Association of thyroid function with insulin resistance: data from two population-based studies

Associations between sensitivity to thyroid hormones and insulin resistance in euthyroid adults with obesity

Background

Impaired sensitivity to thyroid hormones (TH) was associated with metabolic syndrome. The study aimed to explore the association between central TH sensitivity indices and insulin resistance (IR) in euthyroid adults with obesity.

Methods

This cross-sectional study enrolled 293 euthyroid outpatients with obesity in Beijing Chao-Yang Hospital. We used the thyroid feedback quantile-based index (TFQI), thyroid stimulating hormone index (TSHI), and thyrotrophic T4 resistance index (TT4RI) to indicate central TH sensitivity. IR was assessed by homeostasis model assessment of insulin resistance (HOMA-IR), hepatic insulin resistance index (hepatic-IR), the Matsuda index, and the adipose tissue insulin resistance index (Adipo-IR). Participants were categorized according to tertiles of TH sensitivity indices. We used multiple linear regressions to explore the associations.

Results

There was a significant stepwise increase in HOMA-IR and Adipo-IR from the lowest to the highest tertiles of TH sensitivity indices (all P<0.05). After adjustment for age, sex, body mass index, hypertension, hyperlipidemia, and diabetes, only Adipo-IR was significantly associated with TH sensitivity indices. On average, each unit increased in TFQI, TSHI, and TT4RI was associated with 1.19 (P=0.053), 1.16 (P=0.04), and 1.01 (P=0.03) units increased in Adipo-IR, respectively. There was no significant association between TH sensitivity indices and HOMA-IR, hepatic-IR, and the Matsuda index after adjustment for other risk factors.

Conclusions

Reduced central TH sensitivity was associated with increased adipose tissue insulin resistance in euthyroid adults with obesity. The results further confirmed the importance of TH sensitivity on metabolic diseases.

Proteomic analysis of milk fat globule membrane proteins in mature human milk of women with and without gestational diabetes mellitus

Milk fat globule membrane proteins (MFGMP) in human milks have positive effects on infant's health. As gestational diabetes mellitus (GDM) causes variations in MFGMP, it is essential to understand the effects of GDMon MFGMP. This study aims to investigate and compare the MFGMP (>3 months postpartum) of GDM and non-GDM (NGDM) women using four-dimensional-data-independent-acquisition proteomics technology. Principal component analysis shows significant differences in the MFGMP of GDM and NGDM women. A total of 4747 MFGMP were identified in maturehuman milk of GDM and NGDM women. Among these proteins, 174 differentially expressed proteins (DEPs) were identified in MFGM of GDM and NGDM women. Albumin (FC = 7.96) and transthyretin (FC = 2.57) which are related to insulin resistance and involved in thyroid hormone synthesis, are significantly up-regulated in MFGMP of GDM mothers indicating insulin resistance, imbalance of glucose homeostasis and poor glucose metabolism might persist in postpartum period.

Association between the triglyceride-glucose index and thyroid disorders: a cross-sectional survey and Mendelian randomization analysis

BACKGROUND

Metabolic diseases are associated with thyroid disorders. Insulin resistance is the common pathological basis of metabolic diseases. We explored the relationship between the triglyceride-glucose (TyG) index, a simple insulin-resistance marker, and thyroid disorders.

METHODS

Eligible TIDE (Thyroid Diseases, Iodine Status and Diabetes Epidemiology) subjects (n = 47,710) were screened with inclusion/exclusion criteria. Thyroid disorder prevalence among different TyG index groups was stratified by sex. Logistic regression evaluated the correlation between the TyG index and thyroid disorders. Multiple linear regression evaluated the association between the TyG index and TSH. Additionally, two-sample Mendelian randomization (MR) using published genome-wide association study data evaluated causality in the association between the TyG index and TSH.

RESULTS

Men and women with greater TyG indices had a significantly greater prevalence of thyroid disorders than individuals with the lowest quartile (Q1) of TyG index (p < 0.05). Following adjustment for confounding factors, we observed that a greater TyG index significantly increased the risk of subclinical hypothyroidism in men and women (men: Q2: odds ratio (OR) [95% confidence interval (CI)] = 1.22 [1.07-1.38], p = 0.002; Q3: OR [95% CI] = 1.28 [1.12-1.45], p < 0.001; Q4: OR [95% CI] = 1.29 [1.12-1.50], p = 0.001; women: Q2: OR [95% CI] = 1.25 [1.12-1.39], p < 0.001; Q3: OR [95% CI] = 1.47 [1.31-1.64], p < 0.001; Q4: OR [95% CI] = 1.61 [1.43-1.82], p < 0.001). Only among women was the highest TyG index quartile associated with hypothyroidism (OR [95% CI] = 1.70 [1.15-2.50], p = 0.007). Additionally, in men, the association exists only in the more than adequate iodine intake population. In women, the relationship between the TyG index and thyroid disorders disappears after menopause. Furthermore, the TyG index exhibited a linear positive correlation with TSH levels. The MR analysis results revealed a causal relationship between a genetically determined greater TyG index and increased TSH (inverse-variance weighting (IVW): OR [95% CI] = 1.14 [1.02-1.28], p = 0.020); however, this causal relationship disappeared after adjusting for BMI in multivariable MR (MVMR) analysis (MVMR-IVW: OR 1.03, 95% CI 0.87-1.22, p = 0.739).

CONCLUSIONS

A greater TyG index is associated with hypothyroidism and subclinical hypothyroidism and varies by sex and menopausal status. MR analysis demonstrated that the causal relationship between a genetically determined greater TyG index and elevated TSH levels is confounded or mediated by BMI.

Diagnosis and management of thyroid disorders and thyroid hormone supplementation in adult horses and foals

Equine thyroid disorders pose a diagnostic challenge in clinical practice because of the effects of nonthyroidal factors on the hypothalamic-pituitary-thyroid axis, and the horse's ability to tolerate wide fluctuations in thyroid hormone concentrations and survive without a thyroid gland. While benign thyroid tumours are common in older horses, other disorders like primary hypothyroidism or hyperthyroidism in adult horses and congenital hypothyroidism in foals are rare. There is a common misunderstanding regarding hypothyroidism in adult horses, especially when associated with the clinical profile of obesity, lethargy, and poor performance observed in dogs and humans. Low blood thyroid hormone concentrations are often detected in horses as a secondary response to metabolic and disease states, including with the nonthyroidal illness syndrome; however, it is important to note that low thyroid hormone concentrations in these cases do not necessarily indicate hypothyroidism. Assessing equine thyroid function involves measuring thyroid hormone concentrations, including total and free fractions of thyroxine (T4) and triiodothyronine (T3); however, interpreting these results can be challenging due to the pulsatile secretion of thyroid hormones and the many factors that can affect their concentrations. Dynamic testing, such as the thyrotropin-releasing hormone stimulation test, can help assess the thyroid gland response to stimulation. Although true hypothyroidism is extremely rare, thyroid hormone supplementation is commonly used in equine practice to help manage obesity and poor performance. This review focuses on thyroid gland pathophysiology in adult horses and foals, interpretation of blood thyroid hormone concentrations, and evaluation of horses with thyroid disorders. It also discusses the use of T4 supplementation in equine practice.

Are there bidirectional associations between maternal thyroid function and glucose metabolism in singleton live births? A birth cohort study

(1) Aims: To examine the associations between maternal thyroid function and glucose metabolism during pregnancy. (2) Methods: This study was based on Ma' anshan Birth Cohort in China. Totally 2375 pregnant women were included in data analysis. Maternal thyroid-stimulating hormone (TSH), free thyroxine (FT4), thyroid peroxidase antibody (TPOAb) and fasting plasma glucose (FPG) levels during the first, second and third trimesters of pregnancy were measured retrospectively. Mplus 8.0 was used to construct a cross-lagged panel model to examine the potential bidirectional association between thyroid function and FPG levels throughout pregnancy. (3) Results: FT4 levels were positively correlated with FPG levels in the first trimester and negatively correlated with FPG levels in the second trimester. TSH levels were negatively associated with FPG levels in the second trimester, and in the first trimester, it could positively predict FPG levels in the second trimester. No significant association was found between TPOAb levels and FPG levels during pregnancy. (4) Conclusions: There was a non-bidirectional association between maternal thyroid function and glucose metabolism during pregnancy. FT4 and TSH levels influence FPG concentrations in the first and second trimesters of pregnancy.

Interaction between triglyceride-glucose index and thyroid hormones on coronary artery disease risk in patient with euthyroid

Background

Triglyceride-glucose (TyG) index is an effective indicator in indentifying in pre-diabetes, diabetes, and coronary artery disease (CAD). However, the value of TyG index combined with thyroid hormones (THs) to affect CAD has not been fully evaluated. Here, we investigated the association between TyG index and THs and further studied the impacts of TyG index and THs on CAD in euthyroid.

Methods

Subjects (1,297) with euthyroid who underwent selective coronary angiography (CAG) were enrolled in the present study, including 893 patients with CAD and 404 controls. The association between TyG index and THs were analyzed by linear regression models. Multivariate logistic regression analysis was used to evaluate the interaction of TyG and THs with the risk of CAD. According to the cutoff value of free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and TyG index, the patients were respectively separated into four groups: low TyG/FT3 (low or high), high TyG/FT3 (low or high), low TyG/FT4 (low or high), high TyG/FT4 (low or high), low TyG/TSH (low or high), high TyG/TSH (low or high).

Results

The baseline analysis showed that FT4 level differs among the three groups according to the tertile of the TyG index. Multiple linear regression analysis revealed decreased serum FT3 level and serum FT4 level as an independent risk factor for elevated TyG index. After adjusting for confounding variables, multiple logistic regression analysis showed that patients with lower TyG index and higher FT3 level had an important protective effect on CAD when considering patients with lower TyG index and FT3 level as reference(OR = 0.536, 95% CI: 0.369-0.778, P = 0.001). Patients with higher TyG index and FT4 level (lower or higher) had a significantly increased risk of CAD (OR 1.656, 95% CI: 1.117-2.455; OR = 1.920, 95% CI: 1.279-2.848, respectively). The area under the curve for the combined diagnosis of CAD by TyG index and FT3 level is 0.615.

Conclusions

These findings suggest that TyG is independently negatively correlated with FT3 or FT4 in euthyroid. In addition, there was a significant interaction between TyG index and THs on the risk of CAD.

Systematic Review to Gauge the Effect of Levothyroxine Substitution on Progression of Diabetic Nephropathy in Patients With Hypothyroidism and Type 2 Diabetes Mellitus

Diabetes mellitus (DM) and thyroid dysfunction are two disorders that are closely related. This systematic review aimed to investigate the effect of levothyroxine supplementation on diabetic nephropathy in type 2 diabetic patients with co-existing thyroid dysfunction. We explored medical databases such as PubMed, Medline, Multidisciplinary Digital Publishing Institute (MDPI), and Cochrane Library for relevant medical literature. The papers were screened, and 12 research papers involving 10,371 patients were identified after applying eligibility criteria and quality assessment using Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. The included papers analyzed the effect of aberrant thyroid profile on kidney disease in diabetic individuals and the role that achieving euthyroid status with levothyroxine supplementation could play in diabetic nephropathy. Reduced free triiodothyronine (FT3) was the most common independent factor associated with diabetic microvascular and macrovascular complications. Levothyroxine (LT4) regimen was more effective than the placebo in lowering urinary albumin excretion rate (UAER), low-density lipoprotein cholesterol, and uric acid and decreasing oxidative stress overall. However, replacement therapy's effect may differ in the short and long terms. Thyroid hormone replacement therapy (THRT) may reduce the risk of diabetic nephropathy and cardiovascular disease (CVD) development in hypothyroid patients, but more randomized trials are needed to confirm the effect of THRT.

Elevated Free Thyroxine Levels Might Alter the Effect of the Lipid Profile on Insulin Resistance in Type 2 Diabetes Mellitus

Previous studies have shown that hyperthyroidism is associated with heightened insulin resistance and dyslipidemia. Therefore, in this study, we aim to explore the relationship between elevated thyroid hormone levels and the lipid profile in insulin resistance in patients with type 2 diabetes mellitus (T2DM) with hyperthyroidism. A total of 177 participants were included and grouped according to diagnosis. The serum test results demonstrated that free thyroxine (FT4) increased the insulin resistance index (HOMA-IR) by positively correlating with triglyceride (TG) levels (p = 0.005, r2 = 0.35). In patients with T2DM with hyperthyroidism, the decreasing high-density lipoprotein levels showed an association with HOMA-IR (p = 0.005). Among all the patients, with different levels of FT4, the areas under the ROC curve (AUCs) of the TG level, TG/high-density lipoprotein ratio, and HOMA-IR were 0.620 (95% CI: 0.536 to 0.698), 0.614 (95% CI: 0.530 to 0.692), and 0.722 (95% CI: 0.645 to 0.791), respectively. Our results suggest that elevated FT4 levels due to hyperthyroidism could alter the association with the lipid profile and insulin resistance in patients with T2DM. We also suggest that among all the included patients with T2DM, irrespective of the presence of hyperthyroidism, FT4 levels are positively correlated with insulin resistance.

Thyroid hormones as a disease modifier and therapeutic target in nonalcoholic steatohepatitis

INTRODUCTION

Nonalcoholic fatty liver disease (NAFLD) is the most common cause of chronic liver disease worldwide and closely interconnected to the metabolic syndrome. Liver-specific and systemic signaling pathways orchestrating glucose and fatty acid metabolism contribute to intrahepatic accumulation of lipids and inflammatory processes eventually causing disease progression to nonalcoholic steatohepatitis (NASH), liver fibrosis, and cirrhosis. Since a high number of key regulatory genes regarding liver homeostasis are directly mediated via thyroid hormone (TH) signaling, targeting TH receptors (TRs) represent a promising therapeutic potential for the treatment of NAFLD.

AREAS COVERED

In this review, we elucidate the effects of TH on metabolic regulations in the liver via local availability and actions. We discuss recent advances and the potential impact of thyromimetics in basic research and clinical trials including liver-targeted and TRβ-specific agents for the treatment of NAFLD.

EXPERT OPINION

Unselective TR targeting can be accompanied by negative side effects due to high TRβ expression in other organs and TRα-mediated effects. Recent advances in drug development and the introduction of liver-targeted thyromimetics selectively activating TRβ such as Resmetirom (MGL-3196) and VK2809 bring new hope of translating the knowledge on local TH effects into effective hepatic lipid-clearing therapies against NASH.

The analysis of risk factors for diabetic kidney disease progression: a single-centre and cross-sectional experiment in Shanghai

OBJECTIVE

To identify the risk factors for diabetic kidney disease (DKD) development, especially the difference between patients with different courses.

PATIENTS AND METHODS

791 patients were considered to be eligible and were enrolled in the cross-sectional study from Shanghai Tongren Hospital Inpatient Department. 36 variables were initially screened by univariate analysis. The risk factors affecting progression of DKD were determined by logistics regression analysis. Subgroups were grouped according to the course of diabetes disease, and multivariate logistics regression analysis was performed to find out the different risk factors in two subgroups. Finally, the receiver operating characteristics curve is used to verify the result.

RESULTS

The logistic regression model indicated age (OR=1.020, p=0.017, 95% CI 1.004 to 1.040), systolic blood pressure (OR=1.013, p=0.006, 95% CI 1.004 to 1.022), waist circumference (OR=1.021, p=0.015, 95% CI 1.004 to 1.038), white blood cells (WBC, OR=1.185, p=0.001, 95% CI 1.085 to 1.295) and triglycerides (TG, OR=1.110, p=0.047, 95% CI 1.001 to 1.230) were risk factors for DKD, while free triiodothyronine (fT3, OR=0.711, p=0.011, 95% CI 0.547 to 0.926) was a protective factor for DKD in patients with type 2 diabetes mellitus (T2DM). Subgroup analysis revealed that in patients with a short duration of diabetes (<8 years), WBC (OR=1.306, p<0.001, 95% CI 1.157 to 1.475) and TG (OR=1.188, p=0.033, 95% CI 1.014 to 1.393) were risk factors for DKD,fT3 (OR=0.544, p=0.002, 95% CI 0.367 to 0.804) was a protective factor for DKD; whereas for patients with disease course more than 8 years, age (OR=1.026, Pp=0.012, 95%CI=95% CI[ 1.006- to 1.048]) was identified as the only risk factor for DKD and fT3 (OR=0.036, Pp=0.017, 95%CI=95% CI[ 0.439- to 0.922]) was a protective factor for DKD.

CONCLUSION

The focus of attention should especially be on patients with a prolonged course of T2DM, and those with comorbid hypertension and hypertriglyceridaemia waist phenotype. More potential clinical indexes such as thyroid function and inflammatory indicators might be considered as early warning factors for DKD in T2DM. Women should pay attention to controlling inflammation and TGs, and men should strictly control blood pressure. Avoiding abdominal obesity in both men and women will bring great benefits.

Correlation of thyroid-related hormones with vascular complications in type 2 diabetes patients with euthyroid

BACKGROUND

This study aimed to evaluate the relationship between thyroid-related hormones and vascular complications in type 2 diabetes mellitus (T2DM) patients with euthyroidism.

METHODS

We enrolled 849 patients with T2DM after screening out the ineligible. Multivariate logistic regression was used to analyze the relationship between fT3, fT4, the fT3/fT4 ratio, thyroid-stimulating hormone, and diabetic vascular complications. Spearman correlation analysis was used to determine the correlation between thyroid-related hormones and vascular complications.

RESULTS

In this cross-sectional study of T2DM, 538 patients with carotid atherosclerosis (CA) and 299 patients with diabetic peripheral neuropathy (DPN). The prevalence of DPN was negatively correlated with fT3 and the fT3/fT4 ratio but positively correlated with fT4 (all P<0.01). At the same time, the odds ratio for DPN decreased with increasing fT3 (T1: reference; T2: OR: 0.689, 95%CI: 0.477, 0.993; T3: OR: 0.426, 95% CI: 0.286, 0.633, all P<0.05) and fT3/fT4 ratio (T1: reference; T2: OR: 0.528, 95% CI: 0.365, 0.763; T3: OR: 0.413, 95% CI: 0.278, 0.613, all P<0.001). In terms of sensitivity and specificity, fT4 was found to be 39.5% and 71.4% accurate, respectively, with a 95% CI of 0.531-0.611.

CONCLUSIONS

We found a negative correlation between fT3 and fT3/fT4 ratio and the number of individuals with DPN, and a positive correlation between fT4 and the prevalence of DPN.