Estradiol increases the production of sex hormone-binding globulin but not insulin-like growth factor binding protein-1 in cultured human hepatoma cells

The effects of alcohol on testosterone synthesis in men: a review

INTRODUCTION

Testosterone concentrations in men decline with advancing age, with low testosterone concentrations being associated with multiple morbidities, an increased risk of early mortality, and a reduced quality of life. The purpose of this study was to examine the effects of alcohol on testosterone synthesis in men by investigating its effects on each level of the hypothalamic-pituitary-gonadal axis.

AREAS COVERED

Acute consumption of a low-to-moderate amount of alcohol increases testosterone concentrations in men, while consumption of a large volume of alcohol is associated with a reduction in serum testosterone concentrations. Elevated testosterone concentrations result from the increased activity of detoxification enzymes in the liver. Conversely, the primary mechanisms of action involved in the reduction of testosterone are increased hypothalamic-pituitary-adrenal axis activity, inflammation, and oxidative stress. When alcohol is consumed in excess, particularly chronically, it negatively affects testosterone production in men.

EXPERT OPINION

Since testosterone is an important component of men's health and wellbeing, current levels of alcohol consumption in many countries of the world require urgent attention. Elucidating the relationship between alcohol consumption and testosterone may be useful in identifying strategies to attenuate the testosterone-reducing effects of excessive or chronic alcohol consumption.

Sex steroids and sex steroid-binding globulin levels amongst middle-aged and elderly men and women from general population

BACKGROUND AND AIMS

Availability of age- and sex-specific reference values for sex steroids and sex steroid-binding globulin (SHBG) levels allows for appropriate interpretation of research findings and their clinical applications. We report the sex-specific distribution and reference levels of sex steroids, including total estradiol, total testosterone and (calculated) free androgen index (cFAI), SHBG and other androgens dehydroepiandrosterone (DHEA), dehydroepiandrosterone sulphate (DHEAS) and androstenedione across age.

METHODS

Using data from 3291 participants from the prospective population-based Rotterdam Study (2006-2008), we visualised the distribution of sex steroids and SHBG levels by calculating and depicting the 5th, 25th, 50th, 75th and 95th percentiles per year and per age-year across 5-year age bands to provide reference value ranges in men and women. Total estradiol and SHBG were measured using automated immunoassay and androgens using liquid chromatography-mass spectrometry (LC-MS/MS).

RESULT

Mean age was 56.8 (range 45.6-79.9) years in men and 56.9 (range 45.7-79.9) years in women. Amongst men, total estradiol and SHBG showed an increasing trend from 45 years onwards. In women, total estradiol and SHBG showed a decreasing trend from 45 years until the age of 60. From 60 years onwards, SHBG showed an increasing trend. For total testosterone, a clear declining trend was observed amongst men but not women. Other androgens showed a similar decreasing trend in both sexes from 45 years onwards.

DISCUSSION AND CONCLUSION

Our study underlines sex-specific trends in sex steroids and SHBG levels with ageing. This warrants taking into account sex- and age-specific reference values for sex steroids and SHBG when investigating their impact on health outcomes to prevent controversial results and allow for their appropriate clinical application.

Aging, Cardiovascular Risk, and SHBG Levels in Men and Women From the General Population

AIMS

Prior studies have reported inconsistent results for the association between sex hormone-binding globulin (SHBG) and cardiovascular disease among men and women. Although it is suggested that SHBG levels change with aging, the exact trend of SHBG across age and cardiovascular risk and the underlying mechanisms of these changes remain to be elucidated.

METHODS

Using data of 3264 men and women from a large population-based cohort study, we first visualized the distribution of serum SHBG levels across age. Second, we computed a cardiovascular risk factor sum score and investigated the mean SHBG levels across categories of the risk factor sum score and stratified per age-category. Next, linear regression models were used to investigate the associations between serum SHBG levels and age and potential regulators of SHBG, including body mass index (BMI), fasting insulin, sex steroids, thyroxine, and triglycerides.

RESULTS

Among men, a linear increase in SHBG levels with age and among women a U-shaped pattern was observed. Participants with larger number of cardiovascular risk factors had lower SHBG levels. When stratified by age, older participants had higher SHBG levels. A multivariate model including total testosterone and triglyceride levels in men and total testosterone, triglycerides, BMI, and fasting insulin in women explained, respectively, 46.2% and 31.8% of the variance in SHBG levels.

CONCLUSION

We observed a clear sex-specific pattern for SHBG levels with age. Our findings highlight the importance of taking into account the age-related changes in SHBG levels to avoid controversial results in the assessment of the cardiovascular risk associated with SHBG.

Paediatric reference intervals for 17 Roche cobas 8000 e602 immunoassays in the CALIPER cohort of healthy children and adolescents

Background

The diagnostic utility of laboratory tests in paediatric medicine relies heavily on the availability of appropriate reference intervals (RIs). The Canadian Laboratory Initiative on Paediatric Reference Intervals (CALIPER) has established a comprehensive database of covariate-stratified RIs for many paediatric laboratory tests using a large, healthy reference population. Several automated analysers in widespread use in clinical laboratories have already been studied. Here, we extend the testing to Roche immunoassays and report, for the first time, comprehensive paediatric RIs for 17 endocrine and special chemistry markers.

Methods

A total of 741 healthy children and adolescents (1 day to <19 years) were recruited and serum samples were analysed for 17 immunoassays on the Roche cobas 8000 e602 Immunoassay Analyzer. Age and sex-specific RIs were established and corresponding 90% confidence intervals (CIs) were calculated in accordance with Clinical and Laboratory Standards Institute guidelines.

Results

Reference values for all analytes measured required age partitioning, particularly during early life and throughout adolescence. Of the 17 analytes measured, eight required sex partitioning, including ferritin, thyroid stimulating hormone (TSH), total triiodothyronine (TT3) and all fertility/sex hormones, except prolactin.

Conclusions

This is the first study to determine accurate paediatric RIs for Roche immunoassays. RIs were generally similar to those previously published by CALIPER on other analytical platforms, highlighting the reproducibility of age- and sex-specific trends in reference values observed across the paediatric age range. The RIs established in this study will improve the accuracy of test result interpretation and clinical decision-making in clinical laboratories utilising Roche immunoassays.

Sex hormone-binding globulin gene expression in the liver: drugs and the metabolic syndrome

Sex hormone-binding globulin (SHBG) is the main transport binding protein for sex steroid hormones in plasma and regulates their accessibility to target cells. Plasma SHBG is secreted by the liver under the control of hormones and nutritional factors. In the human hepatoma cell line (HepG2), thyroid and estrogenic hormones, and a variety of drugs including the antioestrogen tamoxifen, the phytoestrogen, genistein and mitotane (Op'DDD) increase SHBG production and SHBG gene promoter activity. In contrast, monosaccharides (glucose or fructose) effectively decrease SHBG expression by inducing lipogenesis, which reduces hepatic HNF-4alpha levels, a transcription factor that play a critical role in controlling the SHBG promoter. Interestingly, diminishing hepatic lipogenesis and free fatty acid liver biosynthesis also appear to be associated with the positive effects of thyroid hormones and PPARgamma antagonists on SHBG expression. This mechanism provides a biological explanation for why SHBG is a sensitive biomarker of insulin resistance and the metabolic syndrome, and why low plasma SHBG levels are a risk factor for developing hyperglycemia and type 2 diabetes, especially in women. These important advances in our knowledge of the regulation of SHBG expression in the liver open new approaches for identifying and preventing metabolic disorder-associated diseases early in life.

Testosterone and visceral fat in midlife women: the Study of Women's Health Across the Nation (SWAN) fat patterning study

Visceral fat (VF) increases with the menopause and is an independent predictor of the metabolic syndrome, diabetes, and cardiovascular disease (CVD) in women. Little is known about how hormonal changes during the menopausal transition are related to the increase in VF. We aimed to determine the relationship between bioavailable testosterone and VF in middle-aged women at various stages of the menopausal transition and whether this relationship is independent of age and other CVD risk factors. The Study of Women's Health Across the Nation (SWAN) is a longitudinal, community-based study. This report uses baseline data from a population-based longitudinal ancillary study at the Chicago site to examine the cross-sectional relationship between testosterone and computed tomography (CT)-assessed VF in women at different stages of the menopausal transition. Included are 359 women (47.2% black), aged 42-60 years, who were randomly selected from a complete community census in which a 72% participation rate was achieved. In multivariate models, bioavailable testosterone was associated with VF independent of age, race, percent total body fat, and other cardiovascular risk factors. Bioavailable testosterone was a stronger predictor than estradiol and was interchangeable in its strength of association with sex hormone-binding globulin (SHBG). As bioavailable testosterone was associated with VF even after adjusting for insulin resistance, this suggests that it plays an important role in regional fat distribution. Our findings may have direct implications in explaining the effect of menopause-related testosterone predominance on VF accumulation and subsequent cardiovascular risk.

Changes in sex hormone-binding globulin, insulin, and serum lipids in postmenopausal women on a low-fat, high-fiber diet combined with exercise

Dietary factors including fat and fiber have been reported to play a role in the development of breast cancer, possibly mediated by changes in estradiol. Diet and exercise have been shown to affect levels of sex hormone-binding globulin (SHBG), which in turn regulate the bioavailability of estradiol. Diet and exercise also affect insulin levels, which play a role in the synthesis of SHBG, and the hormone itself is a potent mitogen for many cancer cell lines. This study was designed to measure the effects of a low-fat, high-fiber diet, combined with regular aerobic exercise, on the levels of SHBG, insulin, and serum lipids in postmenopausal women with or without hormone replacement therapy (HRT). Two groups of postmenopausal women, 11 on HRT and 11 not on HRT, underwent a low-fat (1O% fat calories), high-fiber (65-70 g/day) diet-and-exercise intervention for three weeks. Serum SHBG, insulin, and lipids were measured before and after the regimen. After the intervention, SHBG levels were significantly increased for the women on HRT (44.5 +/- 3.4 vs. 62 +/- 6.4 nmol/l) and the women not on HRT (32.1 +/- 4.6 vs. 45.5 +/- 6.1 nmol/l, both changes p < 0.01). Also after the intervention, insulin levels were significantly reduced for the women on HRT (196 +/- 44.4 vs. 119.8 +/- 28.7 pmol/l) and the women not on HRT (144.2 +/- 17.9 vs. 115.5 +/- 20.8 pmol/l, both changes p < 0.01). Body mass index and total cholesterol were significantly reduced for both groups of women (all changes p < 0.01). Although the exact mechanism for the change in SHBG is not known, the increases in SHBG and reductions in insulin as a result of this lifestyle intervention should reduce the risk for breast cancer in postmenopausal women.

Factors regulating insulin-like growth factor binding protein-3 secretion from human hepatoma (HepG2) cells

Insulin-like growth factor (IGF) binding protein-3 (IGFBP-3) is a growth hormone (GH) dependent carrier of the IGFs in human serum. Apart from GH regulation the hormonal control of IGFBP-3 production is not well established and although the liver is considered to be the main source of circulating IGFBP-3, there are no in vitro studies of the effect of both insulin and IGFs on the IGFBP-3 produced in human hepatoma cells. The effect of sex hormones as well as cortisol has not been studied. To elucidate this we performed cell culture studies on HepG2 cells in the presence of various effectors. Insulin, IGF-I and IGF-II brought about a 1.5-2-fold enhancement of IGFBP-3 release at 7.5-30 nM concentrations. In contrast, cortisol decreased IGFBP-3 secretion by 30-40% whereas estradiol, tamoxifen and testosterone had no effect at physiological concentrations. We conclude that, in addition to GH, also insulin, IGF-I and IGF-II and glucocorticoids can modulate IGFBP-3 secretion by human hepatoma cells.

Sex hormone binding globulins and atherosclerotic risk in systemic lupus

Sex hormone binding globulin (SHBG) is a transport protein in human plasma which regulates the bioavailability of sex hormones, mediates membrane receptor signaling and may affect inflammatory processes, suggesting a regulatory role for this protein in the prevention of atherosclerosis. The current report summarizes literature implicating several members of the SHBG family in the regulation of hormonal and inflammatory processes which may be pertinent to the accelerated atherosclerosis seen in systemic lupus.