The relationship between serum thyrotropin and components of metabolic syndrome

Hypothyroidism in Metabolic Syndrome

INTRODUCTION

Metabolic syndrome (MetS) and hypothyroidism are well-established forerunners of atherogenic cardiovascular disease (CVD). It is possible that patients suffering from both these disease entities may have a compounded risk. This study aimed at determining the prevalence of hypothyroidism in MetS.

MATERIALS AND METHODS

This cross-sectional study was conducted from September 2017 to August 2018 in the department of medicine at a tertiary care hospital in Northern India. Ethical approval was obtained from the institutional ethical committee. The study subjects consisted of 157 patients with MetS, the diagnosis of which was based on the International Diabetes Federation criteria. After a detailed history and physical examination, relevant investigations including complete thyroid profile were done. The data were analyzed using appropriate statistical tests (P < 0.05).

RESULTS

In our study, the age of subjects ranged between 14 and 92 years, with a mean ± standard deviation of 48.1 ± 17.01 years. There were more females than males with a male-to-female ratio of 1:1.3. The prevalence of hypothyroidism was 46.5%. Hypothyroidism was more common in females (58.9%) as compared to males (41.1%). Patients with hypothyroidism had significantly higher body weight and body mass index (BMI) in comparison to euthyroid patients. The rest of the anthropometric parameters were comparable. Waist circumference and BMI of overt hypothyroid patients were found to be higher as compared to subclinical hypothyroid patients. Total cholesterol and triglyceride were significantly higher (P = 0.001 and P < 0.001, respectively), while high-density lipoprotein levels were significantly lower in patients with hypothyroidism than the euthyroid group (P < 0.001).

CONCLUSION

Hypothyroidism, especially subclinical hypothyroidism, is a common endocrine disorder in patients with MetS. As MetS and hypothyroidism are independent risk factors for CVD, hence there is a need for screening for hypothyroidism and the treatment of the same can be beneficial in reducing the cardiovascular morbidity and mortality in patients with MetS.

Lipid Metabolism in Pregnancy Women with Hypothyroidism and Potential Influence on Pregnancy Outcome

Thyroid hormone (TH) is essential for maintaining normal physiological processes during pregnancy, including the metabolism of energy materials in both the mother and fetus and the growth and development of fetal bone and nervous system. TH can act on the liver, fat, and other tissues and organs to participate in lipid synthesis and breakdown through multiple pathways. Consequently, abnormal thyroid function is often accompanied by lipid metabolism disorders. Both clinical and subclinical hypothyroidism, as well as dyslipidemia during pregnancy, have been shown to be associated with an increased risk of multiple adverse pregnancy outcomes. Recently, there has been an increased interest in studying the alteration of lipidomic and hypothyroidism (both clinical and subclinical hypothyroidism) during pregnancy. Studies have suggested that altered lipid molecules might be used as potential biomarker and associated with adverse maternal and neonatal outcome. Thus, we summarized the associations between lipid metabolism and clinical or subclinical hypothyroidism during pregnancy in this review. Then, we discussed the underlying mechanisms of thyroid dysfunction and lipid metabolism. In addition, we reviewed the possible effect of dyslipidemia on pregnancy and neonatal outcome. However, the relationship between hypothyroidism during pregnancy and changes in the lipid profile and how to intervene in the occurrence and development of adverse pregnancy outcomes require further study.

Relationship Between Serum Thyrotropin Levels and Metabolic Diseases in Older Adults

CONTEXT

Subclinical hypothyroidism is associated with metabolic diseases; however, it remains controversial in older individuals.

OBJECTIVE

This work aimed to investigate the relationship between thyrotropin (TSH) levels and metabolic diseases.

METHODS

In this cross-sectional study, sampling was conducted from nationally representative general communities from 31 provinces in mainland China. A total of6791 older (aged ≥65 years) and 55 303 young participants (aged 18-64 years) were selected after excluding individuals with overt hyperthyroidism or overt hypothyroidism. According to the kit, TSH reference range (0.27-4.2 mU/L) and the age-specific TSH range previously formulated (an upper limit of 8.86 mU/L for older adults and 6.57 mU/L for young adults), the older adults and young adults were separately divided into 4 groups based on their TSH levels. Main outcome measures included anthropometric assessments, serum concentrations of thyroid functions, and various metabolic parameters.

RESULTS

In contrast to young adults, there was no significant increase in the prevalence of any metabolic disorders assessed in the slightly elevated TSH group (TSH 4.21-8.86 mU/L) compared to the euthyroid group (TSH 0.27-4.2 mU/L) among older adults. After adjusting for interference factors, a TSH level higher than 8.86 mU/L was found to be an independent risk factor for low high-density lipoprotein cholesterol (OR, 1.84; 95% CI, 1.14-2.98) and dyslipidemia (OR, 1.49; 95% CI, 1.09-2.04) when compared to the euthyroid group in older adults.

CONCLUSION

Slightly elevated TSH levels are not associated with an increased risk of metabolic diseases in older adults. Therefore, we recommend raising the upper limit of the TSH range for individuals aged 65 years and older.

Increased thyroid stimulating hormone (TSH) as a possible risk factor for atherosclerosis in subclinical hypothyroidism

Primary hypothyroidism (PHT) is associated with an increased risk for the development of atherosclerosis (AS) and other cardiovascular disorders. PHT induces atherosclerosis (AS) through the induction of endothelial dysfunction, and insulin resistance (IR). PHT promotes vasoconstriction and the development of hypertension. However, patients with subclinical PHT with normal thyroid hormones (THs) are also at risk for cardiovascular complications. In subclinical PHT, increasing thyroid stimulating hormone (TSH) levels could be one of the causative factors intricate in the progression of cardiovascular complications including AS. Nevertheless, the mechanistic role of PHT in AS has not been fully clarified in relation to increased TSH. Therefore, in this review, we discuss the association between increased TSH and AS, and how increased TSH may be involved in the pathogenesis of AS. In addition, we also discuss how L-thyroxine treatment affects the development of AS.

Associations of TSH, free T3, free T4, and conversion ratio with incident hypertension: results from the prospective Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Objective

To evaluate the association of TSH, free T3 (FT3), free T4 (FT4), and conversion (FT3:FT4) ratio values with incident hypertension.

Materials and methods

The study included data from participants of the ELSA-Brasil study without baseline hypertension. Serum TSH, FT4 and FT3 levels, and FT3:FT4 ratio values were assessed at baseline, and incident hypertension (defined by blood pressure levels ≥ 140/90 mmHg) was estimated over a median of 8.2 years of follow-up. The risk of incident hypertension was evaluated considering a 1-unit increase in TSH, FT4, FT3, and conversion ratio values and after dividing these variables into quintiles for further analysis using Poisson regression with robust variance. The results are presented as relative risks (RR) and 95% confidence intervals (CIs) before and after adjustment for multiple variables.

Results

The primary analysis incorporated data from 5,915 euthyroid individuals, and the secondary analysis combined data from all euthyroid individuals, 587 individuals with subclinical hypothyroidism, and 31 individuals with subclinical hyperthyroidism. The rate of incident hypertension was 28% (95% CI: 27%-29.3%). The FT4 levels in the first quintile (0.18-1.06 ng/dL) were significantly associated with incident hypertension (RR: 1.03, 95% CI: 1.01-1.06) at follow-up. The association between FT4 levels in the first quintile and incident hypertension was also observed in the analysis of combined data from euthyroid individuals and participants with subclinical thyroid dysfunction (RR: 1.04, 95% CI: 1.01-1.07). The associations were predominantly observed with systolic blood pressure levels in euthyroid individuals. However, in the combined analysis incorporating euthyroid participants and individuals with subclinical thyroid dysfunction, the associations were more pronounced with diastolic blood pressure levels.

Conclusion

Low FT4 levels may be a mild risk factor for incident hypertension in euthyroid individuals and persons with subclinical thyroid dysfunction.

Exploring the link between obesity and hypothyroidism in autoimmune thyroid diseases: a metabolic perspective

Background: The management of primary hypothyroidism demands a comprehensive approach that encompasses both the implications of autoimmune thyroid disease and the distinct effects posed by obesity and metabolic irregularities. Despite its clinical importance, the interplay between obesity and hypothyroidism, especially in the context of metabolic perspectives, is insufficiently explored in existing research. This study endeavors to classify hypothyroidism by considering the presence of autoimmune thyroid disease and to examine its correlation with various metabolic obesity phenotypes. Method: This research was conducted by analyzing data from 1,170 individuals enrolled in the Thyroid Disease Database of Shandong Provincial Hospital. We assessed four distinct metabolic health statuses among the participants: Metabolically Healthy No Obese Metabolically Healthy Obese Metabolically Unhealthy No Obese and Metabolically Unhealthy Obese Utilizing logistic regression, we investigated the association between various metabolic obesity phenotypes and hypothyroidism. Results: The study revealed a significant correlation between the Metabolically Unhealthy Obese (MUO) phenotype and hypothyroidism, particularly among women who do not have thyroid autoimmunity. Notably, the Metabolically Unhealthy No Obese (MUNO) phenotype showed a significant association with hypothyroidism in individuals with thyroid autoimmunity, with a pronounced prevalence in women. Furthermore, elevated levels of triglycerides and blood glucose were found to be significantly associated with hypothyroidism in men with thyroid autoimmunity and in women without thyroid autoimmunity. Conclusion: Effective treatment of hypothyroidism requires a thorough understanding of the process of thyroid autoimmune development. In patients without concurrent thyroid autoimmunity, there is a notable correlation between obesity and metabolic issues with reduced thyroid function. Conversely, for patients with thyroid autoimmunity, a focused approach on managing metabolic abnormalities, especially triglyceride levels, is crucial.

The Relationship between Subclinical Hypothyroidism and Carotid Intima-Media Thickness as a Potential Marker of Cardiovascular Risk: A Systematic Review and a Meta-Analysis

BACKGROUND AND OBJECTIVES

Thyroid dysfunction is known to have significant consequences on the cardiovascular system. The correlation between carotid intima-media thickness (CIMT) and subclinical hypothyroidism (SCH) has been frequently evaluated in clinical studies in recent years. This study aimed to evaluate the significance of this association through a meta-analysis.

METHODS

We conducted a systematic search of PubMed, MedLine, Scopus, and Web of Science databases using the keywords 'subclinical hypothyroidism and carotid intima-media thickness', from the beginning of each database until January 2023. We established the inclusion and exclusion criteria and considered studies that met the inclusion criteria. We used Jamovi for statistical analysis of the data.

RESULTS

We identified 39 observational studies that met the inclusion criteria, with 3430 subjects: 1545 SCH and 1885 EU. Compared to euthyroid subjects (EU), subjects with subclinical hypothyroidism (SCH) had significantly increased carotid intima-media thickness (CIMT) values; the estimated average mean difference was 0.08 (95% CI 0.05 to 0.10), p < 0.01, I2 = 93.82%. After the sensitivity analysis, a total of 19 from the 39 abovementioned studies were analyzed, with most studies showing a positive association between SCH and thickening of the carotid wall; the estimated average mean difference was 0.04 (95% CI 0.02 to 0.07), p = 0.03, I2 = 77.7. In addition, female sex, advanced age, and high cholesterol levels statistically significantly influenced this association.

CONCLUSIONS

Our meta-analysis indicates a significant positive association between SCH and increased CIMT, but with some limitations.

Thyroid Function and Metabolic Syndrome: A Two-Sample Bidirectional Mendelian Randomization Study

CONTEXT

Thyroid function has been associated with metabolic syndrome (MetS) in a number of observational studies but the direction of effects and the exact causal mechanism of this relationship is still unknown.

OBJECTIVE

To examine genetically predicted effects of thyroid function on MetS risk and its components, and vice versa, using large-scale summary genetic association data.

METHODS

We performed a two-sample bidirectional Mendelian randomization (MR) study using summary statistics from the most comprehensive genome-wide association studies (GWAS) of thyroid-stimulating hormone (TSH, n = 119 715), free thyroxine (fT4, n = 49 269), MetS (n = 291 107), and components of MetS: waist circumference (n = 462 166), fasting blood glucose (n = 281 416), hypertension (n = 463 010), triglycerides (TG, n = 441 016) and high-density lipoprotein cholesterol (HDL-C, n = 403 943). We chose the multiplicative random effects inverse variance weighted (IVW) method as the main analysis. Sensitivity analysis included weighted median and mode analysis, as well as MR-Egger and Causal Analysis Using Summary Effect estimates (CAUSE).

RESULTS

Our results suggest that higher fT4 levels lower the risk of developing MetS (OR = 0.96, P = .037). Genetically predicted fT4 was also positively associated with HDL-C (β = 0.02, P = .008), while genetically predicted TSH was positively associated with TG (β = 0.01, P = .044). These effects were consistent across different MR analyses and confirmed with the CAUSE analysis. In the reverse direction MR analysis, genetically predicted HDL-C was negatively associated with TSH (β = -0.03, P = .046) in the main IVW analysis.

CONCLUSION

Our study suggests that variations in normal-range thyroid function are causally associated with the diagnosis of MetS and with lipid profile, while in the reverse direction, HDL-C has a plausible causal effect on reference-range TSH levels.

Association of Thyroid Function With Lipid Profile in Patients With Metabolic Syndrome: A Prospective Cross-Sectional Study in the Indian Population

Introduction Metabolic syndrome is a group of aberrant metabolic indicators including hypertension, dyslipidemia, impaired fasting blood glucose, and obesity. It has been reported that thyroid hormones have a strong influence on the cardiovascular system, and hypothyroidism has been linked to metabolic syndrome components. The objective of the study was to find out the association of thyroid function with lipid profile in patients with metabolic syndrome. Methods A prospective cross-sectional study was conducted in an apparently healthy adult population visiting the outpatient Department of Indira Gandhi Institute of Medical Sciences (IGIMS), Patna, Bihar, India. Metabolic syndrome was diagnosed according to the International Diabetes Federation (IDF) criteria. Fasting blood glucose, triglyceride, and HDL levels were tested using the enzymatic photometric method. Thyroid-stimulating hormone (TSH), free T4, free T3, and insulin assays were performed using chemiluminescence immunoassay (CLIA). Results Out of 197 subjects recruited, 86 (51 males and 35 females) were diagnosed with metabolic syndrome according to the IDF criteria, and the rest 111 without metabolic syndrome were considered to be the controls. The mean age of subjects with and without metabolic syndrome was 45.8±8.5 and 46.4±9.6 years, respectively. The prevalence of thyroid dysfunction in the present study was 22%. In subjects with metabolic syndrome, most of the clinical and hormonal parameters (waist circumference, waist-height ratio, fasting blood sugar, fasting insulin, triglycerides, T3, and TSH) were significantly higher (p<0.001) as compared to those without metabolic syndrome. In case of lipid profile, the triglycerides in those with metabolic syndrome (262.8±112.3 mg/dL) were significantly higher (p<0.001) than those without metabolic syndrome (137.9±19.01 mg/dL), while the serum levels of HDL were significantly higher (p<0.001) in group without metabolic syndrome (50.5±3.9 mg/dL) as compared to those with metabolic syndrome (43.4±5.2 mg/dL). Also, the TSH levels were significantly higher (p<0.001) in subjects with metabolic syndrome (5.3±3.4 μl/mL) as compared to those without metabolic syndrome (2.6±1.4 μl/mL). Among all the components of metabolic syndrome, waist circumference and HDL showed a significant strong positive correlation (r=0.51) with TSH, and systolic blood pressure (r=0.39), diastolic blood pressure (r=0.39), and fasting blood sugar levels (r=0.44) showed significantly moderate positive correlation with TSH levels. T4 (OR=8.82; 95% CI: 1.56-49.8) and TSH (OR=1.61; 95% CI: 1.19-2.18) levels were observed to have significantly higher odds as risk factors for metabolic syndrome. Conclusion There is a significant association of thyroid function with lipid profile in metabolic syndrome. It was observed that along with metabolic alterations, cardiovascular symptoms of hypothyroidism and subclinical hypothyroidism are possible. Therefore, while evaluating people with metabolic syndrome, it may be appropriate to look into how well their thyroid glands are functioning.

Association between thyroid function and obesity phenotypes in healthy euthyroid individuals: an investigation based on Tehran Thyroid Study

AIMS

We investigated whether thyroid function could be associated with obesity phenotypes amongst euthyroid individuals.

MATERIALS AND METHODS

A cross-sectional analysis was conducted among healthy, euthyroid subjects. The study participants were chosen from the Tehran Thyroid Study (TTS). We analyzed 2988 euthyroid adults and classified them into four obesity phenotype groups: metabolically healthy normal weight (MHNW), metabolically healthy obese (MHO), metabolically unhealthy normal weight (MUNW), and metabolically unhealthy obese (MUO). The statistical differences between thyroid hormones between various obesity phenotypes according to age and sex was compared using analysis of covariance (ANCOVA).

RESULTS

It was found that MHNW participants had higher levels of FT4 when compared with metabolically healthy or unhealthy obese subjects (P < 0.001), even after adjustment for the confounding variables. No difference was observed in the levels of TSH (P = 0.260) among obesity phenotypes. In the subgroup analysis according to the age, a significant difference was observed in the level of FT4 only in subjects with age < 55 years (P = 0.001). However, analyzing men and women separately did not show a significant difference in the FT4 level among obesity phenotypes (P > 0.05).

CONCLUSION

"Metabolically abnormality" was independently related to low normal FT4 levels in overweight/obese euthyroid individuals. There is a need for further research to understand how low FT4 levels are linked to metabolically unhealthy states in euthyroid individuals.

Menopausal Impact on the Association Between Thyroid Dysfunction and Lipid Profiles: A Cross-Sectional Study

BACKGROUND

Both dyslipidemia and thyroid dysfunction have a high prevalence rate and are important risk factors for cardiovascular diseases. However, the relationship between blood lipids and thyroid dysfunction is still controversial. This study aims to analyze the blood lipids in people with different thyroid functions.

METHODS

A total of 80937 adults were included in this population-based cross-sectional TIDE survey, which collected demographic and clinical data on thyroid function, blood lipid levels and other metabolic indicators. After screening, the final analysis included 10,747 participants, who were divided into hypothyroidism (n=311), subclinical hypothyroidism (n=5015), hyperthyroidism (n=203), subclinical hyperthyroidism (n=118) and control (n=5100) groups. The risk of dyslipidemia was analyzed by a logistic regression model and divided into groups of female menopausal.

RESULTS

After full adjustment, significant associations were found between hypothyroidism and hypertriglyceridemia. Subclinical hypothyroidism was associated with a significantly higher risk of hypertriglyceridemia and hyper-low density lipoprotein cholesterolemia. Hyperthyroidism was significantly correlated with a reduced risk of hypercholesterolemia and hyper-low density lipoprotein cholesterolemia but positively correlated with the risk of low-high density lipoprotein cholesterolemia. There was no significant association between subclinical hyperthyroidism and blood lipids. Hypothyroidism increased the risk of hypertriglyceridemia in both premenopausal and postmenopausal females. Subclinical hypothyroidism was significantly associated with increased hypertriglyceridemia and low-high density lipoprotein cholesterolemia in premenopausal females. Hyperthyroidism was significantly associated with a reduced risk of hypercholesterolemia and hyper-low density lipoprotein cholesterolemia in premenopausal females and an increased risk of low-high density lipoprotein cholesterolemia in postmenopausal female.

CONCLUSION

Abnormal thyroid function has an important effect on blood lipids and is closely related to female menopause.

The Association Between Serum Palmitic Acid and Thyroid Function

AIM

Emerging evidence indicates that palmitic acid (PA) can regulate the progression and development of many diseases. However, the studies examining the association between PA and thyroid function remain sparse. We aimed to investigate the association between serum PA (sPA) and thyroid function in the US population.

METHODS

In this retrospective study, a cross-sectional analysis was performed using the data pooled from the database of the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2012. The thyroid parameters investigated were mainly free triiodothyronine (FT3), free thyroxine (FT4), total T3 (TT3), TT4, thyroglobulin (Tg), thyroid-stimulating hormone (TSH), anti-thyroglobulin antibody (TgAb), and anti-thyroperoxidase antibody (TPOAb). The central sensitivity to thyroid function was evaluated by the thyroid feedback quantile-based index (TFQI), thyrotrophin thyroxine resistance index (TT4RI), and thyrotropin index (TSHI). The FT3 to FT4 ratio (FT3/FT4) was employed to evaluate peripheral sensitivity to thyroid hormones. Multiple imputation was applied to handle the missing data, and weighted multivariable linear regression, subgroup, and interaction analyses were then employed to estimate the association between sPA and thyroid parameters.

RESULTS

In the 737 adults, after adjusting covariates, we demonstrated a significant negative association between sPA and FT4 [β = -1.078, 95% confidence interval (CI): -1.729 to -0.427], as well as a positive relationship between sPA and FT3/FT4 ratio (β = 0.073, 95% CI: 0.044 to 0.102). These results did not change on multiple imputations. In the subgroup analyses, the associations were more significant in male and obese subjects.

CONCLUSION

This investigation demonstrated the significant correlation between sPA and thyroid dysfunction, which suggested the close relationship between lipotoxicity and hypothyroidism or subclinical hypothyroidism. Future research is required to confirm these findings.

The Association with Subclinical Thyroid Dysfunction and Uric Acid

The relationship between subclinical thyroid dysfunction and uric acid was not well established. This study aimed to determine if subclinical thyroid dysfunction is associated with hyperuricemia risk and to evaluate the levels of uric acid in patients with different forms of subclinical thyroid dysfunction. A systematic search was conducted in 4 databases to obtain relevant studies on subclinical thyroid dysfunction (subclinical hyperthyroidism and subclinical hypothyroidism) and uric acid. The standardized mean difference (SMD) or odds ratio (OR) and 95% confidence interval (95% CI) were used for evaluation, and the sensitivity analysis was conducted. Publication bias was estimated by funnel plot, Egger's test, and Begg's test. A total of 73 studies were included in this meta-analysis. The results demonstrated that serum levels of uric acid in patients with subclinical hypothyroidism were significantly higher than those of controls and patients with subclinical hyperthyroidism. Patients with subclinical thyroid dysfunction had a higher prevalence of hyperuricemia compared with normal clinical thyroid function. Subclinical thyroid dysfunction was associated with the prevalence of hyperuricemia. Different types of subclinical thyroid dysfunction had varied effects on serum levels of uric acid.

Specific impact of cardiovascular risk factors on coronary microcirculation in patients with subclinical hypothyroidism

Background

Although thyroid hormones have significant effect on cardiovascular system, the impact of subtle thyroid dysfunction such as subclinical hypothyroidism (SCH) remains to be determined. We investigated coronary flow reserve (CFR) in patients with subclinical hypothyroidism.

Methods

Thirty two subjects with SCH and eighteen control subjects with normal serum thyroid hormones and thyroid-stimulating hormone (TSH) levels were included in the study. TSH, free thyroxine, free triiodothyronine, glucose, insulin, HbA1c, cholesterol, triglyceride and plasma levels of C-reactive protein were measured. Coronary diastolic peak flow velocities in left anterior descending coronary artery were measured at baseline and after adenosine infusion. CFR was calculated as the ratio of hyperemic to baseline diastolic peak velocity.

Results

CFR values were not significantly different between the two groups (SCH 2.76±0.35 vs controls 2.76±0.42). There was a significant correlation of CFR with waist to hip ratio, hypertension, smoking habits, markers of glucose status (glucose level, HbA1c, insulin level, HOMA IR), cholesterol, LDL-cholesterol and triglyceride levels in SCH group, whereas only cholesterol level showed significant correlation with CFR in controls. There was no correlation between CFR and thyroid hormones.

Conclusions

We concluded that there is a different impact of cardiovascular risk factors on CFR in SCH patients compared to healthy control and that these two groups behave differently in the same circumstances under the same risk factors. The basis for this difference could be that the altered thyroid axis "set point" changes the sensitivity of the microvasculature in patients with SCH to known risk factors.

Thyroid Function Assessment in Saudi Males with Metabolic Syndrome

Background

Metabolic Syndrome (MetS) is a multifactor condition associated with cardiovascular risk. Thyroid hormones regulate MetS components via controlling energy homeostasis, lipids, and glucose metabolism. The risk ratio for MetS and related disorders changes between males and females. Aim and Objectives: Study aim to access thyroid functions in Saudi population with metabolic syndrome.

Materials and Methods

The current study sought to evaluate the impact of thyroid stimulating hormone (TSH), free triiodothyronine (FT3), and free thyroxine (FT4) in predicting the risk of MetS. A total of 200 (MetS 100 and control 100) Saudi Arabian males were enrolled for the study, and after applying eligibility criteria, the eligible study size was examined for the physical test (chest, abdominal, and general examination with stress on blood pressure measurement) and anthropometric parameters (bodyweight, body mass index, and waist circumference).

Results

In the present study, the biochemical parameters, such as TSH, FT3, FT4, total cholesterol (TC), triglyceride (TG), high-density lipoprotein (HDL), high-density lipoprotein (LDL), fasting glucose, and fasting insulin were measured in the study group, and statistical analysis was also performed. The results revealed that the MetS and control differ in terms of physical, anthropometric, and biochemical markers. The study showed that thyroid dysfunction (TD) and MetS are closely associated with the difference in physical, anthropometric, and metabolic characteristics.

Conclusion

The result demonstrated hypothyroidism major risk factor due to TD in MetS. These findings provide a scientific basis for diagnosis and the management of TD, associated MetS, and cardiovascular disease (CVD).

The association between subclinical hypothyroidism and metabolic syndrome: an update meta-analysis of observational studies

The association between subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) has been widely discussed. This study aimed to conduct an update and comprehensive meta-analysis to reveal the risk of MetS and its components in SCH. PubMed, Embase and ISI Web of Knowledge were searched to identify relevant studies through February 20^th, 2020. Review Manager 5.3 and Stata 14.0 were used to conduct the meta-analysis. Both fixed-effects and random-effects models were used. In total, 18 articles (19 studies) incorporating 79,727 participants were included. The pooled OR for MetS comparing subjects with SCH with euthyroid subjects was 1.28 (95% CI: 1.19 to 1.39, p = 0.04, I² = 40%). Subgroup analysis results showed significant associations of SCH and MetS in the adult subgroup (OR = 1.28, 95% CI: 1.18-1.40), Asian population subgroup (OR = 1.30, 95% CI: 1.19-1.42) and cross-sectional study design subgroup (OR = 1.31, 95% CI: 1.16-1.47). Significant associations of SCH and MetS also existed in all MetS definition criteria subgroups except the Chinese Diabetes Society (CDS) subgroup. SCH was correlated with MetS and was not affected by the subgroup analysis stratified by the proportion of females in the total population, the TSH cutoff value in SCH diagnostic criteria, or the adjustment for confounding factors. SCH was identified to be associated with an increased risk of obesity, hypertension, high triglyceride (TG) levels and low high-density lipoprotein cholesterol (HDL-C) levels. In conclusion, SCH is significantly associated with an increased risk of MetS and four out of five components of MetS.

Obesity and Thyroid Axis

Development of obesity is primarily the result of imbalance between energy intake and energy expenditure. Thyroid hormones influence energy expenditure by regulating cellular respiration and thermogenesis and by determining resting metabolic rate. Triiodothyronine influences lipid turnover in adipocytes and impacts appetite regulation through the central nervous system, mainly the hypothalamus. Thyroid-stimulating hormone may also influence thermogenesis, suppress appetite and regulate lipid storage through lipolysis and lipogenesis control. Subclinical hypothyroidism may induce changes in basal metabolic rate with subsequent increase in BMI, but obesity can also affect thyroid function via several mechanisms such as lipotoxicity and changes in adipokines and inflammatory cytokine secretion. The present study investigated the complex and mutual relationships between the thyroid axis and adiposity.

Insulin Resistance in Association with Thyroid Function, Psychoemotional State, and Cardiovascular Risk Factors

Background: Individuals with insulin resistance (IR) have a high risk of diabetes or metabolic syndrome, and they are more likely to have depression. Furthermore, IR by itself is a major cardiovascular risk factor in healthy persons. Thus, we aimed to investigate IR in association with thyroid function, psychoemotional state, and cardiovascular risk factors among 45–84-year-old citizens of Palanga. Methods: A randomized epidemiological study was performed with 850 subjects. All participants were evaluated for sociodemographic, clinical, and cardiovascular risk factors and biochemical analysis. IR was evaluated by the homeostasis model assessment of IR (HOMA-IR). Results: All study participants were stratified into groups without IR (HOMA-IR ≤ 2.7) and with IR (HOMA-IR > 2.7). The analysis of parameters between the two study groups showed some statistically significant relationships between IR and cardiovascular risk factors. The predictable accuracy was presented using receiver performance characteristic curves for HOMA-IR scores in women and men separately. If the HOMA-IR score is higher than 3.45, individuals are significantly more likely to have type 2 diabetes mellitus (T2DM). Conclusions: An increase of fasting glucose and more frequent incidence of metabolic syndrome, diabetes, and cardiovascular diseases in subjects with IR are associated with the prevalence of cardiovascular risk factors. There was no significant association between thyroid function and HOMA-IR. HOMA-IR cut-offs could predict the presence of T2DM.

Association between blood lead levels and metabolic syndrome considering the effect of the thyroid-stimulating hormone based on the 2013 Korea National health and nutrition examination survey

Imbalances in thyroid-stimulating hormone (TSH) levels are associated with metabolic syndrome (MetS), and the underlying mechanism is partly in alignment with that of lead exposure causing MetS. Many studies have reported the association between lead exposure and MetS, but no study has considered the possibility of TSH mediating lead's effect on MetS. Therefore, we aimed to examine the association between lead exposure and MetS considering TSH as a partial mediator. The data of 1,688 adults (age ≥19 years) from the Korea National Health and Nutrition Examination Survey in 2013 were analyzed. The prevalence of MetS in the Korean population was 21.9%, and the geometric mean of blood lead and serum TSH levels were 1.96 μg/dL and 2.17 μIU/mL, respectively. The associations between blood lead levels, serum TSH levels, and MetS were determined through a multiple logistic regression analysis. Blood lead levels were positively associated with high TSH levels (upper 25%) with an odds ratio (OR) and 95% confidence interval (CI) of 1.79 (1.24, 2.58) per doubled lead levels. The increase in blood lead and serum TSH levels both positively increased the odds of developing MetS. The OR of MetS per doubling of blood lead level was 1.53 (1.00, 2.35), and was not attenuated after adjusting for TSH levels. These findings suggest that higher levels of blood lead are positively associated with serum TSH levels and MetS. By exploring the role of TSH as a partial mediator between lead and MetS, we verified that lead exposure has an independent relationship with MetS, regardless of TSH levels.

Evaluation of biochemical markers of kidney function in patients with subclinical hypothyroidism in comparison with euthyroid people

Background:

Subclinical hypothyroidism (SCH) as a compensated or preclinical type of primary and overt hypothyroidism (OHT) can affect approximately 4–10% of the general population. Treating SCH can slowdown the progression to OHT, the formation of cardiovascular diseases, neuropsychiatric symptoms, and other miscellaneous problems.

Materials and Methods:

The present study is a case-control study that was conducted on 239 adults who were referred to 501 Imam Reza Hospital from March 2019 up to September 2019. Of the 239 patients and their families admitted to the hospital, 121 (50.6%) were euthyroid (as control group) and the remaining participants (118, 49.4%) were SCH (as case group). The serum levels of thyroid stimulating hormone (TSH), urea, uric acid, creatinine, T3, and T4 were asked to be determined at a single laboratory. Biochemical markers of kidney function and the level of thyroid hormones were compared between the two groups of euthyroid and SCH.

Results:

TSH was significantly higher in SCH (7.25 (4.4-18.15)) compared to euthyroid (1.4 (0.2-3.7)) patients (P < 0.001). Among biochemical markers, creatinine (P < 0.001) and uric acid (P = 0.006) had higher serum levels in the case group. There was no remarkable difference in the thyroxine hormone levels and urea between the euthyroid and SCH patients (P > 0.05). Within the SCH group, there was a significant positive correlation between TSH and the level of creatinine (P = 0.001, r = 0.302).

Conclusion:

Regular monitoring of the major function of the kidneys in patients with hypothyroidism and SCH can help early diagnosis of kidney dysfunction, thus increasing the chance of restoring normal kidney function.

Sex differences in subclinical hypothyroidism and associations with metabolic risk factors: a health examination-based study in mainland China

BACKGROUND

The association between subclinical hypothyroidism (SCH) and metabolic risk factors in the general health examination-based population has been widely explored. However, the results have been inconclusive. Additionally, the sex differences in the prevalence of SCH and the association of SCH with metabolic risk factors remain unknown.

METHODS

We conducted this cross-sectional study using data from health examination-based participants between June 2016 and April 2018 in our health examination centre. Sex differences SCH and the association of SCH with metabolic risk factors were explored.

RESULTS

The total prevalence of SCH was 3.40% among the 5319 included participants, and 4.90% among the 2306 female participants, which was much higher than the prevalence of 2.26% among the 3013 male participants (p < 0.05). In males, the difference between participants younger than 60 and aged 60 or older was not significant (p = 0.104); while in females, the difference between participants younger than 40 and participants aged 40 or older was statistically significant (p = 0.023). Multivariate logistic regression analysis demonstrated that age (OR = 0.568, p = 0.004), body-mass index (BMI) (OR = 5.029, p < 0.001) and systolic/diastolic blood pressure (SBP/DBP) (OR = 5.243, p < 0.001) were independent predictors of SCH in females, but no metabolic risk factor was significantly associated with SCH in males. Further analysis revealed that the prevalence was much higher in participants with one or two metabolic risk factors than in those with no above metabolic risk factors regardless of age (p < 0.01).

CONCLUSIONS

Our study demonstrates that high BMI and/or high blood pressure are associated with SCH in female participants, and the prevalence of SCH among women with one or two metabolic risk factors ranges from 7.69-14.81%, which indicates that in such a population, serum concentrations of TSH and FT4 may be routinely screened in mainland China. Certainly, prospective, large-scale studies with long follow-up period are still necessary to further verify our results.

The role of thyroid hormone in metabolism and metabolic syndrome

Metabolic syndrome (MetS) and thyroid dysfunction are common in clinical practice. The objectives of this review are to discuss some proposed mechanisms by which thyroid dysfunctions may lead to MetS, to describe the bidirectional relationship between thyroid hormones (THs) and adiposity and finally, to resume a list of recent studies in humans that evaluated possible associations between thyroid hormone status and MetS or its clinical components. Not solely THs, but also its metabolites regulate metabolic rate, influencing adiposity. The mechanisms enrolled are related to its direct effect on adenosine triphosphate (ATP) utilization, uncoupling synthesis of ATP, mitochondrial biogenesis, and its inotropic and chronotropic effects. THs also act controlling core body temperature, appetite, and sympathetic activity. In a bidirectional way, thyroid function is affected by adiposity. Leptin is one of the hallmarks, but the pro-inflammatory cytokines and also insulin resistance impact thyroid function and perhaps its structure. MetS development and weight gain have been positively associated with thyroid-stimulating hormone (TSH) in several studies. Adverse glucose metabolism may be related to hyperthyroidism, but also to reduction of thyroid function or higher serum TSH, as do abnormal serum triglyceride levels. Hypo- and hyperthyroidism have been related to higher blood pressure (BP), that may be consequence of genomic or nongenomic action of THs on the vasculature and in the heart. In summary, the interaction between THs and components of MetS is complex and not fully understood. More longitudinal studies controlling each of all confounding variables that interact with endpoints or exposure factors are still necessary.

The Association Between Serum Thyrotropin Within the Reference Range and Metabolic Syndrome in a Community-Based Chinese Population

PURPOSE

We aimed to ascertain the association between thyrotropin (TSH) levels in euthyroid state and the prevalence of metabolic syndrome (MetS) in a community-based Chinese population.

PARTICIPANTS AND METHODS

Based on a large and well-characterized community cohort in Beijing, China, 1831 men and 1742 women with serum TSH levels within the reference range (0.50-4.78 µIU/mL) were stratified by quartiles of TSH (Q1-4). MetS was identified according to the criteria of International Diabetes Federation guidelines. Poisson regression models were used to estimate the association between serum TSH and the prevalence of MetS and its components before and after adjustment for potential confounding factors. The reported association was measured using the prevalence ratio (PR) with its respective 95% confidence interval (95% CI).

RESULTS

The prevalence of MetS in euthyroid population across TSH quartiles (Q1-4) was 38.9%, 44.6%, 41.0%, and 47.7%, respectively, in men (P = 0.045), and 47.7%, 46.6%, 46.9%, and 54.6%, respectively, in women (P = 0.032). Compared with the reference group TSH-Q1, the prevalence of MetS was higher among TSH-Q4 group both in men (PR = 1.27; 95% CI: 1.09, 1.48, P = 0.002) and women (PR = 1.21; 95% CI: 1.07, 1.37, P = 0.003) even after adjustment for age, lifestyle factors, serum levels of free triiodothyronine (FT3), and free thyroxine (FT4). Most of the components of MetS were common in higher serum TSH levels within the normal range.

CONCLUSION

The prevalence of MetS and most of its components increased in the higher TSH group in euthyroid Chinese population.

The Relationship between Thyroid Function and Different Obesity Phenotypes in Korean Euthyroid Adults

BACKGROUND

Thyroid disease and metabolic syndrome are both associated with cardiovascular disease. The aim of this study was to investigate the correlation between thyroid hormones and obesity sub-phenotypes using nationwide data from Korea, a country known to be iodine replete.

METHODS

This study was based on data obtained from the sixth Korea National Health and Nutrition Examination Survey, administered from 2013 to 2015. A total of 13,873 participants aged ≥19 years were included, and classified into four groups: metabolically healthy non-obesity (MHNO), metabolically healthy obesity (MHO), metabolically unhealthy non-obesity (MUNO), and metabolically unhealthy obesity (MUO) by body fat on the basis of body mass index and metabolic health.

RESULTS

At baseline, serum free thyroxine (fT4) values were significantly higher in the MHNO phenotype (MHNO, 1.27±0.01 ng/dL; MHO, 1.25±0.01 ng/dL; MUNO, 1.24±0.01 ng/dL; MUO, 1.24±0.01 ng/dL, P<0.001) in total study population. However, this significant association no longer remained after adjustment for age, urine iodine concentration, and smoking (P=0.085). After adjustment for confounders, statistically significant association was observed between lower thyroid stimulating hormone (TSH) and MHNO phenotype (P=0.044). In men participants (not women), higher fT4 values were significantly associated with MHNO phenotype (P<0.001). However, no significant association was observed between thyroid function (TSH or fT4) and obesity phenotypes in groups classified by age (cutoff age of 55 years).

CONCLUSION

Although there was a difference by age and sex, we found that the decrease of TSH and the increase of fT4 values were associated with MHNO.

The Effects of Dyslipidemia in Subclinical Hypothyroidism

Background

Subclinical hypothyroidism (SCH) affects 7.5-8.5% of women and 2.8-4.4% of men globally. Usually, both hypothyroidism and hyperthyroidism are related to cardiovascular and cerebrovascular disease development. The relationship between subclinical hypothyroidism and dyslipidemia has been widely investigated, but the findings remain controversial. Recent evidence shows that serum thyroxine (T4) replacement therapy may improve lipid profiles. The objective of the present study is to assess dyslipidemia among patients with SCH in Benghazi, Libya and compare it with controls.

Methods

The study was conducted from August 2018 to November 2018 and included 36 patients with SCH. All the patients were around 30 years of age. We also included sex-matched healthy subjects (controls) selected from three diabetes and endocrinology clinics in Benghazi: Alhaya clinic, Alrazy clinic, and Alnukbah clinic. Clinical information and medical history were obtained through a questionnaire from all SCH patients and normal control subjects. Blood samples were collected and analyzed for thyroid-stimulating hormone (TSH), free thyroxine (FT4), total cholesterol (T-Chol), serum triglycerides (STG), low-density lipoprotein-cholesterol (LDL-C), and high-density lipoprotein-cholesterol (HDL-C).

Results

Patients with SCH showed significantly higher T-Chol, STG, and LDL-C levels, as well as significantly lower levels of HDL-C in comparison to the healthy controls. No significant correlation was found between TSH and T-Chol, STG, HDL-C, and LDL-C; no significant correlation was found between FT4 and HDL-C either. However, a strong negative correlation was found between FT4 and T-Chol, STG, and LDL-C.

Conclusion

Our study concluded that SCH is associated with dyslipidemia. We strongly recommend biochemical screening for thyroid dysfunction for all patients with dyslipidemia.

Thyroid disease and the metabolic syndrome

PURPOSE OF REVIEW

To summarize recent developments in the association of thyroid function with metabolic syndrome (MetS).

RECENT FINDINGS

Although thyroid hormones even within low normal range are associated with various metabolic abnormalities, the risk of MetS remains a controversial issue. Hyperthyroid state might be associated only with insulin resistance and dysglycemia. Autoimmune thyroid diseases may be a potential risk factor for metabolic abnormalities even in those with low normal thyroid function.

SUMMARY

The interrelation between thyroid stimulating hormone, free T3, freeT4 and metabolic parameters is complex and might be affected by age, sex, BMI, insulin resistance, smoking, iodine intake and inflammatory markers.

High TSH Level within Normal Range Is Associated with Obesity, Dyslipidemia, Hypertension, Inflammation, Hypercoagulability, and the Metabolic Syndrome: A Novel Cardiometabolic Marker

(1) Background: Overt and subclinical hypothyroidism has been associated with increased cardiometabolic risks. Here we further explore whether thyroid function within normal range is associated with cardiometabolic risk factors in a large population-based study. (2) Methods: We screened 24,765 adults participating in health examinations in Taiwan. Participants were grouped according to high-sensitive thyroid-stimulating hormone (hsTSH) level as: <50th percentile (0.47–1.48 mIU/L, the reference group), 50–60th percentile (1.49–1.68 mIU/L), 60–70th percentile (1.69–1.94 mIU/L), 70–80th percentile (1.95–2.3 mIU/L), 80–90th percentile (2.31–2.93 mIU/L), and >90th percentile (>2.93 mIU/L). Cardiometabolic traits of each percentile were compared with the reference group. (3) Results: Elevated hsTSH levels within normal range were dose-dependently associated with increased body mass index, body fat percentage, waist circumferences, blood pressure, hemoglobin A1c (HbA1c), fasting insulin, homeostasis model assessment of insulin resistance (HOMA-IR), high homeostasis model of assessment of beta-cell (HOMA-β), triglycerides, total cholesterols, fibrinogen, and uric acids (p-for-trend <0.001), but not with fasting glucose levels. The association remained significant after adjustment of age, sex, and lifestyle. As compared to the reference group, subjects with the highest hsTSH percentile had significantly increased risk of being overweight (adjusted odds ratio (adjOR): 1.35), increased body fat (adjOR: 1.29), central obesity (adjOR: 1.36), elevated blood pressure (adjOR: 1.26), high HbA1c (adjOR: 1.20), hyperinsulinemia (adjOR: 1.75), increased HOMA-IR (adjOR: 1.45), increased HOMA-β (adjOR: 1.40), hypertriglyceridemia (adjOR: 1.60), hypercholesterolemia (adjOR: 1.25), elevated hsCRP (adjOR: 1.34), increased fibrinogen (adjOR: 1.45), hyperuricemia (adjOR: 1.47), and metabolic syndrome (adjOR: 1.42), but significant risk of low fasting glucose (adjOR: 0.89). Mediation analysis indicates that insulin resistance mediates the majority of the association between thyroid hormone status and the metabolic syndrome. (4) Conclusion: Elevated hsTSH within the normal range is a cardiometabolic risk marker associated with central obesity, insulin resistance, elevated blood pressure, dyslipidemia, hyperuricemia, inflammation, and hypercoagulability.

Thyroid Dysfunction and Diabetes Mellitus: Two Closely Associated Disorders

Thyroid dysfunction and diabetes mellitus are closely linked. Several studies have documented the increased prevalence of thyroid disorders in patients with diabetes mellitus and vice versa. This review critically discusses the different underlying mechanisms linking type 1 and 2 diabetes and thyroid dysfunction to demonstrate that the association of these two common disorders is unlikely a simple coincidence. We assess the current state of knowledge on the central and peripheral control of thyroid hormone on food intake and glucose and lipid metabolism in target tissues (such as liver, white and brown adipose tissue, pancreatic β cells, and skeletal muscle) to explain the mechanism linking overt and subclinical hypothyroidism to type 2 diabetes and metabolic syndrome. We also elucidate the common susceptibility genes and the pathogenetic mechanisms contributing to the autoimmune mechanism involved in the onset of type 1 diabetes mellitus and autoimmune thyroid disorders. An untreated thyroid dysfunction can impair the metabolic control of diabetic patients, and this association can have important repercussions on the outcome of both of these disorders. Therefore, we offer recommendations for the diagnosis, management, and screening of thyroid disorders in patients with diabetes mellitus, including the treatment of diabetic patients planning a pregnancy. We also discuss the major causes of failure to achieve an optimal management of thyroid dysfunction in diabetic patients and provide recommendations for assessing and treating these disorders during therapy with antidiabetic drugs. An algorithm for a correct approach of these disorders when linked is also provided.

Decreased circulating levels of ANGPTL8 in Graves' disease patients

BACKGROUND

Angiopoietin-like protein 8 (ANGPTL8), a newly identified hormone, has been recently characterized as a metabolic regulator which can affect energy homeostasis and has interesting potentials as a metabolic disease therapy. However, little is as yet known as to whether circulating ANGPTL8 levels are altered in thyroid dysfunction. This study measured serum ANGPTL8 levels in patients with Graves' disease and explored the correlations between its serum levels and thyroid index in Graves' disease.

METHODS

The concentration of ANGPTL8 was analyzed in blood samples of 128 well-characterized individuals whose anthropometric parameters, biochemical parameters, and thyroid index were measured. The participants were divided into Graves' disease patients (n = 60) and healthy control subjects (n = 68). Logistic regression was used to evaluate the relationship between ANGPTL8 and Graves' disease.

RESULTS

Serum ANGPTL8 levels were more significantly decreased in Graves' disease patients than in healthy control subjects (177.67 ± 135.07 vs 326.41 ± 194.72 pg/mL; p < 0.001). Serum ANGPTL8 was negatively correlated with free triiodothyronine (FT3), free thyroxine (FT4), and thyroid peroxidase antibodies (TPOAb) while being positively correlated with thyrotropin (TSH). Logistic regression analyses demonstrated that serum ANGPTL8 was significantly associated with Graves' disease (p < 0.05).

CONCLUSIONS

Circulating concentrations of ANGPTL8 showed a significant reduction in Graves' disease patients. Thus, it is suggested that thyroid function should be taken into consideration when evaluating the results of ANGPTL8.

Thyroid disorders in Brazil: the contribution of the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

Thyroid disorders are common diseases, both in Brazil and worldwide. The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study that investigates cardiovascular diseases, diabetes, and associated factors, including non-classical cardiovascular risk factors such as thyroid function. Thyroid function was classified according to thyrotropin stimulating hormone (TSH), free thyroxine (FT4), and use of medication to treat thyroid disorders, after excluding participants who reported use of any medication that could alter the results of the TSH and FT4 tests. All analyses included in this review are cross-sectional using baseline data (2008 to 2010). The results showed an association of subclinical thyroid disorders with biomarkers of subclinical atherosclerosis, measured by carotid intima-media thickness and coronary artery calcium, insulin resistance, metabolic syndrome, and some psychiatric disorders. No association was found with the biomarker of inflammation high-sensitivity C-reactive protein, or changes in pulse wave velocity or heart rate variability.

Hypothyroidism and nonalcoholic fatty liver disease - a chance association?

Background Nonalcoholic fatty liver disease (NAFLD) defines the clinical-pathological spectrum of hepatic lipotoxicity, which may progress to hepatic fibrosis and its complications. Thyroid hormone is a master regulator of cell metabolism and body fat distribution. Whether hypothyroidism is associated or not with an increased risk of developing NAFLD and its fibrotic progression is both clinically and physiopathologically relevant. Indeed, answering this research question would carry major pathogenic and therapeutic implications. Method PubMed database was searched using relevant key-words such as hypothyroidism; NAFLD; nonalcoholic steatohepatitis; cirrhosis; hepatocellular carcinoma; epidemiology; pathogenesis; natural history. The epidemiological studies and the meta-analyses published so far were identified as well as those studies addressing the physiopathology underlying this association. Results Many observational studies have investigated the association between either subclinical or overt hypothyroidism and NAFLD. Data are conflicting: some original and meta-analytical studies demonstrated that hypothyroidism, (mainly subclinical hypothyroidism), was common, occurring in approximately 25% of individuals with imaging-defined or biopsy-proven NAFLD; other studies, however, failed to identify a significant association between hypothyroidism and NAFLD. Moreover, such an association is biologically plausible based on the specific physiopathological impact of thyroid hormone and thyroid stimulating hormone (TSH) on metabolism of hepatocytes and accumulation and distribution of body fat. Conclusions The findings from the present review support a significant association between primary hypothyroidism and risk of development and progression of NAFLD. However, further studies evaluating the relative importance of subclinical versus overt hypothyroidism as well as addressing the mechanisms underlying the association of hypothyroidism with NAFLD are eagerly awaited.

Subclinical hypothyroidism is not a risk factor for polycystic ovary syndrome in obese women of reproductive age

Obese women are at high risk for polycystic ovary syndrome (PCOS). Subclinical hypothyroidism (SCH) has been associated with weight gain, insulin resistance and impaired fertility, which are also factors involved in PCOS. However, there is limited information regarding the influence of SCH on the presence of PCOS. In order to determine whether SCH increases the prevalence of PCOS, we performed a cross-sectional study in a cohort of reproductive-aged obese women. All subjects underwent anthropometric evaluation, laboratory tests and ultrasound examination. Diagnosis of PCOS was based on the Rotterdam criteria. A total of 534 obese women were included and 108 (20.2%) of them were diagnosed with SCH. Patients with SCH showed similar insulin resistance, comparable androgen levels, and higher triglycerides levels (1.7 vs. 1.5 mmol/L, p = .002) compared to those with normal thyroid status. The frequency of PCOS did not differ between the two groups (56.1% for normal thyroid function vs. 60.2% for subclinical hypothyroidism, p = .514). In logistic regression analysis, SCH was not an independent risk factor for PCOS after adjusting for confounding factors (OR = 0.984, 95% CI 0.581-1.667). For the first time, our results suggest that SCH does not increase the risk of PCOS in obese women of reproductive age.

Exploring the association between thyroid- stimulating hormone and metabolic syndrome: A large population-based study

A growing amount of evidence suggests that thyroid-stimulating hormone (TSH) is associated with cardiometabolic risk. However, there have been few longitudinal studies. The aim of this study was to explore the causal relationship between TSH and metabolic syndrome (MetS) in a large population-based longitudinal study. From 2010 to 2016 at the Health Management Center at Tri-Service General Hospital, 25,121 eligible patients were enrolled in our cross-sectional analyses. Cox proportional hazard models were used to investigate the longitudinal association among hypertension (HTN), prediabetes (pre-DM), MetS, diabetes (DM) and TSH levels (N = 12,463). The average follow-up time was 7.2 years. In the cross-sectional analysis, the OR for MetS was 1.06 (95% CI = 1.03–1.09; P< 0.05), while the ORs for DM, pre-DM or HTN were not statistically significant (all P> 0.05). After dividing TSH levels into four quartiles, the ORs for the presence of MetS determined by comparing the highest TSH quartile with the lowest TSH quartile were 1.37 (95% CI = 1.18–1.60), 1.42 (95% CI = 1.20–1.67), and 1.44 (95% CI = 1.22–1.69) (all, P<0.05) in model 1, model 2 and model 3 respectively. The HR for the incidence of MetS was 1.33 (95% CI = 1.17–1.51; P < 0.05). Our study revealed that TSH levels had a strong association with incident MetS.

The association between thyroid function and incidence of metabolic syndrome in euthyroid subjects: Tianjin chronic low-grade systemic inflammation and health cohort study

OBJECTIVE

Thyroid hormones (THs) are primarily responsible for the regulation of energy homeostasis and metabolism. However, few prospective studies have assessed the association between THs and metabolic syndrome (MetS) in a general population. We therefore designed a cohort study to examine whether serum TH levels within the reference range are predictive factors for developing MetS in adults.

DESIGN

Prospective cohort study.

PARTICIPANTS

A prospective study (n = 6119) was performed in Tianjin, China. Participants without a history of MetS were followed up for 1 to 3 years with a median follow-up duration of 2 years.

MEASUREMENTS

Serum free triiodothyronine (FT3), free thyroxine (FT4) and thyroid-stimulating hormone (TSH) levels were measured by chemiluminescence immunoassay. MetS was defined in accordance with the criteria of the American Heart Association scientific statements of 2009. THs, TSH levels and MetS were assessed yearly during the follow-up. Adjusted Cox proportional hazards regression models were used to assess the associations between FT3, FT4 and TSH quintiles and MetS.

RESULTS

The incidence of MetS was 17.7% (96 per 1000 person-years). In the final multivariate models, the hazard ratios (95% confidence interval) for MetS across serum FT3 quintiles were 1.00 (reference), 1.03 (0.84, 1.25), 1.14 (0.94, 1.38), 1.09 (0.90, 1.32) and 1.33 (1.11, 1.61), respectively (P for trend <.01). However, no significant associations between FT4, TSH and MetS were observed.

CONCLUSIONS

This population-based prospective cohort study suggests that increased serum FT3 level, rather than FT4 and TSH, is an independent predictor for developing MetS in euthyroid subjects.

High free triiodothyronine and free-triiodothyronine-to-free-thyroxine ratio levels are associated with metabolic syndrome in a euthyroid population

AIMS

To determine the association between free triiodothyronine (FT3), free thyroxine (FT4) and free-triiodothyronine-to-free-thyroxine ratio (FT3/FT4) levels and Metabolic Syndrome (MetS).

MATERIALS AND METHODS

We carried out an analytical cross-sectional study in euthyroid adults of both sexes, who attended the outpatient service of a private clinic in Lima-Peru during the 2014-2016 period. Participants were divided into tertiles (low, intermediate and high) according to their FT3, FT4, and FT3/FT4 ratio values. MetS was defined when three or more metabolic criteria were met by the participants. ROC curves were constructed, and Youden's Index were used to identify the optimal cut-points of each thyroid marker. We elaborated crude/adjusted Poisson regression models to evaluate the association between the thyroid markers and the presence of MetS. The reported association measure was the prevalence ratio (PR) with their respective 95% confidence intervals (95% CI).

RESULTS

We analyzed 245 participants, the average age was 38.5 ± 10.3 years, 29.8% were males, and the prevalence of MetS was 31%. In the adjusted Poisson regression models, the prevalence of MetS was higher among the high FT3 tertile compared to the low tertile (aPR = 2.01; 95% CI: 1.22-3.34). The prevalence of MetS was higher among the intermediate FT3/FT4 ratio tertile and the high FT3/FT4 ratio tertile compared to the low tertile, (aPR = 1.78; 95% CI: 1.02-3.10) and (aPR = 2.80; 95% CI: 1.67-4.72); respectively. The highest areas under the curve (AUC) were found for FT3 and FT3/FT4 ratio with areas of 0.654 (95% CI: 0.58-0.73) and 0.649 (95% CI: 0.57-0.72); respectively.

CONCLUSION

Elevated levels of FT3 and FT3/FT4 ratio were associated with MetS in a euthyroid population.

Subclinical hypothyroidism and metabolic risk factors association: A health examination-based study in northern Taiwan

Background

Subclinical hypothyroidism (SCH) is defined as elevation in serum thyroid-stimulating hormone (TSH) levels despite normal serum levels of free thyroxine. It remains controversial whether people with SCH have higher total cholesterol and low-density lipoprotein cholesterol levels compared to normal-thyroid subjects. The aim of this study was to assess the metabolic risk factors for SCH.

Methods

Subjects were recruited from the health examination center of Chang Gung Memorial Hospital, Linkou, from January 1, 2010 to December 31, 2011. This was a cross-sectional review of medical records. The subjects were ethnic Taiwanese residents without known thyroid disease at baseline.

Results

A total of 22,324 subjects received annual health examination at Chang Gung Memorial Hospital from 2010 to 2011. Among them, 15,943 subjects were included as the normal thyroid group (NG), and 203 subjects (101 men and 102 women) met the criteria for SCH. The prevalence of metabolic syndrome (MetS) in the NG was 26.2% in men and 18.7% in women, whereas that in the SCH group was 39.6% in men and 29.4% in women. Women in the SCH group showed significantly higher cholesterol, triglyceride, non-high density lipoprotein (HDL) and cholesterol/HDL levels than those in the NG (p < 0.05).

Conclusion

Because SCH is more prevalent in women and the risk increases with age, greater attention to the risk of MetS development is warranted. As for men, regardless of thyroid function, the risk of MetS development with age still warrants attention. Thus, our data suggest that national guidelines for screening for thyroid disease using serum TSH levels in the elderly are mandatory.

Non-invasive markers of cardiovascular risk in patients with subclinical hypothyroidism: A systematic review and meta-analysis of 27 case control studies

It has been reported that subclinical hypothyroidism (SCH) is closely related to subclinical atherosclerosis. According to the impact of SCH on noninvasive markers of cardiovascular risk, we fulfilled a meta-analysis of included studies to provide an integrated overview. We searched electronic databases and included all relevant studies involving SCH and epicardial adipose tissue (EAT), carotid intima-media thickness (CIMT), pulse wave velocity (PWV), flow-mediated dilation (FMD) and glyceryl trinitrate-induced dilation (GNT- induced dilation). The result was calculated in a meta-analysis to assess the impact of SCH on these markers. A total of 27 studies were entered in the final analysis. Compared with euthyroid subjects, SCH patients exhibited a significantly increased CIMT (SMD: 0.369 mm; 95%CI: 0.038, 0.700; P = 0.029) and EAT (SMD: 1.167 mm; 95%CI: 0.869, 1.466; P = 0.000) and increased PWV (SMD: 3.574 m/s; 95%CI: 0.935, 6.213, P = 0.008). We also found significantly lower FMD (SMD: −1.525%, 95%CI: −2.156, −0.894, P = 0.000) and lower GNT-induced dilation (SMD: −0.384%, 95%CI: −0.625, −0.142, P = 0.002). Sensitivity analysis and subgroup analysis confirmed the above results. Our meta-analysis confirmed a significant association of SCH and cardiovascular risk with arterial wall thickening and stiffening and endothelial dysfunction. These findings will help to establish detailed cardiovascular prevention strategies for SCH patients.

Relationship of metabolic syndrome and its components with thyroid dysfunction in Algerian patients

AIMS

The aim of this study is to evaluate the prevalence of the metabolic syndrome and its compounds in subjects with different thyroid status.

MATERIALS AND METHODS

A prospective cross-sectional study was conducted in the internal medicine department at El Okbi Hospital of Guelma (East of Algeria) from January 2014 to September 2015. Eighty six patients attending the specialist consultation for suspected thyroid disorders were included in the study. Gender; blood pressure; body mass index; and serum levels of fasting glucose, total cholesterol (TC), high-density-lipoprotein cholesterol (HDL-C), low-density-lipoprotein cholesterol, and triglyceride were compared between subjects with hypothyroidism, hyperthyroidism and euthyroidism.

RESULTS AND CONCLUSION

Thyroid dysfunction was found in 59.3% (n=42) patients, hypothyroidism (45.3%) was the major thyroid dysfunction followed by hyperthyroidism (14.0%). Overall, the prevalence of metabolic syndrome was 48.8% (n=42). Subjects with hypothyroidism had significantly higher level of BMI, WC, TC, LDL-C, and higher prevalence of abdominal obesity (84.6%, p<0.01) and hypertension (51.2%, p<0.05). The hyperthyroid group had significantly lower level of TC, LDL-C and HDL-C but a higher level of SBP and UA. Furthermore, abdominal obesity, hypertension and low HDL-C level were the most common metabolic syndrome compounds found in the hyperthyroid group compared to the euthyroid group. We found a positive association between TSH level and the prevalence of the metabolic syndrome.

Evaluation of renal function in subclinical hypothyroidism

INTRODUCTION

Patients with subclinical hypothyroidism (SCH) have a few or no symptoms or signs of thyroid dysfunction and thus by its very nature, SCH is a laboratory diagnosis. Serum creatinine is elevated and glomerular filtration rate (GFR) values are reversibly reduced in overt hypothyroid patients. We hypothesize that SCH also may be associated with low GFR.

AIMS AND OBJECTIVES

The objective of this study was (1) to know the effect of SCH on kidney function, (2) to find the correlation between the renal function parameter creatinine, estimated GFR (eGFR), and thyroid-stimulating hormone (TSH), and (3) to know if creatinine values can be predicted by TSH values in SCH cases.

MATERIALS AND METHODS

This is a hospital-based cross-sectional study for 1 year. A total of 608 subjects of either sex were included in the study and were divided into 3 groups: (1) SCH, (2) overt hypothyroidism (OHT), and (3) euthyroidism (ET). TSH, free triiodothyronine, free thyroxine, and serum creatinine were estimated and eGFR was calculated using modification of diet in renal disease study equation and the chronic kidney disease epidemiology collaboration equations.

RESULTS

Serum creatinine levels were higher and eGFR was lower significantly in the subclinical hypothyroid group when compared to the control ET group (P < 0.001). The overtly hypothyroid group had significantly higher levels of serum creatinine and lower eGFR when compared to both the groups (P < 0.001). Significant correlation between TSH, creatinine, and eGFR was found in OHT group only. Linear regression analysis showed the regression in creatinine upon TSH is attributable to 44.5% among OHT group, 48.2% in SCH group.

CONCLUSION

It can be concluded that the SCH group behaves biochemically similar to OHT group and changes in serum creatinine reflect tissue hypothyroidism in SCH cases.

Thyroid Function in Korean Adolescents with Obesity: Results from the Korea National Health and Nutrition Examination Survey VI (2013-2015)

PURPOSE

In this study, we investigated the status of thyroid function and its association with metabolic risk factors in Korean adolescents.

METHODS

Among 2679 subjects aged 10-19 years who participated in the Korea National Health and Nutrition Examination Survey VI (2013-2015), 1067 adolescents (M = 559, F = 508) with available data on free T4 (FT4) and thyroid-stimulating hormone (TSH) were included. Study participants were classified into normal weight [body mass index (BMI) below 85th percentile, 80.7%], overweight (85th ≤ BMI< 95th percentile, 8.7%), and obesity (BMI ≥ 95th percentile, 10.6%).

RESULTS

With increasing levels of BMI category, the means of TSH increased (2.73 ± 0.06, 2.77 ± 0.02, and 3.24 ± 0.22 mIU/L, P = 0.031) and FT4 decreased (1.30 ± 0.01, 1.26 ± 0.02, and 1.25 ± 0.02 ng/mL, P = 0.001). Positive linear associations were observed between TSH and BMI z-score (P = 0.031), waist circumference (P = 0.013), waist-height ratio (P = 0.002), systolic blood pressure (P = 0.001), total cholesterol (P = 0.008), and triglyceride (P = 0.002) after adjusting for age and sex. With per-unit increase in TSH, the odds ratios of having abdominal obesity (OR = 1.18, 95% CI, 1.01-1.38) and triglyceride ≥ 150 mg/dL (OR = 1.18, 95% CI, 1.04-1.34) were significantly increased after adjusting for age, sex, and BMI.

CONCLUSIONS

In adolescents with obesity, TSH was higher and FT4 was lower than in adolescents with normal weight. Hyperthyrotropinemia was associated with abnormal metabolic risk factors including abdominal obesity and elevated triglyceride.

Variations in Serum Free Thyroxine Concentration Within the Reference Range Predicts the Incidence of Metabolic Syndrome in Non-Obese Adults: A Cohort Study

BACKGROUND

The association of changes in thyroid hormone values over time with the incidence of metabolic syndrome (MetS) has not yet been evaluated. For the first time, this study assessed the effect of thyroid hormone variations in the subclinical and euthyroid range on the incidence of MetS and its components over a 10-year follow-up in an adult population.

METHODS

Data were analyzed from the prospective population-based Tehran Thyroid Study. Of 5786 randomly selected subjects aged ≥20 years, after excluding subjects with MetS (n = 1403), those with serum thyrotropin (TSH) >10 or <0.1 mIU/L (n = 104), those taking thyroid drugs (n = 85) or corticosteroids (n = 97), those with a body mass index (BMI) <18.5 kg/m², those with a glomerular filtration rate <30, and those with a history of cancer (12), data for 2393 subjects were analyzed. Body weight, waist circumference, and blood pressure were measured, and serum concentrations of lipids and lipoproteins, fasting blood glucose, insulin, free thyroxine (fT4), and TSH were assayed at baseline and during three follow-up studies at three-year intervals. MetS was determined using definition of the Joint Interim Statement, adjusted for the Iranian population.

RESULTS

An increase in fT4 values overtime was associated with lower odds of abdominal obesity (odds ratio [OR] = 0.49 [confidence interval (CI) 0.35-0.69]) and hypertriglyceridemia (OR = 0.57 [CI 0.41-0.78]), and with higher odds of hypertension (OR = 1.35 [CI 1.05-1.74]), adjusted for age, sex, smoking, BMI, and Homeostasis Model Assessment Index for Insulin Resistance. fT4 was associated with lower odds of MetS in the crude model, and after adjustment for age, sex, and smoking (OR = 0.59 [CI 0.39-0.9]). This association lost its significance after further adjusting for BMI. In a subgroup analysis of obese (i.e. BMI ≥30 kg/m²) and non-obese (i.e., BMI <30 kg/m²) subjects, fT4 was a significant predictor of MetS only in non-obese subjects after adjusting for age, sex, and smoking (β = 0.49 [CI 0.29-0.83], p = 0.007) and also after further adjustment for Homeostasis Model Assessment Index for Insulin Resistance (β = 0.57 [CI 0.34-0.96], p = 0.03). Serum TSH variations over time were not associated with any of the MetS components or with odds of MetS.

CONCLUSION

A decrease in serum fT4 values is associated with an increased risk for MetS, especially in non-obese adults.

Thyroid functions and serum lipid profile in metabolic syndrome

Background

Thyroid hormones are known to affect energy metabolism. Many patients of metabolic syndrome have subclinical or clinical hypothyroidism and vice versa. To study the correlation of thyroid profile and serum lipid profile with metabolic syndrome.

Method

It is a hospital based cross sectional case-control study carried out in tertiary care health center, we studied thyroid functions test and serum lipid profile in 100 metabolic syndrome patients according to IDF criteria and a similar number of age, gender and ethnicity matched healthy controls.

Result

We found that serum HDL was significantly lower (p < 0.001) in cases (41.28 ± 8.81) as compared to controls (54.00 ± 6.31). It was also found that serum LDL, VLDL, triglyceride levels and total cholesterol were found to be significantly higher (p < 0.001) in cases than controls. Serum TSH levels of subjects in cases group (3.33 ± 0.78) were significantly higher (p < 0.001) than that of controls (2.30 ± 0.91) and significantly lower levels of T₄ (p < 0.001) in the patients of metabolic syndrome (117.45) than in controls (134.64) while higher levels of T₃, although statistically insignificant in the patients of metabolic syndrome.

Conclusion

Thyroid hormones up-regulate metabolic pathways relevant to resting energy expenditure, hence, obesity and thyroid functions are often correlated.

Association of triiodothyronine levels with future development of metabolic syndrome in euthyroid middle-aged subjects: a 6-year retrospective longitudinal study

BACKGROUND

Several cross-sectional studies have reported that thyroid hormone levels are associated with cardiovascular risk markers and metabolic syndrome (MetS) even in euthyroid subjects. However, the prognostic role of serum thyroid hormone levels in the risk of incident MetS has not been elucidated.

AIM

We aimed to investigate the associations of baseline serum thyroid hormone levels with the development of MetS in healthy subjects.

METHODS

This 6-year, cross-sectional, longitudinal and follow-up study was conducted in 12 037 euthyroid middle-aged subjects without MetS subjected to comprehensive health examinations. Subjects were grouped according to total triiodothyronine (T3) quartiles. The hazard ratio (HR) for the development of MetS according to T3 quartiles was estimated using Cox proportional hazards model.

RESULTS

During the 6-year period, 3544 incident cases of MetS (29%) were identified. The proportion of subjects with incident MetS increased across the T3 quartiles (P for trend <0.001). The HR and 95% confidence interval (CI) for the development of MetS were significantly higher in the highest T3 quartile compared with the lowest T3 quartile even after adjusting for confounding variables including gender, age and smoking (HR: 1.238, 95% CI: 1.128-1.358, P < 0.001).

CONCLUSION

In euthyroid middle-aged subjects, serum T3 levels are associated with increased risk for future development of MetS.

A cross-sectional analysis of the association between age and gender and prescribed minimum benefit chronic disease list conditions among South Africans with concomitant hypertension, diabetes and dyslipidaemia

BACKGROUND

Prescribed Minimum Benefit Chronic Disease List (PMB CDL) conditions are a regulated list of conditions most common to South Africa.

OBJECTIVES

To investigate the prevalence and association between PMB CDL conditions and age and gender among patients with concomitant hypertension, diabetes and dyslipidaemia.

METHODS

The study population consisted of patients (n = 17 866) with a prescription containing at least one co-prescribed antilipemics, antihypertensive and antidiabetic (identified using the MIMS Desk Reference). ICD-10 codes on claims for PMB CDL conditions were counted.

RESULTS

39.5% of patients had a PMB CDL condition. Women had higher odds for hypothyroidism (OR 6.30, 95% CI; 5.52, 7.19, p < 0.001) and lower odds for coronary artery disease (CAD) (OR 0.63, 95% CI; 0.55, 0.72, p < 0.001) than men. In combination with hypothyroidism the odds for CAD were reversed and strongly increased; 3.54 (95% CI; 2.38, 5.25, p < 0.001). The odds for females having cardiac failure (CF) was insignificant and low (OR 0.87, 95% CI; 0.75, 1.01, p = 0.063); however combined with hypothyroidism, the odds increased to 5.35 (95% CI; 3.52, 8.13, p < 0.001).

CONCLUSION

Hypothyroidism was an important discriminating factor for co-morbidity in women with concomitant hypertension, diabetes and dyslipidaemia, in particular with cardiovascular disease.

Association Between Changes in Thyroid Hormones and Incident Type 2 Diabetes: A Seven-Year Longitudinal Study

BACKGROUND

Thyroid hormones are important regulators of glucose homeostasis. However, the association between thyroid hormones within the reference range and type 2 diabetes mellitus (T2DM) remains unclear. The aim of this study was to clarify the incidence of T2DM according to the baseline levels and changes of thyrotropin (TSH) and thyroid hormones (free thyroxine and triiodothyronine) in euthyroid subjects.

METHODS

Among the participants who consecutively underwent thyroid function tests between 2006 and 2012 through a yearly health checkup program, 6235 euthyroid subjects (3619 men and 2616 women) without T2DM were enrolled in the study. The change in each hormone was calculated by subtracting the baseline value from the level at the end of follow-up or one year before the diagnosis of diabetes.

RESULTS

During 25,692 person-years of follow-up, there were 229 new cases of T2DM. After full adjustment for potential confounders including HbA1c and fasting glucose in Cox proportional hazards models, the individuals in the highest tertile of TSH change (2.5-4.2 μIU/mL) had a greater risk of incident T2DM (hazard ratio [HR] = 1.44 [confidence interval (CI) 1.04-1.98], p = 0.027) in comparison with individuals in the lowest tertile (-4.1 to -0.5 μIU/mL). Simultaneously, the highest tertile of triiodothyronine change (16.3-104.7 ng/dL) and free thyroxine change (0.2-1.6 ng/dL) conferred protective effects against diabetes (HR = 0.60 [CI 0.43-0.85], p = 0.002, and HR = 0.34 [CI 0.24-0.48], p < 0.001, respectively) compared with those in the lowest tertile (-76.5 to -1.8 ng/dL and -0.6 to 0.0 ng/dL, respectively). These associations remained significant when each of the hormones was analyzed as a continuous variable. However, baseline levels or tertiles of TSH and thyroid hormones were not associated with the risk of diabetes.

CONCLUSIONS

Individual changes in TSH and thyroid hormones, even within the normal reference range, were an additional risk factor of incident T2DM.

Insulin Resistance: Any Role in the Changing Epidemiology of Thyroid Cancer?

In the past few decades, the incidence of thyroid cancer (TC), namely of its papillary hystotype (PTC), has shown a steady increase worldwide, which has been attributed at least in part to the increasing diagnosis of early stage tumors. However, some evidence suggests that environmental and lifestyle factors can also play a role. Among the potential risk factors involved in the changing epidemiology of TC, particular attention has been drawn to insulin-resistance and related metabolic disorders, such as obesity, type 2 diabetes, and metabolic syndrome, which have been also rapidly increasing worldwide due to widespread dietary and lifestyle changes. In accordance with this possibility, various epidemiological studies have indeed gathered substantial evidence that insulin resistance-related metabolic disorders might be associated with an increased TC risk either through hyperinsulinemia or by affecting other TC risk factors including iodine deficiency, elevated thyroid stimulating hormone, estrogen-dependent signaling, chronic autoimmune thyroiditis, and others. This review summarizes the current literature evaluating the relationship between metabolic disorders characterized by insulin resistance and the risk for TC as well as the possible underlying mechanisms. The potential implications of such association in TC prevention and therapy are discussed.

The effect of glycaemic control in type 2 diabetic patients with subclinical hypothyroidism

OBJECTIVE

The purpose of this study was to investigate the effect of glycaemic control on subclinical hypothyroidism (SCH) in Chinese type 2 diabetic patients.

METHODS

The study included 476 diabetic patients with SCH admitted for treatment of type 2 diabetes. The controls were selected euthyroid patients with similar characteristics regarding [age, body mass index (BMI), gender, previous hypertension or duration of diabetes, and smoke]. Total cholesterol (TC), LDL cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), triglyceride (TG), the homeostatic model assessment of insulin resistance ratio (HOMA-IR), fasting plasma glucose, hemoglobin A_1c (HbA_1c), as well as plasma levels of thyrotrophin, and free thyroxine (FT4) were assessed at baseline and after 6 months of glycaemic control treatment.

RESULTS

The LDL-C level and HOMA-IR value were significantly higher in the SCH group. Glycaemic control reduced HOMA-IR, HbA_1c, LDL-C, and TG level in patients with SCH. Furthermore, glycaemic control plays a negative effect on thyrotrophin in the SCH group, while this effect was not observed in euthyroid subjects. HbA_1c plays a positive correlation with HOMA-IR (r = 0.048, p < 0.001), fasting plasma glucose (r = 0.086, p < 0.001), LDL-C (r = 0.062, p < 0.001) and TG (r = 0.021, p = 0.009).

CONCLUSION

Our study shows that glycaemic control may bring some benefits to type 2 diabetic patients with SCH.

Thyroid function and cardiovascular disease risk factors in euthyroid adults: a cross-sectional and longitudinal study

OBJECTIVE AND DESIGN

We explored the cross-sectional and longitudinal associations of thyroid function within the normal range with cardiovascular disease (CVD) risk factors and adiposity measures.

PATIENTS AND MEASUREMENTS

A total of 3483 (50·4% women) participants for the cross-sectional CVD study and 1630 (41·2% women) participants for the cross-sectional body composition substudy were drawn from the Framingham Third Generation Exam 1; 2912 participants (50·1% women) for the longitudinal CVD study and 713 participants (35·9% women) for the longitudinal body composition substudy were drawn from the Framingham Third Generation Exams 1-2. Thyroid function was assessed by thyrotropin [thyroid-stimulating hormone (TSH)] and free thyroxine (fT4) concentrations within the reference range at Exam 1. The associations between thyroid function and CVD risk factors were modelled via multivariable-adjusted regression models. Multivariable adjustment included age, sex, current smoking, postmenopausal status and BMI.

RESULTS

Cross-sectionally, higher TSH concentration was associated with increased odds of hypertriglyceridaemia [odds ratio (OR)=1·10], and higher BMI (β = 0·19 kg/m² ), total cholesterol (β = 0·05 mmol/l), triglycerides (β = 0·0006 mmol/l) and subcutaneous adipose tissue (SAT) volume (β = 38·8 cm³ ) (all P < 0·05). Cross-sectionally, fT4 was inversely associated with metabolic and adiposity-related CVD risk factors, including obesity (OR = 1·17), hypertriglyceridaemia (OR = 1·09), BMI (β = 0·42 kg/m² ), total cholesterol (β = 0·05 mmol/l), triglycerides (β = 0·0002 mmol/l), visceral adipose tissue (VAT) volume (β = -20·7 cm³ ) and attenuation (0·17 HU) and VAT/SAT ratio (β = -0·01) (all P < 0·05). However, during 6·1 years of follow-up, baseline TSH and fT4 levels were not longitudinally associated with CVD risk factors and adiposity measures.

CONCLUSIONS

Thyroid function within the normal range is cross-sectionally, but not longitudinally, associated with CVD risk factors and adiposity measures.

Thyroid dysfunction among type 2 diabetic female Egyptian subjects

Purpose

High prevalence of thyroid disorders is more common in type 1 diabetes compared to type 2 diabetes, due to associated autoimmunity. Hypothyroidism is the most common disorder. The objective was to assess the prevalence of thyroid dysfunction among type 2 diabetic Egyptian females and to find the correlation between metabolic syndrome components and autoimmune thyroid dysfunction.

Materials and methods

The study included 62 type 2 diabetic Egyptian females and 27 sex- and age-matched controls. All patients in the study were subjected to anthropometric measures, including HbA_1c, lipid profile, serum uric acid, thyroid-stimulating hormone (TSH), free triiodothyronine, free thyroxine, anti-thyroid peroxidase (TPO), antithyroglobulin (anti-Tg), and thyroid ultrasound.

Results

Hypothyroidism was found in 45.2% of patients (5.49±3.37 μIU/mL) versus 11.1% of controls (1.79±1.21 μIU/mL) (P<0.001). Anti-TPO was found in 75.8% (347.15±244.87 IU/mL) of patients versus 7.4% (32.89±33.26 IU/mL) of controls (P<0.001). Anti-Tg was found in 61.3% (508.03±369.16 IU/mL) of patients versus 0 (51.26±35.53 IU/mL) controls (P<0.001). A significant positive correlation was found between TSH and antithyroid antibodies (anti-Tg, anti-TPO; P=0.002 and P=0.043, respectively) and between TSH and thyroid-gland volume (P=0.002) in diabetic patients. No correlation was found between any components of metabolic syndrome and thyroid antibodies in diabetic patients.

Conclusion

Autoimmune thyroid disease is more common in Egyptian women with type 2 diabetes than nondiabetic women, and thus points to a role of autoimmunity in the pathogenesis of type 2 diabetes.

The relation between changes in thyroid function and anthropometric indices during long-term follow-up of euthyroid subjects: the Tehran Thyroid Study (TTS)

OBJECTIVE

Uncertainties exist regarding the causal relationship between thyroid function tests (TFT) within the euthyroid range and anthropometric measures. This longitudinal cohort is aimed to examine the relationship between the two conditions.

SUBJECTS AND METHODS

Euthyroid participants of Tehran Thyroid Study (TTS) attending phase I (1999-2001) were included in this study and were followed up to phase IV (2008-2011). TSH and free T4 (fT4) levels as well as weight (Wt), waist circumference (WC), hip circumference (HC) and waist-to-hip ratio (WHR) were measured at both phases.

RESULTS

971 women and 784 men were included in the analysis. During 9.7years of follow-up, increases in TSH levels, Wt and WHR as well as a decrease in fT4 level were observed. Multivariable regression analysis showed a significant relationship between TSH changes and alterations in WC in women (β=0.69, P=0.021) and men (β=0.61, P=0.038). Moreover, a significant negative association of ΔfT4 with changes in weight was documented (β=-0.49, P=0.001 in women and β=-0.56, P<0.001 in men). Additionally, we found a negative relationship between ΔfT4 and ΔHC in men (β=-0.36, P=0.001).

CONCLUSION

In both genders, there was a positive relationship between changes in TSH and waist circumference and conversely a negative association of changes of fT4 levels with weight over time.