Longitudinal associations between sex hormone-binding globulin and insulin resistance

Blood lipid levels mediating the effects of sex hormone-binding globulin on coronary heart disease: Mendelian randomization and mediation analysis

Observational studies indicate that serum sex hormone-binding globulin (SHBG) levels are inversely correlated with blood lipid levels and coronary heart disease (CHD) risk. Given that dyslipidemia is an established risk factor for CHD, we aim to employ Mendelian randomization (MR) in conjunction with mediation analysis to confirm the mediating role of blood lipid levels in the association between SHBG and CHD. First, we assessed the causality between serum SHBG levels and five cardiovascular diseases using univariable MR. The results revealed causality between SHBG levels and reduced risk of CHD, myocardial infarction, as well as hypertension. Specifically, the most significant reduction was observed in CHD risk, with an odds ratio of 0.73 (95% CI 0.63-0.86) for each one-standard-deviation increase in SHBG. The summary-level data of serum SHBG levels and CHD are derived from a sex-specific genome-wide association study (GWAS) conducted by UK Biobank (sample size = 368,929) and a large-scale GWAS meta-analysis (60,801 cases and 123,504 controls), respectively. Subsequently, we further investigated the mediating role of blood lipid level in the association between SHBG and CHD. Mediation analysis clarified the mediation proportions for four mediators: high cholesterol (48%), very low-density lipoprotein cholesterol (25.1%), low-density lipoprotein cholesterol (18.5%), and triglycerides (44.3%). Summary-level data for each mediator were sourced from the UK Biobank and publicly available GWAS. The above results confirm negative causality between serum SHBG levels and the risk of CHD, myocardial infarction, and hypertension, with the causal effect on reducing CHD risk largely mediated by the improvement of blood lipid profiles.

Missed Diagnosis of Gestational Diabetes Mellitus Due to Selective Screening: Evidence from a Cross-Sectional Study in the West Nile Sub-Region, Uganda

Purpose

To ascertain the prevalence and risk factors of gestational diabetes mellitus (GDM) in pregnant women receiving antenatal care (ANC) services within the West Nile subregion of Uganda.

Patients and Methods

An analytical cross-sectional study was conducted on 233 pregnant women who are within 24-28 weeks of gestation and are receiving ANC services in selected hospitals. GDM was diagnosed according to the World Health Organization (WHO) criteria (2013). A questionnaire and anthropometric measurements were used to obtain relevant data. The chi-square test and logistic regression were used to determine the association between GDM and the study variables, including participants' sociodemographic and medical characteristics.

Results

The prevalence of hyperglycemia first detected in pregnancy among the participants tested was 8%. Overall, 7.45% had GDM and 0.53% had diabetes mellitus in pregnancy. The fasting plasma glucose test alone was positive in 86.7% of the GDM cases. The factors that were significantly associated with GDM included age ≥25 years (p = 0.017, AOR = 3.51) and body mass index (BMI) ≥25 kg/m2 (p = 0.024, AOR = 2.67). Out of the participants diagnosed with GDM, 28.6% did not have a known risk factor. Of the pregnant women with GDM, 57% would have been missed if the selective screening in the national clinical guidelines had been followed. Urinary tract infection (UTI) and Candida were detected in 36.36% and 13.85% of the participants, respectively.

Conclusion

The study provides new data on the prevalence of GDM in rural settings in the West Nile subregion of Uganda. Of the participants, 7.5% were diagnosed with GDM, of which 57% would have been missed based on the selective screening of the national clinical guidelines. The study findings support the universal screening of GDM in pregnant women.

Circulating sex hormone-binding globulin levels and ischemic stroke risk: a Mendelian randomization study

PURPOSE

Previous studies have presented conflicting findings regarding the protective effects of circulating sex hormone-binding globulin (SHBG) on ischemic stroke (IS). This study aimed to assess the causal effect of SHBG on IS using Mendelian randomization (MR) analysis and to identify potential mediators.

METHODS

First, the causal effect of SHBG on any IS (AIS), cardioembolic stroke (CES), large artery stroke (LAS), and small vessel stroke (SVS) was assessed by inverse variance weighed (IVW) method. Two additional MR methods (weighted median and MR-Egger) were used to supplement the IVW results. Subsequently, a two-step MR was further performed to assess whether three glycemic profiles [fasting glucose, fasting insulin, and glycated hemoglobin (HbA1c)] and five lipid profiles (high-density lipoprotein cholesterol, low-density lipoprotein cholesterol, non-HDL cholesterol, total cholesterol, and triglycerides) mediated the causal effect. Furthermore, Cochrane's Q test, MR-Egger intercept test, MR-PRESSO global test, and leave-one-out analysis were performed for sensitivity analyses.

RESULTS

The IVW results showed that SHBG significantly reduced SVS risk (odds ratio= 0.60, 95% confidence interval: 0.47-0.77, P = 4.60E-05). The weighted median and MR-Egger results were parallel to IVW. However, no significant associations were found between SHBG and AIS, CES, and LAS. Mediation analysis indicated that HbA1c may be involved in SHBG reducing SVS risk. Sensitivity tests demonstrated the reliability of causal estimates.

CONCLUSIONS

Circulating SHBG levels may decrease SVS risk by lowering HbA1c levels. Therefore, individuals with low circulating SHBG levels should focus on glycemic control to reduce future SVS risk.

Sex hormone-binding globulin levels and development of hypertension in middle-aged men and women

OBJECTIVE

To investigate the association between sex hormone-binding globulin (SHBG) levels, change in blood pressure and development of hypertension.

METHODS

In a community-based study, we examined 2816 middle-aged participants with focus on cardiometabolic risk factors in 2002-2005. A representative sample of 1954 men and women was invited to follow-up in 2012-2014 and 1327 were included in a second study visit. Mean follow-up time was 9.7 years. Blood pressure was measured according to the guidelines from the seventh Joint National Committee of Hypertension, and new cases of hypertension were recorded. SHBG was measured at baseline. The association between SHBG, blood pressure and new cases of hypertension was investigated using linear regression analyses and logistic regression analyses after excluding individuals treated with blood pressure-lowering drugs.

RESULTS

Mean SBP and DBP at follow-up was 123 and 72 mmHg, respectively, and mean increase from baseline was 5.8 and 2.9 mmHg. During the follow-up time, 167 new cases of hypertension (16.1%) were identified. One standard deviation (SD) increase in SHBG at baseline was inversely associated with the risk to develop hypertension at follow-up (OR = 0.74, 95% CI 0.58-0.95) in the fully adjusted model. Moreover, one SD increase in SHBG was associated with a decrease in mean SBP (delta = -1.5 mmHg, 95% CI - 2.2 to -0.8) and DBP (delta = - 1.0 mmHg, 95% CI - 1.5 to -0.4), after adjusting for covariates.

CONCLUSION

SHBG levels are inversely associated with development of hypertension and change in blood pressure levels independent of major risk factors.

Sex Hormone Binding Globulin is an Independent Predictor for Insulin Resistance in Male Patients with Newly Diagnosed Type 2 Diabetes Mellitus

INTRODUCTION

This study explored the correlation between sex hormones, sex hormone binding globulin (SHBG), and insulin resistance in male patients with newly diagnosed type 2 diabetes mellitus (T2DM).

METHODS

A total of 48 male patients with newly diagnosed T2DM were enrolled in this study between March 2022 and December 2022. Clinical characteristics, sex hormones, and SHBG levels were collected. All enrolled subjects received intensive hypoglycemic treatment with insulin pump for 1 week to achieve glycemic control, then the steady-state glucose infusion rate (GIR), an indicator of insulin sensitivity, was determined by the hyperinsulinemic-euglycemic clamp. Correlation analysis and multivariate logistic regression analysis were performed to explore the association of clinical characteristics, sex hormones, and SHBG with insulin sensitivity. The optimal cutoff value to predict insulin resistance was calculated using receiver operating characteristic (ROC) curve.

RESULTS

According to the GIR cut-point value of 5.700 mg/(kg min), there were 40 patients with insulin resistance (IR group) and 8 patients without (non-IR group). The IR group exhibited lower testosterone and SHBG levels than the non-IR group (all p < 0.050). Correlation analysis showed that insulin sensitivity was positively associated with testosterone and SHBG, while negatively associated with body mass index, fasting blood glucose, alanine aminotransferase, aspartate aminotransferase, total cholesterol, triglyceride, and apolipoprotein B (all p < 0.050). Multivariate logistic regression analysis demonstrated that SHBG is an independent predictor for insulin resistance (p = 0.029). Further ROC curve analysis revealed that the optimal cutoff value of SHBG to predict insulin resistance is 17.200 nmol/L, with the corresponding area under the curve (AUC) and its 95% confidence interval (CI) being 0.813 and 0.691-0.934.

CONCLUSIONS

SHBG is an independent predictor for insulin resistance in male patients with newly diagnosed T2DM.

TRIAL REGISTRATION NUMBER

KY20220314-01.

Sex Hormones and Diabetes in 45- to 74-year-old Men and Postmenopausal Women: The Hispanic Community Health Study

Previous studies demonstrated associations of endogenous sex hormones with diabetes. Less is known about their dynamic relationship with diabetes progression through different stages of the disease, independence of associations, and role of the hypothalamic-pituitary gonadal axis. The purpose of this analysis was to examine relationships of endogenous sex hormones with incident diabetes, prediabetes, and diabetes traits in 693 postmenopausal women and 1015 men aged 45 to 74 years without diabetes at baseline participating in the Hispanic Community Health Study/Study of Latinos and followed for 6 years. Baseline hormones included estradiol, luteinizing hormone (LH), follicle stimulating hormone (FSH), sex hormone-binding globulin (SHBG), dehydroepiandrosterone sulfate (DHEAS), and, in men, testosterone and bioavailable testosterone. Associations were analyzed using multivariable Poisson and linear regressions. In men, testosterone was inversely associated with conversion from prediabetes to diabetes (incidence rate ratio [IRR] for 1 SD increase in testosterone: 0.821; 95% CI, 0.676, 0.997; P = 0.046), but not conversion from normoglycemia to prediabetes. Estradiol was positively associated with increase in fasting insulin and homeostatic model assessment of insulin resistance. In women, SHBG was inversely associated with change in glycosylated hemoglobin, postload glucose, and conversion from prediabetes to diabetes (IRR = 0.62; 95% CI, 0.44, 0.86, P = 0.005) but not from normoglycemia to prediabetes. Relationships with other hormones varied across glycemic measures. Stronger associations of testosterone and SHBG with transition from prediabetes to diabetes than from normoglycemic to prediabetes suggest they are operative at later stages of diabetes development. Biologic pathways by which sex hormones affect glucose homeostasis await future studies.

The cut-off value for HOMA-IR discriminating the insulin resistance based on the SHBG level in women with polycystic ovary syndrome

Introduction

The study aimed to estimate the cut-off value for homeostatic model assessment for insulin resistance (HOMA-IR) discriminating the insulin resistance based on the sex hormones binding globulin (SHBG) level in women with polycystic ovary syndrome (PCOS).

Materials and methods

Data from medical records of 854 Caucasian women diagnosed with PCOS were analyzed. Anthropometric data, fasting plasma glucose, insulin and SHBG levels were measured. HOMA-IR was calculated with a standard formula. The cut-off value was calculated using receiver-operating characteristics.

Results

Circulating SHBG levels below the normal range (26.1 nmol/L) were found in 25.4% of study participants. This subgroup had a significantly higher BMI, fasting glucose and insulin concentrations and HOMA-IR values. Empirical optimal cut-off values for HOMA-IR corresponding to low SHBG levels was ≥2.1 [area under the curve (AUC) 0.73, accuracy 0.65, sensitivity 72.3%, specificity 63.1%, positive predictive value (PPV) 40.0%, negative predictive value (NPV) 87.0%].

Conclusions

Our study suggests that the cut-off point for HOMA-IR discriminating the insulin resistance based on the SHBG level, in young Caucasian women with polycystic ovary syndrome is 2.1, and is consistent with the cut-off value adopted by the European Group for the Study of Insulin Resistance (above 2.0).

Association Between Sex Hormone-Binding Globulin, Atherogenic Indices of Plasma Among Young Sedentary Males

Background

Males are more likely than females to suffer from cardiovascular disease (CVD). So, sex hormones may modify these variations and affect the lipid profile. We examined the relationship between sex hormone-binding globulin (SHBG) and CVD risk factors among young males in this study.

Methods

Using a cross-sectional design, we measured total testosterone, SHBG, lipids, glucose, insulin, antioxidant parameters, and anthropometric factors in 48 young males in the age range of 18 to 40 years. Atherogenic indices of plasma were calculated. In this study, a partial correlation analysis was carried out to assess the relationship between SHBG and other variables after adjustment for confounders.

Results

According to the results of multivariable analyses adjusted for age and energy, SHBG had a negative correlation with total cholesterol (r = -.454, P =.010), low-density lipoprotein cholesterol (r = -.496, P =.005), quantitative insulin-sensitivity check index, and positive correlation with high-density lipoprotein cholesterol (r = .463, P =.009). No significant correlation was observed between SHBG and triglycerides (P >.05). Several atherogenic indices of plasma have a negative correlation with SHBG levels. These include Atherogenic Index of Plasma (r = -.474, P = .006), Castelli Risk Index (CRI)1 (r = -.581, P < .001), CRI2 (r = -.564, P = .001), and Atherogenic Coefficient (r = -.581, P < .001).

Conclusion

Among young men, high plasma SHBG was associated with reduced CVD risk factors, modified lipid profile and atherogenic ratios, and better glycemic markers. Therefore, reduced SHBG concentrations could be a prognostic marker of CVD among young sedentary males.

High C-reactive protein is associated with increased risk of biochemical hypogonadism: a population-based cohort study

CONTEXT

Obesity seems to decrease levels of testosterone. It is still unknown what role inflammation plays in the secretion of testosterone in men.

OBJECTIVE

The objective is to study the association between levels of C-reactive protein and testosterone and its role in predicting biochemical hypogonadism in men.

DESIGN

This was a longitudinal observational study between 2002 and 2014 in Sweden.

PATIENTS OR OTHER PARTICIPANTS

At the first visit, a random population sample of 1400 men was included, and 645 men fulfilled a similar protocol at a 10-year follow-up visit. After exclusion, 625 men remained to be included in the final analyses.

MAIN OUTCOME MEASURE(S)

Serum concentrations of testosterone and C-reactive protein (CRP) were measured at both visits. Bioavailable testosterone was calculated. Biochemical hypogonadism was defined as total testosterone levels <8 nmol/L.

RESULTS

At the first visit and in the longitudinal analyses, a strong association was found between high levels of CRP and low levels of calculated bioavailable testosterone even after adjustments for age, waist-hip ratio, hypertension, smoking, type 2 diabetes, and leisuretime physical activity (B = -0.31, 95% CI -0.49 to -0.13, P = 0.001, B = -0.26, 95% CI -0.41 to -0.11, P = 0.001). Similarly, increase with one s. d. in CRP was associated with increased risk of having hypogonadism after adjustment in the final model (odds ratio (OR) 1.76, 95% CI 1.12-2.78, P = 0.015, OR 1.80, 95% CI 1.16-2.78, P =0.008).

CONCLUSIONS

In this representative cohort of men in southwestern Sweden, high levels of CRP were longitudinally associated with low concentrations of calculated bioavailable testosterone and increased risk of biochemical hypogonadism.

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.

Evaluation of the Efficacy of Sex Hormone-Binding Globulin in Insulin Resistance Assessment Based on HOMA-IR in Patients with PCOS

This study aimed to evaluate the efficacy of SHBG in predicting insulin resistance (IR) in newly diagnosed, untreated patients with polycystic ovary syndrome (PCOS). Hundred newly diagnosed, untreated patients with PCOS and 61 subjects without PCOS (41 healthy volunteers with normal BMI and 20 subjects with overweight/obese) were included in the study. Receiver-operating characteristic (ROC) analysis was used to assess the effectiveness of SHBG in predicting IR in overweight/obese and non-overweight PCOS patients and the optimal cut-off values of SHBG. The results showed negative correlations between log-SHBG and log-I₀ (r = - 0.372, P < 0.001) and log-SHBG and log-Homeostatic Model Assessment of Insulin Resistance (HOMA-IR) (r = - 0.393, P < 0.001) after adjusting for blood pressure, serum lipid, age, and body mass index (BMI) in all of the PCOS patients. In patients with IR (defined as HOMA-IR ≥2.29), the area under the ROC curves (AUCs) of the SHBG for ROC analysis in the non-overweight group, overweight/obese group, and all PCOS patients were 0.774 (P = 0.0001), 0.922 (P = 0.0001), and 0.885 (P = 0.0001), respectively. The optimal cut-off value of SHBG was 37 nmol/L with a sensitivity of 97.62% and specificity of 80.85% in the overweight group. In patients with IR (HOMA-IR ≥2.5), the AUCs of SHBG for ROC analysis in the non-overweight group, overweight/obese group, and all PCOS patients were 0.741 (P = 0.0003), 0.928 (P = 0.0001), and 0.880 (P = 0.0001), respectively. The optimal cut-off value of SHBG was 30.2 nmol/L with a sensitivity of 97.44% and specificity of 82.69% in the overweight/obese group. In conclusion, this study observed a negative correlation between SHBG and HOMA-IR in PCOS patients after adjustment of confounding factors. SHBG was an independent influential factor of HOMA-IR and can be used as a positive predictive marker for IR in PCOS patients, especially in those who are overweight/obese.

Oxidative stress promotes hyperandrogenism by reducing sex hormone-binding globulin in polycystic ovary syndrome

OBJECTIVE

To determine the relationships between circulating sex hormone-binding globulin (SHBG) and oxidized low-density lipoprotein (ox-LDL), total oxidant status, total antioxidant capacity, oxidative stress index, malondialdehyde, and the high-density lipoprotein (HDL) inflammatory index in patients with polycystic ovary syndrome (PCOS) and to investigate the effect of oxidative stress on the expression of SHBG and its mechanism in HepG2 cells.

DESIGN

Cross-sectional study.

SETTING

University hospital.

PATIENT(S)

A total of 533 women with PCOS and 292 control women were included.

INTERVENTION(S)

None.

MAIN OUTCOME MEASURE(S)

Circulating SHBG, hormones, and metabolic and oxidative stress indices were determined in all subjects. The effects of ox-LDL and ox-HDL on the mRNA and protein expression of SHBG and related transcription factors were observed in HepG2 cells.

RESULT(S)

The HDL inflammatory index, total oxidant status, oxidative stress index, and malondialdehyde levels were significantly higher in the three PCOS subgroups with different SHBG levels than in the controls. The ox-LDL and total antioxidant capacity were higher in the PCOS subgroups with SHBG levels <75th percentile compared with the controls or the PCOS subgroup with SHBG levels ≥75th percentile. In HepG2 cells, the SHBG concentration in the culture supernatant, the mRNA levels of SHBG and hepatocyte nuclear factor-4α (HNF-4α), and the protein levels of HNF-4α were significantly lower in ox-LDL- and ox-HDL-treated cells than in the control cells and lipoprotein-treated cells.

CONCLUSION(S)

Oxidative stress inhibits the expression and secretion of SHBG by downregulating HNF-4α in vitro and may be an important factor promoting the occurrence of hyperandrogenemia in PCOS.