Dyslipidemia in subclinical hypothyroidism requires assessment of small dense low density lipoprotein cholesterol (sdLDL-C)

Atherosclerosis Development and Progression: The Role of Atherogenic Small, Dense LDL

Atherosclerosis is responsible for large cardiovascular mortality in many countries globally. It has been shown over the last decades that the reduction of atherosclerotic progression is a critical factor for preventing future cardiovascular events. Low-density lipoproteins (LDL) have been successfully targeted, and their reduction is one of the key preventing measures in patients with atherosclerotic disease. LDL particles are pivotal for the formation and progression of atherosclerotic plaques; yet, they are quite heterogeneous, and smaller, denser LDL species are the most atherogenic. These particles have greater arterial entry and retention, higher susceptibility to oxidation, as well as reduced affinity for the LDL receptor. Increased proportion of small, dense LDL particles is an integral part of the atherogenic lipoprotein phenotype, the most common form of dyslipidemia associated with insulin resistance. Recent data suggest that both genetic and epigenetic factors might induce expression of this specific lipid pattern. In addition, a typical finding of increased small, dense LDL particles was confirmed in different categories of patients with elevated cardiovascular risk. Small, dense LDL is an independent risk factor for cardiovascular diseases, which emphasizes the clinical importance of both the quality and the quantity of LDL. An effective management of atherosclerotic disease should take into account the presence of small, dense LDL in order to prevent cardiovascular complications.

The effect of Thyroid Autoimmunity on Dyslipidemia in patients with Euthyroid Hashimoto Thyroiditis

Background & Objective:

The relationship between thyroid disorders and dyslipidemia has now been clearly demonstrated, but the relationship between thyroid autoimmunity and dyslipidemia in euthyroid patients is still controversial. Our aim in this study was to determine whether there is a risk of dyslipidemia in our patients with euthyroid hashimoto thyroiditis.

Methods:

Fifty-five autoantibody positive hashimoto patients and 55 antibody negative control groups who came to Sakarya University Medicine Faculty Endocrinology Outpatient Clinics between January 2018 and November 2019 were included in our case control study. The groups were similar in terms of age, cardiovascular risk factors and BMI. Both groups were compared according to the lipid profile results.

Results:

All type of lipids; including LDL (p = 0.008), HDL (p = 0.041), triglyceride (p = 0.045) and total cholesterol (p = 0.002), were higher in the patient group, and these differences were statistically significant. Anti-TPO and Anti-TG antibody titers and lipid levels were evaluated by separate correlation analysis. There was a significant positive correlation between Anti-TPO and LDL (r = 0.331, p <0.001), triglyceride (r = 0.267, p = 0.005) and total cholesterol (r = 0.316, p = 0.001), however no significant correlation was observed between Anti-TPO and HDL. Similarly, there was a significant positive correlation between Anti-TG and LDL (r = 0.318, p = 0.001), triglyceride (r = 0.218, p = 0.022), and total cholesterol (r = 0.301, p = 0.001), but HDL correlation relationship was not detected.

Conclusion:

The relationship between thyroid autoimmunity and dyslipidemia has been demonstrated in our study even in the euthyroid phase. Whether antibody positive patients should be followed more closely for dyslipidemia and cardiovascular events is still controversial. This question will be answered with larger randomized controlled trials.

Association between Subclinical Hypothyroidism and Incident Hypertension in Women: A Systematic Review and Meta-Analysis

Subclinical hypothyroidism (SCH) has been found to be associated with an increased risk of cardiovascular diseases. However, there is no clear consensus on the relationship between SCH and hypertension (HTN). We sought to investigate the association between SCH and incident HTN in women. MEDLINE and EMBASE databases were searched for studies that reported the incidence of HTN in females with SCH versus without SCH. Pooled odds ratio (OR) and 95% confidence interval (CI) of the outcome were obtained using a random-effects model. Studies were also divided into the middle-aged (mean age < 65) and the older (mean age ≥ 65) subgroups, and a subgroup analysis was performed to examine the potential age-effect on the association between SCH and HTN. Nine studies with a total of 21,972 subjects met the inclusion criteria. SCH was found to be positively associated with HTN (OR = 1.32, 95% CI = 1.02–1.71). Such association varied depending on the age of women. In the middle-aged subgroup, SCH was more positively associated with HTN (OR = 1.64, 95% CI = 1.18–2.27), while there was no significant association in the older subgroup (OR = 0.97, 95% CI = 0.80–1.16). Our study showed that the middle-aged females with SCH had an increased risk of HTN, while there was no significant association in the older females with SCH.

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.

[State of the coronary arteries and assessment of the role of hormone replacement therapy in patients with coronary heart disease against the background of primary manifest hypothyroidism]

Aim To study features of coronary damage and incidence of different types of acute coronary syndrome (ACS) in history associated with primary symptomatic hypothyroidism in patients with ischemic heart disease (IHD) and possible associations of replacement hormonal therapy with lipidogram indexes.Material and methods This retrospective study included 344 patients with IHD and functional class I-III stable angina (ССS, 1976). Of them 100 patients had primary symptomatic hypothyroidism and 244 had no hypothyroidism. Coronary angiography was performed for all patients included into this study. Routine laboratory, instrumental and clinical indexes were analyzed. Hypothyroidism was confirmed by levels of thyrotropic hormone, free triiodothyronine, and thyroxine. Comparative analysis was performed for the incidence of ACS types in history, types of coronary injury, and laboratory, instrumental and clinical indexes with assessment of potential interrelations. Statistically significant results were reported. Type of data distribution was evaluated with the Kolmogorov-Smirnov test. Quantitative data with normal (Gaussian) distribution were presented as mean (M) and standard deviation (SD). Data with attributes of non-normal distribution were presented as median (Me) with maximum and minimum values (min; max). Statistical significance of differences between means was assessed with the Mann-Whitney test. Logistic regression analysis was used in parallel for evaluating dependence of a quantitative variable on values of two or more quantitative or qualitative variables (factors). Significance level for testing of statistical hypotheses was р&lt;0.05.Results Incidence of ST segment elevation ACS (STEACS) was significantly higher in IHD patients with hypothyroidism than in the group without hypothyroidism (61.6 and 35.6 %, р=0.03) and also with three-vessel coronary artery disease (60.6 and 30.6 %, р=0.001). In the IHD group with hypothyroidism, levels of total cholesterol, triglycerides, and low- and very low-density lipoproteins were significantly increased compared to the respective values in patients without hypothyroidism (р&lt;0.0001). An inverse correlation was found between lipidogram indexes and L-thyroxine (р&lt;0.0001).Conclusion The incidence of STEACS associated with primary symptomatic hypothyroidism in history was significantly higher in the patient group with IHD on the background of primary symptomatic hypothyroidism compared to the comparison group. Also, the incidence of three-vessel coronary disease was significantly greater than in the IHD patient group without hypothyroidism. A significant association was found between the replacement hormonal therapy and the best lipidogram indexes. The authors suggested that the key factor for prevention of adverse cardiovascular events in IHD with hypothyroidism is achieving control of clinical manifestations of hypothyroidism with replacement hormonal therapy.

gp91phox, a Novel Biomarker Evaluating Oxidative Stress, Is Elevated in Subclinical Hypothyroidism

BACKGROUND

gp91^phox, the catalytic core of NADPH oxidase (NOX) and biomarker of NOX activation, has been recently recognized as a parameter of systemic oxidative stress in several studies. Subclinical hypothyroidism (SH) is characteristic of elevated level of serum thyroid stimulating hormone (TSH) and is frequently accompanied with cholesterolemia. In this study, the levels of serum soluble gp91^phox were measured to assess the oxidative stress in patients with SH. And the relationship among gp91^phox, low-density lipoprotein-C (LDL-C), and TSH was also investigated.

METHODS

A total of 51 subjects were enrolled and categorized into four groups: the healthy controls subjects (n = 13), controls with high level of LDL-C alone (n = 12), SH with normal level of LDL-C (n = 11), and SH with high level of LDL-C (n = 15). The related clinical and laboratory data were collected for statistical analysis. All the patients were newly diagnosed and did not take any medication. The information of lipid profile and thyroid function was extracted, and the concentrations of gp91phox were obtained with ELISA.

RESULTS

The levels of serum soluble gp91phox evidently increased in the patients with SH with a high level of LDL-C (81.52 ± 37.00 ug/mL) as compared to the healthy controls (54.98 ± 1.83ug/mL, p < 0.001), controls with high level of LDL-C (61.21 ± 4.48 ug/mL, p=0.038) and SH with a normal level of LDL-C (62.82 ± 11.67ug/mL, p=0.027). Additionally, the levels of gp91^phox showed a significant positive correlation with both the levels of LDL-C (r = 0.595, p < 0.001) and TSH (r = 0.346, p=0.013) by the Spearman correlation analyses. The correlation remained significant even when the effect of another factor was controlled (TSH: when the effect of LDL-C was controlled, r = 0.453, p=0.001; LDL-C: when the effect of TSH was controlled, r = 0.291, p=0.040). The main effect analysis showed an independent main effect of either LDL-C (p = 0.041) or TSH (p=0.022) on gp91^phox without interaction (p=0.299).

CONCLUSIONS

Our work demonstrated that the levels of gp91^phox, a novel biomarker for measuring the oxidative stress, were significantly elevated in the patients with SH. And LDL-C and TSH were both independent predictors of gp91^phox. Abbreviations. BMI : Body mass index; TC : Total cholesterol; LDL-C : Low-density lipoprotein cholesterol; HDL-C : High-density lipoprotein cholesterol; TG : Triglyceride; FBG : Fasting blood glucose; FT3 : Free triiodothyronine; FT4 : Free thyroxine; TSH: Thyroid stimulating hormone; SBP : Systolic blood pressure; DBP : Diastolic blood pressure; SD : Standard deviation; LSD: Least significant difference.

FABP4 levels in hypothyroidism and its relationship with subclinical atherosclerosis

Background/aim

The aim of this study is to evaluate the relationship between serum fatty acid binding protein 4 (FABP4) levels and carotid intima media thickness (CIMT) in patients with hypothyroidism.

Materials and methods

Forty subclinical hypothyroidism patients, 40 overt hypothyroidism patients, and 40 healthy controls were enrolled in the study. Blood pressure, body mass index, CIMT, fasting blood sugar, creatine, alanine aminotransferase, lipid parameters, insulin, free thyroxine, triiodothyronine, thyroid-stimulating hormone (TSH), thyroid peroxidase antibody (anti-TPO), thyroglobulin antibody (anti-TG), high-sensitivity C-reactive protein (Hs-CRP), and FABP4 levels of all participants were measured.

Results

Serum FABP4 levels were significantly higher in patients with subclinical and overt hypothyroidism than healthy controls (HCs) (P = 0.044 and P = 0.014, respectively). There was no significant difference in terms of FABP4 levels between patients with subclinical and overt hypothyroidism (P = 0.641). Serum TSH levels and serum FABP4 levels were positively correlated (r = 0.201, P = 0.039). CIMT was found to be higher in patients with subclinical and overt hypothyroidism than in HCs (P = 0.042 and P < 0.001, respectively). No correlation was found between CIMT and FABP4 levels (r = 0.038, P = 0.702). There was a positive correlation between CIMT and TSH, anti-TPO, anti-TG, triglycerides (TG), and total cholesterol levels. It was found that high TG levels were an independent factor that increased CIMT (r = 0.382, r2 = 0.146).

Conclusion

In patients with subclinical and overt hypothyroidism, the level of FABP4 increases and this increase is correlated with the increase in TSH level. It is thought that FABP4 does not play a role in atherosclerosis development in patients with hypothyroidism without metabolic disorder.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, the National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in 3 cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in 3 broad areas: (1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; (2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and (3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, The National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in three cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in three broad areas: 1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; 2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and 3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.