Association of bioavailable, free, and total testosterone with insulin resistance: influence of sex hormone-binding globulin and body fat

Testosterone and ageing: what have we learned since the Institute of Medicine report and what lies ahead?

A 2003 report by the Institute of Medicine (IOM) surveyed the literature on the benefits and risks of testosterone replacement therapy in older men and identified knowledge gaps and research needs. This review summarises some key studies published since the IOM report. The possible relationship of testosterone to risk of prostate cancer remains a concern; however, no new evidence has emerged to suggest that testosterone replacement therapy increases the risk. Recent studies have demonstrated that hypogonadism in men may be more prevalent than previously thought, is strongly associated with metabolic syndrome, and may be a risk factor for type 2 diabetes and cardiovascular disease. Clinical studies have shown that testosterone replacement therapy in hypogonadal men improves metabolic syndrome indicators and cardiovascular risk factors. Maintaining testosterone concentrations in the normal range has been shown to contribute to bone health, lean muscle mass, and physical and sexual function, suggesting that testosterone replacement therapy may help to prevent frailty in older men. Based on current knowledge, testosterone replacement therapy is unlikely to pose major health risks in patients without prostate cancer and may offer substantial health benefits. Larger, longer-term randomised studies are needed to fully establish the effects of testosterone replacement therapy.

The association between birth weight and visceral fat in middle-age adults

OBJECTIVE

Low birth weight, a proxy for fetal underdevelopment, is associated with increased risk of developing type 2 diabetes during adulthood. Low birth weight is also associated with central obesity, but little is known about the association between birth weight and visceral adiposity. The purpose of this study is to test the hypothesis that lower birth weight is associated with increased amounts of visceral fat in middle-age adults.

RESEARCH METHODS AND PROCEDURES

This is an observational study of 91 adults (58 men and 33 women) 40+/-6 years of age (mean+/-standard deviation). Ethnicity was either Japanese American (79%) or non-Hispanic white (21%). Birth weight was obtained from State Departments of Health. Measurements included smoking status, BMI, and visceral (intra-abdominal) fat measured by computed tomography.

RESULTS

Visceral fat was not associated with birth weight after adjustment for age, sex, ethnicity, BMI, or smoking status (p=0.76). There was no evidence that the association between birth weight and visceral fat varied by age, sex, or ethnicity.

DISCUSSION

We found no evidence that low birth weight is associated with increased visceral fat in middle-age adults.

Effects of tumor necrosis factor blockade on cardiovascular risk factors in psoriatic arthritis: A double-blind, placebo-controlled study

OBJECTIVE

To conduct a robust, double-blind, placebo-controlled study examining the effects of tumor necrosis factor (TNF) modulation on concentrations of traditional and novel cardiovascular disease risk factors in patients with an inflammatory condition.

METHODS

In this double-blind study, 127 patients with psoriatic arthritis (PsA) and active psoriasis were randomized to 1 of 3 treatment arms (placebo, onercept 50 mg, or onercept 100 mg for 12 weeks). Traditional and novel biochemical risk factors were evaluated at baseline and at the end of the treatment period.

RESULTS

At baseline, an elevated C-reactive protein (CRP) level correlated positively with lipoprotein(a) (Lp[a]), intercellular adhesion molecule 1, interleukin-6, and homocysteine levels but was inversely correlated with concentrations of all other lipid moieties and sex hormone binding globulin (SHBG). Onercept at a dose of 100 mg induced significant (P < or = 0.002) reductions in the levels of CRP (-14.0 versus 6.5 mg/liter with placebo), Lp(a) (-3.11 versus 1.52 mg/dl with placebo), and homocysteine (-1.72 versus 0.34 mumoles/liter with placebo) and an increase in the SHBG concentration (4.3 versus -1.3 mmoles/liter with placebo). The 100-mg dose of onercept was also associated with significant (P < 0.05) increases in the level of circulating apolipoprotein AI (Apo A-I) (4.0 versus -5.6 mg/dl with placebo); however, levels of Apo B (6.3 versus -0.4 mg/dl with placebo) and triglycerides (0.09 versus 0.04 mmoles/liter) were also increased.

CONCLUSION

This study is the first to demonstrate that targeting the TNF pathway can significantly decrease Lp(a) and homocysteine levels and elevate Apo A-I and SHBG concentrations. These data support an important precursor role for high-grade inflammation in modulating these putative risk parameters. However, TNF blockade-induced increases in triglyceride and Apo B levels were unexpected and suggest that it is not possible, on the basis of biochemical changes in isolation, to suggest that cardioprotection would necessarily follow; rather, direct measures of atherosclerotic progression with TNF blockade (e.g., using carotid ultrasound) would be better.

Low testosterone levels and unimpaired melatonin secretion in young males with metabolic syndrome

The interrelations between testosterone, insulin and melatonin levels in males with metabolic syndrome (MS) are still not clarified, especially in young age groups. The aim of the present study was to compare the testosterone serum levels in young men with MS to those in healthy controls, and to determine the possible changes in their melatonin rhythm, as well as the relation between melatonin, insulin and lipid profile. Fasting insulin and testosterone concentrations were measured in 10 healthy nonobese and 10 MS patients. Blood samples for melatonin, insulin and luteinizing hormone (LH) were collected at 19.00, 03.00 and 11.00 hours. A significant difference was found between the testosterone levels in controls and patients. Luteinizing hormone levels in both groups were similar, however, higher night LH levels in MS patients were observed. No changes in the melatonin concentrations of the two groups were found. In conclusion, total testosterone levels were significantly lower in young men with MS compared with healthy age-matched controls. Mild hypoandrogenia in hyperinsulinaemic patients was not related with changes in their melatonin levels. No alterations in the endogenous melatonin rhythm of the MS patients were found.

Relationship between BMI, total testosterone, sex hormone-binding-globulin, leptin, insulin and insulin resistance in obese men

The objective of this work was to evaluate the relationship between sex steroid hormones, sex hormone-binding-globulin, leptin, insulin and insulin resistance in obese men. Anthropometrical indexes, total testosterone (Tt), free testosterone (fT), estradiol (E), sex hormone-binding-globulin (SHBG), glucemia, insulin and leptin were measured in 77 men, with ages between 20 and 60 years. According to their body mass index (BMI), subjects were grouped into three categories: normal body weight (< 24.9 kg/m2), overweight (25-29.9 kg/m2) and obese group (> 30 kg/m2). Insulin resistance index was obtained by the homeostasis assessment model for insulin resistance (HOMA-IR). Total testosterone and SHBG concentrations were lower in the obese group compared with normal and overweight subjects (p < 0.05). The mean insulin concentration was significantly higher in the obese group compared with the other groups (p < 0.05). T was negatively correlated with the BMI (r = -0.447; p < .01), WC (r = -0.464); p < .01, leptin (r = -0.382; p < .01), insulin (r = -0.391; p < 0.01) and also with the HOMA-IR (r = -0.416; p < 0.01). The SHBG negatively and significantly correlated with BMI (r = -0.334; p < 0.01) and WC index (= -0.322; p < 0.01), as well with insulin levels (r = -0.313; p < 0.01) and insulin resistance (= -0.266; p < 0.05). Our results shows that in a sample of men, Tt and SHBG concentrations proportionally diminished with both the increase of BMI and insulin resistance index.

The metabolic syndrome is frequent in Klinefelter's syndrome and is associated with abdominal obesity and hypogonadism

OBJECTIVE

Klinefelter's syndrome is associated with an increased prevalence of diabetes, but the pathogenesis is unknown. Accordingly, the aim of this study was to investigate measures of insulin sensitivity, the metabolic syndrome, and sex hormones in patients with Klinefelter's syndrome and an age-matched control group. RESEARCH DESIGN AN METHODS: In a cross-sectional study, we examined 71 patients with Klinefelter's syndrome, of whom 35 received testosterone treatment, and 71 control subjects. Body composition was evaluated using dual-energy X-ray absorptiometry scans. Fasting blood samples were analyzed for sex hormones, plasma glucose, insulin, C-reactive protein (CRP), and adipocytokines. We analyzed differences between patients with untreated Klinefelter's syndrome and control subjects and subsequently analyzed differences between testosterone-treated and untreated Klinefelter's syndrome patients.

RESULTS

Of the patients with Klinefelter's syndrome, 44% had metabolic syndrome (according to National Cholesterol Education Program/Adult Treatment Panel III criteria) compared with 10% of control subjects. Insulin sensitivity (assessed by homeostasis model assessment 2 modeling), androgen, and HDL cholesterol levels were significantly decreased, whereas total fat mass and LDL cholesterol, triglyceride, CRP, leptin, and fructosamine levels were significantly increased in untreated Klinefelter's syndrome patients. In treated Klinefelter's syndrome patients, LDL cholesterol and adiponectin were significantly decreased, whereas no difference in body composition was found in comparison with untreated Klinefelter's syndrome patients. Multivariate analyses showed that truncal fat was the major determinant of metabolic syndrome and insulin sensitivity.

CONCLUSIONS

The prevalence of metabolic syndrome was greatly increased, whereas insulin sensitivity was decreased in Klinefelter's syndrome. Both correlated with truncal obesity. Hypogonadism in Klinefelter's syndrome may cause an unfavorable change in body composition, primarily through increased truncal fat and decreased muscle mass. Testosterone treatment in Klinefelter's syndrome only partly corrected the unfavorable changes observed in untreated Klinefelter's syndrome, perhaps due to insufficient testosterone doses.

Association of hypogonadism and type II diabetes in men attending an outpatient erectile dysfunction clinic

Patients with diabetes mellitus (DM) were more often hypogonadal than normal fasting glucose subjects. The aim of this investigation is the assessment of characteristics and psychobiological correlates of DM associated with hypogonadism (DMAH). The Structured Interview SIEDY was used along with several biochemical, psychological and instrumental investigations in a series of more than 1200 patients with erectile dysfunction (ED); 16% of whom with type II DM. Hypogonadism was defined as circulating total testosterone (T) below 10.4 nmol/l. The prevalence of hypogonadism was 24.5% in DM versus 12.6% in the rest of the sample (P < 0.0001); differences in the prevalence of hypogonadism retained significance after adjustment for age and BMI. DMAH was associated with typical hypogonadism-related symptoms, such as reduction in sexual desire, leading to a decreased number of sexual attempts, and with higher depressive symptomatology. In DMAH, testis size and LH concentrations were significantly reduced, suggesting a central origin of the disease. At penile Duplex ultrasound examination, diabetic patients and in particular hypogonadal type II diabetic patients showed lower levels of basal and dynamic (after PGE1 injection) peak systolic velocity and acceleration, when compared to the rest of the sample, even after adjustment for age and BMI. Our results show that hypogonadism is frequently associated with type II DM, at least in the 6th decade. DMAH might exacerbate sexual dysfunction by reducing libido and mood and further compromising penile vascular reactivity.

Male hypogonadism. Part I: Epidemiology of hypogonadism

Male hypogonadism is a frequent and potentially undertreated condition. A number of longitudinal epidemiologic studies, including the Baltimore Longitudinal Study of Aging, the New Mexico Aging Process Study, and the Massachusetts Male Aging Study, have demonstrated age-related increases in the likelihood of developing hypogonadism. In addition to advancing age, increasing body mass index and/or type II diabetes mellitus may be associated with lower circulating androgen levels. Owing to the demographic trends toward increasing population age and life expectancy, together with the emerging pandemic of diabetes and recent trend toward an increasing prevalence of obesity in the United States, clinicians are likely to encounter increasing cases of hypogonadism in the near future.

Low sex hormone-binding globulin, total testosterone, and symptomatic androgen deficiency are associated with development of the metabolic syndrome in nonobese men

BACKGROUND

The metabolic syndrome (MetS), characterized by central obesity, lipid and insulin dysregulation, and hypertension, is a precursor state for cardiovascular disease. The purpose of this analysis was to determine whether low serum sex hormone levels or clinical androgen deficiency (AD) predict the development of MetS.

METHODS

Data were obtained from the Massachusetts Male Aging Study, a population-based prospective cohort of 1709 men observed at three time points (T1, 1987-1989; T2, 1995-1997; T3, 2002-2004). MetS was defined using a modification of the ATP III guidelines. Clinical AD was defined using a combination of testosterone levels and clinical signs and symptoms. The association between MetS and sex hormone levels or clinical AD was assessed using relative risks (RR), and 95% confidence intervals (95% CI) were estimated using Poisson regression models.

RESULTS

Analysis was conducted in 950 men without MetS at T1. Lower levels of total testosterone and SHBG were predictive of MetS, particularly among men with a body mass index (BMI) below 25 kg/m2 with adjusted RRs for a decrease in 1 sd of 1.41 (95% CI, 1.06-1.87) and 1.65 (95% CI, 1.12-2.42). Results were similar for the AD and MetS association, with RRs of 2.51 (95% CI, 1.12-5.65) among men with a BMI less than 25 compared with an RR of 1.22 (95% CI, 0.66-2.24) in men with a BMI of 25 or greater.

CONCLUSIONS

Low serum SHBG, low total testosterone, and clinical AD are associated with increased risk of developing MetS over time, particularly in nonoverweight, middle-aged men (BMI, <25). Together, these results suggest that low SHBG and/or AD may provide early warning signs for cardiovascular risk and an opportunity for early intervention in nonobese men.

The relationship between serum resistin, leptin, adiponectin, ghrelin levels and bone mineral density in middle-aged men

OBJECTIVE

Body weight is a significant predictor of bone mass. Hormonal factors such as sex hormones, insulin, leptin and adiponectin are thought to play a role in the mechanisms controlling the association of body weight and fat mass with bone mass. However, contradictory results have been reported for the association between serum adipocytokines and bone mineral density (BMD). We therefore examined whether the serum adipocytokine and ghrelin levels, markers of fat metabolism, are associated with BMD in male adults.

PATIENTS AND MEASUREMENTS

For 80 male adults (average age 54.5 +/- 6.4 years; average body mass index (BMI) 24.4 +/- 2.5 kg/m2), the correlations between serum resistin, leptin, adiponectin and ghrelin levels with BMD were investigated.

RESULTS

Among the adipocytokines, serum resistin levels were negatively correlated with lumbar spine BMD (r = -0.237, P = 0.05). After adjustment was made for age and BMI, log-transformed serum leptin showed a significant negative correlation with lumbar spine BMD, which was not seen on bivariate analysis (r = -0.237, P = 0.039). Femoral neck BMD was marginally associated only with serum adiponectin levels (r = -0.226, P = 0.062). In multiple regression analyses, among the adipokines, only resistin was a significant determinant of lumbar spine BMD, although the variance was small (R2 = 0.256). Serum ghrelin levels were not correlated with the BMD of either body site.

CONCLUSIONS

Serum resistin level showed a significant negative correlation with lumbar spine BMD, although the variance was small. Further studies are needed to elucidate the role of adipocytokines in bone metabolism.

Evaluation of insulin sensitivity in patients with Klinefelter's syndrome: a hyperinsulinemic euglycemic clamp study

Patients with Klinefelter's syndrome have a higher incidence of diabetes mellitus and the percentage of insulin resistance was reported to be high in these patients. However, little is known about the insulin sensitivity assessed by the hyperinsulinemic euglycemic clamp in these patients. In the present study, subjects included 13 newly diagnosed patients with Klinefelter's syndrome, and 9 age- and body mass index-matched healthy males. The hyperinsulinemic euglycemic clamp was performed in all patients and controls. Insulin resistance was present in five (38.5%) patients with Klinefelter's syndrome. Compared with control subjects, patients with Klinefelter's syndrome had elevated plasma concentrations of fasting insulin, follicle-stimulating hormone, luteinizing hormone, estradiol, and sex hormone-binding globulin, whereas they had reduced plasma free testosterone and total testosterone concentrations. The multivariate linear regression analysis showed that fasting glucose, fasting insulin, free testosterone, and total testosterone were independently associated with M-value. In conclusion, the present study by using hyperinsulinemic euglycemic clamp indicates the high prevalence of insulin resistance in Klinefelter's syndrome patients. However, these patients did not have reduced mean M-values compared with the controls, although their plasma insulin levels were significantly elevated. It is possible that hyperinsulinemia may be the primary metabolic abnormality rather than insulin resistance.

ISA, ISSAM and EAU recommendations for the investigation, treatment and monitoring of late-onset hypogonadism in males: scientific background and rationale

Prescription sales for testosterone products have substantially increased over the last several years reflecting the growing awareness of physicians for the potential benefits of testosterone replacement therapy in men with hypogonadism. Indiscriminate administration of testosterone poses a risk and has to be deprecated. Testosterone supplementation to treat late-onset hypogonadism (LOH), a term for androgen deficiency in elderly men, is still controversially discussed mainly due to a lack of large, controlled clinical trials on efficacy and safety. To provide guidance for physicians primarily dealing with aging men, ISSAM is periodically updating and publishing its recommendations as new data become available [Morales A, Lunenfeld B. International Society for the Study of the Aging Male. Investigation, treatment and monitoring of late-onset hypogonadism in males. Official recommendations of ISSAM. International Society for the Study of the Aging Male. Aging Male 2002;5:74-86 and Morales A, Lunenfeld B. Androgen replacement therapy in aging men with secondary hypogonadism. Draft recommendations for endorsement by ISSAM. Aging Male 2001;4:1]. Following a panel discussion at the 4th ISSAM Congress in Prague in February 2004, the International Society of Andrology (ISA), the International Society for the Study of the Aging Male (ISSAM) and the European Association of Urology (EAU) revised existing recommendations on the definition, diagnosis and management of LOH. The recommendations are based on the currently available scientific data on androgen supplementation therapy and should be regarded as provisional until larger-scale, long-term studies are available. While certainly not intending to be exhaustive, this review will highlight some relevant background information and provide the underlying scientific rationale for the ISA, ISSAM and EAU recommendations on LOH published in this issue.

Metabolic implications of obesity: before and after gastric bypass

Obesity is recognized as an inherited disease state, and attributes of modern civilization have enhanced its phenotypic penetrance greatly. Two thirds or more of obese persons suffer comorbidities,many of which are characteristic of (dys)metabolic syndrome of insulin resistance. Unfortunately patients with body mass index over 35 infrequently can achieve or maintain weight loss adequate to resolve these metabolic (and anatomic) issues by lifestyle or pharmacologic strategies and are served better by gastric bypass, in spite of its attendant risks, both surgical and nutritional. This article evaluates the metabolic consequences of obesity and highlights which of these are amenable to correction with weight reduction achieved by gastric bypass.