure of EM could result in higher flexibility of the erythrocytes. The increase of the SM-metabolizing enzyme neutral sphingomyelinase, which regulates the content of ceramide in membranes has a possible impact on the SM signaling pathway.

CONCLUSION

We presume that the observed effect of TRT on the composition and fluidity of the EM contributes for improvement of blood rheology and may diminish the thrombosis risk. Larger studies are needed to confirm the findings of this pilot study.

Diagnosis, prevention, and management of statin adverse effects and intolerance: proceedings of a Canadian Working Group Consensus Conference

While the proportion of patients with significant statin-associated adverse effects or intolerance is very low, the increasing use and broadening indications have led to a significant absolute number of such patients commonly referred to tertiary care facilities and specialists. This report provides a comprehensive overview of the evidence pertaining to a broad variety of statin-associated adverse effects followed by a consensus approach for the prevention, assessment, diagnosis, and management. The overview is intended both to provide clarification of the untoward effects of statins and to impart confidence in managing the most common issues in a fashion that avoids excessive ancillary testing and/or subspecialty referral except when truly necessary. The ultimate goal is to ensure that patients who warrant cardiovascular risk reduction can be treated optimally, safely, and confidently with statin medications or alternatives when warranted.

Testosterone and phosphodiesterase type-5 inhibitors: new strategy for preventing endothelial damage in internal and sexual medicine?

Normal vascular endothelium is essential for the synthesis and release of substances affecting vascular tone (e.g. nitric oxide; NO), cell adhesion (e.g. endothelins, interleukins), and the homeostasis of clotting and fibrinolysis (e.g. plasminogen inhibitors, von Willebrand factor). The degeneration of endothelial integrity promotes adverse events (AEs) leading to increased atherogenesis and to the development of vascular systemic and penile end-organ disease. Testosterone (T) is an important player in the regulation of vascular tone through non-genomic actions exerted via blockade of extracellular-calcium entry or activation of potassium channels; also, adequate T concentrations are paramount for the regulation of phosphodiesterase type-5 (PDE5) expression and finally, for the actions exerted by hydrogen sulphide, a gas involved in the alternative pathway controlling vasodilator responses in penile tissue. It is known that an age-related decline of serum T is reported in approximately 20 to 30% of men whereas T deficiency is reported in up to 50% of men with metabolic syndrome or diabetes. A number of laboratory and human studies have shown the combination of T and other treatments for erectile dysfunction (ED), such as PDE5 inhibitors, to be more beneficial in patients with ED and hypogonadism, who fail monotherapy for sexual disturbances.The aim of this review is to show evidence on the role of T and PDE5 inhibitors, alone or in combination, as potential boosters of endothelial function in internal medicine diseases associated with reduced T or NO bioavailability, i.e. metabolic syndrome, obesity, diabetes, coronary artery disease, hyperhomocysteinemia, that share common risk factors with ED. Furthermore, the possibility of such a strategy to prevent endothelial dysfunction in men at increased cardiovascular risk is discussed.

Testosterone, endothelial health, and erectile function

Experimental and clinical studies have reported that testosterone has a critical role in the maintenance of homeostatic and morphologic corpus cavernosum components, essential for normal erectile physiology. Although the exact mechanisms mediated by testosterone in erectile function are still under investigation, recent research has suggested an important role in the regulation of endothelial cell (EC) biological functions. Besides stimulating the production of EC mediators, testosterone is also thought to promote the vasculogenic reendothelialization process, mediated by bone marrow-derived endothelial progenitor cells. Additionally, testosterone seems to modulate other erectile tissue components, including trabecular smooth muscle cells, nerve fibers, and tunica albuginea structure, all essential for the erectile process. This paper summarizes current data regarding testosterone-induced cellular and molecular mechanisms that regulate penile tissue components, focusing particularly on the role of testosterone in endothelial health and erectile function.

The effect of Tulbaghia violacea extracts on testosterone secretion by testicular cell cultures

AIM OF THE STUDY

This study aimed to determine the effect of Tulbaghia violacea Harv. on the male reproductive system in vitro by using testicular cell cultures. Tulbaghia violacea is a plant species indigenous to southern Africa and is used locally as a herbal remedy/medicine to treat several ailments.

MATERIALS AND METHODS

A 50% ethanol extract of Tulbaghia violacea was prepared. Three-month old male Balb/C mice were sacrificed and testicular cell cultures were prepared. Cells were then treated with varying concentrations of the Tulbaghia violacea ethanol extract (with/without Luteinizing hormone (LH)-treatment) and incubated for 4 h. Hormone production and cell viability were evaluated.

RESULTS

Treatment of cells with Tulbaghia violacea (312.5-5000 μg ml(-1)) significantly increased (P<0.05) LH-induced testosterone production as compared to vehicle-treated control (DMSO) whereas cells without LH-treatment showed no significant change in testosterone concentrations. No significant effect on cell viability was observed at all concentrations tested.

CONCLUSIONS

The data presented shows that Tulbaghia violacea has androgenic properties. Further studies are warranted to determine and clarify the exact mechanisms involved.

Testosterone and the metabolic syndrome

Metabolic syndrome and testosterone deficiency in men are closely Linked. Epidemiological studies have shown that Low testosterone Levels are associated with obesity, insulin resistance and an adverse Lipid profile in men. Conversely in men with metabolic syndrome and type 2 diabetes have a high prevalence of hypogonadism. Metabolic syndrome and Low testosterone status are both independently associated with increased all-cause and cardiovascular mortality. Observational and experimental data suggest that physiological replacement of testosterone produces improvement in insulin resistance, obesity, dyslipidae-mia and sexual dysfunction along with improved quality of Life. However, there are no Long-term interventional studies to assess the effect of testosterone replacement on mortality in men with Low testosterone Levels. This article reviews the observational and interventional clinical data in relation to testosterone and metabolic syndrome.

Effects of testosterone on Type 2 diabetes and components of the metabolic syndrome

Observations from clinical studies suggest that low serum levels of testosterone in men are often associated with obesity, insulin resistance, and metabolic compromise. Indeed, the clinical symptoms of late-onset hypogonadism are markedly similar to those of Type 2 diabetes mellitus (T2DM) and metabolic syndrome, and may share a similar pathophysiology. Observational and experimental data suggest that testosterone treatment improves a number of hallmark features of T2DM and metabolic syndrome, namely insulin resistance, obesity, dyslipidemia, and sexual dysfunction. Consequently, clinical studies have been undertaken to assess the impact of testosterone-replacement therapy in this patient group. The present article reviews the observational clinical data suggesting an association between low serum testosterone and metabolic impairment, the clinical data relating to the effects of testosterone treatment on components of the metabolic syndrome, and the randomized clinical trails that have formally investigated whether testosterone-replacement therapy provides clinical benefit to hypogonadal men with T2DM and/or metabolic syndrome.

Testosterone deficiency: a risk factor for cardiovascular disease?

Male gender is a major risk factor for premature cardiovascular death, a relationship not yet explained. Low testosterone in men is a risk factor for the metabolic syndrome and type 2 diabetes and is associated independently with individual components of the metabolic syndrome--visceral obesity, insulin resistance, hyperglycemia, hypertension and dyslipidemia. Epidemiological studies report increased mortality in men with low testosterone. Testosterone replacement in the short-term reduces waist circumference, cholesterol and circulating pro-inflammatory cytokines and improves insulin sensitivity and glycemic control in diabetics. Testosterone also has beneficial effects on cardiac ischemia, angina and chronic heart failure. This manuscript reviews the current evidence supporting a link between low testosterone and cardiovascular disease, highlighting the need for larger, longer-term studies.

Statin therapy is associated with lower total but not bioavailable or free testosterone in men with type 2 diabetes

OBJECTIVE

There is a high prevalence of hypogonadism in men with type 2 diabetes. This will lead to an increase in assessments of hypogonadism. Statins could potentially decrease testosterone levels by reducing the availability of cholesterol for androgen synthesis. We compared testosterone levels and hypogonadal symptoms with statin use in a cross-sectional study of 355 men with type 2 diabetes.

RESEARCH DESIGN AND METHODS

Total testosterone, sex hormone-binding globulin (SHBG), and estradiol were measured by an enzyme-linked immunosorbent assay. Bioavailable testosterone was measured by the modified ammonium sulfate precipitation method. Free testosterone was calculated using Vermeulen's formula. Symptoms of hypogonadism were assessed using the Androgen Deficiency in the Aging Male questionnaire.

RESULTS

Statins were associated with lower total testosterone (11.9 vs. 13.4 nmol/l, P = 0.006) and a trend toward lower SHBG (29.4 vs. 35.3 nmol/l, P = 0.034) compared with no treatment. Bioavailable testosterone, free testosterone, estradiol, and hypogonadal symptoms were not affected. Subanalysis showed that atorvastatin was associated with reduced total testosterone (11.4 vs. 13.4 nmol/l, P = 0.006) and a trend toward reduced SHBG (27.6 vs. 35.3 nmol/l, P = 0.022) compared with no treatment, and there was an apparent dose-response effect with the lowest levels of total testosterone seen in men treated with >or=20 mg atorvastatin (9.6 nmol/l, P = 0.017). Simvastatin use was not associated with significant reductions in testosterone or SHBG levels.

CONCLUSIONS

Assessing androgen status using total testosterone in men with type 2 diabetes treated with statins, particularly atorvastatin, may potentially lead to diagnostic error. Levels of bioavailable testosterone or free testosterone are recommended for the assessment of hypogonadism in this group if total testosterone levels are borderline.

Androgen deficiency as a predictor of metabolic syndrome in aging men: an opportunity for intervention?

The prevalence of metabolic syndrome is increasing globally and is an important risk factor for the development of cardiovascular disease. Longitudinal population studies have found that low testosterone status in men is a risk factor for the later development of metabolic syndrome. Men with metabolic syndrome and type 2 diabetes mellitus have a higher incidence of hypotestosteronaemia. Furthermore, in men, testosterone levels are inversely associated with the degree of carotid and aortic atherosclerosis. Early interventional, short-term studies have shown that testosterone replacement therapy has a beneficial effect on visceral obesity, insulin sensitivity, glycaemic control and lipid profiles in men with diagnosed hypogonadism with and without diabetes. The effect of testosterone therapy on atherogenesis in men is unknown; however, animal studies have shown that testosterone is atheroprotective and can ameliorate the degree of atherosclerosis. Testosterone is an arterial vasodilator and has been shown to improve myocardial ischaemia in men with coronary artery disease. This review discusses the role that testosterone may play in the pathogenesis of metabolic syndrome in men and also examines the potential role of testosterone replacement therapy in this condition.

Rosiglitazone increases bioactive testosterone and reduces waist circumference in hypogonadal men with type 2 diabetes

The purpose of this study was to assess the effect of rosiglitazone on bioavailable, free and total testosterone levels in hypogonadal men with type 2 diabetes. Sixteen type 2 diabetic men with hypogonadism were studied before and after administration of rosiglitazone (8 mg/day) for six months, with assessments performed every two months on two consecutive days. We measured testosterone and sex hormone binding globulin (SHBG), visceral adiposity, high-sensitivity CRP (hs-CRP), lipids, microalbuminuria and blood pressure. There was a significant increase in free (p=0.01), bioavailable (p=0.007) and total testosterone (p=0.002), as well as SHBG (p=0.03) levels, with rosiglitazone treatment. Waist circumference and waist / hip ratio decreased with the improvement in insulin sensitivity and glycaemic control (p=0.01). There was also a significant reduction in hs-CRP (p=0.02) and urinary albumin excretion. No significant effect on blood pressure or the ratio of low-density lipoprotein cholesterol to high-density lipoprotein cholesterol (LDL to HDL) was seen. In conclusion, the insulin-sensitiser rosiglitazone increases bioavailable, free and total testosterone and SHBG levels in hypogonadal men with type 2 diabetes.

The prevalence of and risk factors for androgen deficiency in aging Taiwanese men

INTRODUCTION

Androgen deficiency in aging men has attracted much medical interest. Most studies on androgen deficiency have been conducted in Caucasian populations, and data from other ethnicities are lacking.

AIM

To evaluate the prevalence of and risk factors for androgen deficiency and symptomatic androgen deficiency in Taiwanese men over 40 years old.

METHODS

From August 2007 to April 2008, a free health screening was conducted by a medical center in Kaohsiung, Taiwan, and 819 men participated in this health screening. All participants completed a health questionnaire, received a detailed physical examination, and blood samples were drawn between 8:00 and 12:00 am.

MAIN OUTCOME MEASURES

Serum total testosterone (TT), albumin, and sex hormone-binding globulin levels were measured. The level of free testosterone (FT) was calculated. Clinical symptoms of androgen deficiency were assessed using the Androgen Deficiency in the Aging Male (ADAM) questionnaire.

RESULTS

Seven hundred thirty-four men who met the inclusion criteria (mean age 57.4 +/- 6.7 years; range: 43-87 years) were included in this study. The prevalence of androgen deficiency was 24.1% based on the criterion of TT level < 300 ng/dL, and 16.6% based on the criterion of both TT < 300 ng/dL and FT < 5 ng/dL. The prevalence of symptomatic androgen deficiency was 12.0%. Both prevalence of androgen deficiency and symptomatic androgen deficiency increased with age. Older age, obesity, and diabetes mellitus were independent risk factors for androgen deficiency and symptomatic androgen deficiency.

CONCLUSIONS

In a sample of aging Taiwanese men, a substantial proportion had androgen deficiency and symptomatic androgen deficiency, and the prevalence increased with age. Older age, obesity, and diabetes mellitus were independent risk factors for androgen deficiency and symptomatic androgen deficiency. Those potentially modifiable risk factors like obesity and diabetes mellitus should be prevented to maintain normal testosterone levels during aging in men.