Interrelation between plasma testosterone and plasma insulin in healthy adult men: the Telecom Study

Association between body mass index, metabolic syndrome and common urologic conditions: a cross-sectional study using a large multi-institutional database from the United States

INTRODUCTION

The study aims to determine whether body mass index (BMI), metabolic syndrome (MS) or its individual components (primary hypertension, type 2 diabetes mellitus and dyslipidemias) are risk factors for common urological diseases.

MATERIALS AND METHODS

Cross-sectional study with data collected on February 28, 2022 from the TriNetX Research Network. Patients were divided in cohorts according to their BMI, presence of MS (BMI > 30 kg/m2, type 2 diabetes mellitus, primary hypertension and disorders of lipoprotein metabolism) and its individual components and its association with common urological conditions was determined. For each analysis, odds ratio (OR) with 95% confidence intervals were calculated. Statistical significance was assessed at p < .05.

RESULTS

BMI > 30 kg/m2 was associated with increased risk of lithiasis, kidney cancer, overactive bladder, male hypogonadism, benign prostatic hyperplasia, and erectile dysfunction (p < .05). On the contrary, BMI was inversely associated with ureteral, bladder and prostate cancer (p < .05). In all urological diseases, MS was the strongest risk factor, with prostate cancer (OR = 2.53) showing the weakest and male hypogonadism the strongest (OR = 13.00) associations.

CONCLUSIONS

MS and its individual components were significant risk factors for common urological conditions. Hence holistic approaches with lifestyle modification might prevent common urological disease.Key messagesOverall, metabolic syndrome is the strongest risk factor for all the analysed urological diseases.Abnormally high body mass index can be a risk or protective factor depending on the threshold and urological disease that are being evaluated.Metabolic syndrome and increased BMI should be considered important factors associated to the prevalence of common urological diseases.

The Role of Testosterone in the Elderly: What Do We Know?

Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains.

The Role of Testosterone in the Elderly: What Do We Know?

Testosterone is the most important hormone in male health. Aging is characterized by testosterone deficiency due to decreasing testosterone levels associated with low testicular production, genetic factors, adiposity, and illness. Low testosterone levels in men are associated with sexual dysfunction (low sexual desire, erectile dysfunction), reduced skeletal muscle mass and strength, decreased bone mineral density, increased cardiovascular risk and alterations of the glycometabolic profile. Testosterone replacement therapy (TRT) shows several therapeutic effects while maintaining a good safety profile in hypogonadal men. TRT restores normal levels of serum testosterone in men, increasing libido and energy level and producing beneficial effects on bone density, strength and muscle as well as yielding cardioprotective effects. Nevertheless, TRT could be contraindicated in men with untreated prostate cancer, although poor findings are reported in the literature. In addition, different potential side effects, such as polycythemia, cardiac events and obstructive sleep apnea, should be monitored. The aim of our review is to provide an updated background regarding the pros and cons of TRT, evaluating its role and its clinical applicability in different domains.

Testosterone, Diabetes Risk, and Diabetes Prevention in Men

Middle-aged and older men with lower testosterone concentrations are more likely to have or to develop metabolic syndrome and type 2 diabetes. Central adiposity is a risk factor for metabolic syndrome and diabetes and predisposes to lower testosterone concentrations. Conversely, testosterone treatment reduces fat mass and insulin resistance. In a randomized controlled trial of 1007 men with either impaired glucose tolerance or newly diagnosed type 2 diabetes, 2 years of testosterone treatment on a background of lifestyle intervention reduced the risk of type 2 diabetes by 40%; this demonstrates the potential utility for testosterone pharmacotherapy to prevent diabetes in men.

Testosterone therapy for prevention and reversal of type 2 diabetes in men with low testosterone

Men with obesity and/or type 2 diabetes (T2D) have a high prevalence of testosterone deficiency (TD). Similarly, men with TD have an increased risk of developing obesity and/or T2D, and further body fat accumulation and deterioration of glycemic control create a vicious cycle. The landmark testosterone for diabetes mellitus trial, the largest randomized controlled trial of testosterone therapy (TTh) to date, confirms the beneficial effects of TTh on fat loss and gain in muscle mass, and that TTh for 2 years significantly reduces the risk of incident T2D, and may also reverse T2D. The testosterone for diabetes mellitus trial suggests that TTh reduces the risk of T2D and results in greater improvement in sexual function and wellbeing, beyond lifestyle intervention alone.

Association of Leptin with Total and Free Testosterone: Results from the National Health and Nutrition Examination Surveys

Introduction

Obese men can have testosterone deficiency (TD) but the etiology is uncertain. Leptin is a 16-kDa protein produced primarily by adipose tissue and, therefore, is positively associated with the amount of body fat and can affect testosterone (T) production. We hypothesized that increased leptin can be independently associated with low T.

Materials and Methods

We performed a cross-sectional analysis of men from National Health and Nutrition Examination III database to evaluate the association of leptin with serum T and calculated free testosterone (cFT). Linear regression was performed with leptin, age, waist circumference, hypertension, and diabetes as independent variables predicting cFT/T. Multiple linear regression was used to determine predictors for cFT and T using variables previously significant in the univariate analysis.

Results

A total of 1193 men were analyzed. As expected, older and obese men were associated with having lower T. Interestingly, increasing leptin levels were an independent predictor of decreasing T and cFT on multivariable analysis. Increasing 1ng/mL in leptin resulted in a decrease of 5.13 and 0.11 ng/dL of T and cFT, respectively (p < 0.05). Also, every additional year of life led to a T and cFT reduction of 2.87 and 0.13 ng/dL, respectively, and increasing 1 cm in waist circumference corresponded to decrease of 4ng/dL in T (p < 0.05).

Conclusions

We concluded that increasing leptin, age, and waist circumference were associated with decreasing of T and cFT. Elevated leptin levels could be one of the potential etiologies of TD.

Considerations for the use of gonadotropin-releasing hormone agonists and antagonists in patients with prostate cancer

Prostate cancer is the second most common cause of cancer-related deaths in men, representing a major source of morbidity and mortality. Androgen deprivation therapy is the primary treatment for patients with advanced prostate cancer at disease presentation, which can be achieved either with surgical or chemical castration. The development of gonadotropin-releasing hormone agonists revolutionized the treatment of advanced prostate cancer, replacing the need for surgical castration. Agonists downregulate gonadotropin-releasing hormone agonist receptors in the pituitary gland, and thus decrease the release of luteinizing hormone and testosterone. Although agonists are a common therapeutic option to date, their use is associated with testosterone surges, metabolic dysfunction and an increase in the risk of cardiovascular disease; they might contribute to tumor flares and potentially an increase in non-cancer mortality. More recently, gonadotropin-releasing hormone antagonists have entered the prostate cancer treatment landscape. Unlike agonists, antagonists directly inhibit the androgen receptor in the pituitary gland, and thus do not cause initial testosterone surges. In this article, we provide a concise review of the mechanism of actions, safety and efficacy of the approved agonists and antagonists for prostate cancer treatment.

The Interplay Between Pituitary Health and Diabetes Mellitus - The Need for 'Hypophyseo-Vigilance'

The anterior and posterior hypophyseal hormones alter glucose metabolism in health and disease. Secondary diabetes may occur due to hypersecretion of anterior pituitary hormones like adrenocorticotrophic hormone in Cushing's disease and growth hormone in acromegaly. Other hormones like prolactin, gonadotropins, oxytocin and vasopressin, though not overtly associated with causation of diabetes, have important physiological role in maintaining glucose homeostasis. Hypoglycaemia is not an unusual occurrence in hypopituitarism. Many of the medications that are used for treatment of hypophyseal diseases alter glucose metabolism. Agents like pasireotide should be used with caution in the setting of diabetes, whereas pegvisomant should be given preference. Diabetes mellitus itself, on the other hand, can alter the functioning of hypothalamic pituitary axis; this is documented in both type 1 and type 2 diabetes. This review focuses on the clinically relevant interplay of hypophyseal hormones and glucose homeostasis. The authors define 'hypophyseo-vigilance' as an approach which keeps the bidirectional, multifaceted interactions between the pituitary and glucose metabolism in mind while managing diabetes and pituitary disease.

Metabolic Disorders and Male Hypogonadotropic Hypogonadism

Several studies highlight that testosterone deficiency is associated with, and predicts, an increased risk of developing metabolic disorders, and, on the other hand, is highly prevalent in obesity, metabolic syndrome and type-2 diabetes mellitus. Models of gonadotropin releasing hormone deficiency, and androgen deprivation therapy in patients with prostate cancer, suggest that hypogonadotropic hypogonadism might contribute to the onset or worsening of metabolic conditions, by increasing visceral adiposity and insulin resistance. Nevertheless, in functional hypogonadism, as well as in late onset hypogonadism, the relationship between hypogonadotropic hypogonadism and metabolic disorders is bidirectional, and a vicious circle between the two components has been documented. The mechanisms underlying the crosstalk between testosterone deficiency and metabolic disorders include increased visceral adipose tissue and insulin resistance, leading to development of metabolic disorders, which in turn contribute to a further reduction of testosterone levels. The decrease in testosterone levels might be determined by insulin resistance-mediated and, possibly, pro-inflammatory cytokine-mediated decrease of sex hormone binding globulin, resulting in a temporary increased free testosterone available for aromatization to estradiol in visceral adipose tissue, followed by a subsequent decrease in free testosterone levels, due to the excess of visceral adipose tissue and aromatization; by a direct inhibitory effect of increased leptin levels on Leydig cells; and by a reduced gonadotropin secretion induced by estradiol, inflammatory mediators, leptin resistance, and insulin resistance, with the ultimate determination of a substantial hypogonadotropic hypogonadism. The majority of studies focusing on the effects of testosterone replacement therapy on metabolic profile reported a beneficial effect of testosterone on body weight, waist circumference, body mass index, body composition, cholesterol levels, and glycemic control. Consistently, several interventional studies demonstrated that correction of metabolic disorders, in particular with compounds displaying a greater impact on body weight and insulin resistance, improved testosterone levels. The aim of the current review is to provide a comprehensive overview on the relationship between hypogonadotropic hypogonadism and metabolism, by clarifying the independent role of testosterone deficiency in the pathogenesis of metabolic disorders, and by describing the relative role of testosterone deficiency and metabolic impairment, in the context of the bidirectional relationship between hypogonadism and metabolic diseases documented in functional hypogonadotropic hypogonadism. These aspects will be assessed by describing metabolic profile in men with hypogonadotropic hypogonadism, and androgenic status in men with metabolic disorders; afterwards, the reciprocal effects of testosterone replacement therapy and corrective interventions on metabolic derangements will be reported.

Insulin Sensitivity and Testicular Function in a Cohort of Adult Males Suspected of Being Insulin-Resistant

A cohort of 141 males (18–80 yo, 42.9 ± 12.9) strongly suspected of being Insulin Resistant (IR) was prospectively studied by determining their insulin sensitivity (Pancreatic Suppression Test, PST) and testicular function (total testosterone and SHBG). The subjects were labeled as IR when the Steady State Plasma Glucose (SSPG) was ≥150 mg/dL and Non-Insulin Resistant (NIR) when SSPG was <150 mg/dl; similarly, the subjects were labeled as Hypogonadal (HYPOG) when total testosterone was ≤3.0 ng/mL and Eugonadal (EUG) when total testosterone was >3.0 ng/mL. Two out of three subjects turned out to be IR, while around one in four subjects were HYPOG. Contingency analysis indicated a significant interdependence between insulin resistance and hypogonadism (chi-square was 4.69, p = 0.0303). Age (>43 yo) predicted hypogonadism (AUROC 0.606, p = 0.0308). Twice as many HYPOG subjects were IR as compared with EUG subjects. Also, HYPOG subjects exhibited higher SSPG values as compared with EUG subjects. Statistically, neither Weight nor BMI predicted hypogonadism, while Waist Circumference (>110 cm) was only a mediocre predictor (AUROC 0.640, p = 0.009). SSPG (>224 mg/dL) on the other hand, was the best predictor of hypogonadism (AUROC 0.709, p = 0.002), outperforming Waist Circumference (half of the subjects with an SSPG >224 mg/dL were HYPOG). Age did not predict insulin resistance, while Weight (>99 kg), BMI (>29), and especially, Waist Circumference (>99 cm, AUROC 0.812, p < 0.0001) were all predictors of insulin resistance. Almost 90% of the subjects with a waist circumference >99 cm was IR. As a logical consequence of the selection criteria (various clues suggesting insulin resistance), most subjects with normal weight in this cohort were IR (53.3%) while 20% were HYPOG. On the other hand, 13.6% of the obese subjects were NIR, and 2 out of 3 of them were both NIR and EUG. In conclusion, Waist Circumference predicted both insulin resistance (>99 cm) and hypogonadism (>110 cm), suggesting that the first hit of abdominal obesity is insulin resistance and the second hit is male hypogonadism. Normal weight did not protect from IR, while a relevant proportion of obese subjects were NIR (with 2/3 being also EUG).

Testosterone a key factor in gender related metabolic syndrome

Metabolic syndrome (MetS) is highly correlated with cardiovascular diseases. Although an excess of body fat is a determinant factor for MetS development, a reduced level of testosterone plays a fundamental role in its regulation. Low testosterone level is highly related to insulin resistance, visceral obesity and MetS. We have searched in Pubmed clinical trial with the password: testosterone and insulin resistance, and testosterone and MetS. We found 19 studies on the correlation between testosterone level with insulin resistance and 18 on the effect of testosterone therapy on MetS. A high correlation between low testosterone and insulin resistance has been found in men, but not in women. Testosterone administration in hypogonadal men improved MetS and reduced the mortality risk. Androgen and oestrogen receptors are expressed in adipocytes, muscle and liver tissue, and their activation is necessary to improve metabolic control. Normalization of testosterone level should be the primary treatment in men, along with caloric restriction and physical exercise. These findings come mainly from correlative data, and there remains a need for randomized trials to strengthen this evidence. This review will consider the effects of testosterone on the regulation and development of MetS in men and women.

Determination of steroid hormones in human plasma by GC-triple quadrupole MS

A fast and sensitive GC-MS/MS method is proposed to determine pregnenolone, dehydroepiandrosterone (DHEA), testosterone and dihydrotestosterone from human plasma. Steroids were extracted by liquid/liquid extraction, and derivatized with N-methyl-N-trimethylsilyl-trifluoracetamide. Electron ionization at 30eV was applied to generate high abundant precursor ions. Specific precursor/product transitions were generated a priori for each compound of interest and these assays were then used to selectively detect and quantify these steroids. Using the selected reaction monitoring mode, detection limits in the pg/ml (subnmol/l) range could be achieved for all four steroid compounds. The method was validated for imprecision, and recovery and applied in a pilot study in patients with hypercholesterolemia. Associations of increased cholesterol biosynthesis and low testosterone and dihydrotestosterone concentrations were found.

Androgen deficiency and mitochondrial dysfunction: implications for fatigue, muscle dysfunction, insulin resistance, diabetes, and cardiovascular disease

Among the major physiological functions of steroid hormones is regulation of carbohydrate, fat, and protein metabolism. Mitochondria, through oxidative phosphorylation, play a critical role in modulating a host of complex cellular metabolic pathways to produce chemical energy to meet the metabolic demand for cellular function. Thus, androgens may regulate cellular metabolism and energy production by increased mitochondrial numbers, activation of respiratory chain components, and increased transcription of mitochondrial-encoded respiratory chain genes that code for enzymes responsible for oxidative phosphorylation. Androgen deficiency is associated with increased insulin resistance, type 2 diabetes (T2DM), metabolic syndrome, obesity, and increased overall mortality. One common link among all these pathologies is mitochondrial dysfunction. Contemporary evidence exists suggesting that testosterone deficiency (TD) contributes to mitochondrial dysfunction, including structural alterations and reduced expression and activities of metabolic enzymes. Here, we postulate that TD contributes to symptoms of fatigue, insulin resistance, T2DM, cardiovascular risk, and metabolic syndrome through a common mechanism involving impairment of mitochondrial function.

Testosterone level in men with type 2 diabetes mellitus and related metabolic effects: A review of current evidence

A significant proportion of patients with type 2 diabetes mellitus have a low testosterone level relative to reference ranges based on healthy young men. Only a small number of these patients suffer from classical hypogonadism as a result of recognizable hypothalamic-pituitary-gonadal axis pathology. The cut-off value of the serum testosterone level in men without obvious hypothalamic-pituitary-gonadal axis pathology is controversial. It is unclear to what extent a low serum testosterone level causally leads to type 2 diabetes and/or the metabolic syndrome. From a theoretical standpoint, there can be complex interactions among the hypothalamic-pituitary-gonadal axis, body composition and insulin resistance, which can be further influenced by intrinsic and extrinsic factors to give rise to metabolic syndrome, glucose intolerance, and low-grade inflammation to increase the risk of cardiovascular disease. Although a low serum testosterone level frequently coexists with cardiometabolic risk factors and might serve as a biomarker, more studies are required to clarify the causal, mediating or modifying roles of low serum testosterone level in the development of adverse clinical outcomes. Currently, there are insufficient randomized clinical trial data to evaluate the effects of testosterone replacement therapy on meaningful clinical outcomes. The risk-to-benefit ratio of testosterone therapy in high-risk subjects, such as those with type 2 diabetes, also requires elucidation. The present article aims to review the current evidence on low serum testosterone levels in patients with type 2 diabetes, and its implications on cardiovascular risk factors, metabolic syndrome and adverse clinical outcomes.

Androgen receptor roles in insulin resistance and obesity in males: the linkage of androgen-deprivation therapy to metabolic syndrome

Prostate cancer (PCa) is one of the most frequently diagnosed malignancies in men. Androgen-deprivation therapy (ADT) is the first-line treatment and fundamental management for men with advanced PCa to suppress functions of androgen/androgen receptor (AR) signaling. ADT is effective at improving cancer symptoms and prolonging survival. However, epidemiological and clinical studies support the notion that testosterone deficiency in men leads to the development of metabolic syndrome that increases cardiovascular disease risk. The underlying mechanisms by which androgen/AR signaling regulates metabolic homeostasis in men are complex, and in this review, we discuss molecular mechanisms mediated by AR signaling that link ADT to metabolic syndrome. Results derived from various AR knockout mouse models reveal tissue-specific AR signaling that is involved in regulation of metabolism. These data suggest that steps be taken early to manage metabolic complications associated with PCa patients receiving ADT, which could be accomplished using tissue-selective modulation of AR signaling and by treatment with insulin-sensitizing agents.

The Association of Free Testosterone Levels in Men and Lifestyle Factors and Chronic Disease Status: A North Texas Healthy Heart Study

PURPOSE

Hypogonadism is highly prevalent in men older than 45 years and is associated with an increased risk of chronic diseases, including obesity, metabolic syndrome, diabetes, and cardiovascular disease. The objective of this study was to determine whether lifestyle factors such as smoking, diet, and exercise are associated with reduced testosterone levels.

METHODS

In this cross-sectional study, 147 men older than 44 years were recruited from a collaborative network of primary care clinics in the Dallas/Fort Worth, Texas, metropolitan area. Free testosterone levels were measured in plasma samples via an enzyme-linked immunosorbent assay-based method, and analyzed by simple and multiple linear regression in relationship to age, race/ethnicity, smoking, diet, exercise, obesity, diabetes, hypertension, and dyslipidemia.

RESULTS

The participants had a mean free testosterone level of 3.1 ng/mL (standard deviation [SD] = 1.5) and mean age of 56.8 years (SD = 7.9). In simple regression analysis, free testosterone levels were associated with increased age (β = -0.04; P = .02), diet (β = -0.49; P = .05), diabetes (β = -0.9; P = .003), and hypertension (β = -0.55; P = .03) but not with race/ethnicity, smoking, exercise, obesity, or dyslipidemia. In multiple regression analysis, free testosterone values were significantly associated only with age (β = -0.05; P = .01) and diet (β = -0.72; P = .01).

CONCLUSIONS

This study implicates diet, in addition to advanced age as a possible risk factor in the development of reduced testosterone levels.

Insulin resistance is an independent determinate of ED in young adult men

Background

Insulin resistance (IR) triggers endothelial dysfunction, which contributes to erectile dysfunction (ED) and cardiovascular disease.

Aim

To evaluate whether IR was related to ED in young adult patients.

Methods

A total of 283 consecutive men complaining of ED at least six months were enrolled, with a full medical history, physical examination, and laboratory tests collected. Quantitative Insulin Sensitivity Check Index (QUICKI) was used to determine IR. The severity of ED was assessed by IIEF-5 questionnaire. Endothelial function was assessed by ultrasonographic examination of brachial artery flow mediated dilation (FMD).

Results

IR was detected in 52% patients. Subjects with IR had significant higher total cholesterol, triglycerides, low density lipoprotein-cholesterol (LDL-c), glycated haemoglobin (HBA1c), high sensitivity C-reactive protein (hs-CRP) and body mass index (BMI), but showed significant lower IIEF-5 score, FMD%, high density lipoprotein -cholesterol (HDL-c), testosterone, sex hormone binding globulin (SHBG) levels than patients without IR. Multiple regression analysis showed QUICKI and testosterone were independent predictors of IIEF-5 score. Furthermore, the incidence of IR was correlated with the severity of ED.

Conclusions

Compared with other CVFs, IR was found as the most prevalent in our subjects. Besides, IR was independently associated with ED and its severity, suggesting an adverse effect of insulin resistance on erectile function.

Castration-induced testosterone deficiency increases fasting glucose associated with hepatic and extra-hepatic insulin resistance in adult male rats

BACKGROUND

Testosterone deficiency is associated with insulin resistance. However, how testosterone deficiency affects insulin actions remains unclear. The aim of this study was to investigate the influence of castration-induced testosterone deficiency on the metabolic kinetics of glucose and to evaluate the hepatic and extra-hepatic insulin sensitivity, in advanced-age male Sprague-Dawley (SD) rats.

METHODS

Ten-week-old male SD rats were randomly divided into three groups: (1) a control group (n = 10) in which the rats underwent sham castration (2) a castrated group (TD group for testosterone deficiency, n = 10) in which the rats underwent bilateral orchidectomy surgery and (3) a castrated group given testosterone propionate via intraperitoneal injection (25 mg/kg/day) to supplement androgen (TD + TP group, n = 10). At ten weeks after castration in the noted groups, all rats were subjected to an oral glucose tolerance test (OGTT), a pyruvate tolerance test (PTT) and an insulin tolerance test (ITT). Twenty weeks following that treatment, all rats underwent a hyperinsulinemic-euglycemic clamp procedure in conjunction with isotope--labeled glucose and glycerol tracer infusions. The rate of appearance (Ra) of glucose, glycerol and gluconeogenesis (GNG), hepatic glucose production and the rate of glucose disappearance (Rd) were assessed. Glucose uptake was determined by measuring the 2-deoxy-D-14C-glucose in the gastrocnemius muscles.

RESULTS

Ten weeks after castration in the TD group, the fasting blood glucose and insulin levels were significantly increased (p < 0.01), the glucose-- induced insulin secretion was impaired and ITT revealed a temporarily increased whole body insulin sensitivity compared with the control group; 30 weeks after castration, the Ra of glucose, Ra of glycerol, as well as the HGP and GNG were also increased (p < 0.01), while the exogenous glucose infusion rate and uptake glucose in the muscle markedly decreased (p < 0.01).

CONCLUSIONS

Castration-induced testosterone deficiency primarily increases fasting blood glucose levels. The clamp experiments revealed a clear insulin resistance both at the hepatic and extra-hepatic levels.

Prediabetes is associated with an increased risk of testosterone deficiency, independent of obesity and metabolic syndrome

OBJECTIVE

The association between type 2 diabetes and low testosterone has been well recognized. However, testosterone levels in men with prediabetes have been rarely reported. We aimed to investigate whether prediabetes was associated with an increased risk of testosterone deficiency.

METHODS

This study included 1,306 men whose sex hormones was measured during a medical examination. Serum total testosterone and sex hormone-binding globulin were measured; free and bioavailable testosterone concentrations were calculated by Vermeulen's formula. Prediabetes was defined by impaired fasting glucose (IFG), impaired postprandial glucose (IPG), or glycated hemoglobin (HbA1c) 5.7%-6.4%. Logistic regression was performed to obtain the odds ratios (OR) for subnormal total testosterone (<300 ng/dL) or free testosterone (<6 ng/dL) in prediabetic and diabetic men compared with normoglycemic individuals, while adjusting for age, BMI, waist circumference, and metabolic syndrome (MetS).

RESULTS

Normoglycemia, prediabetes, and diabetes were diagnosed in 577 (44.2%), 543 (41.6%), and 186 (14.2%) men, respectively. Prediabetes was associated with an increased risk of subnormal total testosterone compared to normoglycemic individuals (age-adjusted OR=1.87; 95%CI=1.38-2.54). The risk remained significant in all multivariate analyses. After adjusting for MetS, the OR in prediabetic men equals that of diabetic patients (1.49 versus 1.50). IFG, IPG, and HbA1c 5.7%-6.4% were all associated with an increased risk of testosterone deficiency, with different levels of significance in multivariate analyses. However, neither prediabetes nor diabetes was associated with subnormal free testosterone in multivariate analyses.

CONCLUSIONS

Prediabetes is associated with an increased risk of testosterone deficiency, independent of obesity and MetS. After adjusting for MetS, the risk equals that of diabetes. Our data suggest that testosterone should be measured routinely in men with prediabetes.

New players for advanced prostate cancer and the rationalisation of insulin-sensitising medication

Obesity and type 2 diabetes are recognised risk factors for the development of some cancers and, increasingly, predict more aggressive disease, treatment failure, and cancer-specific mortality. Many factors may contribute to this clinical observation. Hyperinsulinaemia, dyslipidaemia, hypoxia, ER stress, and inflammation associated with expanded adipose tissue are thought to be among the main culprits driving malignant growth and cancer advancement. This observation has led to the proposal of the potential utility of "old players" for the treatment of type 2 diabetes and metabolic syndrome as new cancer adjuvant therapeutics. Androgen-regulated pathways drive proliferation, differentiation, and survival of benign and malignant prostate tissue. Androgen deprivation therapy (ADT) exploits this dependence to systemically treat advanced prostate cancer resulting in anticancer response and improvement of cancer symptoms. However, the initial therapeutic response from ADT eventually progresses to castrate resistant prostate cancer (CRPC) which is currently incurable. ADT rapidly induces hyperinsulinaemia which is associated with more rapid treatment failure. We discuss current observations of cancer in the context of obesity, diabetes, and insulin-lowering medication. We provide an update on current treatments for advanced prostate cancer and discuss whether metabolic dysfunction, developed during ADT, provides a unique therapeutic window for rapid translation of insulin-sensitising medication as combination therapy with antiandrogen targeting agents for the management of advanced prostate cancer.

Association between sex hormone levels and abnormal metabolism in a population of elderly Chinese men

OBJECTIVE

Low testosterone levels may be a signal of poor health. This study aimed to investigate the effects of age and abnormal metabolism on sex hormones in Chinese male.

METHODS

Three hundred and thirty-seven elder men were enrolled into this single-center, cross-sectional study, and their sex hormone levels and metabolic parameters were assessed.

RESULTS

Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and sex-hormone-binding globulin (SHBG) concentrations increased with age, while free testosterone index (FTI), testosterone secretion index (TSI), estradiol (E2)/SHBG and progestin (PROG) decreased. Abnormal metabolisms were related to androgen indices (TT, FT, BT, FTI, TSI, T/E2), SHBG and E2/SHBG even after adjusting by age and macrovascular disease. Obesity and overweight, hyperglycemia and dyslipidemia were the most important abnormal metabolism that related to decreased androgen indices. Including SHBG in the stepwise regression increased the explanation effect of TT and BT by 32.7% and 28.5%, respectively, and all metabolic indices were excluded. Abnormal metabolism indies (BMI and PBG) were correlated to the decrease in SHBG levels, while age and LH was positively correlated to SHBG levels.

CONCLUSIONS

Age and abnormal metabolism were independently important factors associated with the sex hormone levels in elderly Chinese men, which were all mediated by SHBG.

Prostate cancer, androgen deprivation therapy, obesity, the metabolic syndrome, type 2 diabetes, and cardiovascular disease: a review

Prostate cancer is the most frequently diagnosed malignancy among UK men and accounts for 12% of male deaths. Androgen deprivation therapy (ADT) is commonly used as part of the treatment for prostate cancer. It is effective at suppressing prostate-specific antigen, stabilizing disease, alleviating symptoms in advanced disease, and potentially prolonging survival. However ADT, presumably at least in part owing to low testosterone levels is associated with insulin resistance, the development of metabolic syndrome plus increased overall and cardiovascular disease mortality. We have reviewed the relationship between prostate cancer, ADT, metabolic syndrome, type 2 diabetes, and cardiovascular disease. We have not reviewed other potential medical problems such as osteoporosis. We suggest that there should be a baseline assessment of patients' risk for cardiovascular disease before starting ADT. Consideration should be given to starting appropriate therapies including lifestyle advice, antihypertensive and lipid-lowering agents, insulin sensitizer, plus possibly aspirin. Having started ADT, the patients should have a regular (possibly annual) assessment of their cardiovascular risk factors.

Fasting blood glucose and lipid profile alterations following twelve-month androgen deprivation therapy in men with prostate cancer

PURPOSE

In this retrospective study, we aimed to investigate the effects of androgen deprivation therapy (ADT) on blood glucose and blood cholesterol levels over a 12-month period.

MATERIALS AND METHODS

Between January 2010 and June 2012, the data of 44 patients with prostate cancer who were receiving ADT were collected from a hospital database. Patients with additional malignancy or diabetes and those who had been prescribed and were currently taking cholesterol-lowering medication were excluded from the study. Data (including fasting blood glucose levels and a cholesterol profile) were collected and analysed statistically. A P value <0.05 was considered statistically significant.

RESULTS

Twelve months after the initiation of ADT, fasting blood glucose (FBG), total cholesterol (TC), low-density lipoprotein (LDL) cholesterol, high-density lipoprotein (HDL) cholesterol, and triglyceride (TG) levels changed. FBG, TC, LDL cholesterol, and TG increased significantly (P = 0.009, 0.000, 0.000, and 0.000, resp.), while HDL cholesterol decreased (P = 0.000).

CONCLUSION

ADT may increase FBG, TC, LDL cholesterol, and TG but decrease HDL cholesterol by the end of a year of treatment. Therefore, close followup may be needed as a consequence of one-year ADT regarding metabolic alterations.

Association between Relative Hypogonadism and Metabolic Syndrome in Newly Diagnosed Adult Male Patients with Impaired Glucose Tolerance or Type 2 Diabetes Mellitus

Sex steroid hormones are known to be important regulators of the lipid and glucose metabolism. Lower levels of testosterone (T) or sex hormone-binding globulin (SHBG) have been reported in men with type 2 diabetes. On the other hand, the relationship between relative hypogonadism and metabolic syndrome has not yet to be thoroughly studied. Ninety-eight Japanese adult (age 20-64) male patients with impaired glucose tolerance (IGT) or type 2 diabetes mellitus were divided into either an metabolic syndrome group (n = 42) or a non- metabolic syndrome (n = 56) group according to the definition of metabolic syndrome from WHO, or into three tertiles according to their sex hormone index level. The metabolic syndrome group had a significantly lower T/estradiol (E(2)) and SHBG level (p < 0.01). The age and subcutaneous fat surface area (SFA) were significantly different within the tertiles in SHBG and T/E(2). Logistic regression analyses were performed to investigate the association between the sex steroid hormone index level and the incidence of metabolic syndrome. Regarding the highest tertiles as a criterion, lower SHBG, T/E(2) or free T/E(2) had a higher odds ratio of prevalence of metabolic syndrome even after adjusting for age and SFA. Relative hypogonadism was strongly associated with the prevalence of metabolic syndrome in Japanese adult men who were newly diagnosed to have IGT or type 2 diabetes.

Androgen Treatment of Abdominally Obese Men

Middle-aged men with abdominal obesity were treated in a double-blind study with moderate doses of transdermal preparations of testosterone (T), dihydrotestosterone (DHT), or placebo. This resulted in moderately elevated T concentrations and marked decreases in follicle stimulating and luteinizing hormones in the group treated with T, while the DHT group showed elevated DHT, markedly lower T values, and less diminution of gonadotropin concentrations. In the group treated with T visceral fat mass decreased (measured by computerized tomography) without significant changes in other depot fat regions. Lean body mass did not change. In the group treated with T, glucose disposal rate, measured with the euglycemic hyperinsulinemic clamp method, was markedly augmented. Plasma triglycerides, cholesterol, and fasting blood glucose concentrations as well as diastolic blood pressure decreased. There were no such changes in the DHT or placebo treatment groups. The men treated with T reported increased well-being and energy. In none of the groups did prostate volume, specific prostate antigen concentration, genito-urinary history, or urinary flow measurement change. It is suggested that supplementation of abdominal obese men with moderate doses of T might have several beneficial effects.

The Interactions between Insulin and Androgens in Progression to Castrate-Resistant Prostate Cancer

An association between the metabolic syndrome and reduced testosterone levels has been identified, and a specific inverse relationship between insulin and testosterone levels suggests that an important metabolic crosstalk exists between these two hormonal axes; however, the mechanisms by which insulin and androgens may be reciprocally regulated are not well described. Androgen-dependant gene pathways regulate the growth and maintenance of both normal and malignant prostate tissue, and androgen-deprivation therapy (ADT) in patients exploits this dependence when used to treat recurrent and metastatic prostate cancer resulting in tumour regression. A major systemic side effect of ADT includes induction of key features of the metabolic syndrome and the consistent feature of hyperinsulinaemia. Recent studies have specifically identified a correlation between elevated insulin and high-grade PCa and more rapid progression to castrate resistant disease. This paper examines the relationship between insulin and androgens in the context of prostate cancer progression. Prostate cancer patients present a promising cohort for the exploration of insulin stabilising agents as adjunct treatments for hormone deprivation or enhancers of chemosensitivity for treatment of advanced prostate cancer.

Plasma testosterone in adult normoglycaemic men: impact of hyperinsulinaemia

This study analysed the relationship of plasma testosterone with β-cell secretion, insulin sensitivity and other pituitary-target gland hormones in normoglycaemic adult men. The sample frame was the 'Offspring of individuals with diabetes study' database. A total of 358 offspring of individuals with type-2 diabetes (T2DM) and 287 individuals without known family history of T2DM were recruited for the study. Normoglycaemic men aged ≥18 years (maximum 55) were selected for this analysis. All participants underwent 75 g oral glucose tolerance test (OGTT); blood samples were collected at 0, 30, 60 and 120 min for plasma insulin and C-peptide. Total testosterone, cortisol, adrenocorticotropic hormone, thyroid stimulating hormone and thyroxine (T4) were measured in the fasting sample. A total of 164 men (age 28 ± 7.7 years) were included in analysis. Testosterone correlated negatively with BMI, waist to hip ratio (WHR), area under curve (AUC) of C-peptide and insulin (during OGTT) and was positively correlated with insulin sensitivity (r ~ 0.4). Cortisol and T4 positively correlated (weak) with testosterone (r ~ 0.2). In multivariate analysis, AUC C-peptide, BMI, WHR (negatively) and cortisol (positively) were related to testosterone. Concluding, testosterone correlated negatively with BMI and β-cell secretion. There was a positive association of testosterone with insulin sensitivity, cortisol and T4.

Decreased serum testosterone levels in long-term adult survivors with fatty liver after childhood stem cell transplantation

Fatty liver and male gonadal dysfunction are potential late effects of therapy in adult survivors treated with stem cell transplantation (SCT) in childhood. Obesity and metabolic syndrome also are associated with low serum testosterone levels in the general population. However, the relationship between the degree of fatty liver and changes in serum testosterone levels in adult survivors has not been fully studied. We reviewed the clinical records of 34 male patients who received allogeneic SCT in childhood or adolescence. The median age at SCT was 10.0 years, and the median follow-up after SCT was 15.9 years. All but one patient showed no tendency toward overweight/obesity during the follow-up period. Fatty liver was diagnosed by ultrasound in 15 patients at 4 to 20 years after SCT. Patients who received cranial radiation therapy before SCT were more likely to develop fatty liver and insulin resistance. Moreover, fatty liver was statistically associated with decreased serum testosterone levels, whereas nonfatty liver was not (median, 527 ng/dL [range, 168-944 ng/dL] versus 302 ng/dL [165-698 ng/dL]; P < .0001). Changes in testosterone levels after SCT are affected not only by primary gonadal dysfunction but also by subsequent development or exacerbation of fatty liver.

Relationship between testosterone deficiency and cardiovascular risk and mortality in adult men

Classic male hypogonadism is associated with known adverse effects including decreased libido, erectile dysfunction, osteoporosis, and changes in body composition. Recently, we have come to appreciate that reduction in serum testosterone (T) levels resulting from aging or chronic disease or androgen deprivation therapy (ADT) have consequences similar to those seen in classic male hypogonadism which include increased fat mass, decreased lean body mass, decreased muscle strength, and sexual dysfunction. These data suggest that low T levels may represent a newly recognized cardiometabolic risk factor. Therefore, we carried out a careful review of the literature, focusing on major turning points of research and studies which gave more important and controversial contribution to the cardiovascular role of T. Observational studies and clinical trials investigating the relationship between T levels and cardiovascular disease and mortality were identified byMedline search. The results were synthesized, tabulated, and interpreted. The aim of this review is to discuss the association between low T levels and adverse metabolic profile such as insulin resistance, metabolic syndrome, and diabetes. We will also investigate the potential mechanisms by which male hypogonadism, especially age related or induced by ADT, may increase cardio-metabolic risk. Finally we will detail the emerging relationship between low T and mortality in men addressing also the reverse hypothesis that low T has a protective role by turning off T-dependent functions.

Prevalence of late-onset hypogonadism in men with type 2 diabetes mellitus

Late-onset hypogonadism (LOH) or age-associated testosterone deficiency syndrome is defined as a clinical and biochemical syndrome associated with advancing age and characterised by symptoms and a deficiency in serum testosterone levels. This condition may result in significant detriment in the quality of life and adversely affect the function of multiple organ systems. It has been suggested that sex steroid hormones may play a causal role in the development of insulin resistance and type II diabetes. This comparative study was aimed at determining the prevalence of LOH in diabetic men with erectile dysfunction and investigating the effect of testosterone replacement therapy on erectile function and on glycaemic control.

Effect of testosterone replacement treatment in testosterone deficiency syndrome patients with metabolic syndrome

Purpose

This study was conducted to investigate the effect of testosterone replacement treatment (TRT) in testosterone deficiency syndrome (TDS) patients with metabolic syndrome.

Materials and Methods

We reviewed the data of 200 men who were diagnosed with TDS and were undergoing TRT between August 2006 and August 2009. The 200 patients were divided into two groups (group 1: 71 patients with metabolic syndrome, group 2: 129 patients without metabolic syndrome) depending on metabolic syndrome, which was diagnosed according to the NCEP III criteria for Asians. Age, BMI (body mass index), waist circumference, serologic tests, AMS (the Aging Males' Symptoms scale), and IIEF (International Index of Erectile Function) were measured.

Results

In group 1, waist circumference and fasting glucose were significantly decreased; hemoglobin and total testosterone were increased; and the somatovegetative scale score of the AMS, the total AMS score, the erectile function score of the IIEF, the overall satisfaction score of the IIEF, and the total IIEF score were significantly improved after TRT. On the other hand, in group 2, waist circumference, BMI, total cholesterol, LDL, and fasting glucose were significantly decreased; hemoglobin and total testosterone were increased; and the 2 subscale scores of the AMS (psychologic and somatovegetative), the total AMS score, all subscale scores of the IIEF, and the total IIEF score were significantly improved after TRT.

Conclusions

Overall, the patients who had TDS with metabolic syndrome showed less improvement in AMS, IIEF, and serum variables. Therefore, the correction of metabolic syndrome, such as diabetes, obesity, and hypertension, should be considered during TRT.

Urological aspects of the metabolic syndrome

The metabolic syndrome is common in countries with Western lifestyles. It comprises a number of disorders-including insulin resistance, hypertension and obesity-that all act as risk factors for cardiovascular diseases. Urological diseases have also been linked to the metabolic syndrome. Most established aspects of the metabolic syndrome are linked to benign prostatic hyperplasia (BPH) and prostate cancer. Fasting plasma insulin, in particular, has been linked to BPH and incident, aggressive and lethal prostate cancer. The metabolic syndrome has also been shown to be associated with nonprostatic urological conditions such as male hypogonadism, nephrolithiasis, overactive bladder and erectile dysfunction, although data on these conditions are still sparse. Overall, the results of studies on urological aspects of the metabolic syndrome seem to indicate that BPH and prostate cancer could be regarded as two new aspects of the metabolic syndrome, and that an increased insulin level is a common underlying aberration that promotes both BPH and clinical prostate cancer. Urologists need to be aware of the effect that the metabolic syndrome has on urological disorders and should transfer this knowledge to their patients.

Sleep duration as a risk factor for cardiovascular disease- a review of the recent literature

Sleep loss is a common condition in developed countries, with evidence showing that people in Western countries are sleeping on average only 6.8 hour (hr) per night, 1.5 hr less than a century ago. Although the effects of sleep deprivation on our organs have been obscure, recent epidemiological studies have revealed relationships between sleep deprivation and hypertension (HT), coronary heart disease (CHD), and diabetes mellitus (DM). This review article summarizes the literature on these relationships. Because sleep deprivation increases sympathetic nervous system activity, this increased activity serves as a common pathophysiology for HT and DM. Adequate sleep duration may be important for preventing cardiovascular diseases in modern society.

Endocrinology of the aging male

The endocrinology of the aging male is complex, with multiple hormones along the hypothalamic-pituitary-testicular (HPT) axis interacting with one another in feedback. As men age, there is a small and progressive (not precipitous, as in women) decline in several sex hormones, in particular testosterone and dehydroepiandrosterone, and related increases in luteinizing hormone, follicle-stimulating hormone, and sex hormone-binding globulin. The importance of these changes is wide-ranging because of the ubiquitous role of sex hormones in male physiology. This chapter discusses the endocrinology of the aging male. We provide an overview of the regulation of the HPT axis with an emphasis on the changes that occur with aging and the measurement of gonadal steroids, including hormone pulsatility, within-subject and circadian variations. The difficulties of assessing the symptoms of late-onset hypogonadism are highlighted. There is a comprehensive discussion of the epidemiology of sex hormone changes, including their age associations, prevalence of symptomatic hypogonadism, secular changes, risk factors, and the association of sex hormones with outcomes.

Treatment of hypogonadism with testosterone in patients with type 2 diabetes mellitus

OBJECTIVE

To investigate the effect of testosterone treatment on insulin resistance, glycemic control, and dyslipidemia in Asian Indian men with type 2 diabetes mellitus (T2DM) and hypogonadism.

METHODS

We conducted a double-blind, placebo-controlled, crossover study in 22 men, 25 to 50 years old, with T2DM and hypogonadism. Patients were treated with intramuscularly administered testosterone (200 mg every 15 days) or placebo for 3 months in random order, followed by a washout period of 1 month before the alternative treatment phase. The primary outcomes were changes in fasting insulin sensitivity (as measured by homeostasis model assessment [HOMA] in those patients not receiving insulin), fasting blood glucose, and hemoglobin A1c. The secondary outcomes were changes in fasting lipids, blood pressure, body mass index, waist circumference, waist-to-hip ratio, and androgen deficiency symptoms. Statistical analysis was performed on the delta values, with the treatment effect of placebo compared with the effect of testosterone.

RESULTS

Treatment with testosterone did not significantly influence insulin resistance measured by the HOMA index (mean treatment effect, 1.67 +/- 4.29; confidence interval, -6.91 to 10.25; P>.05). Mean change in hemoglobin A1c (%) (-1.75 +/- 5.35; -12.46 to 8.95) and fasting blood glucose (mg/dL) (20.20 +/- 67.87; -115.54 to 155.94) also did not reach statistical significance. Testosterone treatment did not affect fasting lipids, blood pressure, and anthropometric determinations significantly.

CONCLUSION

In this study, testosterone treatment showed a neutral effect on insulin resistance and glycemic control and failed to improve dyslipidemia, control blood pressure, or reduce visceral fat significantly in Asian Indian men with T2DM and hypogonadism.

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.

[Testosterone and the metabolic syndrome]

Abdominal obesity as a key cardiovascular risk factor as well as metabolic syndrome and type 2 diabetes mellitus are associated with low testosterone levels. In line with these facts, investigations of patients undergoing androgen ablation therapy for prostate cancer have shown a negative effect of this treatment approach on insulin sensitivity and body fat mass. The effects of physiological doses of testosterone seem to have less impact on the parameters of lipid metabolism. However, supraphysiological levels of testosterone can lower HDL levels. At present data on glycemic control in patients with type 2 diabetes are not yet uniform, but negative effects on glycemic control in type 2 diabetics have not been reported. In fact two studies were able to demonstrate a positive effect of testosterone on glycemic control in patients with type 2 diabetes. It is currently not yet possible to conclusively evaluate the significance of testosterone treatment in patients with metabolic syndrome and type 2 diabetes mellitus. Only larger, randomized prospective trials will show whether testosterone therapy is helpful in metabolic syndrome or type 2 diabetes. However, administration of testosterone in hypogonadal men with metabolic syndrome appears to be a promising treatment option to improve metabolic control.

Studies on hypoglycaemic effects of polyherbal preparation in streptozotocin-induced diabetic male albino rats

Many traditional treatments have been recommended in the alternative system of medicine for diabetes mellitus. However, the mode of action of most of the herbals used has not been defined. It has been reported that sex hormones are important regulators of insulin-mediated events in skeletal muscles. In view of this, a novel herbal preparation containing antidiabetic and aphrodisiac plants was used in the present study. Adult male albino rats were divided into following groups after induction of diabetes. Rats were given an intraperitoneal (i.p.) injection of streptozotocin (STZ), at a dose of 65 mg/kg body weight after overnight fasting, to induce diabetic state with blood glucose levels >250 mg/dL. Group 1-Control rats treated with single i.p. injection of vehicle, Group 2-Rats treated with polyherbal preparation (PHP; 500 mg/kg body weight by oral intubation, morning and evening for 30 days), Group 3-STZ-diabetic rats treated orally with equal volumes of vehicle (water) alone and Group 4-STZ-diabetic rats treated with PHP after 10 days of diabetic induction. STZ-diabetes decreased the body weight, serum insulin level and glucose oxidation in liver and skeletal muscles but increased the fasting blood glucose level. After polyherbal treatment, body weight and glucose oxidation were completely restored to control level while serum insulin level was restored partially and the glucose tolerance was significantly improved. There was a significant decrease in total haemoglobin (Hb) level of diabetic rats when compared to control but polyherbal treatment significantly improved the same. However, the other parameters studied (red blood cell [RBC], white blood corpuscle [WBC], packed cell volume [PCV], mean corpuscular volume [MCV] and mean corpuscular haemoglobin [MCH]) were unaltered. In conclusion, the anti-diabetic properties of PHP appear to be mediated through pancreatic beta-cell regeneration, resulting in maintenance of optimal blood glucose and its oxidation in liver and skeletal muscles.

The benefits and risks of testosterone replacement therapy: a review

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

Testosterone therapy in men

Androgens exert effects on virtually all bodily tissues, and have a multitude of physiological roles in health. Testosterone, the predominant androgen in men, when deficient (hypogonadism), leads to a multiplicity of symptoms and signs that are corrected with physiological substitution. The impact of hypogonadism depends on the age at which it occurs. In any case, when testosterone replacement is initiated close monitoring for efficacy and safety is advised. The relation of ageing, the metabolic syndrome, type 2 diabetes, obesity and survival with plasma testosterone has been closely examined in recent studies. However, the effect of testosterone replacement therapy on the above clinical states needs to be clarified in large long-term duration/outcome studies. Recent research has shed light on possible molecular testosterone targets. Based on those research outcomes, drugs targeting the androgen receptor, which spare androgenic effects and preserve anabolic tissue effects, called selective androgen receptor modulators (SARMS), are under clinical trials. The role of testosterone in regulating erectile function has been studied in animal models and critical tissue testosterone targets have been elucidated.

The GGN and CAG repeat polymorphisms in the exon-1 of the androgen receptor gene are, respectively, associated with insulin resistance in men and with dyslipidemia in women

The human androgen receptor (AR) gene possesses two trinucleotide repeats of CAG and GGN in exon-1. The GGN repeat affects the amount of AR protein translated, while the CAG repeat affects the efficiency of AR transcriptionaly. In this study, we have genotyped these polymorphic tracts in a representative sample of 557 Caucasian adult individuals (314 women and 243 men) from the Canary Islands, Spain (the ENCA Study), and investigated their association with fasting serum levels of lipids, glucose and insulin. The number of CAG repeats in women (expressed as the average length of the two alleles) was inversely correlated with serum levels of LDL-cholesterol (Spearman rho=-0.179; P<0.01). Women with an average number of CAG repeats in the upper tertile showed significantly lower levels of LDL-cholesterol than those grouped in the lower and middle tertile, after adjusting for age, body mass index, waist-to-hip ratio, smoking and alcohol drinking. The number of GGN repeats in men was correlated with fasting insulin levels (Spearman rho=-0.206; P<0.01), the homeostasis model assessment of insulin resistance (HOMA-IR; Spearman rho=-0.230; P<0.01) and the McAuley index of insulin sensitivity (Spearman rho=0.194; P<0.01). Men with a number of GGN repeats in the upper tertile showed lower levels of insulin and HOMA and a higher level of the McAuley index than those grouped in the lower and middle tertile, after adjusting for the variables listed above. These results support the hypothesis that the longer alleles of the CAG and GGN polymorphisms in the exon-1 of the AR gene, indicative of lower androgenic signaling, respectively protect women from developing dyslipemia and men from developing insulin resistance.