Adipokine expression and endothelial function in subclinical hypothyroidism rats

Hypothyroidism and Risk of Cardiovascular Disease

Thyroid hormones (TH) have a significant impact on cellular oxidative metabolism. Besides that, they maintain vascular homeostasis by positive effects on endothelial and vascular smooth muscle cells. Subclinical (SCH) and clinical (CH) hypothyroidism influences target organs by changing their morphology and function and impaired blood and oxygen supply induced by accelerated atherosclerosis. The increased risk of acceleration and extension of atherosclerosis in patients with SCH and CH could be explained by dyslipidemia, diastolic hypertension, increased arterial stiffness, endothelial dysfunction, and altered blood coagulation. Instability of atherosclerotic plaque in hypothyroidism could cause excessive activity of the elements of innate immunity, which are characterized by: the significant presence of macrophages in atherosclerotic plaques, increased nuclear factor kappa B (NFkB) expression, and elevated levels of tumor necrosis factor α (TNF-α) and matrix metalloproteinase (MMP) 9, with reduced interstitial collagen, which all together creates inflammation milieu resulted in plaque rupture. Optimal substitution by levothyroxine (LT4) restores biochemical euthyroidism. In postmenopausal women and elderly patients with hypothyroidism and associated vascular comorbidity, excessive LT4 substitution could lead to atrial rhythm disorders and osteoporosis. Therefore, it is of interest to maintain thyroid-stimulating hormone (TSH) levels in the reference range, thus eliminating the deleterious effects of lower or higher TSH levels on the cardiovascular system. This review summarizes the recent literature on subclinical and clinical hypothyroidism and atherosclerotic cardiovascular disease and discusses the effects of LT4 replacement therapy on restoring biochemical euthyroidism and atherosclerosis processes.

Characteristics of coronary artery disease in patients with subclinical hypothyroidism: evaluation using coronary artery computed tomography angiography

Background

Subclinical hypothyroidism (SCH) has recently been acknowledged as an independent risk factor for coronary artery disease (CAD). However, the characteristics of CAD in patients with SCH are not fully understood. This study aims to evaluate the features of CAD in patients with SCH using coronary computed tomographic angiography (CCTA).

Materials and methods

From 1 April, 2018 to 30 June, 2020, 234 consecutive SCH patients with coronary plaques identified on CCTA were included retrospectively. They were further subdivided into different degree of SCH groups (mild SCH vs. moderate SCH vs. severe SCH: 143 vs 62 vs 28) and different gender groups (men with SCH vs. women with SCH:116 vs 118). The distributions and types of plaques, luminal narrowing, segment involvement scores (SIS) and segment stenosis scores (SSS) were evaluated and compared among the different groups.

Results

Patients with severe SCH had fewer calcified plaques (0.7 ± 0.9 vs. 2.0 ± 1.9, p < 0.001) and more non-calcified plaques (0.9 ± 1.0 vs. 0.3 ± 0.5, p < 0.001) than those with mild SCH. As the SCH condition worsened, the proportion of non-calcified plaques significantly increased. Whereas there were no significant discrepancies in SIS and SSS among patients with different grades of SCH (all p > 0.05). Men with SCH had higher SIS (3.9 ± 2.3 vs. 3.0 ± 2.3, p = 0.004) and SSS (7.8 ± 5.4 vs. 5.4 ± 3.0, p = 0.002) than women. Multivariate logistic and linear regression analysis demonstrated that grades of SCH (Moderate SCH, odds ratio [OR] 2.11; 95% CI 1.03–4.34, p = 0.042; severe SCH, OR: 10.00; 95% CI 3.82–26.20, p < 0.001, taken mild SCH as a reference) was independently associated with the presence of non-calcified plaques, whereas sex (B: 1.67; 95% CI 0.27–3.10, p = 0.009) was independently associated with SSS.

Conclusions

Severe SCH is associated with non-calcified plaques, and men with SCH have higher total plaque burden than women. We suggest that it is important to evaluate for coronary plaque in SCH patients, especially those with severe SCH and men with SCH.

Relation of kidney function and homocysteine in patients with hypothyroidism

OBJECTIVE

It has been found that both serum homocysteine (Hcy) and serum creatinine levels were increased in hypothyroidism patients. The aim of this study was to investigate the correlation between serum Hcy and kidney function in patients with subclinical hypothyroidism or hypothyroidism.

METHODS

A total of 448 subjects were enrolled and divided into three groups: hypothyroidism (n = 129), subclinical hypothyroidism (n = 141), and control group (n = 168). Anthropometric information, metabolic parameters, serum Hcy and creatinine levels, and estimated glomerular filtration rate (eGFR) were analyzed.

RESULTS

Compared with healthy subjects, patients with subclinical hypothyroidism or hypothyroidism had significantly higher serum Hcy and creatinine levels and lower eGFR level (all P < 0.001). Serum Hcy was negatively correlated with eGFR in subclinical hypothyroidism patients (r = -0.220, P = 0.009), and in hypothyroidism patients (r = -0.422, P < 0.001). After adjusting for age, sex and BMI, eGFR was still significantly correlated with serum Hcy in subclinical hypothyroidism or hypothyroidism patients (both P < 0.05). Levothyroxine treatment resulted in significantly decreased Hcy and increased eGFR in hypothyroidism patients (both P < 0.001). The decrease in Hcy was correlated with the increased eGFR after treatment (P = 0.001).

CONCLUSION

Serum Hcy was negatively correlated with eGFR in subclinical hypothyroidism or hypothyroidism patients. After levothyroxine treatment, a correlation was found between the decrease in serum Hcy and the increase in eGFR in hypothyroidism patients.

High-Normal Serum Thyrotropin Levels Increased the Risk of Non-Alcoholic Fatty Liver Disease in Euthyroid Subjects with Type 2 Diabetes

PURPOSE

The aim of this study was to investigate the association between high-normal thyrotropin (TSH) levels and the prevalence of non-alcoholic fatty liver disease (NAFLD) in euthyroid patients with T2DM.

METHODS

A total of 2289 euthyroid adults with T2DM were included in this cross-sectional study conducted at the Third Affiliated Hospital of Sun Yat-sen University from January 2016 to December 2018. NAFLD was diagnosed by abdominal ultrasound. Thyroid function parameters, including the levels of TSH, free triiodothyronine (FT3) and free thyroxine (FT4), were analyzed. The patients were stratified by quartiles (Q1-4) of TSH levels. Multivariate logistic regression models were used to evaluate the association between the quartiles of TSH levels and the risk of NAFLD in euthyroid adults with T2DM.

RESULTS

There were 940 (41.1%) euthyroid adults with T2DM who were diagnosed with NAFLD. The subjects were divided according to the thyroid function parameter quartiles. The prevalence of NAFLD increased with increasing TSH level quartiles (Q1 to Q4: 34.8%, 37.5%, 44.9% and 47.0%, P<0.01) but not with increasing FT3 or FT4 level quartiles. In the multivariate logistic regression model, compared with the lowest TSH level quartile (Q1), the highest TSH level quartile (Q4) (OR=1.610, 95% CI=1.131-2.289, P=0.008) was independently associated with an increased risk of NAFLD in euthyroid adults with T2DM after adjusting for multiple confounders. After additional stratification by the level of glycosylated haemoglobin (HbA1c) and body mass index (BMI), the highest TSH level quartile was still independently associated with an increased risk of NAFLD in euthyroid patients with T2DM who had an HbA1c level≥7% or a BMI<28 kg/m².

CONCLUSION

High-normal serum TSH levels are significantly associated with the presence of NAFLD in T2DM patients with euthyroid function, which provide novel insight for treating NAFLD.

Hypothyroidism-Induced Nonalcoholic Fatty Liver Disease (HIN): Mechanisms and Emerging Therapeutic Options

Nonalcoholic fatty liver disease (NAFLD) is an emerging worldwide problem and its association with other metabolic pathologies has been one of the main research topics in the last decade. The aim of this review article is to provide an up-to-date correlation between hypothyroidism and NAFLD. We followed evidence regarding epidemiological impact, immunopathogenesis, thyroid hormone-liver axis, lipid and cholesterol metabolism, insulin resistance, oxidative stress, and inflammation. After evaluating the influence of thyroid hormone imbalance on liver structure and function, the latest studies have focused on developing new therapeutic strategies. Thyroid hormones (THs) along with their metabolites and thyroid hormone receptor β (THR-β) agonist are the main therapeutic targets. Other liver specific analogs and alternative treatments have been tested in the last few years as potential NAFLD therapy. Finally, we concluded that further research is necessary as well as the need for an extensive evaluation of thyroid function in NAFLD/NASH patients, aiming for better management and outcome.