Thyroid function is associated with carotid intima-media thickness in euthyroid subjects

Association between eating speed and atherosclerosis in relation to growth differentiation factor-15 levels in older individuals in a cross-sectional study

Although fast eating speed has been associated with cardiovascular risk factors, no studies have reported an association between fast eating speed and atherosclerosis as evaluated by carotid intima-media thickness (CIMT). Rapid glucose ingestion is known to cause glucose spikes, which may accelerate atherogenesis and increase levels of growth differentiation factor 15 (GDF-15). Therefore, GDF-15 levels may influence the association between fast eating speed and atherosclerosis. To evaluate the association between eating speed and atherosclerosis in relation to GDF-15, this cross-sectional study analyzed 742 Japanese aged 60-69 years. They were required to have normal thyroid hormone levels, because both GDF-15 levels and atherosclerosis (CIMT ≥ 1.1 mm) can be influenced by thyroid dysfunction. Participants were stratified by the median GDF-15 level. A significant positive association was observed between fast eating speed and atherosclerosis, but only among participants with a high GDF-15 level: the sex- and age-adjusted odds ratios (95% confidence intervals) were 1.95 (1.09, 3.48) in participants with a high GDF-15 level, and 0.83 (0.37, 1.88) in those with a low GDF-15 level. This association remained even after further adjustment for thyroid function and metabolic factors. Serum concentrations of GDF-15 may mediate the association between fast eating speed and atherosclerosis.

Impaired Thyroid Hormone Sensitivity Increases Risk of Cardiovascular Events in Patients Undergoing Coronary Angiography

CONTEXT

Previous studies found inconsistent results on the relationship between thyroid function and cardiovascular risks.

OBJECTIVE

This study aimed to investigate the association of thyroid hormone sensitivity with the risk of major adverse cardiovascular events (MACE) and cardiovascular death in a euthyroid population undergoing coronary angiography.

METHODS

This prospective cohort study enrolled 1470 euthyroid participants who underwent coronary angiography between March and November of 2013. The participants were followed up from July to November in 2022. Thyrotroph thyroxine resistance index (TT4RI), TSH index (TSHI), and feedback quantile-based index (TFQI) were calculated to evaluate the sensitivity to thyroid hormone. Kaplan-Meier curve and multivariable Cox proportional hazard model were performed to analyze the association between thyroid hormone sensitivity and risk of MACE and cardiovascular death.

RESULTS

Among 1089 participants who completed the follow-up, 342 cases of MACE and 77 cardiovascular deaths were identified during a medium follow-up duration of 111 months. In the multivariable Cox proportional hazard model, the higher levels of TFQI (hazard ratio [HR] = 1.41; 95% CI, 1.08-1.84; P for trend = .01), TT4RI (HR = 1.40; 95% CI, 1.06-1.84; P for trend = .02) and TSHI (HR = 1.61; 95% CI, 1.22-2.13; P for trend = .001) were associated with increased risk of MACE. The higher levels of TFQI (HR = 2.21; 95% CI, 1.17-4.17; P for trend = .02) and TSHI (HR = 2.05; 95% CI; 1.08-3.91; P for trend = .03) were also associated with increased risk of cardiovascular death.

CONCLUSION

Impaired sensitivity to thyroid hormone is associated with higher risks of MACE and cardiovascular death in a euthyroid population undergoing coronary angiography.

Chronic Inflammation Plays a Role of a Bridge Between Cardiovascular Disease and Hyperglycemia

Background: Chronic inflammation is believed to play a key role in managing cardiovascular disease (CVD) and glycometabolism, but the specific effects remain unclear. The subclinical features of CVD events and hyperglycemia linked to inflammatory status were evaluated in this study. In addition, independent factors associated with inflammatory status were identified. Methods: Inflammatory status was measured by high-sensitivity C-reactive protein (hs-CRP), CVD events estimated by carotid intima-media thickness (cIMT), and hyperglycemia determined by glycated hemoglobin (HbA1c). Univariate analysis was performed to identify the characteristics of HbA1c-defined normoglycemia, prediabetes, and diabetes, whereas multivariate linear regression analysis was conducted to identify independent factors that correlated with hs-CRP levels. Results: Compared with HbA1c-defined normoglycemia, individuals with prediabetes and diabetes had significantly higher risks of cIMT thickening [risk ratio (RR) was 2.21 and 2.40, respectively], carotid atherosclerosis (RR was 2.29 and 3.04, respectively), and carotid plaque (RR was 2.15 and 2.63, respectively). Diabetes had higher risks of carotid atherosclerosis (RR was 1.33) and carotid plaque (RR was 1.22) than prediabetes. Increasing prevalence of cIMT thickening, atherosclerosis, and plaque was correlated with hs-CRP levels rising. There was a notable linear relationship between HbA1c and hs-CRP levels (R2 = 0.8685). In addition, both men and women showed an independent correlation of hs-CRP levels with HbA1c and low-density lipoprotein cholesterol, whereas men also had thyroid-stimulating hormone and women had age as an independent factor. Conclusions: Chronic inflammation links hyperglycemia to CVD events, and the relevant risk factors would be potential targets for alleviating inflammation and delaying the progression of the atherogenic process.

Causal Association of Thyroid Signaling with C-Reactive Protein: A Bidirectional Mendelian Randomization

Methods

Based on the latest genome-wide association study summary data, bidirectional two-sample Mendelian randomization (MR) was employed to detect the causal relationship and effect direction between TSH, fT4, and CRP. Furthermore, in view of obesity being an important risk factor of CVD, obesity trait waist-hip ratio (WHR) and body mass index (BMI) were treated as the research objects in MR analyses for exploring the causal effects of TSH and fT4 on them, respectively.

Results

Genetically increased CRP was associated with increased TSH (β = −0.02, P = 0.011) and with increased fT4 (β = 0.043, P = 0.001), respectively, but there was no evidence that TSH or fT4 could affect CRP. In further analyses, genetically increased TSH was associated with decreased WHR (β = −0.02, P = 3.99e − 4). Genetically increased WHR was associated with decreased fT4 (β = −0.081, P = 0.002). Genetically increased BMI was associated with increased TSH (β = 0.03, P = 0.028) and with decreased fT4 (β = −0.078, P = 1.05e − 4). Causal associations of WHR and BMI with thyroid signaling were not supported by weighted median analysis in sensitivity analyses.

Conclusion

TSH and fT4 were increased due to the higher genetically predicted CRP. WHR was decreased due to the higher genetically predicted TSH. These findings will provide reference for the prevention and treatment of inflammation and metabolic syndrome.

Economic and Cardiometabolic Risk Factors Are Predictors of Lower Thyroid Stimulating Hormone (TSH) Levels in Hispanic/Latinx Adults with Euthyroidism-A Community-Based Study

Thyroid hormone abnormalities are among the most common endocrine disorders comorbidly suffered alongside metabolic syndrome and type 2 diabetes mellitus (T2DM), and within the euthyroid range they may also impact other outcomes, such as mood disorders. This study aimed to observationally examine the relationship between TSH and social determinants of health and clinical measures in a euthyroid Hispanic/Latinx patient sample with a diagnosis of anxiety and/or depression disorders from a community health clinic. A needs assessment was completed using a random sample of 100 de-identified medical records of individuals who received free medical care, including mental health, at a community-based clinic. Those with low normal TSH (<2 mIU/L) compared with high normal TSH (≥2 mIU/L) had a greater odds of food insecurity (p = 0.016) and being at 100% of the federal poverty level (p = 0.015). The low normal TSH group had significantly higher fasting glucose (p = 0.046), hemoglobin A1c (p = 0.018), and total cholesterol (p = 0.034) compared with the high normal TSH group. In those with T2DM, individuals with low normal TSH had six-times greater odds of having high fasting glucose (p = 0.022) and high hemoglobin A1c (p = 0.029). These relationships warrant further study, to inform future public health policies and follow-up care for underserved and vulnerable communities.

Assessment of causal direction between thyroid function and cardiometabolic health: a Mendelian randomization study

BACKGROUND

Growing evidence have demonstrated that thyroid hormones have been involved in the processes of cardiovascular metabolism. However, the causal relationship of thyroid function and cardiometabolic health remains partly unknown.

METHODS

The Mendelian randomization (MR) was used to test genetic, potentially causal relationships between instrumental variables and cardiometabolic traits. Genetic variants of free thyroxine (FT4) and thyrotropin (TSH) levels within the reference range were used as instrumental variables. Data for genetic associations with cardiometabolic diseases were acquired from the genome-wide association studies of the FinnGen, CARDIoGRAM and CARDIoGRAMplusC4D, CHARGE, and MEGASTROKE. This study was conducted using summary statistic data from large, previously described cohorts. Association between thyroid function and essential hypertension (EHTN), secondary hypertension (SHTN), hyperlipidemia (HPL), type 2 diabetes mellitus (T2DM), ischemic heart disease (IHD), myocardial infarction (MI), heart failure (HF), pulmonary heart disease (PHD), stroke, and non-rheumatic valve disease (NRVD) were examined.

RESULTS

Genetically predicted FT4 levels were associated with SHTN (odds ratio = 0.48; 95% CI = 0.04−0.82,P = 0.027), HPL (odds ratio = 0.67; 95% CI = 0.18−0.88,P = 0.023), T2DM (odds ratio = 0.80; 95% CI = 0.42−0.86,P = 0.005), IHD (odds ratio = 0.85; 95% CI = 0.49−0.98,P = 0.039), NRVD (odds ratio = 0.75; 95% CI = 0.27−0.97,P = 0.039). Additionally, genetically predicted TSH levels were associated with HF (odds ratio = 0.82; 95% CI = 0.68−0.99,P = 0.042), PHD (odds ratio = 0.75; 95% CI = 0.32−0.82,P = 0.006), stroke (odds ratio = 0.95; 95% CI = 0.81−0.97,P = 0.007). However, genetically predicted thyroid function traits were not associated with EHTN and MI.

CONCLUSIONS

Our study suggests FT4 and TSH are associated with cardiometabolic diseases, underscoring the importance of the pituitary-thyroid-cardiac axis in cardiometabolic health susceptibility.

Association of longitudinal trends in thyroid function with incident carotid atherosclerosis in middle-aged and older euthyroid subjects: the Tianjin Chronic Low-Grade Systemic Inflammation and Health (TCLSIH) cohort study

BACKGROUND

Previous studies have posited that an association exists between thyroid function and the heart and vasculature. It remains unclear, however, whether longitudinal trends in thyroid function contribute to the development of atherosclerosis. We conducted a cohort study to examine the association of longitudinal trends in thyroid function with incident carotid atherosclerosis (CA) in middle-aged and older euthyroid subjects.

METHODS

This cohort study's participants were recruited from the Tianjin Chronic Low-grade Systemic Inflammation and Health Cohort Study in Tianjin, China. Free triiodothyronine (FT3), thyroxine (FT4) and thyroid-stimulating hormone (TSH) were measured using chemiluminescence immunoassay. CA was assessed using carotid ultrasonography. Thyroid function and ultrasonography were assessed yearly during follow-up. Multivariable Cox proportional hazards regression models were used to assess the association between thyroid function and incident CA.

RESULTS

A total of 3,181 participants were enrolled in the cohort study. Within 7,762 person-years of follow-up, 944 participants developed CA, the incidence rate of CA was 122 per 1,000 person-years. The fully adjusted hazards ratios (95% confidence interval) of CA for per 1-unit increase in changes of FT3, FT4 and TSH were 1.34(1.22-1.47), 1.22(1.19-1.26) and 0.92 (0.77-1.09) (P < 0.0001, <0.0001 and = 0.32, respectively), respectively. Similar significant associations between mean levels of FT3 and FT4 and incident CA were observed. However, baseline thyroid function was not associated with incident CA.

CONCLUSIONS

These findings suggest that higher mean levels and higher values of changes in thyroid hormones were associated with a higher risk of incident CA in middle-aged and older euthyroid subjects.

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.

The role of thyroid hormones in carotid arterial wall remodeling in women

INTRODUCTION

Thyroid hormones affect the cardiovascular system, but the precise mechanisms of their effects on the development of atherosclerosis are not entirely clear. The relationship between subclinical hypothyroidism, dyslipidemia and carotid atherosclerosis has been widely investigated, but the findings were controversial. The aim of the present study was to determine whether female subjects with subclinical hypothyroidism (SHypo) have increased carotid intima-media thickness (IMT) compared with euthyroid subjects, as well as to examine the association of SHypo, carotid atherosclerosis and dyslipidemia.

METHODS

This research included 100 women aged 30 to 70 years who were divided into two groups: the SHypo group including subjects with signs of subclinical hypothyroidism and the control group of euthyroid subjects. Carotid IMT thickness using B mode ultrasound was determined and its correlation with serum concentrations of fT4, TSH, CRP, and lipid profile including small dense LDL (sdLDL) was analysed.

RESULTS

Subjects with SHypo had significantly increased carotid IMT (IMT ≥ 75th centile) in all three measured segments of the right (p <0.001) and the left (p = 0.001) carotid artery compared to the control group, with a significantly more frequent appearance of plaque (25% vs. 9%; p = 0.05). Significant positive correlations were found between higher TSH and higher IMT values. Increased age, LDL cholesterol, and TSH predicted thickening of the carotid artery IMT.

CONCLUSIONS

It is important to screen people showing early, subclinical signs of thyroid gland dysfunction due to its impact on carotid atherosclerosis development.

Dyslipidemia, Insulin Resistance, Ectopic Lipid Accumulation, and Vascular Function in Resistance to Thyroid Hormone β

PURPOSE

In resistance to thyroid hormone due to mutations in thyroid hormone receptor β, peripheral tissues are variably refractory to the action of circulating thyroid hormones. We evaluated parameters contributing to atherosclerotic risk in this disorder.

METHODS

We measured low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), high-density lipoprotein cholesterol (HDL-C), nonesterified fatty acids (NEFA), intrahepatic lipid (IHL) and intramyocellular lipid (IMCL), Homeostasis-model assessment of insulin resistance (HOMA-IR), augmentation index (AIx) and pulse wave velocity (PWV), flow-mediated dilatation, and carotid intima-media thickness (cIMT) in an unselected, genetically confirmed cohort of adult RTHβ patients (n = 27-77) and compared these with measurements in healthy subjects (up to n = 100) and thyrotoxic patients (n = 40).

RESULTS

Resistance to thyroid hormone beta (RTHβ) patients exhibited higher LDL-C (P = 0.008) and TG (P = 0.002) and lower HDL-C concentrations (P = 0.015 × 10-2) than control subjects, with LDL-C being higher than in thyrotoxic patients with comparable hyperthyroxinemia. Proprotein convertase subtilisin/kexin 9 (P = 0.002) and apolipoprotein B (P = 0.0009) levels were reduced in thyrotoxic patients but not lower in RTHβ patients or control subjects. Intrahepatic lipid (P = 0.02 × 10-4), IMCL (P = 0.002), HOMA-IR (P = 0.01 × 10-2), and NEFA (P = 0.04 × 10-6) were significantly higher in RTHβ patients than control subjects. Flow-mediated dilatation was increased (P = 0.04) but cIMT (P = 0.71), PWV P = 0.81), and AIx (P = 0.95) were unaltered in RTHβ patients.

CONCLUSIONS

We have documented mixed dyslipidemia with hepatic and IMCL accumulation in RTHβ, suggesting that surveillance for these metabolic abnormalities is warranted. How they combine with enhanced endothelial function and unaltered vessel wall thickness and compliance to determine overall cardiometabolic risk in this disorder remains to be defined.

Assessment of causal association between thyroid function and lipid metabolism: a Mendelian randomization study

Background:

Thyroid dysfunction is associated with cardiovascular diseases. However, the role of thyroid function in lipid metabolism remains partly unknown. The present study aimed to investigate the causal association between thyroid function and serum lipid metabolism via a genetic analysis termed Mendelian randomization (MR).

Methods:

The MR approach uses a genetic variant as the instrumental variable in epidemiological studies to mimic a randomized controlled trial. A two-sample MR was performed to assess the causal association, using summary statistics from the Atrial Fibrillation Genetics Consortium (n = 537,409) and the Global Lipids Genetics Consortium (n = 188,577). The clinical measures of thyroid function include thyrotropin (TSH), free triiodothyronine (FT3) and free thyroxine (FT4) levels, FT3:FT4 ratio and concentration of thyroid peroxidase antibodies (TPOAb). The serum lipid metabolism traits include total cholesterol (TC) and triglycerides, high-density lipoprotein, and low-density lipoprotein (LDL) levels. The MR estimate and MR inverse variance-weighted method were used to assess the association between thyroid function and serum lipid metabolism.

Results:

The results demonstrated that increased TSH levels were significantly associated with higher TC (β = 0.052, P = 0.002) and LDL (β = 0.041, P = 0.018) levels. In addition, the FT3:FT4 ratio was significantly associated with TC (β = 0.240, P = 0.033) and LDL (β = 0.025, P = 0.027) levels. However, no significant differences were observed between genetically predicted FT4 and TPOAb and serum lipids.

Conclusion:

Taken together, the results of the present study suggest an association between thyroid function and serum lipid metabolism, highlighting the importance of the pituitary-thyroid-cardiac axis in dyslipidemia susceptibility.

Association of left ventricular hypertrophy with the level of thyroid hormone in euthyroid state

PURPOSE

It has been demonstrated that variation in thyroid hormone levels even within normal range was associated with increased cardiovascular risk. However, available data are still insufficient on association between left ventricular hypertrophy (LVH) and thyroid hormone levels within euthyroid state.

METHODS

In 69,298 Koreans with euthyroid function, we evaluated association between echocardiographically detected LVH and thyroid hormone levels within the normal range. Study participants were categorized into elderly (age ≥ 40) and younger (age < 40) groups, where subjects were divided into four groups according to quartile levels of thyroxine (FT4), triiodothyronine (FT3), and thyroid-stimulating hormone (TSH). Multivariable adjusted logistic regression analysis was used to calculate odds ratios (ORs) and 95% confidence interval (CI) for LVH (adjusted ORs [95% CI]) across quartile levels of thyroid hormones.

RESULTS

In elderly group, adjusted ORs for LVH generally higher in the first quartile group than other quartile groups, despite no statistical significance in some cases (first quartile: reference, second quartile: 0.86 [0.67-1.11] in TSH, 0.75 [0.58-0.95] in FT4 and 0.63 [0.49-0.81] in FT3, third quartile: 0.70 [0.54-0.92] in TSH, 0.79 [0.61-1.02] in FT4 and 0.72 [0.55-0.93] in FT3, fourth quartile: 0.81 [0.65-1.04] in TSH, 0.85 [0.65-1.10] in FT4 and 0.58 [0.44-0.77] in FT3). This finding was similarly found in the younger group, despite discrepancy in some cases.

CONCLUSION

In euthyroid state, low normal levels in FT4, FT3 and TSH were more strongly associated with LVH.

Association between high normal-range thyrotropin concentration and carotid intima-media thickness in euthyroid premenopausal, perimenopausal and postmenopausal women

OBJECTIVE

There are currently no established cutoff levels for thyrotropin (TSH) within the reference intervals associated with carotid atherosclerosis to prevent the onset of cardiovascular diseases. The present study aimed to determine the TSH cutoff level associated with carotid maximum intima-media thickness (max IMT) in euthyroid premenopausal, perimenopausal and postmenopausal women.

STUDY DESIGN

We conducted a cross-sectional study of 468 euthyroid women who had not been treated for or diagnosed with cardiovascular diseases and/or metabolic disorders among 1221 Japanese women who participated in a comprehensive medical examination at the Hidaka Hospital, Japan. Participants' weight, blood pressure, plasma glucose, serum lipoprotein, free thyroxine and TSH were measured and an interview about menstruation was conducted. Carotid ultrasonography was performed to determine max IMT.

RESULTS

Max IMT significantly increased stepwise as menopausal status progressed (p < 0.001). Serum TSH levels were significantly higher in participants with carotid plaques, defined as max IMT ≥1.1 mm (p = 0.038), and were independently associated with the presence of carotid plaque using multivariate logistic regression analysis (β =1.218, p = 0.036). In postmenopausal women, significantly higher carotid max IMT values were observed in women with serum TSH ≥2.5 μIU/mL compared with women with concentrations <2.5 μIU/mL (p = 0.018) without elevated total cholesterol and low-density lipoprotein cholesterol concentrations. These differences were not observed in premenopausal women.

CONCLUSIONS

Laboratory finding of serum TSH concentration ≥2.5 μIU/mL may be useful to assess risk of atherosclerosis, especially in postmenopausal women.

Vascular Age as a Cardiovascular Risk Marker in Asymptomatic Patients with Type 2 Diabetes

AIM

There is a wide variety of cardiovascular outcomes in patients with type 2 diabetes (T2DM), even in asymptomatic individuals. Carotid intima-media thickness (CIMT) is a marker of subclinical atherosclerosis and can be considered as a predictor of cardiovascular risk (CVR). The aim of this study was to evaluate the relationship between CIMT-determined vascular age (VA), CVR scores, and thyroid function in asymptomatic patients with T2DM.

PATIENTS AND METHODS

Clinical laboratory and CIMT parameters were measured in 154 asymptomatic patients with T2DM. The Framingham risk score (FRS) was performed with chronological age (CA) and with VA. A multinomial logistic regression model was used to analyze variables related to CVR reclassification.

RESULTS

The use of CIMT-determined VA led to the reclassification of 54 (35.52%) out of 152 asymptomatic T2DM patients, being 20 (37.03%) to a lower categorical risk and 34 (62.96%) to a higher categorical risk according to FRS. The variables that were associated to reclassification to a higher categorical risk were positive family history (FH) of premature coronary artery disease (p=0.046), FH of thyroid disease (p=0.010), use of statins (p=0.027), and free T4 levels (p=0.009).

CONCLUSION

VA determined from CIMT allowed the reclassification of the CVR in asymptomatic T2DM patients. FH of premature CAD, FH of known thyroid disease, use of statins, and free T4 levels were associated to a reclassification into a higher risk category. The use of doppler to perform CIMT measure is currently more accessible, especially in a low-middle income country like Brazil. However, further prospective studies must be performed to establish the predictive values of CIMT on atherosclerosis and how thyroid function acts like cardiovascular risk marker on CVR scores.

Calcification Patterns in Papillary Thyroid Carcinoma are Associated with Changes in Thyroid Hormones and Coronary Artery Calcification

Recent studies suggested that a lower serum thyroid hormone level is associated with more vascular calcification. However, it has been rarely evaluated whether lower thyroid hormone levels affect the calcification of thyroid cancer and there is a relationship between calcification patterns of papillary thyroid carcinoma (PTC) and coronary artery calcification (CAC). The study was divided into two groups: First, we retrospectively reviewed 182 PTC patients and examined the correlation between PTC calcification patterns and CAC by coronary computed tomography (CT). Second, the correlation between the calcification pattern of PTC and thyroid hormone concentration was investigated (n = 354). The calcification pattern of PTC was evaluated by thyroid ultrasonography and classified into four groups: no-calcification, microcalcification, macrocalcification, and mixed-calcification. In PTC patients with microcalcification and mixed calcification, more CAC was observed and coronary calcium score (CCS) was higher. Lower free T4 and higher thyroid-stimulating hormone (TSH) levels were associated with microcalcification and mixed calcification, not with macrocalcification and no calcification. PTC with microcalcification and mixed calcification showed more aggressive phenotypes like lymph node metastasis and more advanced TNM (tumor, node, and metastasis) stage than those with no calcification and macrocalcification. Calcification patterns of PTC showed close association with thyroid hormone levels and CAC. Further research is needed to determine how these findings are related to cardiovascular risk and disease-specific mortality.

High-normal serum thyrotropin levels and increased glycemic variability in type 2 diabetic patients

PURPOSE

High-normal thyrotropin (TSH) is related to reduced insulin sensitivity and may contribute to glycemic disorders in diabetes. We investigated the relationship between normal serum TSH levels and glycemic variability in euthyroid type 2 diabetic patients.

METHODS

A total of 432 newly diagnosed type 2 diabetic patients with euthyroid function and normal serum TSH levels were recruited between March 2013 and February 2017. Insulin sensitivity was evaluated by the Matsuda index (ISI_Matsuda) following a 75-g oral glucose tolerance test. Multiple glycemic variability indices, including the mean amplitude of glycemic excursions (MAGE), mean of daily differences (MODD), and standard deviation of glucose (SD), were calculated from glucose data obtained with a continuous glucose monitoring system. Average glucose accessed by 24-h mean glucose (24-h MG) was also calculated.

RESULTS

A normal serum TSH level was positively correlated with MAGE, MODD, SD, and 24-h MG (r = 0.206, 0.178, 0.186, and 0.132, respectively, p < 0.01). After adjusting for somatometric parameters, lipid profiles, ISI_Matsuda, and HbA1c via multiple linear regression analysis, mean differences [B(95% CI)] in MAGE, MODD, SD, and 24-h MG between the patients in the lowest and highest quartiles of TSH levels were 0.128(0.031, 0.226), 0.085(0.022, 0.148), 0.039(0.001, 0.078), and 0.002(-0.264, 0.267) mmol/L, respectively. High-normal TSH was independently associated with MAGE, MODD, and SD, but not 24-h MG.

CONCLUSIONS

High-normal serum TSH is a significant additional risk factor for increased glycemic variability in type 2 diabetic patients.

Relationship of thyroid function with intracranial arterial stenosis and carotid atheromatous plaques in ischemic stroke patients with euthyroidism

This study aimed to help clarify the possible relationships of thyroid function with intracranial arterial stenosis or carotid atheromatous plaques in ischemic stroke patients with euthyroidism. We retrospectively reviewed the medical records of a consecutive series of ischemic stroke patients prospectively entered into the Chengdu Stroke Registry between February 2010 and March2012. We performed univariate and multivariate analysis to assess possible relationships of thyroid function with intracranial artery stenosis or carotid atheromatous plaques. Of the 172 patients analyzed (42 women; 61.7 ± 14.0 years old), 62 (32.0%) had carotid atheromatous plaques, and 81 (47.1%) had intracranial artery stenosis. Free thyroxine levels were lower in patients with carotid atheromatous plaques than in patients without plaques (15.80±2.09 vs. 16.92±2.69, P = 0.005). After adjusting for age, gender, hyperlipidemia, and previous smoking, free thyroxine levels were independently associated with carotid atheromatous plaques (OR 0.73, 95% CI 0.54-0.99, P = 0.04). In contrast, thyroid function indicators showed no associations with intracranial arterial stenosis. In conclusion, low free thyroxine levels were independently associated with carotid atheromatous plaques in ischemic stroke patients with euthyroidism, but thyroid function indicators were not associated with intracranial artery stenosis.

Haemostatic effects of levothyroxine and selenomethionine in euthyroid patients with Hashimoto’s thyroiditis

The aim of this prospective study was to investigate for the first time whether levothyroxine and selenomethionine, administered alone or in combination, affect coagulation and fibrinolysis in Hashimoto’s thyroiditis patients with normal thyroid function tests. A group of 155 ambulatory women with recently diagnosed and previously untreated Hashimoto’s thyroiditis, of whom 149 completed the study, were randomly assigned in a double-blind fashion to six months of treatment with levothyroxine, selenomethionine, levothyroxine plus selenomethionine, or placebo. The control group included 39 matched healthy women. The prothrombin time ratio, the activated partial thromboplastin time, and plasma levels/activities of fibrinogen, factor VII, von Willebrand factor, factor X and plasminogen activator inhibitor-1 (PAI-1) were assessed at baseline and after three and six months of treatment. Compared with the healthy subjects, Hashimoto’s thyroiditis patients exhibited higher plasma levels/activities of all of the parameters studied, as well as were characterised by the abnormal prothrombin time ratio and activated partial thromboplastin time. All these haemostatic disturbances were reduced or normalised by levothyroxine + selenomethionine treatment, while the effect of levothyroxine or selenomethionine was limited to fibrinogen and PAI-1, respectively. Our results demonstrate that euthyroid women with Hashimoto’s thyroiditis are characterised by abnormal coagulation and fibrinolysis. Levothyroxine and selenomethionine, especially if administered together, produce a beneficial effect on haemostasis in euthyroid patients with this disorder.

Note: This study was in part a sub-study of another trial (ACTRN 12611000238976), which assessed the effect of levothyroxine and selenomethionine, administered alone or in combination, on monocyte and lymphocyte cytokine release in Hashimoto“s thyroiditis patients. Trial no.: ACTRN12612000271808.

MMP-9 Levels and IMT of Carotid Arteries are Elevated in Obese Children and Adolescents Compared to Non-Obese

BACKGROUND

Childhood obesity is associated with increased risk of atherosclerosis and cardiovascular disease in adulthood. Increased intima-media thickness (IMT) of the carotid artery is linked to the initiation and progression of the chronic inflammatory processes implicated in cardiovascular disease. Matrix metalloproteinase-9 (MMP-9) plays an important role in the degradation of the extracellular matrix and, consequently, in the development, morphogenesis, repair and remodeling of connective tissues.

OBJECTIVES

(i) to determine and compare the concentrations of MMP-9, tissue inhibitor of metalloproteinase -1 (TIMP-1), and MMP-9/TIMP-1 ratio in obese and non-obese children and adolescents; (ii) to investigate the association of these markers with common and internal IMT of carotid arteries.

METHODS

Cross-sectional study involving 32 obese and 32 non-obese (control) individuals between 8 - 18 years of age.

RESULTS

Significantly (p < 0.05) higher values of MMP-9 concentration, as well as a higher MMP-9/TIMP-1 ratio were detected in the obese group compared to control counterparts. Common and internal carotid IMT values were significantly higher (p < 0.001) in the obese group compared to the control group. Positive correlations were observed between the common carotid IMT values and MMP-9 concentrations as well as MMP-9/TIMP-1 ratio.

CONCLUSIONS

Our data demonstrate that obese children and adolescents present higher mean IMT values, plasma MMP-9 and MMP-9/TIMP-1 ratio compared to the non-obese. Thus, these findings indicate that this group presents a risk profile for early atherosclerosis.

Thyroid function and ischemic heart disease: a Mendelian randomization study

To clarify the role of thyroid function in ischemic heart disease (IHD) we assessed IHD risk and risk factors according to genetically predicted thyroid stimulating hormone (TSH), free thyroxine (FT4) and thyroid peroxidase antibody (TPOAb) positivity. Separate-sample instrumental variable analysis with genetic instruments (Mendelian randomization) was used in an extensively genotyped case (n = 64,374)-control (n = 130,681) study, CARDIoGRAMplusC4D. Associations with lipids, diabetes and adiposity were assessed using the Global Lipids Genetics Consortium Results (n = 196,475), the DIAbetes Genetics Replication And Meta-analysis case (n = 34,380)-control (n = 114,981) study, and the Genetic Investigation of ANthropometric Traits (body mass index in 152,893 men and 171,977 women, waist-hip ratio in 93,480 men and 116,741 women). Genetically predicted thyroid function was not associated with IHD (odds ratio (OR) per standard deviation for TSH 1.05, 95% confidence interval (CI) 0.97 to 1.12; for FT4 1.01, 95% CI 0.91 to 1.12; for TPOAb positivity 1.10, 95% CI 0.83 to 1.46) or after Bonferroni correction with risk factors, except for an inverse association of FT4 with low-density lipoprotein-cholesterol. The associations were generally robust to sensitivity analyses using a weighted median method and MR Egger. This novel study provides little indication that TSH, FT4 or TPOAb positivity affects IHD, despite potential effects on its risk factors.

Metabolic syndrome is associated with an increased incidence of subclinical hypothyroidism - A Cohort Study

Prior cross-sectional analyses have demonstrated an association between subclinical hypothyroidism and metabolic syndrome and selected components. However, the temporal relation between metabolic syndrome and declining thyroid function remains unclear. In a prospective study, an unselected cohort of 66,822 participants with and without metabolic syndrome were followed. A proportional hazards regression model was used to estimate hazard ratios (HRs) and 95% CIs for hypothyroidism. Exploratory analyses for the relation between components of metabolic syndrome and declining thyroid function were also undertaken. During an average follow-up of 4.2 years, the incident rates for subclinical hypothyroidism were substantially higher in participants who began the study with metabolic syndrome compared with metabolically normal controls. After controlling for risk factors, patients with metabolic syndrome were at a 21% excess risk of developing subclinical hypothyroidism (adjusted HR 1.21; 95% CI 1.03–1.42). When individual components were analyzed, an increased risk of subclinical hypothyroidism was associated with high blood pressure (1.24; 1.04–1.48) and high serum triglycerides (1.18; 1.00–1.39), with a trend of increasing risk as participants had additional more components. Individuals with metabolic syndrome are at a greater risk for developing subclinical hypothyroidism, while its mechanisms and temporal consequences of this observation remain to be determined.

Subclinical hypothyroidism, lipid metabolism and cardiovascular disease

Subclinical hypothyroidism is defined by elevated serum thyrotropin in presence of normal free thyroid hormones. Lipid metabolism is influenced by thyroid hormone and many reports showed that lipids status worsen along with TSH level. Subclinical hypothyroidism has been also linked to other cardiovascular risk factors such as alteration in blood pressure and increased atherosclerosis. Further evidences suggested that mild dysfunction of thyroid gland is associated with metabolic syndrome and heart failure. Thyrotropin level seems the best predictor of cardiovascular disease, in particular when its levels are above 10mU/L. However, despite these observations, there is no clear evidence that levothyroxine therapy in subjects with milder form of subclinical hypothyroidism could improve lipid status and the other cardiovascular risk factors. In this review, we address the effect of thyroid hormone and cardiovascular risk, with a focus on lipid metabolism.

Increased leptin/adiponectin ratio relates to low-normal thyroid function in metabolic syndrome

Background

Low-normal thyroid function within the euthyroid range may contribute to increased atherosclerosis susceptibility. The leptin/adiponectin (L/A) ratio is associated with cardiovascular disease and reflects adipose tissue dysfunction. Relationships of the L/A ratio with low-normal thyroid function are unknown.

Methods

Relationships of thyroid stimulating hormone (TSH) and free thyroxine (free T₄) with leptin, adiponectin and the L/A ratio in euthyroid subjects were documented in 67 fasting subjects with metabolic syndrome (Mets) and 86 euthyroid subjects without MetS (TSH and free T₄ levels within the institutional reference range).

Results

Neither plasma leptin nor adiponectin was significantly correlated with TSH or free T₄ in subjects with and without MetS. In the whole group, high sensitivity C-reactive protein (hs-CRP) was positively correlated with the L/A ratio (r = 0.485, P < 0.001). Notably, the L/A ratio was positively correlated with TSH in subjects with MetS (r = 0.252, P = 0.040) but not in subjects without MetS (r = −0.068, P = 0.54; interaction term, P = 0.027). In MetS subjects, the L/A ratio remained positively related with TSH after adjustment for age, sex, diabetes status, hs-CRP and the use of antihypertensive and glucose lowering medication (β = 0.283, P = 0.018), as well as after adjustment for individual MetS components (β = 0.294, P = 0.020).

Conclusions

In the context of MetS, a higher TSH within the euthyroid range confers an increased L/A ratio, a proposed marker of atherosclerosis susceptibility and adipocyte dysfunction.

Association of low baseline free thyroxin levels with progression of coronary artery calcification over 4 years in euthyroid subjects: the Kangbuk Samsung Health Study

OBJECTIVE

Overt and subclinical hypothyroidism are risk factors for atherosclerosis and cardiovascular diseases. It is unclear whether thyroid hormone levels within the normal range are also associated with atherosclerosis measured by coronary artery calcium (CAC).

CONTEXT

This study aimed to examine the relationship between normal variations in thyroid function and changes in CAC.

MEASUREMENTS

We conducted a 4-year retrospective study of 2173 apparently healthy men and women with normal thyroid hormone levels. Their free thyroxin (FT4), free triiodothyronin (FT3) and thyroid-stimulating hormone (TSH) levels were measured by electrochemiluminescent immunoassay. The CAC score (CACS) of each subject was measured by multidetector computed tomography in both 2010 and 2014. Progression of CAC was defined as a CACS change over 4 years > 0.

RESULTS

The mean CACS changes over 4 years by quartiles of baseline FT4 level (lowest to highest) were 12·9, 8·43, 7·82 and 7·81 (P = 0·028). CAC progression was not significantly associated with either the baseline FT3 or TSH levels. The odds ratios (OR) for CAC progression over 4 years (highest vs lowest quartile for baseline FT4) were 0·647 (95% confidence interval (CI) 0·472-0·886) after adjustment for confounding factor, which were attenuated with further adjustment for lipid profiles, homoeostasis model assessment of insulin resistance, high-sensitivity C-reactive protein and hypertension [0·747 (95% CI 0·537-1·038)]. Quartiles of baseline FT3 or TSH level did not show any increased OR for CAC progression after adjustment for confounding factors.

CONCLUSIONS

In this cohort of euthyroid men and women, a low baseline FT4 level was associated with a high risk of CACS progression over 4 years.

Association between Hyperhomocysteinemia and Thyroid Hormones in Euthyroid Diabetic Subjects

Objectives. The concept now emerging is that higher thyroid-stimulating hormone (TSH) and lower thyroid hormone levels within the euthyroid range may adversely affect atherosclerosis. The present study aimed to investigate the potential associations between thyroid parameters and hyperhomocysteinaemia in a cohort of euthyroid diabetic subjects. Material and Methods. Two hundred and seventy-three euthyroid diabetic subjects (167 males and 106 females) were consecutively recruited in this cross-sectional study. Clinical and biomedical data was collected. Results. TSH level was higher in females than males. Compared to normal-homocysteine group, hyperhomocysteinaemia group was more likely to be elderly, males, with longer diabetes history, and with lower diastolic blood pressure. Free thyroxine (FT4) level was lower in hyperhomocysteinaemia group than in normal-homocysteine group; however, it was not statistically significant. Adjusted for age, sex, body mass index, duration of diabetes, blood pressure, fasting glucose, total cholesterol, and triglyceride in logistic regression analyses, hyperhomocysteinaemia was significantly correlated with FT4 (P = 0.021). No significant association was found with TSH or free triiodothyronine. When analyzed in subjects with TSH < 2.5 uIU/mL separately, we got similar results. Conclusions. In conclusion, we identified a relation between hyperhomocysteinemia and FT4 in a group of euthyroid diabetic patients.

High levels of thyroid-stimulating hormone are associated with aortic wall thickness in the general population

OBJECTIVES

Our aim was to investigate the association of thyroid function defined by serum concentrations of thyroid-stimulating hormone (TSH) with thoracic aortic wall thickness (AWT) as a marker of atherosclerotic processes.

METHODS

We pooled data of 2,679 individuals from two independent population-based surveys of the Study of Health in Pomerania. Aortic diameter and AWT measurements were performed on a 1.5-T MRI scanner at the concentration of the right pulmonary artery displaying the ascending and the descending aorta.

RESULTS

TSH, treated as continuous variable, was significantly associated with descending AWT (β = 0.11; 95 % confidence interval (CI) 0.02-0.21), while the association with ascending AWT was not statistically significant (β = 0.20; 95 % CI -0.01-0.21). High TSH (>3.29 mIU/L) was significantly associated with ascending (β = 0.12; 95 % CI 0.02-0.23) but not with descending AWT (β = 0.06; 95 % CI -0.04-0.16). There was no consistent association between TSH and aortic diameters.

CONCLUSIONS

Our study demonstrated that AWT values increase with increasing serum TSH concentrations. Thus, a hypothyroid state may be indicative for aortic atherosclerosis. These results fit very well to the findings of previous studies pointing towards increased atherosclerotic risk in the hypothyroid state.

KEY POINTS

• Serum TSH concentrations are positively associated with aortic wall thickness. • Serum TSH concentrations are not associated with the aortic diameters. • Serum 3,5-diiodothyronine concentrations may be positively associated with aortic wall thickness.

L-Arginine Derivatives Are Associated with the Hyperthyroid State in the General Population

BACKGROUND

Arginine (ARG) derivatives and thyroid function independently influence atherosclerotic processes. Since thyroid hormones may mediate the association between ARG derivatives and atherosclerosis, this study investigated whether asymmetric and symmetric dimethylarginines (ADMA and SDMA, respectively) as well as homoarginine (hARG) are associated with parameters of thyroid function in the general population.

METHODS

Cross-sectional data from 3689 individuals aged 20-81 years from the population-based Study of Health in Pomerania (SHIP-0) were analyzed. Thyroid function was defined according to serum concentrations of thyrotropin (TSH), free triiodothyronine (fT3), and free thyroxine (fT4). Low and high serum TSH were defined by the cutoffs 0.3 mIU/L and 3 mIU/L, respectively. Serum concentrations of ARG, ADMA, SDMA, and hARG were measured using liquid chromatography-tandem mass spectrometry. ARG, ADMA, SDMA, and hARG were associated with serum concentrations of TSH, fT3, and fT4 by median regression and with categorized TSH values by multinomial logistic regression adjusted for age, sex, smoking status, physical activity, body mass index, and estimated glomerular filtration rate.

RESULTS

Levels of ADMA (relative risk [RR] = 5.40 [confidence interval (CI) 1.96-14.86]) and SDMA (RR = 3.55 [CI 1.01-12.70]) were associated with low TSH. In addition, ADMA (β = 0.38 [CI 0.23-0.45]) was positively associated with fT3, while both ADMA (β = 0.98 [CI 0.43-1.54]) and SDMA (β = 1.19 [CI 0.50-1.88]) were positively associated with fT4. No consistent associations of ARG and hARG with thyroid function were detected.

CONCLUSIONS

The positive associations of ADMA and SDMA with low TSH, fT3, and fT4 argue for a relationship of arginine derivatives with increased thyroid function. This suggests that the atherogenic properties of ADMA and SDMA may be partially mediated by thyroid function.

Relationship between thyroid function and carotid artery plaque ulceration

Carotid artery plaque ulceration (PU) is known to be associated with cerebrovascular events (CVE). Even within euthyroid ranges, thyroid function has been reported to be associated with carotid atherosclerosis. However, the relationship between thyroid function and carotid PU remains unclear. Our aim was to determine the relationship between thyroid function and PU in patients with internal carotid artery stenosis (ICS). Records of patients with CVE were retrospectively reviewed. A total of 250 consecutive patients with ICS who had computed tomography angiography (CTA) of the carotid arteries following hospitalization were included in the study. CTA was used for the evaluation of carotid artery plaque morphology and ulceration. Plaque morphology was classified as fatty, mixed or calcified. Patients were divided into two groups according to the presence or absence of PU. Subclinical hypothyroidism (SCH) and hypothyroidism were significantly more common in patients with PU (p < 0.001 and p = 0.003, respectively). Patients with PU had higher incidence of low-normal FT4 levels (p = 0.02). Compared with patients who had no PU, patients with PU had decreased FT4 levels and elevated TSH levels (p = 0.001 and p = 0.001, respectively). TSH level (OR 1.33, p = 0.001), SCH (OR 4.2, p = 0.001), hypothyroidism (OR 3.15, p = 0.037), fatty plaque (OR 2.16, p = 0.01) and calcified plaque (OR 0.19, p < 0.001) were independently associated with PU. Our results suggest that SCH and hypothyroidism could be a risk factor for PU and subsequent CVE. Thyroid functions may be useful for risk stratification of patients with ICS.

No evidence of association between subclinical thyroid disorders and common carotid intima medial thickness or atherosclerotic plaque

BACKGROUND AND AIMS

Increased carotid artery intima-media thickness (IMT) and the presence of plaques have been shown to be predictors of cardiovascular disease. The cardiovascular risk in patients with overt thyroid diseases is related to increased risk of atherosclerosis, but there has been no clear evidence about subclinical disorders. We have assessed whether subclinical thyroid dysfunction is associated with arterial thickening and plaque.

METHODS AND RESULTS

The SardiNIA study is a population-based survey on the Italian island of Sardinia. We reviewed data from 5815 subjects (aged 14-102 years), none of whom had overt hyperthyroidism or hypothyroidism or was taking thyroid medication. Serum thyrotropin (TSH), free thyroxine, together with carotid ultrasound IMT and the presence of common carotid plaques were analysed in all subjects. Possible association of IMT and carotid plaques with thyroid parameters was evaluated by univariate and multivariate analyses. IMT was significantly associated with age, sex, smoking, low density lipoprotein cholesterol (LDL), high density lipoprotein cholesterol, pulse pressure (PP), history of arterial hypertension, diabetes, and previous cardiovascular events (p = 0.001 or lower, R(2) = 0.47). Carotid plaques were predicted by age, sex, LDL, PP, history of diabetes, previous cardiovascular events, and the use of statins (p = 0.029 or lower). Thyroid hormone was not predictive of carotid atherosclerosis when adjusted for confounders.

CONCLUSION

Thyroid hormone is not associated with increased IMT or with the presence of carotid artery plaque. Our data do not support the idea that treating subclinical disorders might help to prevent arterial remodelling or carotid atherosclerosis.

Low serum free thyroxine concentrations associate with increased arterial stiffness in euthyroid subjects: a population-based cross-sectional study

Some studies suggest that even in euthyroid subjects, thyroid function may affect arteriosclerotic risk factors. We aimed to determine whether thyroid hormones or thyroid autoantibodies are associated with arterial stiffness in middle-aged and elderly Chinese subjects with euthyroidism. A cross-sectional, population-based study was conducted in Nanjing, China. A total of 812 euthyroid subjects (mean age [56.75 ± 8.34] years; 402 men) without vascular disease and major arteriosclerotic risk factors were included. Clinical factors, oral glucose tolerance test results, homeostasis model assessment for insulin resistance (HOMA-IR) results, and serum levels of lipids, free triiodothyronine (FT3), free thyroxine (FT4), thyroid-stimulating hormone (TSH), and thyroid autoantibodies were measured. Arterial stiffness was assessed using brachial-ankle pulse wave velocity (baPWV). In Pearson correlation analyses, baPWV correlated inversely with FT4 (r = -0.146, P < 0.001), but not with FT3 (r = 0.008, P = 0.816) or TSH (r = 0.055, P = 0.118). Subsequently, a multiple stepwise regression analysis revealed a significant and independent association of FT4 with baPWV in euthyroid subjects (β = -0.076, P = 0.005). After adjusting for potential cardiovascular risk factors, mean diastolic blood pressure (DBP), HOMA-IR, and baPWV levels decreased across increasing FT4 quartiles (DBP, P < 0.001; HOMA-IR, P < 0.001; baPWV, P = 0.003). No difference in baPWV was observed between the positive and the negative thyroid antibody groups (15.23 ± 3.30 m/s vs. 15.73 ± 3.05 m/s, P > 0.05). FT4 levels were inversely associated with arterial stiffness in euthyroid subjects. A prospective study is warranted to validate whether subjects with low-normal FT4 levels have a high incidence of cardiovascular disease.

Subclinical Hypothyroidism and Cardiovascular Disease

Subclinical hypothyroidism (SCH) is a common disorder that is characterized by elevated thyroid-stimulating hormone levels in conjunction with free thyroxine concentrations within the normal reference range. Thyroid hormones are known to affect the heart and vasculature and, as a result, the impact of SCH on the cardiovascular (CV) system has recently become an important topic of research. Strong evidence points to a link between SCH and CV risk factors such as alterations in blood pressure, lipid levels, and atherosclerosis. Additionally, accumulating evidence indicates that SCH is associated with metabolic syndrome and heart failure. The present review proposes that SCH may be a potentially modifiable risk factor of CV disease and mortality. However, large-scale clinical trials with appropriate power investigating the risks and benefits of SCH treatment are required to determine whether these benefits can be achieved with levothyroxine therapy.

Pre-β-HDL formation relates to high-normal free thyroxine in type 2 diabetes mellitus

OBJECTIVES

Low-normal thyroid function within the euthyroid range may influence plasma lipoprotein levels. Associations between variation in thyroid function and pre-β-high density lipoproteins (pre-β-HDL), i.e. lipid-poor or lipid free HDL particles that act as initial acceptor of cell-derived cholesterol, are unknown. We determined relationships of plasma pre-β-HDL with thyroid function in euthyroid subjects with and without type 2 diabetes mellitus (T2DM).

DESIGN AND SUBJECTS

TSH, free T4, plasma (apo)lipoproteins, pre-β-HDL, pre-β-HDL formation (pre-β-HDL generation during incubation with lecithin:cholesterol acyltransferase being inhibited) and phospholipid transfer protein (PLTP) activity were measured in fasting plasma from 72 T2DM and 82 non-diabetic subjects.

RESULTS

TSH was similar and free T4 was slightly higher (P < 0.05) in T2DM vs. non-diabetic subjects. HDL cholesterol and apoA-I were lower, whereas pre-β-HDL (expressed as % of apoA-I), triglycerides and PLTP activity were higher in T2DM (P < 0.05 to P < 0.001). In T2DM, pre-β-HDL formation (in apoA-I concentration and in % of apoA-I) was positively related to free T4, PLTP activity, total cholesterol and triglycerides (P < 0.05 for each). Multivariable linear regression analyses, adjusted for age, sex, PLTP activity, total cholesterol and triglycerides, demonstrated that pre-β-HDL formation was positively related to free T4 (in apoA-I concentration: β = 0.278, P = 0.014; in % of apoA-I: β = 0.343, P = 0.003) in T2DM, but not in non-diabetic subjects (both P > 0.30; interaction terms: both P < 0.05).

CONCLUSIONS

Variations in thyroid function within the euthyroid range may influence the metabolism of pre-β-HDL in T2DM.

Low-normal thyroid function and the pathogenesis of common cardio-metabolic disorders

BACKGROUND

Subclinical hypothyroidism may adversely affect the development of cardiovascular disease (CVD). Less is known about the role of low-normal thyroid function, that is higher thyroid-stimulating hormone and/or lower free thyroxine levels within the euthyroid reference range, in the development of cardio-metabolic disorders. This review is focused on the relationship of low-normal thyroid function with CVD, plasma lipids and lipoprotein function, as well as with metabolic syndrome (MetS), chronic kidney disease (CKD) and nonalcoholic fatty liver disease (NAFLD).

MATERIALS AND METHODS

This narrative review, which includes results from previously published systematic reviews and meta-analyses, is based on clinical and basic research papers, obtained via MEDLINE and PubMed up to November 2014.

RESULTS

Low-normal thyroid function could adversely affect the development of (subclinical) atherosclerotic manifestations. It is likely that low-normal thyroid function relates to modest increases in plasma total cholesterol, LDL cholesterol and triglycerides, and may convey pro-atherogenic changes in lipoprotein metabolism and in HDL function. Most available data support the concept that low-normal thyroid function is associated with MetS, insulin resistance and CKD, but not with high blood pressure. Inconsistent effects of low-normal thyroid function on NAFLD have been reported so far.

CONCLUSIONS

Observational studies suggest that low-normal thyroid function may be implicated in the pathogenesis of CVD. Low-normal thyroid function could also play a role in the development of MetS, insulin resistance and CKD, but the relationship with NAFLD is uncertain. The extent to which low-normal thyroid function prospectively predicts cardio-metabolic disorders has been insufficiently established so far.

Serum free thyroxine levels are positively associated with arterial stiffness in the SardiNIA study

OBJECTIVE

Thyroid dysfunction may accelerate atherosclerosis. Aortic pulse wave velocity (PWV) is an early index of arterial stiffness and an important risk factor for cardiovascular disease and might therefore be linked to changes in thyroid activity. We investigated the relationship between thyroid function and carotid-femoral PWV, as an index of arterial stiffness.

DESIGN

Cross-sectional cohort study.

PATIENTS

Participants from the SardiNIA study. Those being treated for thyroid diseases were excluded, yielding a sample of 5875 aged 14-102.

MEASUREMENTS

Clinical parameters, blood tests including serum TSH and serum FT4, and carotid-femoral PWV were measured.

RESULTS

After adjusting for confounders, a direct and linear association between FT4 and PWV was shown (multiple regression analysis). The model containing age, mean blood pressure, body mass index, heart rate, FT4, hypertension, diabetes and dyslipidaemia accounted for 55% of the variation in PWV.

CONCLUSIONS

Like several other known risk factors, serum FT4 levels are associated with carotid-femoral PWV, suggesting that high FT4 levels have a detrimental effect on aortic stiffness and may contribute to ageing process of the vascular system. This finding may help to understand the pathogenesis of cardiovascular disease and contribute to improve prevention therapy.

Low-normal thyroid function and novel cardiometabolic biomarkers

The concept is emerging that low-normal thyroid function, i.e., either higher thyroid-stimulating hormone or lower free thyroxine levels within the euthyroid reference range, could contribute to the development of atherosclerotic cardiovascular disease. It is possible that adverse effects of low-normal thyroid function on cardiovascular outcome may be particularly relevant for specific populations, such as younger people and subjects with high cardiovascular risk. Low-normal thyroid function probably relates to modest increases in plasma total cholesterol, low density lipoprotein cholesterol, triglycerides and insulin resistance, but effects on high density lipoprotein (HDL) cholesterol and non-alcoholic fatty liver disease are inconsistent. Low-normal thyroid function may enhance plasma cholesteryl ester transfer, and contribute to an impaired ability of HDL to inhibit oxidative modification of LDL, reflecting pro-atherogenic alterations in lipoprotein metabolism and HDL function, respectively. Low-normal thyroid function also confers lower levels of bilirubin, a strong natural anti-oxidant. Remarkably, all these effects of low-normal thyroid functional status appear to be more outspoken in the context of chronic hyperglycemia and/or insulin resistance. Collectively, these data support the concept that low-normal thyroid function may adversely affect several processes which conceivably contribute to the pathogenesis of atherosclerotic cardiovascular disease, beyond effects on conventional lipoprotein measures.

Thyroid hormone attenuates vascular calcification induced by vitamin D3 plus nicotine in rats

Thyroid hormones (THs) including thyroxine (T4) and triiodothyronine (T3) play critical roles in bone remodeling. However, the role and mechanism of THs in vascular calcification (VC) have been unclear. To explore the pathophysiological roles of T3 on VC, we investigated the changes in plasma and aortas of THs concentrations and the effect of T3 on rat VC induced by vitamin D3 plus nicotine (VDN). VDN-treated rat showed decreased plasma T3 content, increased vascular calcium deposition, and alkaline phosphatase (ALP) activity. Administration of T3 (0.2 mg/kg body weight IP) for 10 days greatly reduced vascular calcium deposition and ALP activity in calcified rat aortas when compared with controls. Concurrently, the loss of smooth muscle lineage markers α-actin and SM22a was restored, and the increased bone-associated molecules, such as runt-related transcription factor2 (Runx2), Osterix, and osteopontin (OPN) levels in calcified aorta, were reduced by administration of T3. The suppression of klotho in calcified rat aorta was restored by T3. Methimazole (400 mg/L) blocked the beneficial effect of T3 on VC. These results suggested that T3 can inhibit VC development.

Effects of levothyroxine replacement therapy on parameters of metabolic syndrome and atherosclerosis in hypothyroid patients: a prospective pilot study

The aim of this study was to investigate the effect of levothyroxine (LT4) replacement therapy during three months on some parameters of metabolic syndrome and atherosclerosis in patients with increased thyroid-stimulating hormone (TSH) level. This study included a group of 30 female patients with TSH level >4 mIU/L and 15 matched healthy controls. Intima media complex thickness (IMCT) and peak systolic flow velocity (PSFV) of superficial femoral artery were determined by Color Doppler scan. In hypothyroid subjects, BMI, SBP, DBP, and TSH were significantly increased versus controls and decreased after LT4 administration. FT4 was significantly lower in hypothyroid subjects compared with controls and significantly higher by treatment. TC, Tg, HDL-C, and LDL-C were similar to controls at baseline but TC and LDL-C were significantly decreased by LH4 treatment. IMCT was significantly increased versus controls at baseline and significantly reduced by treatment. PSFV was similar to controls at baseline and significantly decreased on treatment. In this study, we have demonstrated the effects of LT4 replacement therapy during three months of treatment on correction of risk factors of metabolic syndrome and atherosclerosis.

Association of thyroid-stimulating hormone and cardiovascular risk factors

Thyroid hormone plays an important role in regulating the lipid and glucose metabolism. Previously, much attention has been drawn to define the pathophysiological relationship between thyroid dysfunction and the incidence of cardiovascular diseases (CVDs). While the conditions of overt hypothyroidism and subclinical hypothyroidism were both emphasized, the association between CVD risks and the deregulated circulating thyroid-stimulating hormone (TSH) level remains to be elucidated. Nevertheless, multiple TSH-mediated physiological adaptations, including alteration of the serum lipids, body mass index, blood pressure and insulin sensitivity, have led to the difficulty of clearly examining the association between the TSH level and CVD prevalence. The current review aims to 1) summarize the evidence for the role of thyroid dysfunction and TSH abnormality in CVD pathogenesis and 2) explore the possible underlying molecular mechanisms of TSH-mediated cardiovascular pathology in hopes of providing better therapeutic strategies for the patients with deregulated TSH.

Thyroid hormones and coronary artery calcification in euthyroid men and women

OBJECTIVE

Overt and subclinical hypothyroidism are risk factors for atherosclerosis. It is unclear whether thyroid hormone levels within the normal range are also associated with atherosclerosis measured by coronary artery calcium (CAC).

APPROACH AND RESULTS

We conducted a cross-sectional study of 41 403 apparently healthy young and middle-aged men and women with normal thyroid hormone levels. Free thyroxin, free triiodothyronine, and thyroid-stimulating hormone levels were measured by electrochemiluminescent immunoassay. CAC score was measured by multidetector computed tomography. The multivariable adjusted CAC ratios comparing the highest versus the lowest quartile of thyroid hormones were 0.74 (95% confidence interval, 0.60-0.91; P for trend <0.001) for free thyroxin, 0.81 (0.66-1.00; P for trend=0.05) for free triiodothyronine, and 0.78 (0.64-0.95; P for trend=0.01) for thyroid-stimulating hormone. Similarly, the odds ratios for detectable CAC (CAC >0) comparing the highest versus the lowest quartiles of thyroid hormones were 0.87 (0.79-0.96; P for linear trend <0.001) for free thyroxin, 0.90 (0.82-0.99; P for linear trend=0.02) for free triiodothyronine, and 0.91 (0.83-1.00; P for linear trend=0.03) for thyroid-stimulating hormone.

CONCLUSIONS

In a large cohort of apparently healthy young and middle-aged euthyroid men and women, low-normal free thyroxin and thyroid-stimulating hormone were associated with a higher prevalence of subclinical coronary artery disease and with a greater degree of coronary calcification.

Thyroid hormones and mortality risk in euthyroid individuals: the Kangbuk Samsung health study

CONTEXT

Hyperthyroidism and hypothyroidism, both overt and subclinical, are associated with all-cause and cardiovascular mortality. The association between thyroid hormones and mortality in euthyroid individuals, however, is unclear.

OBJECTIVE

To examine the prospective association between thyroid hormones levels within normal ranges and mortality endpoints.

SETTING AND DESIGN

A prospective cohort study of 212 456 middle-aged South Korean men and women who had normal thyroid hormone levels and no history of thyroid disease at baseline from January 1, 2002 to December 31, 2009. Free T4 (FT4), free T3 (FT3), and TSH levels were measured by RIA. Vital status and cause of death ascertainment were based on linkage to the National Death Index death certificate records.

RESULTS

After a median follow-up of 4.3 years, 730 participants died (335 deaths from cancer and 112 cardiovascular-related deaths). FT4 was inversely associated with all-cause mortality (HR = 0.77, 95% confidence interval 0.63-0.95, comparing the highest vs lowest quartile of FT4; P for linear trend = .01), and FT3 was inversely associated cancer mortality (HR = 0.62, 95% confidence interval 0.45-0.85; P for linear trend = .001). TSH was not associated with mortality endpoints.

CONCLUSIONS

In a large cohort of euthyroid men and women, FT4 and FT3 levels within the normal range were inversely associated with the risk of all-cause mortality and cancer mortality, particularly liver cancer mortality.

High levels of procoagulant factors mediate the association between free thyroxine and the risk of venous thrombosis: the MEGA study

BACKGROUND

Thyroid hormone affects the coagulation system, but its effect on clinical disease is not clear. We determined the associations of levels of free thyroxine (FT4), thyroid-stimulating hormone (TSH) and anti-thyroid peroxidase antibodies (antiTPO) with levels of coagulation factors and the risk of venous thrombosis.

METHODS

In a large population based case-control study (Multiple Environmental and Genetic Assessment of risk factors for venous thrombosis study) on the etiology of venous thrombosis, we determined the levels of FT4, TSH, antiTPO, factor FII, FVII, FVIII, FIX, FX, von Willebrand factor (VWF), antithrombin, protein C, protein S and fibrinogen in 2177 cases and 2826 controls.

RESULTS

High levels of FT4 were associated with increased concentrations of procoagulant factors, and not with levels of anticoagulant factors. High levels of FT4 were also associated with the risk of venous thrombosis, up to an odds ratio (OR) of 2.2 (95% confidence interval [CI] 1.0-4.6) for levels above 24.4 pm relative to FT4 levels between 15.5 and 18.9 pm. In 11 cases and one control, clinical hyperthyroidism had been diagnosed within a year of the thrombotic event, leading to an OR of 17.0 (95% CI 2.2-133.0) for thrombosis. The ORs approached unity after adjustment for FVIII and VWF, which suggests that the effect was mediated by these factors. Low TSH levels were also, but less evidently, associated with thrombosis, whereas there was no association between antiTPO and venous thrombosis risk.

CONCLUSIONS

High levels of FT4 increase the concentrations of the procoagulant proteins FVIII, FIX, fibrinogen, and VWF, and by this mechanism increase the risk of venous thrombosis.

Association between the serum concentration of triiodothyronine with components of metabolic syndrome, cardiovascular risk, and diet in euthyroid post-menopausal women without and with metabolic syndrome

PURPOSE

To determine the association between the serum concentration of triiodothyronine (T3) with components of metabolic syndrome (MetS), cardiovascular risk (CVR), and diet in euthyroid post-menopausal women without and with MetS.

METHODS

A cross-sectional study was performed in 120 voluntary women of an indigenous population from Tlaxcala-México. Euthyroid status was assessed measuring the serum concentration of thyrotropin (TSH) and thyroid hormones, while that of estradiol was measured to confirm the postmenopausal condition. MetS was diagnosed using the American Heart Association/National Heart, Lung, and Blood Institute Scientific Statement (AHA/NHLBI) criterion. Estimation of CVR was calculated based on the Framingham scale. Diet components were evaluated based on survey applications. Correlations, logistic regression analyses, ANOVA or Kruskall-Wallis, and chi-square tests were used to determine significant differences (P ≤ 0.05) between women without MetS and women with MetS having different serum concentrations of T3.

RESULTS

Triiodothyronine was positively correlated with insulin but negatively correlated with glucose, high-density lipoprotein cholesterol (HDL-C), and CVR. Compared to women without MetS, women with MetS and low-normal T3 concentration showed a high risk for hyperglycemia and moderate/high risk for CVR. In contrast, a high-normal T3 concentration increased the risk to have a big waist circumference, a high concentration of HDL-C, and insulin resistance. Diet analysis showed a high grade of malnutrition in women from all groups. The intake of calories was positively affected by the T3 concentration, albeit it did not affect the extent of malnutrition.

CONCLUSIONS

In contrast to concentrations of TSH, total thyroxin (T4), and free T4, the concentration of serum T3 was strongly correlated with cardio-metabolic variables in euthyroid postmenopausal women. In comparison to women without MetS, a high-normal serum concentration of T3 in women with MetS is positively associated with reduced glycaemia and CVR but negatively related to body mass index (BMI), insulin, insulin resistance, and HDL-C. Although the analyzed population had a nutritional deficiency, both calories and iron intake were positively affected by the T3 concentration. Our results suggest the necessity of health programs monitoring T3 in old people in order to treat hyperglycemia, cardio-metabolic components, and the ageing anorexia.

Triiodothyronine and free thyroxine levels are differentially associated with metabolic profile and adiposity-related cardiovascular risk markers in euthyroid middle-aged subjects

BACKGROUND

We have previously shown that in healthy young men, a less favorable body composition is associated with higher free triiodothyronine (fT3) levels within the euthyroid range. Besides, a higher free-triiodothyronine-to-free-thyroxin (fT3-to-fT4) ratio has been related to a less favorable metabolic phenotype and more placental growth in pregnant women. In the present study, we therefore investigated whether serum thyrotropin (TSH), thyroid hormone levels, and the fT3-to-fT4 ratio are associated with metabolic and adiposity-related cardiovascular risk markers in a healthy population of middle-aged euthyroid men and women.

METHODS

Thyroid parameters were measured in 2524 generally healthy subjects from the Asklepios Study (35-55 years, mean age 46 years). Analyses were restricted to 2315 subjects (1138 women and 1177 men), not using thyroid medication, not having anti-TPO levels above clinical cutoff values or TSH levels outside the reference range (0.27-4.2 mU/L). Twenty-seven percent of the women and 47.5% of the men were overweight, while 13% of women and 17% of men were obese. Twenty percent of the subjects were active smokers. Serum thyroid function parameters were determined by electrochemiluminescence.

RESULTS

fT3 and the fT3-to-fT4 ratio were positively related to body mass index (BMI), waist circumference, and components of metabolic syndrome, that is, triglycerides, systolic and diastolic blood pressure, and fasting plasma glucose, and negatively with HDL-cholesterol levels, whereas fT4 was negatively associated with BMI, waist circumference, and triglycerides (p<0.001). TSH related positively with total cholesterol levels (p<0.01), triglycerides, and systolic and diastolic blood pressure (p<0.001). The fT3-to-fT4 ratio was further positively associated with the adiposity-related inflammation markers interleukin-6 and high-sensitivity C-reactive protein and to pulse wave velocity. All associations were adjusted for sex, age, height, and smoking, and most associations persisted after additional adjustment for weight or waist circumference.

CONCLUSION

In healthy euthyroid middle-aged men and women, higher fT3 levels, lower fT4 levels, and thus a higher fT3-to-fT4 ratio are consistently associated with various markers of unfavorable metabolic profile and cardiovascular risk.