Effect of 2 years of testosterone replacement on insulin secretion, insulin action, glucose effectiveness, hepatic insulin clearance, and postprandial glucose turnover in elderly men

Diagnosing and treating the elderly individual with hypopituitarism

Hypopituitarism in the elderly is an underestimated condition mainly due to the non-specific presentation that can be attributed to the effects of aging and the presence of comorbidities. Diagnosis and treatment of hypopituitarism often represent a challenging task and this is even more significant in the elderly. Diagnosis can be insidious due to the physiological changes occurring with aging that complicate the interpretation of hormonal investigations, and the need to avoid some provocative tests that carry higher risks of side effects in this population. Treatment of hypopituitarism has generally the goal to replace the hormonal deficiencies to restore a physiological balance as close as possible to that of healthy individuals but in the elderly this must be balanced with the risks of over-replacement and worsening of comorbidities. Moreover, the benefit of some hormonal replacement therapies in the elderly, including sex hormones and growth hormone, remains controversial.

Developing the UVA/Padova Type 1 Diabetes Simulator: Modeling, Validation, Refinements, and Utility

Arguably, diabetes mellitus is one of the best quantified human conditions. In the past 50 years, the metabolic monitoring technologies progressed from occasional assessment of average glycemia via HbA1c, through episodic blood glucose readings, to continuous glucose monitoring (CGM) producing data points every few minutes. The high-temporal resolution of CGM data enabled increasingly intensive treatments, from decision support assisting insulin injection or oral medication, to automated closed-loop control, known as the "artificial pancreas." Throughout this progress, mathematical models and computer simulation of the human metabolic system became indispensable for the technological progress of diabetes treatment, enabling every step, from assessment of insulin sensitivity via the now classic Minimal Model of Glucose Kinetics, to in silico trials replacing animal experiments, to automated insulin delivery algorithms. In this review, we follow these developments, beginning with the Minimal Model, which evolved through the years to become large and comprehensive and trigger a paradigm change in the design of diabetes optimization strategies: in 2007, we introduced a sophisticated model of glucose-insulin dynamics and a computer simulator equipped with a "population" of N = 300 in silico "subjects" with type 1 diabetes. In January 2008, in an unprecedented decision, the Food and Drug Administration (FDA) accepted this simulator as a substitute to animal trials for the pre-clinical testing of insulin treatment strategies. This opened the field for rapid and cost-effective development and pre-clinical testing of new treatment approaches, which continues today. Meanwhile, animal experiments for the purpose of designing new insulin treatment algorithms have been abandoned.

Treating Hypopituitarism in the Over 65s: Review of Clinical Studies

The current increase of life expectancy is associated with the presence of endocrine diseases in the elderly. The management of hypopituitarism in this group of patients is a challenging task. A correct diagnosis, which represents an essential requisite for an appropriate medical treatment, can be difficult because of the physiological changes occurring in pituitary function with aging, which may lead to challenges in the interpretation of laboratory results. Furthermore, the treatment requires several careful considerations: the need to restore the hormonal physiology with replacement therapies must be balanced with the need to avoid the risks of the over-replacement, especially in the presence of concomitant cardiovascular and metabolic disease. Interactions with other drugs able to modify the absorption and/or the metabolism of hormonal replacement therapies should be considered, in particular for the treatment of hypoadrenalism and hypothyroidism. The most important challenges stem from the lack of specific studies focused on the management of hypopituitarism in older people.

The Effects of Testosterone Treatment on Cardiovascular Health

Current evidence suggests that testosterone therapy has numerous benefits and risks on cardiovascular health. Examples of this include published data that support improvements in insulin sensitivity and body composition which may reduce the risk of diabetes. On the other hand, testosterone therapy may offset such benefits by mild impairments in lipid parameters. Consequently, controversy on the effects of testosterone therapy on cardiovascular health remains. Studies are underway to clarify this important question for the benefit of men with hypogonadism.

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.

Efficacy of testosterone replacement therapy for treating metabolic disturbances in late-onset hypogonadism: a systematic review and meta-analysis

PURPOSE

Late onset hypogonadism (LOH) is an age-dependent reduction of testosterone associated with alterations of metabolic profile, including glucose control, insulin sensitivity, and lipid profile. The purpose of this study was to investigate the efficacy of testosterone replacement therapy (TRT) for treating metabolic disturbances through a meta-analysis of randomized clinical trials (RCTs).

METHODS

A systematic review of literature published from 1964 to November, 2019 was performed using the PubMed/Medline, Embase, and Cochrane databases. Among the 1562 articles screened, 17 articles were selected for qualitative analysis and 16 articles (n = 1373) were included for data synthesis following the Preferred Reporting Items for Systematic Reviews and Meta-analysis (PRISMA). Criteria for final inclusion were RCTs.

RESULTS

Sixteen studies were finally included (TRT group, n = 709; placebo group, n = 664). Among the metabolic markers, HbA1C [Mean difference (MD) = - 0.172, 95% CI - 0.329, - 0.015], HOMA IR (MD = - 0.514, 95% CI - 0.863, - 0.165), serum insulin (MD = - 12.622, 95% CI - 19.660, - 5.585), and leptin (MD = - 2.381, 95% CI - 2.952, - 1.810) showed significant improvement after TRT versus placebo. Among the lipid profiles, total cholesterol showed significant improvement (MD = - 0.433, 95% CI - 0.761, - 0.105) after TRT. However, HDL showed a decrease (MD = - 0.069, 95% CI - 0.121, - 0.018) after TRT. Among anthropometric markers, waist circumference showed significant improvement (MD = - 0.1640, 95% CI - 2.857, - 0.423).

CONCLUSION

This study demonstrated greater improvement in metabolic profiles for patients given TRT versus placebo. Further well-designed trials are needed to verify our findings and further elucidate effects of TRT on lipid profiles. This systematic review demonstrates that TRT can exert a net beneficial effect on metabolic profiles.

Virilizing doses of testosterone decrease circulating insulin levels and differentially regulate insulin signaling in liver and adipose tissue of females

Transgender men undergoing hormone therapy are at risk for insulin resistance. However, how virilizing testosterone therapy affects serum insulin and peripheral insulin sensitivity in transgender men is unknown. This study assessed the effect of acute, virilizing testosterone on serum insulin concentrations and insulin signaling in liver, skeletal muscle, and white adipose tissue (WAT) of female pigs as a translational model for transgender men. Females received three doses of intramuscular testosterone cypionate (TEST females; 50 mg/day/pig) or corn oil (control) spaced 6 days apart starting on the day of estrus (D0). Fasting blood was collected on D0, D3, D5, D11, and D13, and females were euthanized on D13. On D13, TEST females had virilizing concentrations of serum testosterone with normal concentrations of serum estradiol. Virilizing serum testosterone concentrations (D13) were associated with decreased serum insulin and C-peptide concentrations. Blood glucose and serum glycerol concentrations were not altered by testosterone. Virilizing concentrations of testosterone downregulated AR and ESR1 in subcutaneous (sc) WAT and upregulated transcript levels of insulin-signaling pathway components in WAT and liver. At the protein level, virilizing testosterone concentrations were associated with increased PI3K 110α in liver and increased insulin receptor (INSR) and phospho(Ser256)-FOXO1 in visceral (v) WAT but decreased phospho(Ser473)-AKT in vWAT and scWAT. These results suggest that acute exposure to virilizing concentrations of testosterone suppresses circulating insulin levels and results in increased abundance of proteins in the insulin-signaling pathway in liver and altered phosphorylation of key proteins in control of insulin sensitivity in WAT.NEW & NOTEWORTHY Acute virilizing doses of testosterone administered to females suppress circulating insulin levels, upregulate components of the insulin-signaling pathway in liver, and suppress insulin signaling in white adipose tissue. These results suggest that insulin resistance in transgender men may be due to suppression of the insulin-signaling pathway and decreased insulin sensitivity in white adipose tissue.

Association between T2DM and the lowering of testosterone levels among Kashmiri males

OBJECTIVE

The objective of this study is to study association between testosterone and diabetes in Kashmiri males.

METHODS

A total of 300 males with Type 2 diabetes visited an outpatient and inpatient clinic at Shri Maharaja Hari Singh (SMHS) hospital, Srinagar, J&K India. The blood sugar and HbA1c, which are the markers of diabetes, and sérum testosterone levels were measured. The blood samples from both the cases and controls were collected.

RESULTS

Out of 300 subjects, 42% had a testosterone deficiency. A relationship between type 2 diabetic males and healthy males was observed, and testosterone levels were determined to be significantly lower among diabetic males (p < 0.001) when compared to healthy males. Then, we compared diabetic markers among testosterone deficient and normal testosterone level groups; the mean fasting plasma glucose (p = 0.0019) and glycated haemoglobin (HbA1c; p = 0.0449) levels were significantly higher in the testosterone deficient group than in the control group. To elucidate the relationship between the serum total testosterone level and fasting plasma glucose and HbA1c values, Pearson's correlation test was performed. Fasting plasma glucose levels (r = -0.252, p = 0.001) and HbA1c values (r = -0.697, p = 0.001) showed a significant negative correlation with serum testosterone levels among diabetic males.

CONCLUSION

This study shows that diabetes causes low testosterone levels among males, and lower testosterone levels can act as a marker for diabetes. Thus, with timely intervention, mortality and co-morbidity associated with diabetes can be prevented.

Hormonal and Metabolic Changes of Aging and the Influence of Lifestyle Modifications

Increased life expectancy combined with the aging baby boomer generation has resulted in an unprecedented global expansion of the elderly population. The growing population of older adults and increased rate of age-related chronic illness has caused a substantial socioeconomic burden. The gradual and progressive age-related decline in hormone production and action has a detrimental impact on human health by increasing risk for chronic disease and reducing life span. This article reviews the age-related decline in hormone production, as well as age-related biochemical and body composition changes that reduce the bioavailability and actions of some hormones. The impact of hormonal changes on various chronic conditions including frailty, diabetes, cardiovascular disease, and dementia are also discussed. Hormone replacement therapy has been attempted in many clinical trials to reverse and/or prevent the hormonal decline in aging to combat the progression of age-related diseases. Unfortunately, hormone replacement therapy is not a panacea, as it often results in various adverse events that outweigh its potential health benefits. Therefore, except in some specific individual cases, hormone replacement is not recommended. Rather, positive lifestyle modifications such as regular aerobic and resistance exercise programs and/or healthy calorically restricted diet can favorably affect endocrine and metabolic functions and act as countermeasures to various age-related diseases. We provide a critical review of the available data and offer recommendations that hopefully will form the groundwork for physicians/scientists to develop and optimize new endocrine-targeted therapies and lifestyle modifications that can better address age-related decline in heath.

Mechanisms underlying the metabolic actions of testosterone in humans: A narrative review

The role of testosterone in improving sexual symptoms in men with hypogonadism is well known. However, recent studies indicate that testosterone plays an important role in several metabolic functions in males. Multiple PubMed searches were conducted with the use of the terms testosterone, insulin sensitivity, obesity, type 2 diabetes, anaemia, bone density, osteoporosis, fat mass, lean mass and body composition. This narrative review is focused on detailing the mechanisms that underlie the metabolic aspects of testosterone therapy in humans. Testosterone enhances insulin sensitivity in obese men with hypogonadism by decreasing fat mass, increasing lean mass, decreasing free fatty acids and suppressing inflammation. At a cellular level, testosterone increases the expression of insulin receptor β subunit, insulin receptor substrate-1, protein kinase B and glucose transporter type 4 in adipose tissue and adenosine 5'-monophosphate-activated protein kinase expression and activity in skeletal muscle. Observational studies show that long-term therapy with testosterone prevents progression from prediabetes to diabetes and improves HbA1c. Testosterone increases skeletal muscle satellite cell activator, fibroblast growth factor-2 and decreases expression of the muscle growth suppressors, myostatin and myogenic regulatory factor 4. Testosterone increases haematocrit by suppressing hepcidin and increasing expression of ferroportin along with that of transferrin receptor and plasma transferrin concentrations. Testosterone also increases serum osteocalcin concentrations, which may account for its anabolic actions on bone. In conclusion, testosterone exerts a series of potent metabolic effects, which include insulin sensitization, maintenance and growth of the skeletal muscle, suppression of adipose tissue growth and maintenance of erythropoiesis and haematocrit.

Testosterone treatment longer than 1 year shows more effects on functional hypogonadism and related metabolic, vascular, diabetic and obesity parameters (results of the 2-year clinical trial)

OBJECTIVE

We evaluated long-term effects of testosterone undecanoate on glycemic control, metabolic syndrome, vascular function and morphology in obese men with functional hypogonadism (FH) and type 2 diabetes (T2D) in a 2-year prospective clinical trial.

METHODS

A total of 55 participants were enrolled in this study; group P (n = 27) received placebo during first and testosterone therapy (TTh) during second year, group T (n = 28) received TTh both years. We pooled results after 1 year of TTh to obtain more statistical power. Results for group T after 2 years of TTh are also presented. We evaluated wide assortment of biochemical (fasting plasma glucose-FPG, glycated hemoglobin-HbA1c and lipid profile), hormonal, vascular (flow-mediated dilatation-FMD and intima-media thickness-IMT), anthropometrical and derived parameters (BMI, HOMA-IR, non-HDL cholesterol, bioavailable and calculated free testosterone). Quality of life was assessed using Aging Males' Symptoms (AMS) questionnaire.

RESULTS

FPG, HbA₁c, HOMA-IR and IMT decreased, FMD increased, lipid profile and AMS sexual sub-score improved, and testosterone levels fully normalized after 2 years of TTh.

CONCLUSIONS

Two-year of TTh resulted in normalized serum testosterone levels, improved glycemia, endothelial function, lipids and insulin sensitivity, and quelled the symptoms of hypogonadism, potentially reducing cardiovascular risk in obese men with FH and T2D.

Hypogonadism, Type-2 Diabetes Mellitus, and Bone Health: A Narrative Review

One of the complications from chronic hyperglycemia and insulin resistance due to type 2 diabetes mellitus (T2DM) on the hypothalamic-pituitary-gonadal axis in men is the high prevalence of hypogonadotropic hypogonadism (HH). Both T2DM and hypogonadism are associated with impaired bone health and increased fracture risk but whether the combination results in even worse bone disease than either one alone is not well-studied. It is possible that having both conditions predisposes men to an even greater risk for fracture than either one alone. Given the common occurrence of HH or hypogonadism in general in T2DM, a significant number of men could be at risk. To date, there is very little information on the bone health men with both hypogonadism and T2DM. Insulin resistance, which is the primary defect in T2DM, is associated with low testosterone (T) levels in men and may play a role in the bidirectional relationship between these two conditions, which together may portend a worse outcome for bone. The present manuscript aims to review the available evidences on the effect of the combination of hypogonadism and T2DM on bone health and metabolic profile, highlights the possible metabolic role of the skeleton, and examines the pathways involved in the interplay between bone, insulin resistance, and gonadal steroids.

Aging and the Male Reproductive System

This narrative review presents an overview of current knowledge on fertility and reproductive hormone changes in aging men, the factors driving and modulating these changes, their clinical consequences, and the benefits and risks of testosterone (T) therapy. Aging is accompanied by moderate decline of gamete quality and fertility. Population mean levels show a mild total T decline, an SHBG increase, a steeper free T decline, and a moderate LH increase with important contribution of comorbidities (e.g., obesity) to these changes. Sexual symptoms and lower hematocrit are associated with low T and are partly responsive to T therapy. The relationship of serum T with body composition and metabolic health is bidirectional; limited beneficial effects of T therapy on body composition have only marginal effects on metabolic health and physical function. Skeletal changes are associated primarily with estradiol and SHBG. Cognitive decline is not consistently linked to low T and is not improved by T therapy. Although limited evidence links moderate androgen decline with depressive symptoms, T therapy has small beneficial effects on mood, depressive symptoms, and vitality in elderly patients with low T. Suboptimal T (and/or DHT) has been associated with increased risk of stroke, but not of ischemic heart disease, whereas an association with mortality probably reflects that low T is a marker of poor health. Globally, neither severity of clinical consequences attributable to low T nor the nature and magnitude of beneficial treatment effects justify the concept of some broadly applied "T replacement therapy" in older men with low T. Moreover, long-term safety of T therapy is not established.

Benefits and risks of testosterone therapy in older men

Adult-onset hypogonadism is used to define androgen deficiency and its associated symptoms commonly occurring in middle-aged and elderly men, who are unable to mount an adequate compensatory gonadotropin response but may also have an element of testicular failure. It often occurs in relation with chronic metabolic conditions such as diabetes and the metabolic syndrome. There is a growing demand from elderly men for testosterone therapy. The physician should therefore be well-informed so as the patient can make an informed decision. Indeed, testosterone therapy in older men has been a matter of debate, especially with regard to its impact on cardiovascular events and mortality. Not all studies have reported consistent results regarding its effect on diabetes, obesity and the metabolic syndrome. In contrast, it appears to improve sexual, physical function and bone density and it does not appear to increase the risk of prostate cancer; however, it increases hematocrit and hemoglobin levels. Therefore, testosterone therapy might provide significant beneficial effects in older symptomatic hypogonadal men; treatment should be individualized, and comorbidities addressed. Further research is required into its long-term effects.

The impact of testosterone replacement therapy on glycemic control, vascular function, and components of the metabolic syndrome in obese hypogonadal men with type 2 diabetes

OBJECTIVE

This study set out to assess effects of testosterone replacement therapy (TRT) on parameters of metabolic syndrome and vascular function in obese hypogonadal males with type 2 diabetes mellitus (DM2).

STUDY DESIGN

Fifty-five obese hypogonadal diabetic males on oral hypoglycemic treatment were enrolled into this one-year, double-blind, randomized, placebo-controlled clinical study. Group T (n = 28) was treated with testosterone undecanoate (1000 mg i.m. every 10 weeks) while group P (n = 27) received placebo.

METHODS

Anthropometrical and vascular measurements - flow-mediated dilatation (FMD) and intima media thickness (IMT) - biochemical and hormonal blood sample analyses were performed at the start of the study and after one year. Derived parameters (BMI, HOMA-IR, calculated free testosterone (cFT) and bioavailable testosterone (BT)) were calculated.

RESULTS

TRT resulted in reduction of HOMA-IR by 4.64 ± 4.25 (p < .001), HbA1c by 0.94 ± 0.88% points (p < .001), and an increase in FMD by 2.40 ± 4.16% points (p = .005).

CONCLUSION

TRT normalized serum testosterone levels, improved glycemic control and endothelial function while exerting no ill effects on the study population.

The complex association between metabolic syndrome and male hypogonadism

BACKGROUND

The complex association between metabolic syndrome (MetS) and male hypogonadism is well established. A number of observational studies show that low testosterone is associated with insulin resistance and an increased risk for diabetes mellitus and MetS in men.

AIMS

To elucidate the association between MetS and male hypogonadism, present epidemiological data on the co-existence of the two comorbidities, enlighten the underlying pathophysiology and appraise the effects of testosterone supplementation therapy (TTh) and lifestyle modifications on MetS and body composition in men.

MATERIALS AND METHODS

Systematic search to PubMed and Medline databases for publications reporting data on association between MetS and male hypogonadism.

RESULTS

Both MetS and male hypogonadism have a high prevalence in the general population and are frequently co-existing e.g. in males with diabetes. Accumulating evidence from animal and human studies suggests that MetS is involved in the pathogenesis of hypogonadism in males as well as the other way around. On the other hand, there is evidence for a favorable effect of testosterone supplementation in testosterone deficient men with MetS and/or diabetes mellitus.

CONCLUSIONS

Studies with superior methodological characteristics are needed in order to establish a role for testosterone supplementation in men with MetS and/or diabetes mellitus.

GONADOPENIA AND AGING IN MEN

OBJECTIVE

The decrease in testosterone levels that occurs with aging has become an important clinical issue both due to the growth of the geriatric population and patient interest in testosterone therapy. The decision to assess for testosterone deficiency and the ability to determine whether the benefits exceed the risks require a comprehensive evaluation of the aging patient. This article is part of a series of papers focused on the endocrinology of aging. This review addresses common issues needed for clinical decision making, including how to interpret test results, differential diagnosis, potential impact of testosterone treatment on insulin resistance and cardiovascular disease, and options for therapy.

METHODS

Papers reviewed were identified through literature searches conducted on PubMed.

RESULTS

Assessment of testosterone levels in the geriatric male requires an understanding of the limitations of the assay that is used, the symptoms associated with low testosterone, the impact of comorbid conditions on levels, and risks of therapy. Successful treatment requires setting realistic expectations of the benefits of replacement therapy.

CONCLUSION

While the prevalence of low testosterone concentrations is increased with aging, the common comorbidities such as obesity and diabetes may contribute to changes in testosterone levels. Clinical trial evidence shows modest benefit for treatment of low testosterone in the presence of symptoms. Assessment of the geriatric male should include evaluation of their testosterone level in the context of their functional status and comorbidities.

ABBREVIATIONS

CDC = Centers for Disease Control and Prevention; CI = confidence interval; CVD = cardiovascular disease; DXA = dual-energy X-ray absorptiometry; EMAS = European Male Aging Study; FDA = U.S. Food and Drug Administration; FHS = Framingham Heart Study; HDL = high-density lipoprotein; HOMA-IR = homeostasis model assessment of insulin resistance; LH = luteinizing hormone; OR = odds ratio; PSA = prostate-specific antigen; SHBG = sex hormone-binding globulin; T2DM = type 2 diabetes mellitus; vBMD = volumetric bone mineral density.

Adult-Onset Hypogonadism

In August 2015, an expert colloquium commissioned by the Sexual Medicine Society of North America (SMSNA) convened in Washington, DC, to discuss the common clinical scenario of men who present with low testosterone (T) and associated signs and symptoms accompanied by low or normal gonadotropin levels. This syndrome is not classical primary (testicular failure) or secondary (pituitary or hypothalamic failure) hypogonadism because it may have elements of both presentations. The panel designated this syndrome adult-onset hypogonadism (AOH) because it occurs commonly in middle-age and older men. The SMSNA is a not-for-profit society established in 1994 to promote, encourage, and support the highest standards of practice, research, education, and ethics in the study of human sexual function and dysfunction. The panel consisted of 17 experts in men's health, sexual medicine, urology, endocrinology, and methodology. Participants declared potential conflicts of interest and were SMSNA members and nonmembers. The panel deliberated regarding a diagnostic process to document signs and symptoms of AOH, the rationale for T therapy, and a monitoring protocol for T-treated patients. The evaluation and management of hypogonadal syndromes have been addressed in recent publications (ie, the Endocrine Society, the American Urological Association, and the International Society for Sexual Medicine). The primary purpose of this document was to support health care professionals in the development of a deeper understanding of AOH, particularly in how it differs from classical primary and secondary hypogonadism, and to provide a conceptual framework to guide its diagnosis, treatment, and follow-up.

Accurate Measurement of Postprandial Glucose Turnover: Why Is It Difficult and How Can It Be Done (Relatively) Simply?

Fasting hyperglycemia occurs when an excessive rate of endogenous glucose production (EGP) is not accompanied by an adequate compensatory increase in the rate of glucose disappearance (Rd). The situation following food ingestion is more complex as the amount of glucose that reaches the circulation for disposal is a function of the systemic rate of appearance of the ingested glucose (referred to as the rate of meal appearance [Rameal]), the pattern and degree of suppression of EGP, and the rapidity of stimulation of the Rd In an effort to measure these processes, Steele et al. proposed what has come to be referred to as the dual-tracer method in which the ingested glucose is labeled with one tracer while a second tracer is infused intravenously at a constant rate. Unfortunately, subsequent studies have shown that although this approach is technically simple, the marked changes in plasma specific activity or the tracer-to-tracee ratio, if stable tracers are used, introduce a substantial error in the calculation of Rameal, EGP, and Rd, thereby leading to incorrect and at times misleading results. This Perspective discusses the causes of these so-called "nonsteady-state" errors and how they can be avoided by the use of the triple-tracer approach.

Effect of Dehydroepiandrosterone and Testosterone Supplementation on Systemic Lipolysis

CONTEXT

Dehydroepiandrosterone (DHEA) and T hormones are advertised as antiaging, antiobesity products. However, the evidence that these hormones have beneficial effects on adipose tissue metabolism is limited.

OBJECTIVE

The objective of the study was to determine the effect of DHEA and T supplementation on systemic lipolysis during a mixed-meal tolerance test (MMTT) and an iv glucose tolerance test (IVGTT).

DESIGN

This was a 2-year randomized, double-blind, placebo-controlled trial.

SETTING

The study was conducted at a general clinical research center.

PARTICIPANTS

Sixty elderly women with low DHEA concentrations and 92 elderly men with low DHEA and bioavailable T concentrations participated in the study.

INTERVENTIONS

Elderly women received 50 mg DHEA (n = 30) or placebo (n = 30). Elderly men received 75 mg DHEA (n = 30), 5 mg T (n = 30), or placebo (n = 32).

MAIN OUTCOME MEASURES

In vivo measures of systemic lipolysis (palmitate rate of appearance) during a MMTT or IVGTT.

RESULTS

At baseline there was no difference in insulin suppression of lipolysis measured during MMTT and IVGTT between the treatment groups and placebo. For both sexes, a univariate analysis showed no difference in changes in systemic lipolysis during the MMTT or IVGTT in the DHEA group and T group when compared with placebo. There was no change in the results after adjusting for the resting energy expenditure, except for a small, but significant (P = .03) lowering of MMTT nadir palmitate rate of appearance in women who received DHEA.

CONCLUSION

In elderly individuals with concentrations of DHEA (men and women) or T (men) below the normal range for young adults, supplementation of these hormones has no effect on insulin suppression of systemic lipolysis.

Insulin Resistance and Inflammation in Hypogonadotropic Hypogonadism and Their Reduction After Testosterone Replacement in Men With Type 2 Diabetes

OBJECTIVE

One-third of men with type 2 diabetes have hypogonadotropic hypogonadism (HH). We conducted a randomized placebo-controlled trial to evaluate the effect of testosterone replacement on insulin resistance in men with type 2 diabetes and HH.

RESEARCH DESIGN AND METHODS

A total of 94 men with type 2 diabetes were recruited into the study; 50 men were eugonadal, while 44 men had HH. Insulin sensitivity was calculated from the glucose infusion rate (GIR) during hyperinsulinemic-euglycemic clamp. Lean body mass and fat mass were measured by DEXA and MRI. Subcutaneous fat samples were taken to assess insulin signaling genes. Men with HH were randomized to receive intramuscular testosterone (250 mg) or placebo (1 mL saline) every 2 weeks for 24 weeks.

RESULTS

Men with HH had higher subcutaneous and visceral fat mass than eugonadal men. GIR was 36% lower in men with HH. GIR increased by 32% after 24 weeks of testosterone therapy but did not change after placebo (P = 0.03 for comparison). There was a decrease in subcutaneous fat mass (-3.3 kg) and increase in lean mass (3.4 kg) after testosterone treatment (P < 0.01) compared with placebo. Visceral and hepatic fat did not change. The expression of insulin signaling genes (IR-β, IRS-1, AKT-2, and GLUT4) in adipose tissue was significantly lower in men with HH and was upregulated after testosterone treatment. Testosterone treatment also caused a significant fall in circulating concentrations of free fatty acids, C-reactive protein, interleukin-1β, tumor necrosis factor-α, and leptin (P < 0.05 for all).

CONCLUSIONS

Testosterone treatment in men with type 2 diabetes and HH increases insulin sensitivity, increases lean mass, and decreases subcutaneous fat.

Metabolic effects of testosterone replacement therapy on hypogonadal men with type 2 diabetes mellitus: a systematic review and meta-analysis of randomized controlled trials

This systematic review was aimed at assessing the metabolic effects of testosterone replacement therapy (TRT) on hypogonadal men with type 2 diabetes mellitus (T2DM). A literature search was performed using the Cochrane Library, EMBASE and PubMed. Only randomized controlled trials (RCTs) were included in the meta-analysis. Two reviewers retrieved articles and evaluated the study quality using an appropriate scoring method. Outcomes including glucose metabolism, lipid parameters, body fat and blood pressure were pooled using a random effects model and tested for heterogeneity. We used the Cochrane Collaboration's Review Manager 5.2 software for statistical analysis. Five RCTs including 351 participants with a mean follow-up time of 6.5-months were identified that strictly met our eligibility criteria. A meta-analysis of the extractable data showed that testosterone reduced fasting plasma glucose levels (mean difference (MD): −1.10; 95% confidence interval (CI) (−1.88, −0.31)), fasting serum insulin levels (MD: −2.73; 95% CI (−3.62, −1.84)), HbA1c % (MD: −0.87; 95% CI (−1.32, −0.42)) and triglyceride levels (MD: −0.35; 95% CI (−0.62, −0.07)). The testosterone and control groups demonstrated no significant difference for other outcomes. In conclusion, we found that TRT can improve glycemic control and decrease triglyceride levels of hypogonadal men with T2DM. Considering the limited number of participants and the confounding factors in our systematic review; additional large, well-designed RCTs are needed to address the metabolic effects of TRT and its long-term influence on hypogonadal men with T2DM.

Testosterone deficiency associated with poor glycemic control in korean male diabetics

BACKGROUND

Recent studies have shown that men with diabetes have lower testosterone levels than healthy men. However, studies on the correlation between testosterone and diabetes are rare in Korea. We examined the relationship between testosterone deficiency and markers related to diabetes in adult Korean men.

METHODS

A total 464 men with diabetes who visited an outpatient clinic at Ajou University Hospital and had serum total testosterone and serum insulin levels measured between January 2000 and September 2013 were selected. Blood samples were collected after the subjects had fasted overnight. We divided the participants into testosterone deficient and normal groups. Testosterone deficiency was defined as having a serum total testosterone level <3.5 ng/mL.

RESULTS

Of 464 subjects, 34.9% had a testosterone deficiency. The mean levels of fasting plasma glucose (P=0.007) and glycated hemoglobin (HbA1c; P=0.038) were significantly higher in the testosterone deficiency group than in the normal group. To clarify the relationship between serum total testosterone level and fasting plasma glucose or HbA1c values, Pearson's correlation test was performed. Fasting plasma glucose levels (r=-0.142, P=0.002) and HbA1c values (r=-0.097, P=0.040) showed a significant negative correlation with serum testosterone levels in men with diabetes.

CONCLUSION

Major markers of diabetes that are associated with testosterone deficiency are fasting plasma glucose and HbA1c values. Poor glycemic control appears to be associated with testosterone deficiency in Korean men with diabetes.

Acute and short-term chronic testosterone fluctuation effects on glucose homeostasis, insulin sensitivity, and adiponectin: a randomized, double-blind, placebo-controlled, crossover study

CONTEXT

Low levels of adiponectin and T in men have been shown to predict development of the metabolic syndrome, but the effects of T on glucose metabolism are incompletely understood and may be influenced either directly or indirectly through changes in body composition or in levels of adiponectin.

OBJECTIVE

The aim of the study was to test whether T exerts its effects on glucose metabolism directly or indirectly.

DESIGN, SETTING, AND PARTICIPANTS

In a randomized, double-blind, placebo-controlled, crossover study, 12 healthy young males were studied on four separate occasions. They received GnRH agonist treatment 1 month before 3 of 4 trial days to induce castrate levels of T. On trial days, T gel containing either high or low physiological T dose or placebo was applied to the body. On a fourth trial day, participants constituted their own eugonadal controls.

INTERVENTION

Each study comprised a 5-hour basal period and a 3-hour hyperinsulinemic euglycemic clamp.

MAIN OUTCOME MEASURES

We measured the effect of acute T on peripheral glucose disposal, total adiponectin and subforms, and other indices of glucose metabolism.

RESULTS

Short-term hypogonadism was associated with increased high molecular weight adiponectin levels (P < .03) and increased oxidative glucose disposal (P = .03) but not total glucose disposal (P = .07). Acute T treatment was an independent suppressor of high molecular weight adiponectin levels (P = .04) but did not affect total glucose disposal (P = .17).

CONCLUSIONS

These data show that T can act through putative fast nongenomic pathways to affect adiponectin levels in humans. The early hypogonadal state is characterized by a marked shift in fuel oxidation from lipids toward glucose, which may rely partly on buffering capabilities of adiponectin.

Male hypogonadism

Male hypogonadism is a clinical syndrome that results from failure to produce physiological concentrations of testosterone, normal amounts of sperm, or both. Hypogonadism may arise from testicular disease (primary hypogonadism) or dysfunction of the hypothalamic-pituitary unit (secondary hypogonadism). Clinical presentations vary dependent on the time of onset of androgen deficiency, whether the defect is in testosterone production or spermatogenesis, associated genetic factors, or history of androgen therapy. The clinical diagnosis of hypogonadism is made on the basis of signs and symptoms consistent with androgen deficiency and low morning testosterone concentrations in serum on multiple occasions. Several testosterone-replacement therapies are approved for treatment and should be selected according to the patient's preference, cost, availability, and formulation-specific properties. Contraindications to testosterone-replacement therapy include prostate and breast cancers, uncontrolled congestive heart failure, severe lower-urinary-tract symptoms, and erythrocytosis. Treatment should be monitored for benefits and adverse effects.

Endogenous sex hormones, metabolic syndrome, and diabetes in men and women

Endogenous sex hormones predict impairments of glucose regulation. Cross-sectional studies suggest that lower levels of testosterone in men and higher levels in women increase risk of metabolic syndrome and diabetes, whereas lower levels of sex hormone binding globulin in both men and women increase risk of metabolic syndrome and diabetes. In a systematic review, we summarize existing longitudinal studies, which suggest similar patterns. However, these studies are often limited to a single sex steroid measure. Whether these associations are primarily a marker of adiposity, and whether these associations differ between younger eugonadal vs older hypogonadal adults is also uncertain. The impact of exogenous sex steroid therapy may not reflect relationships between sex hormones and impaired glucose regulation that occur without supplementation. Therefore, examination of endogenous sex steroid trajectories and obesity trajectories within individuals might aid our understanding of how sex steroids contribute to glucose regulation.

Sex-dependent expression of caveolin 1 in response to sex steroid hormones is closely associated with development of obesity in rats

Caveolin-1 (CAV1) is a conserved group of structural membrane proteins that form special cholesterol and sphingolipid-rich compartments, especially in adipocytes. Recently, it has been reported that CAV1 is an important target protein in sex hormone-dependent regulation of various metabolic pathways, particularly in cancer and diabetes. To clarify distinct roles of CAV1 in sex-dependent obesity development, we investigated the effects of high fat diet (HFD) and sex steroid hormones on CAV1 expression in adipose tissues of male and female rats. Results of animal experiments revealed that estrogen (17-β-estradiol, E2) and androgen (dihydrotestosterone, DHT) had opposite effects on body weight gain as well as on the regulation of CAV1, hormone sensitive lipase (HSL) and uncoupling protein 1 (UCP1) in adipose tissues. Furthermore, sex hormone receptors and aromatase were differentially expressed in a sex-dependent manner in response to E2 and DHT treatments. In vivo data were confirmed using 3T3-L1 and HIB1B cell lines, where Cav1 knock down stimulated lipogenesis but suppressed sex hormone receptor signaling proteins. Most importantly, co-immunoprecipitation enabled the identification of previously unrecognized CAV1-interacting mitochondrial or lipid oxidative pathway proteins in adipose tissues. Taken together, current data showed that CAV1 may play important preventive role in the development of obesity, with more prominent effects in females, and proved to be an important target protein for the hormonal regulation of adipose tissue metabolism by manipulating sex hormone receptors and mitochondrial oxidative pathways. Therefore, we can report, for the first time, the molecular mechanism underlying the effects of sex steroid hormones in the sex-dimorphic regulation of CAV1.

Testosterone and glucose metabolism in men: current concepts and controversies

A wealth of observational studies show that low testosterone is associated with insulin resistance and with an increased risk of diabetes and the metabolic syndrome. Experimental studies have identified potential mechanisms by which low testosterone may lead to insulin resistance. Visceral adipose tissue is an important intermediate in this relationship. Actions of testosterone or its metabolite oestradiol on other tissues such as muscle, liver, bone or the brain, and body composition-independent effects may also play a role. However, definitive evidence from randomised controlled trials (RCTs) to clarify whether the association of low testosterone with disordered glucose metabolism is causative is currently lacking. It therefore remains possible that this association is due to reverse causation, or simply originates by association with common health and lifestyle factors. RCTs of testosterone therapy in men with or without diabetes consistently show modest metabolically favourable changes in body composition. Despite this, testosterone effects on glucose metabolism have been inconsistent. Recent evidence suggests that the hypothalamic-pituitary-testicular axis suppression in the majority of obese men with metabolic disorders is functional, and may be, at least in part, reversible with weight loss. Until further evidence is available, lifestyle measures with emphasis on weight reduction, treatment of comorbidities and optimisation of diabetic control should remain the first-line treatment in these men. Such measures, if successful, may be sufficient to normalise testosterone levels in men with metabolic disorders, who typically have only modest reductions in circulating testosterone levels.

Testosterone Supplementation Improves Carbohydrate and Lipid Metabolism in Some Older Men with Abdominal Obesity

Background/Objectives

The effects of testosterone supplementation on carbohydrate and lipid metabolism in obese older men are uncertain. We conducted a single-arm open-label prospective pilot study to investigate the effects of testosterone supplementation on central and peripheral insulin sensitivity in older men with upper body obesity and insulin resistance.

Subjects/Methods

Twenty men (62–78 years-old) with morning testosterone levels <13.9 nmol/L (400 ng/dL), waist circumference ≥ 102 cm, and HOMA-IR ≥ 4.0 or HgbA1C 5.7–6.4% applied transdermal testosterone (10 mg) daily for 20 weeks. Insulin sensitivity (Si) was determined by a 2-stage glucose clamp, liver and intramyocellular lipid by ¹H-MR spectroscopy and body composition by DEXA.

Results

Testosterone supplementation significantly reduced total fat (−.9 ± 2.4 kg, p=0.002), trunk fat (−1.3 ± 1.4 kg, p=0.0007) and extremity fat (−0.7 ± 1.1 kg, p=0.01), and increased extremity lean tissue (+1.3 ± 1.4 kg, p=0.0006). Whole body (WB) Si improved by 21% (0.76 ± 1.57 dL/min per µU/mL, p=0.04) and insulin-stimulated glucose uptake (Rd) by 24% (0.91 ± 1.74 dL/min per µU/mL, p=0.03). Improvements in glucose kinetics were limited to men with reductions in trunk and extremity fat greater than median declines for the entire group. Reductions in intramyocellular lipid were associated with improvements in WB Si (p=0.04) and Rd (p=0.03). Change in Rd accounted for 90% of the change in WB Si. Hepatic glucose output and liver lipid/H₂O were unchanged (p>0.05). Multivariable analyses revealed that reductions in extremity fat, trunk fat, and FFA levels during the clamp accounted for 45% (p=0.004), 31% (p=0.002) and 8% (p=0.04) of respective changes in Rd. Triglycerides decreased by −0.40 ± 0.67mmol/L (p=0.02), LDL-C by-0.35 ± 0.57 mmol/L (p=0.02), and HDL-C by −0.14 ± 0.19 mmol/L (p=0.004).

Conclusions

Testosterone supplementation that resulted in greater reductions in regional adiposity was associated with improved insulin sensitivity, lower LDL-C and fasting triglycerides, but lower HDL-C. Placebo controlled trials need to further examine the potential cardiometabolic risks/benefits of androgen supplementation for older men with low testosterone levels, central obesity, and insulin resistance.

Single-nucleotide polymorphism, rs1799941 in the Sex Hormone-Binding Globulin (SHBG) gene, related to both serum testosterone and SHBG levels and the risk of myocardial infarction, type 2 diabetes, cancer and mortality in men: the Tromsø Study

Low testosterone levels are associated with metabolic and cardiovascular disease risk factor, and have been shown to predict type 2 diabetes mellitus (T2DM), myocardial infarction (MI) and all-cause mortality. It is not known if these associations are causal or not. Recently, it has been shown that the serum testosterone levels are associated with single-nucleotide polymorphisms (SNPs), and we therefore studied the associations between one of these SNPs, rs1799941 on the Sex Hormone-Binding Globulin (SHBG) gene, and MI, T2DM, cancer and death. DNA was prepared from men who participated in the fourth survey of the Tromsø Study in 1994-1995 and who were registered with the endpoints MI, T2DM, cancer or death and a randomly selected control group. For mortality, the observation time was set from 1994, and for the other endpoints from birth. The endpoint data were completed up to 2010-2013. Genetic analyses were successfully performed in 5309 men, of whom 1454 were registered with MI, 638 with T2DM, 1534 with cancer and in 2226 who had died. Men with the minor homozygote genotype had significantly higher levels of total testosterone (14.7%) and SHBG (24.7%) compared with men with the major homozygote genotype, whereas free testosterone levels did not differ significantly between the genotypes. The SNP rs1799941 was not significantly associated with MI, T2DM, cancer or mortality. Thus, our result does not support a causal relationship between total testosterone and SHBG and MI, T2DM, cancer or mortality, suggesting that low testosterone more likely is a marker of poor health.

Andropause: Current concepts

Andropause or late-onset hypogonadism is a common disorder which increases in prevalence with advancing age. Diagnosis of late-onset of hypogonadism is based on presence of symptoms suggestive of testosterone deficiency - prominent among them are sexual symptoms like loss of libido, morning penile erection and erectile dysfunction; and demonstration of low testosterone levels. Adequate therapeutic modalities are currently available, but disparate results of clinical trial suggest further evaluation of complex interaction between androgen deficiency and ageing. Before initiating therapy benefits and risk should be discussed with patients and in case of poor response, alternative cause should be investigated.

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.

Assessment of insulin action on carbohydrate metabolism: physiological and non-physiological methods

Carbohydrate metabolism in humans is regulated by insulin secretion from pancreatic β-cells and glucose disposal by insulin-sensitive tissues. Insulin facilitates glucose utilization in peripheral tissues and suppresses hepatic glucose production. Any defects in insulin action predispose an individual to glucose intolerance and Type 2 diabetes mellitus. Early detection of defects in insulin action could provide opportunities to prevent or delay progression of the disease state. There are different approaches to assess insulin action. Initial methods, such as peripheral insulin concentration and simple indices, have several limitations. Subsequently, researchers developed methodologies using intravenous glucose infusion to determine glucose fluxes. However, these methodologies are limited by being non-physiological. Newer, innovative techniques that have been developed are more sophisticated and physiological. By modelling glucose kinetics using isotope dilution techniques, several robust parameters can be obtained that are physiologically relevant and sound. This brief review summarizes most of the non-physiological and physiological methodologies used to measure the variables of insulin action.

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.

Insulin-mediated FFA suppression is associated with triglyceridemia and insulin sensitivity independent of adiposity

CONTEXT

A central/visceral fat distribution and excess free fatty acid (FFA) availability are associated with dyslipidemia and insulin resistance. However, these two characteristics often coexist, making it difficult to detect the independent contributions of each. Whether FFA suppression is more closely linked to metabolic abnormalities is not clear.

OBJECTIVE

The aim of the study was to examine the relationship between FFA suppression, body fat distribution, and fitness as contributors toward insulin resistance and hypertriglyceridemia.

DESIGN

We measured systemic palmitate turnover using an iv infusion of [9,10-(3)H]palmitate; upper body sc adipose tissue (UBSQ) and visceral adipose tissue (VAT) with dual-energy x-ray absorptiometry and a single-slice abdominal computed tomography scan; fitness with a graded exercise treadmill test; and insulin sensitivity with both the iv glucose tolerance test (IVGTT) (SI(IVGTT)) and mixed meal tolerance test (SI(Meal)).

SETTING

The study was conducted at a General Clinical Research Center.

PARTICIPANTS

Baseline data were obtained from 140 elderly adults (age, 60-88 yr; 83 males) and 60 young adults (age, 18-31 yr; 31 males) who participated in a previously published trial assessing the effects of 2-yr supplementation of dehydroepiandrosterone or testosterone on body composition, glucose metabolism, and bone density.

INTERVENTIONS

There were no interventions.

MAIN OUTCOME MEASURES

We measured fasting plasma triglyceride (TG) concentrations, SI(IVGTT), and SI(Meal).

RESULTS

Using multivariate regression analysis, the strongest combined predictors of TG concentrations were VAT, postmeal nadir FFA concentrations, sex, and age. The best predictors of SI(IVGTT) were IVGTT nadir palmitate concentration, VAT, UBSQ fat, fitness, and age, whereas the best predictors of SI(Meal) were meal nadir palmitate concentration, UBSQ fat, fitness, and sex.

CONCLUSIONS

FFA suppression is associated with both fasting TG concentrations and insulin sensitivity, independent of measures of adiposity.

Effect of royal jelly ingestion for six months on healthy volunteers

BACKGROUND

Royal jelly is a widely ingested supplement for health, but its effects on humans are not well known. The objective was to evaluate the effects of long-term royal jelly ingestion on humans.

METHODS

We conducted a randomized placebo-controlled, double-blind trial. A total of 61 healthy volunteers aged 42-83 years were enrolled and were randomly divided into a royal jelly group (n = 31) and a control group (n = 30). Three thousand mg of royal jelly (RJ) or a placebo in 100 ml liquid/day were ingested for 6 months. The primary outcomes were changes in anthropometric measurements and biochemical indexes from baseline to 6 months after intervention.

RESULTS

Thirty subjects in the RJ group and 26 in the control group were included in the analysis of endpoints. In an adjusted mean change of the variables from the baseline, significant differences between the two groups could be found in red blood cell counts (+0.16x10⁶/μL for the RJ group vs. -0.01x10⁶/μL for the control group, P = 0.0134), hematocrit (+0.9% vs. -0.8%, P = 0.0251), log (fasting plasma glucose) (+0.01 ± 0.01 log mg/dL vs. +0.05 ± 0.01 log mg/dL, P = 0.0297), log (insulinogenic index) (+0.25 vs. -0.13, P = 0.0319), log dehydroepiandrosterone sulfate (DHEA-S) (+0.08 log μg/dL vs. +0.20 log μg/dL, P = 0.0483), log testosterone (T) (+0.12 ± 0.04 log ng/mL vs. -0.02 ± 0.05 log ng/mL, P = 0.0416), log T/DHEA-S ratio (+0.05 ± 0.05 vs. -0.23 ± 0.59, P = 0.0015), and in one of the SF-36 subscale scores, mental health (MH) (+4 vs. -7, P = 0.0276).

CONCLUSIONS

Six-month ingestion of RJ in humans improved erythropoiesis, glucose tolerance and mental health. Acceleration of conversion from DHEA-S to T by RJ may have been observed among these favorable effects.

Hypopituitarism in the elderly

Pituitary dysfunction in elderly can represent a true diagnostic and therapeutic challenge to clinicians caring for these patients. Symptoms associated with partial or total hypopituitarism, such as fatigue, lower muscle strength and decreased libido, are nonspecific and can be often attributed to normal aging. Gold standard pituitary diagnostic testing carries higher risks in elderly and is classically replaced by alternative testing. Furthermore, the benefits and safety of selective pituitary hormonal replacement, specifically sexual and growth hormone replacement, remain subject of controversy in this group of patients. Recognizing and appropriately treating hypopituitarism in elderly is crucial for the survival and well being of the older patients with this disease.

Hormone replacement therapy and physical function in healthy older men. Time to talk hormones?

Improving physical function and mobility in a continuously expanding elderly population emerges as a high priority of medicine today. Muscle mass, strength/power, and maximal exercise capacity are major determinants of physical function, and all decline with aging. This contributes to the incidence of frailty and disability observed in older men. Furthermore, it facilitates the accumulation of body fat and development of insulin resistance. Muscle adaptation to exercise is strongly influenced by anabolic endocrine hormones and local load-sensitive autocrine/paracrine growth factors. GH, IGF-I, and testosterone (T) are directly involved in muscle adaptation to exercise because they promote muscle protein synthesis, whereas T and locally expressed IGF-I have been reported to activate muscle stem cells. Although exercise programs improve physical function, in the long-term most older men fail to comply. The GH/IGF-I axis and T levels decline markedly with aging, whereas accumulating evidence supports their indispensable role in maintaining physical function integrity. Several studies have reported that the administration of T improves lean body mass and maximal voluntary strength in healthy older men. On the other hand, most studies have shown that administration of GH alone failed to improve muscle strength despite amelioration of the detrimental somatic changes of aging. Both GH and T are anabolic agents that promote muscle protein synthesis and hypertrophy but work through separate mechanisms, and the combined administration of GH and T, albeit in only a few studies, has resulted in greater efficacy than either hormone alone. Although it is clear that this combined approach is effective, this review concludes that further studies are needed to assess the long-term efficacy and safety of combined hormone replacement therapy in older men before the medical rationale of prescribing hormone replacement therapy for combating the sarcopenia of aging can be established.

Testosterone therapy increased muscle mass and lipid oxidation in aging men

The indication for testosterone therapy in aging hypogonadal men without hypothalamic, pituitary, or testicular disease remains to be elucidated. The aim of this study was to investigate the effect of testosterone therapy on insulin sensitivity, substrate metabolism, body composition, and lipids in aging men with low normal bioavailable testosterone levels using a predefined cutoff level for bioavailable testosterone. A randomized, double-blinded, placebo-controlled study of testosterone treatment (gel) was done on 38 men, aged 60-78 years, with bioavailable testosterone <7.3 nmol/l and a waist circumference >94 cm. Insulin-stimulated glucose disposal (Rd) and substrate oxidation were assessed by euglycemic hyperinsulinemic clamps combined with indirect calorimetry. Lean body mass (LBM) and total fat mass (TFM) were measured by dual x-ray absorptiometry, and serum total testosterone was measured by tandem mass spectrometry. Bioavailable testosterone was calculated. Coefficients (b) represent the placebo-controlled mean effect of intervention. LBM (b = 1.9 kg, p = 0.003) increased while HDL-cholesterol (b = -0.12 mmol/l, p = 0.043) and TFM decreased (b = -1.2 kg, p = 0.038) in the testosterone group compared to placebo. Basal lipid oxidation (b = 5.65 mg/min/m(2), p = 0.045) increased and basal glucose oxidation (b = -9.71 mg/min/m(2), p = 0.046) decreased in response to testosterone therapy even when corrected for changes in LBM. No significant changes in insulin-stimulated Rd was observed (b = -0.01mg/min/m(2), p = 0.92). Testosterone therapy increased muscle mass and lipid oxidation in aging men with low normal bioavailable testosterone levels; however, our data did not support an effect of testosterone on whole-body insulin sensitivity using the euglycemic hyperinsulinemic clamp technique.

Sex hormone-binding globulin and type 2 diabetes mellitus

Sex hormone-binding globulin (SHBG) has emerged as one of the multiple genetic and environmental factors that potentially contribute to the pathophysiology of type 2 diabetes mellitus (T2DM). In addition to epidemiologic studies demonstrating a consistent relationship between decreased levels of serum SHBG and incident T2DM, recent genetic studies also reveal that transmission of specific polymorphisms in the SHBG gene influence the risk of T2DM. At the molecular level, the multiple interactions between SHBG and its receptors in various target tissues suggest physiologic roles for SHBG that are more complex than the simple transport of sex hormones in serum. Taken together, these data provide support for an expanded role of SHBG in the pathophysiology of insulin resistance and T2DM.

Sex hormones, insulin resistance, and diabetes mellitus among men with or at risk for HIV infection

OBJECTIVE

To examine the relationship of free testosterone (FT) and sex hormone-binding globulin (SHBG) with insulin resistance and diabetes mellitus (DM) in HIV disease.

DESIGN

Cross-sectional analysis from 322 HIV-uninfected and 534 HIV-infected men in the Multicenter AIDS Cohort Study.

METHODS

: The main outcomes were DM and homeostasis model assessment-insulin resistance (HOMA-IR). DM was defined as fasting serum glucose ≥126 or self-reported DM and use of DM medications. HOMA-IR was calculated from fasting serum glucose and fasting insulin.

RESULTS

Compared with HIV-uninfected men in our sample, HIV-infected men were younger, with lower body mass index, and more often black. HIV-infected men had lower FT (P < 0.001) and higher SHBG (P < 0.0001). The adjusted odds ratio for DM was 1.98 (95% confidence interval: 1.04 to 3.78); mean adjusted log HOMA-IR was 0.21 units higher in HIV-infected men (P < 0.0001). Log SHBG, but not log FT, was associated with DM (odds ratio = 0.44, 95% confidence interval: 0.25 to 0.80) in both groups. Log FT and log SHBG were inversely related to insulin resistance (P < 0.05 for both) independent of HIV.

CONCLUSIONS

Compared with HIV-uninfected men, HIV-infected men had lower FT, higher SHBG, and more insulin resistance and DM. Lower FT and lower SHBG were associated with insulin resistance regardless of HIV serostatus. This suggests that sex hormones play a role in the pathogenesis of glucose abnormalities among HIV-infected men.

The role of the urologist in the prevention and early detection of cardiovascular disease

In this review we identify whether problems encountered in urology, such as erectile dysfunction, have a bearing on general health, in particular cardiovascular health. Testosterone, traditionally regarded as the hormone subserving male reproductive and sexual functioning, appears to have a much wider role. Recent findings show that testosterone is involved in the metabolic control of glucose and lipids, of strength of bone and muscle, and psychological aspects such as mood and energy. Serum testosterone levels decline with ageing, free testosterone levels more so than total testosterone. At least 10 publications have shown that low testosterone levels are associated with an increased risk of death. The metabolic syndrome is a clustering of risk factors predisposing to diabetes mellitus type 2, atherosclerosis, and cardiovascular morbidity and mortality. There is a direct correlation between plasma testosterone and insulin sensitivity, and low testosterone levels are associated with an increased risk of type 2 diabetes mellitus, dramatically illustrated by androgen deprivation in men with prostate carcinoma. Lower total testosterone and sex hormone-binding globulin levels predict a higher incidence of the metabolic syndrome. Administration of testosterone to hypogonadal men reverses part of the unfavourable risk profile for the development of diabetes and atherosclerosis, thus also improving risk factors for erectile dysfunction. We conclude that urologists diagnosing and treating erectile problems are in a unique position to include general aspects of men's health in their work, and thus contribute to general health and to cardiovascular health in particular.

Does low testosterone affect adaptive properties of adipose tissue in obese men?

Obesity and (pre)diabetes in males is associated with low serum testosterone and increased oestradiol levels. It is unknown whether these changes in sex steroids are part of a vicious circle resulting in an increase of risk for metabolic complications of obesity, or whether it presents merely an epiphenomenon. The risk for metabolic complications in obesity seems to be determined by adaptation and integrity of adipose tissue. It is unknown whether the typical changes in sex steroids seen in obese men are desirable or ominous with respect to these functions. However, it might be clinically relevant, as low serum testosterone can be treated, and well with different forms of interventional therapy. The present review provides a short summary on findings, obstacles and future research needed to gain better insight into consequences of changes in sex steroids for adaptation of adipose tissue in obese men.

Modulation of insulin sensitivity and caveolin-1 expression by orchidectomy in a nonobese type 2 diabetes animal model

Previously, we found that male JYD mice developed type 2 diabetes but female mice did not, and that decreased expression levels of caveolin-1 were correlated with the development of a diabetic phenotype in these mice. Therefore, we hypothesized that sex hormones affect the expression of caveolin-1 and contribute to the development of insulin resistance and hyperglycemia in JYD mice. We used glucose and insulin tolerance tests to examine insulin sensitivity in male, female and orchidectomized male JYD mice. Glucose uptake was analyzed by using (18)F-fluorodeoxyglucose positron emission tomography. We also examined insulin-signaling molecules and caveolin proteins in various tissues in these mice by Western blotting. In addition, we examined changes of caveolin-1 expression in L6 skeletal muscle cells treated with 17-β estradiol or dihydroxytestosterone. We found that glucose and insulin tolerance were impaired and hyperglycemia developed in male, but not female, JYD mice. Expression of insulin-signaling molecules such as insulin receptor, protein kinase B, and glucose transporter-4 were decreased in male JYD mice compared with female mice. Orchidectomized JYD male mice showed improved glucose and insulin tolerance with a concomitant increase in the expression of insulin-signaling molecules and caveolin-1 in adipose tissue and skeletal muscle. Moreover, 17-β-estradiol treatment increased the expression of caveolin-1 in differentiated skeletal muscle cells. We conclude that sex hormones modulate the expression of caveolin-1 and insulin-signaling molecules, subsequently affecting insulin sensitivity and the development of type 2 diabetes in JYD mice.

Androgens and cardiovascular disease

PURPOSE OF REVIEW

There is increasing interest in age-related changes in sex hormone levels as a potentially treatable cause of ill-health in men. Relationships between androgens and cardiovascular disease will be discussed, with particular attention to more recently published research.

RECENT FINDINGS

In middle-aged and older men, lower testosterone levels are associated with insulin resistance, metabolic syndrome and diabetes, interrelated conditions that predispose to cardiovascular disease. The relationship between androgens and preclinical atherosclerosis requires confirmation. Nevertheless, lower testosterone levels predict cardiovascular events, such as stroke and transient ischaemic attack, in older men and are associated with higher cardiovascular and overall mortality. Testosterone is aromatized to oestradiol, and both higher and lower oestradiol levels have been associated with cardiovascular risk. Randomized trials have shown that testosterone supplementation in men with existing coronary artery disease can be protective against myocardial ischaemia. However, additional interventional studies are needed with endpoints of cardiovascular events.

SUMMARY

Observational studies continue to relate reduced circulating testosterone to cardiovascular risk, atherosclerosis and mortality in men. The role of oestradiol as a marker for cardiovascular disease requires clarification. Larger randomized trials are needed to establish whether hormonal therapy would reduce the burden of cardiovascular disease in ageing men.