SHBG and total testosterone levels in men with adult onset hypogonadism: what are we overlooking?

Hypogonadism and nonalcoholic fatty liver disease

Nonalcoholic fatty liver disease (NAFLD), recently proposed to be renamed to metabolic dysfunction-associated steatotic liver disease (MASLD), is a major global public health concern, affecting approximately 25-30% of the adult population and possibly leading to cirrhosis, hepatocellular carcinoma, and liver transplantation. The liver is involved in the actions of sex steroids via their hepatic metabolism and production of the sex hormone-binding globulin (SHBG). Liver disease, including NAFLD, is associated with reproductive dysfunction in men and women, and the prevalence of NAFLD in patients with hypogonadism is considerable. A wide spectrum of possible pathophysiological mechanisms linking NAFLD and male/female hypogonadism has been investigated. As therapies targeting NAFLD may impact hypogonadism in men and women, and vice versa, treatments of the latter may affect NAFLD, and an insight into their pathophysiological pathways is imperative. This paper aims to elucidate the complex association between NAFLD and hypogonadism in men and women and discuss the therapeutic options and their impact on both conditions.

Examining the associations between testosterone and biomarkers as men age

OBJECTIVES

Testosterone concentrations in men decline with advancing age. However, the cause of the decline is yet to be fully elucidated. Therefore, the aims of this study were to examine the associations between chronic diseases such as obesity and type 2 diabetes mellitus (T2DM) with total testosterone (TT) and sex hormone-binding globulin (SHBG), using a large nationally-representative data set (National Health and Nutrition Examination Survey; NHANES).

METHODS

NHANES is a cross-sectional survey, physical examination, and laboratory evaluation of a nationally-representative sample of a non-institutionalized United States population. Male participants aged ≥18 years during the NHANES 2013-2014 and NHANES 2015-2016 survey periods were selected for this analysis. The analysis included the following data: body mass index (BMI), oral glucose tolerance test (OGTT), homeostatic model assessment of insulin resistance (HOMA-IR), insulin, glucose, and age.

RESULTS

An overweight or obese condition was significantly inversely associated with TT and SHBG, even after adjusting for other variables. Several variables associated with T2DM (OGTT, HOMA-IR, insulin, and glucose) were also inversely associated with TT; however, only the associations between OGTT and insulin with TT remained significant after adjusting for the other variables. Insulin and HOMA-IR levels were significantly inversely associated with SHBG; however, only the association between SHBG and pre-diabetic HOMA-IR levels remained significant after adjusting for the other variables. OGTT became significantly associated with SHBG after adjusting for the other variables. Age was significantly inversely associated with TT, but positively associated with SHBG, even after adjusting for other variables.

CONCLUSION

The results of the present study, which is the largest to date, indicate that a marker of obesity, BMI, and some markers of T2DM are both independently and significantly inversely associated with TT and SHBG.

Gene-based burden scores identify rare variant associations for 28 blood biomarkers

BACKGROUND

A relevant part of the genetic architecture of complex traits is still unknown; despite the discovery of many disease-associated common variants. Polygenic risk score (PRS) models are based on the evaluation of the additive effects attributable to common variants and have been successfully implemented to assess the genetic susceptibility for many phenotypes. In contrast, burden tests are often used to identify an enrichment of rare deleterious variants in specific genes. Both kinds of genetic contributions are typically analyzed independently. Many studies suggest that complex phenotypes are influenced by both low effect common variants and high effect rare deleterious variants. The aim of this paper is to integrate the effect of both common and rare functional variants for a more comprehensive genetic risk modeling.

METHODS

We developed a framework combining gene-based scores based on the enrichment of rare functionally relevant variants with genome-wide PRS based on common variants for association analysis and prediction models. We applied our framework on UK Biobank dataset with genotyping and exome data and considered 28 blood biomarkers levels as target phenotypes. For each biomarker, an association analysis was performed on full cohort using gene-based scores (GBS). The cohort was then split into 3 subsets for PRS construction and feature selection, predictive model training, and independent evaluation, respectively. Prediction models were generated including either PRS, GBS or both (combined).

RESULTS

Association analyses of the cohort were able to detect significant genes that were previously known to be associated with different biomarkers. Interestingly, the analyses also revealed heterogeneous effect sizes and directionality highlighting the complexity of the blood biomarkers regulation. However, the combined models for many biomarkers show little or no improvement in prediction accuracy compared to the PRS models.

CONCLUSION

This study shows that rare variants play an important role in the genetic architecture of complex multifactorial traits such as blood biomarkers. However, while rare deleterious variants play a strong role at an individual level, our results indicate that classical common variant based PRS might be more informative to predict the genetic susceptibility at the population level.

Putative causal inference for the relationship between obesity and sex hormones in males: a bidirectional Mendelian randomization study

Background

Obesity is a chronic disease with a high prevalence rate and is an established risk factor for human health. Body mass index (BMI) is a common and primary indicator used in assessing obesity. This work aims to investigate the putative causal relationship among BMI, sex hormone-binding globulin (SHBG), bioavailable testosterone (BioT), and estradiol levels.

Materials and Methods

We conducted a bidirectional Mendelian randomization study, using single-nucleotide polymorphisms (SNPs) strongly associated with BMI, SHBG, BioT, and estradiol as instrumental variables. All SNPs were identified from the genome-wide association study (GWAS) summary data of large sample studies recruiting more than 150,000 European adult male individuals. The inverse-variance-weighted (IVW) approach was used as a primary algorithm for putative causal estimation.

Results

Genetically predicted elevated BMI was associated with decreased SHBG (IVW, β = -0.103, 95% confidence interval [CI] [-0.113 to -0.092], P = 1.50 × 10^-77) and BioT levels (IVW, β = -0.139, 95% CI [-0.165 to -0.113], P = 9.54 × 10^-26) and high estradiol levels (IVW, β = 0.014, 95% CI [0.009-0.019], P = 2.19 × 10^-7). Increased SHBG levels were causally associated with low BMI (IVW, β = -0.051, 95% CI [-0.098 to -0.005], P = 0.030) and BioT (IVW, β = -0.126, 95% CI [-0.175 to -0.077], P = 5.97 × 10^-7) and high estradiol levels (IVW, β = 0.046, 95% CI [0.035-0.056], P = 6.51 × 10^-17). Conversely, no evidence of an effect of estradiol imbalance on SHBG levels (IVW, β = 1.035, 95% CI [-0.854 to 2.926], P = 0.283) and BMI (IVW, β = 0.091, 95% CI [-0.094 to 0.276], P = 0.336) was obtained. However, increased BioT levels were causally associated with lower SHBG levels (IVW, β = -0.044, 95% CI [-0.061 to -0.026], P = 8.76 × 10^-7), not BMI (IVW, β = -0.006, 95% CI [-0.035 to 0.023], P = 0.679).

Conclusions

The findings support a network putative causal relationship among BMI, SHBG, BioT, and estradiol. SHBG, BioT, and estradiol may partly mediate the effect of obesity on male health. Reasonably modulating BioT and estradiol, especially SHBG, facilitated the attenuation of the harmful effects of obesity on male health.

Stress Induced Cortisol Release Depresses The Secretion of Testosterone in Patients With Type 2 Diabetes Mellitus

Background

Both hormonal and genetic data reveal that the stress hormone cortisol and its regulating genes may affect the level of testosterone in humans. It is uncertain whether type 2 diabetes mellitus would manifest similarly. Furthermore, a genetic strategy to screen out the stress system genes that may contribute to testosterone decline in humans is less understood.

Objectives

In this study, we aimed to elucidate the link between stress and testosterone levels, both hormonally and genetically.

Method

This study comprised 37 individuals with type 2 diabetes mellitus and 50 healthy individuals. For the analysis of hormones and the targeted genes, we used the RIA system and bioinformatics expertise.

Results

The patients had significantly elevated cortisol and lower testosterone readings, according to data from hormonal analyses. The bioinformatics approach reveals that SHBG was intracellularly suppressed by 2 defined stress system genes: FKB5 and CYP17. TCF4/TCF8, ATRX, and AR in skeletal muscle were inversely related to stress system genes. Furthermore, all testosterone regulated genes were positively linked with SHBG in the current study. A strong relationship between GNAS and PKA with CYP17 and FKBP5 reveals that the Gαs-cAMP/PKA signaling pathway may be one of the regulatory pathways through which the suppression of testosterone system genes happens. In conclusion, this study demonstrated that beyond stress, the key stress system genes might affect cortisol levels, which in turn affect testosterone figures via the Gαs-cAMP/PKA signaling pathway.

Nonpharmacological Interventions for the Management of Testosterone and Sperm Parameters: A Scoping Review

PURPOSE

Testosterone replacement and associated pharmacologic agents are effective strategies to treat male hypogonadism; however, nutraceutical agents and lifestyle modification approaches have gained medical interest. The purpose of this scoping review is to highlight the evidence (or lack thereof) of nutraceuticals and lifestyle modification approaches in the management of testosterone levels and sperm parameters.

METHODS

A scoping review of nonpharmacologic interventions (supplements, herbal medicines, diets, sleep, and exercise) with the potential to improve male health was undertaken to elucidate changes in testosterone levels and sperm parameters in men with hypogonadism or infertility compared with healthy patients.

FINDINGS

A multitude of nutraceuticals and functional nutrients are purported to stimulate testosterone production; however, only a select few have had promising results, such as zinc, vitamin D (in case of hypovitaminosis D), l-arginine, mucuna, and ashwagandha, based on well-controlled randomized clinical trials of men with low testosterone levels and related problems. Except for l-arginine, these natural agents, as well as tribulus and ω3 fatty acids, can improve some degree of sperm parameters in infertile men. Before implementing these nutraceutical agents, adequate sleep, exercise, and weight loss in patients with obesity are imperative. The effects of nonpharmacologic interventions on testosterone levels are modest and hence do not directly translate into clinical benefits. Correspondingly, androgen receptor content, but not endogenous androgens, has been regarded as the principal factor in muscle hypertrophy.

IMPLICATIONS

A limited number of supplements and herbal medicines can be considered as adjunctive approaches in the management of testosterone levels and sperm parameters, primarily in men with low testosterone levels and infertility, whereas most nonpharmacologic supplements appear to lack evidence. Although proper physical exercise, sleep, and diet are indisputable approaches because of the general benefits to health, the use of nutraceuticals, if considered, must be personalized by physicians and/or registered dietitians.

Associations of body shape phenotypes with sex steroids and their binding proteins in the UK Biobank cohort

Associations of sex steroids and their binding proteins with body shape are unclear, because waist and hip circumference are correlated strongly with body size. We defined body shape using “a body shape index” (ABSI) and hip index (HI), which are independent of weight and height by design, and examined associations in multivariable generalised linear models for the UK Biobank cohort (179,902 men, 207,444 women). Total testosterone was associated inversely with ABSI, especially in men. Free testosterone was lowest for large-ABSI-large-HI (“wide”) and highest for small-ABSI-small-HI (“slim”) in men, but lowest for small-ABSI-large-HI (“pear”) and highest for large-ABSI-small-HI (“apple”) in women. Oestradiol was associated inversely with ABSI in obese pre-menopausal women but positively with HI in obese men and post-menopausal women not using hormone replacement therapy. Sex-hormone binding globulin (SHBG) was associated inversely with ABSI but positively with HI and was lowest for “apple” and highest for “pear” phenotype in both sexes. Albumin was associated inversely with HI in women, but matched the pattern of free testosterone in obese men (lowest for “wide”, highest for “slim” phenotype). In conclusion, sex steroids and their binding proteins are associated with body shape, including hip as well as waist size, independent of body size.

Effect of Intermittent Fasting on Reproductive Hormone Levels in Females and Males: A Review of Human Trials

Intermittent fasting is a popular diet for weight loss, but concerns have been raised regarding the effects of fasting on the reproductive health of women and men. Accordingly, we conducted this literature review to clarify the effects of fasting on reproductive hormone levels in humans. Our results suggest that intermittent fasting decreases androgen markers (i.e., testosterone and the free androgen index (FAI)) while increasing sex hormone-binding globulin (SHBG) levels in premenopausal females with obesity. This effect was more likely to occur when food consumption was confined to earlier in the day (eating all food before 4 pm). In contrast, fasting did not have any effect on estrogen, gonadotropins, or prolactin levels in women. As for men, intermittent fasting reduced testosterone levels in lean, physically active, young males, but it did not affect SHBG concentrations. Interestingly, muscle mass and muscular strength were not negatively affected by these reductions in testosterone. In interpreting these findings, it is important to note that very few studies have been conducted on this topic. Thus, it is difficult to draw solid conclusions at present. From the limited data presented here, it is possible that intermittent fasting may decrease androgen markers in both genders. If this is the case, these results would have varied health implications. On the one hand, fasting may prove to be a valuable tool for treating hyperandrogenism in females with polycystic ovarian syndrome (PCOS) by improving menstruation and fertility. On the other hand, fasting may be shown to decrease androgens among males, which could negatively affect metabolic health and libido. More research is warranted to confirm these preliminary findings.

Distinctive features of the hypothalamic-pituitary-gonadal axis and the level of dopamine in men of the European and Asian North

In recent years, there has been a decrease in reproductive potential, especially among residents of the Arctic territories, having the greatest stress from various body systems, including the state of the hormonal regulation of the male reproductive system. The study of the dopamine levels and the content of sex hormones in the male population of various Arctic regions is relevant due to the increased stress on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis in residents of the Northern regions, as well as the lack of information about their interaction among the apparently healthy population. The aim of the investigation is to study the possible effect of various plasma concentrations of the dopamine on the content of sex hormones and sex-steroid-binding β-globulin (SHBG) in apparently healthy men in the Arctic zone of the Russian Federation, taking into account the territory of residence. There were examined 181 men aged 22-60 years, living in the territories of the European and Asian North. The levels of sex hormones, SHBG, and dopamine were determined by the enzyme-linked immunosorbent assay. The inhabitants of the Asian North in comparison with the men of the European North have higher levels of dopamine, luteinizing hormone, progesterone, prolactin, estradiol and SHBG with decreased serum levels of free fractions of testosterone. Reference levels of dopamine in men from the European North are combined with the stimulatory effect of dopamine on LH levels, which may indicate an increase steroidogenesis. The high levels of dopamine in men from the Asian North are combined with increased level of estradiol, which may be related to the effect of dopamine on testosterone aromatization. The separate region with its ecological differences is characterized by the presence of features of compensatory-adaptive reactions of an organism in male representatives on the part of the dopaminergic system and the hypothalamic-pituitary-gonadal axis. The identified features can help in carrying out preventive measures aimed at preserving the male reproductive potential of the inhabitants of the Arctic territories.

Relationship between total testosterone, sex hormone-binding globulin levels and the severity of non-alcoholic fatty liver disease in males: a meta-analysis

BACKGROUND

In recent years, many studies have reported the relationship between non-alcoholic fatty liver disease (NAFLD) and sex hormones, especially total testosterone (TT) and sex hormone-binding globulin (SHBG). However, the relationship between sex hormones and the severity of NAFLD is still unclear.

METHODS

PubMed, Embase, Cochrane Library, Web of Science, WanFang, China National Knowledge Infrastructure and VIP databases were searched for relevant studies from inception to 31 August 2021. Values of weighted mean differences (WMDs) and odds ratios (ORs) with their 95% confidence intervals (CIs) were combined by Stata 12.0 software to evaluate the relationship between TT, SHBG and the severity of NAFLD in males.

RESULTS

A total of 2995 patients with NAFLD from 10 published cross-sectional studies were included for further analysis. The meta-analysis indicated that the moderate-severe group had a lower TT than the mild group in males with NAFLD (WMD: -0.35 ng/ml, 95% CI = -0.50 to -0.20). TT and SHBG were important risk factors of moderate-severe NAFLD in males (OR_TT = 0.79, 95% CI = 0.73 to 0.86; OR_SHBG = 0.22, 95% CI = 0.12 to 0.39; p < 0.001). Moreover, when the analysis was limited to men older than age 50, SHBG levels were lower in those with moderate-severe disease (WMD: -11.32 nmol/l, 95% CI = -14.23 to -8.40); while for men with body mass index (BMI) >27 kg/m², moderate-severe NAFLD had higher SHBG levels than those with mild disease (WMD: 1.20 nmol/l, 95% CI = -2.01 to 4.42).

CONCLUSION

The present meta-analysis shows that lower TT is associated with the severity of NAFLD in males, while the relationship between SHBG and severity of NAFLD is still to be further verified.

Androgen dysfunction in non-alcoholic fatty liver disease: Role of sex hormone binding globulin

Non-alcoholic fatty liver disease (NAFLD) is the most common form of chronic liver disease in the world. It is linked mainly to insulin resistance and metabolic syndrome including obesity and dyslipidemia. In addition, various endocrine dysfunctions including polycystic ovary syndrome (PCOS) and hypogonadism are involved in the development and progression of NAFLD. We need to know the disease pathophysiology more accurately due to the heterogeneity of clinical presentation of fatty liver disease. The liver is the major metabolic organ with sexual dimorphism. Sexual dimorphism is associated not only with behavioral differences between men and women, but also with physiological differences reflected in liver metabolism. In men, normal androgen levels prevent hepatic fat accumulation, whereas androgen deficiency induce hepatic steatosis. In women, higher androgens can increase the risk of NAFLD in PCOS. Sex hormone binding globulin (SHBG) is involved in androgen regulation. Recently, SHBG may be reported as a surrogate marker for NAFLD. Therefore, this review will focus on the mechanism of androgen dysfunction in the regulation of hepatic metabolism, the risk of developing NAFLD, and the potential role of SHBG in the course of NAFLD.; Keywords: Non-alcoholic fatty liver disease, insulin resistance, sexual dimorphism, androgen, sex hormone binding globulin.

Examining the effects of calorie restriction on testosterone concentrations in men: a systematic review and meta-analysis

CONTEXT

Testosterone concentrations decline with age, and lower testosterone concentrations are associated with several morbidities, including sexual dysfunction, obesity, type 2 diabetes mellitus (T2DM), and metabolic syndrome.

OBJECTIVE

Because dietary habits play a critical role in weight regulation and T2DM management, the aim of this systematic review and meta-analysis was to summarize and critically evaluate the evidence from randomized controlled trials to determine the effects of calorie restriction (CR) on testosterone concentrations in men.

DATA SOURCES

A literature search was conducted across 4 databases, from their inception until March 2020.

DATA EXTRACTION

The screening and data extraction were completed by 2 authors independently, and in a blinded manner, according to a priori inclusion and exclusion criteria.

DATA ANALYSIS

Of the 4198 studies identified from the initial search, 7 randomized controlled trials were included for data extraction. Significant increases in total testosterone concentrations were reported in 3 of 4 studies in which CR was examined with overweight or obese men, compared with the control groups. Significant decreases in total testosterone concentrations were reported in 2 of 3 studies in which the effects of CR were examined with normal-weight, healthy men, compared with the control groups. In all 4 studies that examined the effect of CR on sex hormone-binding globulin concentrations, the intervention significantly increased sex hormone-binding globulin concentrations compared with that of the control groups irrespective of body composition.

CONCLUSION

This systematic review and meta-analysis provide some evidence that CR affects testosterone concentrations in men and this effect depends on their body mass index. PROSPERO registration no. CRD42020173102.