Impaired Hemorheological Parameters and Increased Carotid Intima-Media Thickness in Children with Subclinical Hypothyroidism

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

BACKGROUND AND OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Erythrocyte Deformability and Na,K-ATPase Activity in Various Pathophysiological Situations and Their Protection by Selected Nutritional Antioxidants in Humans

The physicochemical and functional properties of erythrocytes are worsened in a variety of diseases. Erythrocyte deformability refers to their ability to adjust their shape according to external forces exerted against them in the circulation. It is influenced by the functionality of the Na,K-ATPase enzyme, which is localized in their membranes. The proposed review is focused on knowledge regarding changes in erythrocyte Na,K-ATPase activity, and their impact on erythrocyte deformability in various pathophysiological situations observed exclusively in human studies, as well as on the potential erytroprotective effects of selected natural nutritional antioxidants. A clear link between the erythrocyte properties and the parameters of oxidative stress was observed. The undesirable consequences of oxidative stress on erythrocyte quality and hemorheology could be at least partially prevented by intake of diverse antioxidants occurring naturally in foodstuffs. Despite intensive research concerning the effect of antioxidants, only a small number of investigations on erythrocyte properties in humans is available in databases. It is worth shifting attention from animal and in vitro experiments and focusing more on antioxidant administration in human studies in order to establish what type of antioxidant, in what concentration, and in which individuals it may provide a beneficial effect on the human organism, by protecting erythrocyte properties.

Thyroid Dysfunction and Atherosclerosis: A Systematic Review

BACKGROUND/AIM

Thyroid dysfunction, both hypo- and hyperthyroidism, has been associated with cardiovascular disease. The aim of this study was to evaluate the association between thyroid dysfunction and atherosclerosis measured mostly by carotid intima-media thickness, as well as discuss whether L-T4 replacement is able to reverse or slow down the progression of atherosclerosis.

MATERIALS AND METHODS

The review was conducted according the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines. We performed on PubMed a literature search from May 2004 to January 2020, using the search terms 'subclinical hypothyroidism' or 'thyroid disorders' and 'carotid artery', 'carotid intima-media thickness (IMT)', 'levothyroxine', and 'atherosclerosis'.

RESULTS

Twenty-six studies were eligible and included in the analysis. Overall, the studies encompassed a total of 36.434 patients included in this review. Most studies indicated a proportional correlation between IMT and thyroid dysfunction. Levothyroxine (L-T4) replacement led to significant decrease of IMT after 1 year in most studies.

CONCLUSION

Most studies have concluded that thyroid dysfunction is associated with arterial wall remodeling and, thus, with increased cardiovascular risk. However, the exact mechanistic background of pathological structural changes in the arterial wall is still unsettled. Large randomized controlled studies are required to definitively address the extent to which T4 replacement therapy might benefit patients with subclinical thyroid disorders.

Epicardial Fat Thickness in Children with Subclinical Hypothyroidism and Its Relationship to Subclinical Atherosclerosis: A Pilot Study

BACKGROUND/AIMS

Thyroid hormones (TSH) play a key role in the working of the cardiovascular system, with direct effects on cardiac function, vascular system, and atherosclerotic factors. Epicardial adipose tissue, the visceral fat of the heart, has emerged as a new cardiometabolic risk marker because of its close anatomical proximity to the myocardium and coronary artery. This study aimed to evaluate epicardial fat thickness (EFT) in children with subclinical hypothyroidism (SH) and its relation to early atherosclerotic changes.

METHODS

The study included 32 children with SH due to autoimmune thyroiditis and 32 healthy children matched for age and gender as control group. Patients and controls underwent anthropometric evaluation and measurement of fasting lipids, glucose, insulin, homeostasis model assessment for insulin resistance and high-sensitivity C-reactive protein (hs-CRP). TSH, free thyroxine (FT4 and FT3) and antithyroid autoantibodies (antithyroid peroxidase and thyroglobulin antibodies) were also measured. Conventional echo-cardiography was used to assess EFT. Noninvasive ultrasound was used to measure carotid intima-media thickness and brachial artery flow-mediated dilation (FMD) responses.

RESULTS

Compared to controls, patients had higher atherogenic index (AI) and hs-CRP (p = 0.001 for each). Conventional echocardiography revealed that patients with SH had higher EFT (p = 01) and significantly lower FMD response compared with the control (p = 0.001). In multivariate analysis, EFT values were significantly correlated with TSH (OR 1.2; 95% CI 1.04-1.34; p = 0.01), hs-CRP (OR 1.1; 95% CI 1.09-1.14; p = 0.001, AI (OR 1.6; 95% CI 1.17-2.03; p = 0.001), and FMD response (OR 2.4; 95% CI 1.14-2.53; p = 0.01).

CONCLUSIONS

Our study demonstrated that EFT is higher in children with SH compared with controls and associated with FMD responses. Measurement of EFT by echocardiography in children with SH may help to identify those at high risk of developing subclinical atherosclerosis.

Hemorheology and oxidative stress in patients with differentiated thyroid cancer following I-131 ablation/metastasis treatment

BACKGROUND

Although radioiodine theraphy (RAIT) is thought to affect blood cells and oxidative stress, hemorheological alterations following dose-dependent RAIT remains unknown.

OBJECTIVE

The aim of this study was to determine the effects of RAIT on hemorheological and oxidative stress parameters in patients with differentiated thyroid cancers (DTC).

METHODS

Totally 31 DTC patients (mean age 46.32±11.15 years) and 26 healthy controls (mean age 50.50±6.22 years) were included. Venous blood samples were collected from each patient before and after treatment (7th day, 1th month and 6th month). Erythrocyte aggregation-deformability and oxidative stress parameters were determined. p < 0.05 was considered as statistically significant.

RESULTS

Erythrocyte deformability of the patients determined at 16.87 and 30 Pascal were significantly lower than healthy individuals. Erythrocyte aggregation index (AI) of the patients was higher, whereas erythrocyte aggregation half-time (t½) was lower compared to control. Erythrocyte deformability values and AI were not significantly different from the pre- and post-radioiodine treatment groups. There was no statistically significant difference between the oxidative stress parameters before and after the treatment.

CONCLUSIONS

Patients were in a worse hemorheological condition compared to healthy individuals. After RAIT, RBC deformability and aggregation were not affected and no significant change in oxidative stress parameters was detected.

Serum TSH level in obese children and its correlations with atherogenic lipid indicators and carotid intima media thickness

Objective: Moderately elevated level of thyroid-stimulating hormone accompanied by normal serum concentrations of free thyroxine, suggesting subclinical hypothyroidism, is the most common hormonal abnormality in obese children. Controversy remains, whether a thyroid dysfunction related to obesity has an influence on the cardiovascular risk factors. The aim of the study was to assess correlation between thyroid-stimulating hormone and free thyroxine and chosen atherogenic lipid indicators, and carotid intima media thickness in obese children and adolescents. Methods: A study group consisted of 110 obese children (11.5 ± 2.9 years) and 38 healthy children (13.4 ± 2.6 years). Obesity was defined using International Obesity Task Force criteria. In each patient anthropometric measurements, thyroid-stimulating hormone, free thyroxine, a lipid profile were evaluated. Carotid intima-media thickness was measured in 74 obese children and 28 lean children. The resulting data were used to calculate indicators of atherogenesis: total cholesterol to HDL cholesterol ratio; triglycerides to HDL cholesterol ratio and LDL cholesterol to HDL cholesterol ratio. Results: Obese children had higher mean serum thyroid-stimulating hormone levels compared to their lean peers and an adverse atherogenic lipid profile. Serum free thyroxine concentrations were comparable between the groups. Serum thyroid-stimulating hormone values correlated with total cholesterol to HDL cholesterol ratio; triglycerides to HDL cholesterol ratio, LDL cholesterol to HDL cholesterol ratio, and intima-media thickness. In a multivariate regression analysis, thyroid-stimulating hormone weakly correlated only with intima-media thickness after adjustment for age, gender and Body Mass Index (β = 0.249, p = 0.04). This relationship weakened after considering a lipid profile (β = 0.242, p = 0.058). No relationship was found for free thyroxine. Conclusion: Serum level of thyroid-stimulating hormone in obese children did not seem to impact atherogenic lipid indicators and carotid intima-media thickness. Therefore, an adverse lipid profile should still be considered the main risk factor for development of cardiovascular diseases in obese children.

Follow-up in children with non-obese and non-autoimmune subclinical hypothyroidism

Background The aim of our study was to evaluate clinical, laboratory and imaging findings and to have an idea about the clinical course of subclinical hypothyroidism in children. Methods Our study included 25 patients who were diagnosed with non-autoimmune subclinical hypothyroidism without goitre, between the ages of 3 and 18 and with body mass index (BMI) below the 85th percentile. Results The mean thyroid-stimulating hormone (TSH) level was 6.92±0.92 μIU/mL at diagnosis, 4.77±1.57 μIU/mL in the third month and 4.51±1.79 μIU/mL in the first year of follow-up. About 73.7% of subclinical hypothyroidism was recovered. There was no statistically significant difference between heart rate, diastolic blood pressure, lipid profile, fasting blood glucose (FBG), fasting insulin level, homeostatic model assessment of insulin resistance (HOMA-IR), hemoglobin, white blood cell, platelet, C-reactive protein (CRP) levels and thyroid volume at diagnosis and in the first year of follow-up. In the first year of follow-up, systolic blood pressure and high-sensitivity CRP value were significantly higher than at diagnosis. However, it was observed that these values were similar in the present group with subclinical hypothyroidism. Conclusions We concluded that there was no progression to overt hypothyroidism during 1-year follow-up and that subclinical hypothyroidism had no effect on height standard deviation score (SDS), BMI SDS, blood pressure, glucose and lipid metabolism during follow-up without treatment.

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

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

Association of Subclinical Hypothyroidism with Dyslipidemia and Increased Carotid Intima-Media Thickness in Children

OBJECTIVE

Subclinical hypothyroidism (SH) is defined as an elevated serum thyroid-stimulating hormone (TSH) level with free thyroxine (fT4) level in the normal range. There are very few studies in the literature reporting on the effect of SH on lipid metabolism and carotid intima-media thickness (CIMT) in children.

METHODS

The study included 38 children diagnosed with SH and a control group comprising 38 healthy, euthyroid children. SH was diagnosed based on an elevated TSH level (4.2-20 mIU/L) and normal fT4 level measured in two morning fasting blood samples obtained at an interval of 2 to 6 weeks. Blood samples were collected by venipuncture in the morning after an overnight fast.

RESULTS

The patient group included 38 children (16 male, 22 female) with SH and the control group -38 healthy, euthyroid children (20 male, 18 female). Mean age was 8.1±3.6 (range, 3.5-15) years in the patient group and 8.9±2.4 (range, 4.5-15) years in the control group. In the patient group, total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), TC/high-density lipoprotein cholesterol (HDL-C), and LDL-C/HDL-C were higher compared to the control group (p=0.049, p=0.014, p=0.002, and 0.003, respectively). In the patient group, CIMT was also significantly higher compared to the control group (p=0.001). The patient group was further divided into two subgroups based on their serum TSH level: (I) patients with mildly elevated TSH (TSH=4.2±10 mIU/L) (n=33) and (II) patients with high TSH (TSH≥10 mIU/L) (n=5). However, no significant difference was found between the patients with mild and severe SH with regard to TC, LDL-C, HDL-C, triglyceride level and CIMT levels (p=0.635, p=0.424, p=0.310, p=0.342, and 0.610, respectively).

CONCLUSION

Subclinical hypothyroidism leads to increased dyslipidemia (increased TC and LDL) and increased CIMT, which leads to increased risk of cardiovascular disease. Further studies are needed to substantiate these findings in children with SH.

Cardiac autonomic function and vascular profile in subclinical hypothyroidism: Increased beat-to-beat QT variability

BACKGROUND

Patients with subclinical hypothyroidism (SH) may have higher incidence of coronary heart disease and autonomic dysfunction.

DESIGN OF THE STUDY

Prospective case control study.

AIM AND OBJECTIVES

To evaluate beat-to-beat QT variability and vascular stiffness in patients with SH compared to normal controls.

MATERIALS AND METHODS

We compared linear and nonlinear measures of cardiac repolarization liability using beat-to-beat QT intervals derived from the surface electrocardiogram during supine posture and vascular indices including pulse wave velocity and ankle-brachial index (ABI) during supine posture between female patients with SH and age- and sex-matched normal controls. Spectral analysis was done at very low frequency (LF) (0.003-0.04 Hz), Low frequency (LF) (0.04-0.15 Hz), and high frequency (HF) (0.15-0.4 Hz). The HF represents vagal regulation (parasympathetic) and LF represents both parasympathetic and sympathetic regulation.

RESULTS

We recruited 58 women with a mean age of 31.83 ± 8.9 years and 49 controls with mean age of 32.4 ± 9.9 years (P = NS). QT variability index (QTvi) was higher in cases compared to controls (P = 0.01). The ratio of LF/HF of R-R interval which is an index of sympathovagal tone was significantly more in cases compared to controls (P = 0.02). The difference in the left minus the right ABI was significant between cases and controls (P = 0.03).

CONCLUSIONS

The cases had lower parasympathetic activity as compared to controls, and there was a predominance of sympathetic activity in cases. QTvi may be an important noninvasive tool in this group of patients to study the risk of cardiovascular mortality.