Association between thyroid function and lipid profiles, apolipoproteins, and high-density lipoprotein function

Association of the thyroid hormone sensitivity index with triglycerides in adolescents: a cross-sectional study

BACKGROUND

Inconsistent findings have emerged from studies examining the relationship between thyroid hormone sensitivity indices and triglycerides (TGs), especially in pediatric and adolescent cohorts. The present study investigates this relationship within adolescent populations in the United States.

METHODS

Data spanning three periods from 2007 to 2012 were analyzed, including 1813 participants. The thyroid hormone sensitivity index was calculated and weighted multiple linear regression was used to assess the relationships between TG levels and individual thyroid hormone sensitivity indices. Subgroup analyses were conducted as needed and smooth curve fitting plots visualized the linear relationships.

RESULTS

The FT3/FT4 ratio was positively correlated with TG (β = 0.649, 95% CI: 0.360-0.938, P < 0.001). This correlation persisted after adjusting for all variables (β = 0.439, 95% CI: 0.154-0.725, P < 0.01). The relationship between the TFQI score and TG concentration demonstrated a significant negative correlation, which remained after controlling for all covariates (β = -0.153, 95% CI: -0.239-0.067, P < 0.01). When stratified into quartiles, the FT3/FT4 ratio and TG exhibited a positive correlation only in the Q3 and Q4 groups. Conversely, the TFQI was significantly correlated with TG exclusively in the Q4 group's positive values. Stratified analyses by sex and age showed clearer associations in female adolescents.

CONCLUSIONS

The study confirmed the relationship between thyroid hormone sensitivity indices and TGs. Maintaining the FT3/FT4 ratio within a specific range may reduce TG levels. The TFQI may predict TG levels when actual TSH values exceed expected values based on FT4. These findings were most pronounced in female adolescents, highlighting the importance of early monitoring of thyroid health in this group. These results point to the need for improved thyroid function testing in predicting TG levels and preventing hypertriglyceridemia.

TSH is independently associated with remnant cholesterol in euthyroid adults: a cross-sectional study based on 29,708 individuals

PURPOSE

The study aims to investigate the relationship between thyroid-stimulating hormone (TSH) and remnant cholesterol (RC) in euthyroid adults.

METHODS

The adults who were recruited for the study had undergone physical examination at Beijing Chao-Yang Hospital. High RC levels were defined as the upper quartile of RC levels in males and females, respectively. The relationship between TSH and RC was assessed using the logistic and linear regression models.

RESULTS

A total of 29,708 adults (14,347 males and 15,361 females) were enrolled in this study. RC ≥ 0.77 mmol/L in males and RC ≥ 0.60 mmol/L in females were defined as high RC levels. With increasing serum TSH levels, the percentage of adults with high RC levels increased. The odds ratios (ORs (95% confidence intervals (CIs)) for high RC levels increased as TSH quartiles (Q) rose after full adjustments [males: Q2 1.11 (1.00-1.24), P < 0.05; Q3 1.03 (0.92-1.15), P > 0.05; Q4 1.25 (1.12-1.40), P < 0.001; and females: Q2 1.07 (0.96-1.20), P > 0.05; Q3 1.17 (1.05-1.31), P < 0.01, Q4 1.33 (1.20-1.48), P < 0.001, all P for trend < 0.001], using Q1 as the reference.

CONCLUSION

Higher TSH levels were independently associated with higher RC levels in euthyroid adults, this underscoring the significance of regulating TSH levels appropriately.

Correlation Between Thyroid Hormone and Controlled Attenuation Parameters: A Cross-Sectional Population-Based Study

Objective

The aim of the present study was to investigate how thyroid hormone levels are related to controlled attenuation parameters (CAP), which may provide insights for understanding the role of these factors in hepatic steatosis.

Methods

A total of 3461 participants who underwent CAP diagnosis between 2018 and 2023 were included. The associations between thyroid hormone levels and CAP were evaluated through multiple linear regression, restricted cubic splines (RCS) and threshold effect analyses.

Results

Multiple linear regression analysis revealed an inverse relationship between free thyroxine (FT4) and CAP, with a coefficient of -0.855 and a confidence interval of -1.297 to -0.412. The negative connection in a subset examination persisted in males [-0.729 (-1.295, -0.162)] and females [-1.234 (-1.996, -0.473)]. A strong correlation was found between free 3,5,3'-triiodothyronine (FT3) and CAP, with values of 2.182 (1.154, 3.211). Further analysis was conducted on both male [1.626 (0.188, 3.065)] and female [2.835 (1.137, 4.533)] subgroups. In the severe liver steatosis group, there was a significant negative correlation between FT3 and CAP based on the subgroup analysis stratified by the level of liver steatosis [-3.804 (-6.711, -0.898)]. The RCS analysis showed a nonlinear association between FT4 and CAP, with a turning point at 11.14 pmol/L.

Conclusion

There was a significant linear and nonlinear relationship between FT4, FT3 and CAP. Thyroid hormones could have a significant impact on liver steatosis, offering fresh perspectives on how to prevent and treat this condition.

Application of Human Plasma Targeted Lipidomics and Analysis of Toxic Elements to Capture the Metabolic Complexities of Hypothyroidism

BACKGROUND

Hypothyroidism (HT) affects millions worldwide and can lead to various lipid disorders. The metabolic complexity and the influence of toxic elements in autoimmune and non-autoimmune HT subtypes are not fully understood. This study aimed to investigate the relationships between plasma lipidome, toxic elements, and clinical classifications of HT in unexposed individuals.

METHODS

Samples were collected from 120 adults assigned to a study group with Hashimoto's disease and non-autoimmune HT, and a healthy control group. Quantification of 145 pre-defined lipids was performed by using triple quadrupole tandem mass spectrometry (TQ MS/MS) in multiple reactions monitoring (MRM) mode via positive electrospray ionization (ESI). Levels of toxic elements were determined using inductively coupled plasma mass spectrometry (ICP-MS).

RESULTS

Significant associations between altered levels of several components of the plasma lipidome and Al, Cd, Ni, As, and Pb with HT were found. We show metabolic differences in lysophosphatidylcholines (LPC) and phosphatidylcholines (PC) between HT and controls, with distinct predicted activation patterns for lysolecithin acyltransferase and phospholipase A2.

CONCLUSIONS

There are significant changes in the lipidome profiles of healthy subjects compared to euthyroid HT patients treated with L-thyroxine, which are related to the type of hypothyroidism and non-occupational exposure to toxic elements.

Relationship between thyroid function and lipid atherogenic profile in pediatric patients with multisystem inflammatory syndrome associated with COVID-19

Introduction

Concurrent alterations in the metabolic profile and thyroid dysfunction, including non-thyroidal illness syndrome (NTIS) has been reported in multisystem inflammatory syndrome in children (MIS-C). Considering the influence of thyroid hormones (TH) on lipid metabolism, we explored the relationship between thyroid function and the atherogenic lipid profile in children with MIS-C at admission and during a 12-month follow-up.

Patients and methods

we considered children admitted for MIS-C. Total and HDL cholesterol, triglycerides (TG), fasting plasma glucose, fasting plasma insulin as well as free T3 (FT3), free T4 (FT4), and TSH were assessed at diagnosis within 24 h of admission and during follow-up. TG/HDL ratio, no-HDL/HDL ratio and atherogenic index of plasma was also considered as atherogenic risk markers.

Results

we monitored 56 children. On admission, pathological levels of FT3, FT4, TSH, TG, TC, HDL, TG/HDL ratio, no-HDL/HDL ratio, and AIP were detected. Correlation analyses revealed associations between FT3, FT4, and lipid markers and TSH with TG. During monitoring, while complete restoration of TH balance was achieved at 12 months, some patients still exhibited an altered lipid profile, without correlation between thyroid function and lipid markers.

Conclusions

we supported a relationship between thyroid function and an atherogenic lipid profile in children with MIS-C. This may result from interactions between adaptive and innate metabolic responses and genetic predisposition. Elucidating the relationship between TH and metabolic pathways during infections could help identify new biomarkers to prevent acute and fatal outcomes, improving patient prognosis and protecting long-term health.

The role of thyroid-stimulating hormone in regulating lipid metabolism: Implications for body-brain communication

Thyroid-stimulating hormone (TSH) is a pituitary hormone that stimulates the thyroid gland to produce and release thyroid hormones, primarily thyroxine and triiodothyronine. These hormones are key players in body-brain communication, influencing various physiological processes, including the regulation of metabolism (both peripheral and central effects), feedback mechanisms, and lipid metabolism. Recently, the increasing incidence of abnormal lipid metabolism has highlighted the link between thyroid function and lipid metabolism. Evidence suggests that TSH can affect all bodily systems through body-brain communication, playing a crucial role in growth, development, and the regulation of various physiological systems. Lipids serve dual purposes: they are involved in energy storage and metabolism, and they act as vital signaling molecules in numerous cellular activities, maintaining overall human health or contributing to various diseases. This article reviews the role of TSH in regulating lipid metabolism via body-brain crosstalk, focusing on its implications for common lipid metabolism disorders such as obesity, atherosclerosis, nonalcoholic fatty liver disease, neuropsychiatric disorders (including Alzheimer's disease, Parkinson's disease, multiple sclerosis, epilepsy, and depression), and cerebrovascular disorders such as stroke.

Correlation between thyroid hormone sensitivity and diabetic peripheral neuropathy in euthyroid patients with type 2 diabetes mellitus

Previous studies have revealed that thyroid hormone (TH) levels are associated with the risk of diabetic peripheral neuropathy (DPN) in euthyroid patients with type 2 diabetes mellitus (T2DM). However, the relationship between TH sensitivity, a complementary method for assessing thyroid function, and DPN remains unclear. This study aimed to investigate the correlation between DPN and TH sensitivity in euthyroid patients with T2DM. Exactly 708 euthyroid adults with T2DM were retrospectively enrolled. The FT3/FT4 ratio was used to estimate peripheral TH sensitivity. Central TH sensitivity was assessed using the Thyrotroph T4 Resistance Index (TT4RI), Thyroid-Stimulating Hormone Index (TSHI), Thyroid Feedback Quantile-based Index (TFQI), and Parametric TFQI (PTFQI). DPN was assessed using neurologic symptoms, signs, and nerve conduction velocity tests. The relationship between DPN and TH sensitivity was examined using logistic regression analysis. We observed that an elevated FT3/FT4 ratio was associated with DPN (OR = 1.36, 95%CI: 1.13-1.63, p = 0.0012). For each standard deviation (SD) increase in the TT4RI, TSHI, TFQI, and PTFQI, the OR of DPN was 0.80 (95%CI: 0.68-0.94, p = 0.0078), 0.72 (95%CI: 0.60-0.86, p = 0.0002), 0.69 (95%CI: 0.58-0.83, p < 0.0001), and 0.69 (95%CI: 0.58-0.82, p < 0.0001), respectively. These results suggested that reduced central and peripheral TH sensitivity is associated with a decreased risk of developing DPN.

Levothyroxine sodium tablets reversed Hashimoto thyroiditis-induced kidney injury, muscle injury, and lipid metabolism disorder: A case report and literature review

RATIONALE

Hashimoto thyroiditis (HT), a common cause of hypothyroidism, has shown an increasing incidence in recent years, particularly among women. In addition to the common complications such as lipid metabolism disorders, patients with HT may also experience some serious complications, acute kidney injury and severe muscle damage for instance. This article explored the effectiveness of levothyroxine sodium tablets (L-T4) replacement therapy in severe complications of hypothyroidism, including treatment dosage, duration of complication recovery, and whether additional treatment is needed.

PATIENT CONCERNS, DIAGNOSES, AND INTERVENTIONS

We described a case of a 52-year-old woman with HT who exhibited kidney injury, muscle injury, and lipid metabolism disorders. The increased levels of serum creatinine, creatine kinase, cholesterol, triglyceride, low density lipoprotein cholesterol, high density lipoprotein cholesterol, and the decreased levels of estimated glomerular filtration rate were obviously observed. This patient was started on L-T4 (75 and 100 µg, alternate).

OUTCOMES AND LESSONS

Following a two-month treatment, the serum creatine kinase level decreased to within normal range. The estimated glomerular filtration rate level was restored, and the serum creatinine level was down-regulated, although slightly higher than the normal range. L-T4 partially reversed HT-induced the disorders of muscle, renal function, and lipid profile of this patient and remarkably alleviated her HT-related symptoms.

Expressions of glycemic parameters, lipid profile, and thyroid hormone in patients with type 2 diabetes mellitus and their correlation

OBJECTIVE

This study aimed to investigate the expressions of glycemic parameters, lipid profile, and thyroid hormone in type 2 diabetes mellitus (T2DM) patients and their correlation.

METHODS

Eighty-four patients with T2DM in our hospital were included as the observation group. The T2DM patients were divided into mild group, moderate group, and severe group according to the fasting plasma glucose (FPG) level. Another 84 healthy subjects in the same period of health examination in our hospital were included as the control group. The levels of glycemic parameters, (HbA1c and FPG), lipid profile (TC, TG, LDL-C, and HDL-C) and thyroid hormone (FT3, TSH, and FT4) were measured by automatic biochemical analyzer. The correlation between glycemic parameters, lipid profile, and thyroid hormone was analyzed by Pearson correlation analysis.

RESULTS

The FPG, TC, TG, LDL-C, HbA1c, and TSH levels were significantly elevated, while the HDL-C and FT3 levels were significantly declined in the observation group versus to control group (p < .05). The levels of HbA1c, FPG, TC, LDL-C, and TSH were significantly increased, while the levels of HDL-C and FT3 were decreased in moderate and severe groups, when compared to mild group (p < .05). The levels of HbA1c, FPG, TC, LDL-C and TSH were higher, while the level of FT3 was lower in severe group than those in moderate group (p < .05). Pearson Correlation analysis showed that FT3 level in T2DM patients was positively correlated with FPG, HbAlc, TC, TG, and LDL-C levels (p < .05), but negatively correlated with HDL-C level (p < .05). TSH level was negatively correlated with FPG, HbAlc, TC, TG, and LDL-C levels (p < .05), while positively correlated with HDL-C level.

CONCLUSION

The thyroid hormone levels were of clinical significance in evaluating glycolipid metabolism and severity of T2DM. Clinical detection of glycolipid metabolism and thyroid hormone levels in T2DM patients is of great significance for diagnosis, evaluation, and targeted treatment of the disease.

Exploring the diagnostic performance of machine learning in prediction of metabolic phenotypes focusing on thyroid function

In this study, we employed various machine learning models to predict metabolic phenotypes, focusing on thyroid function, using a dataset from the National Health and Nutrition Examination Survey (NHANES) from 2007 to 2012. Our analysis utilized laboratory parameters relevant to thyroid function or metabolic dysregulation in addition to demographic features, aiming to uncover potential associations between thyroid function and metabolic phenotypes by various machine learning methods. Multinomial Logistic Regression performed best to identify the relationship between thyroid function and metabolic phenotypes, achieving an area under receiver operating characteristic curve (AUROC) of 0.818, followed closely by Neural Network (AUROC: 0.814). Following the above, the performance of Random Forest, Boosted Trees, and K Nearest Neighbors was inferior to the first two methods (AUROC 0.811, 0.811, and 0.786, respectively). In Random Forest, homeostatic model assessment for insulin resistance, serum uric acid, serum albumin, gamma glutamyl transferase, and triiodothyronine/thyroxine ratio were positioned in the upper ranks of variable importance. These results highlight the potential of machine learning in understanding complex relationships in health data. However, it's important to note that model performance may vary depending on data characteristics and specific requirements. Furthermore, we emphasize the significance of accounting for sampling weights in complex survey data analysis and the potential benefits of incorporating additional variables to enhance model accuracy and insights. Future research can explore advanced methodologies combining machine learning, sample weights, and expanded variable sets to further advance survey data analysis.

Hypothyroidism, lipids, and lipidomics

PURPOSE

Hypothyroidism is a relatively common endocrine disorder and is well documented to be associated with lipid abnormalities.

METHODS

A narrative review was conducted of studies describing the alterations in the lipid profile accompanying both subclinical and overt hypothyroidism.

RESULTS

Lipid abnormalities are seen with TSH values in the upper end of the accepted reference range, as well as with subclinical and overt hypothyroidism. The degree of lipid derangement is generally proportional to the degree of TSH elevation. Other factors such as age, sex, and body mass index can also influence the pattern of the lipid abnormalities seen. The most robust finding with TSH elevation is increases in the low density lipoprotein cholesterol. Thyroid hormone treatment is efficacious in reversing the lipid abnormalities in both subclinical and overt hypothyroidism.

CONCLUSION

Given the association of lipid abnormalities with metabolic and cardiovascular disease, consideration of hypothyroidism as an important non-communicable disease may facilitate studies that test the hypothesis that thyroid hormone treatment to reverse hypothyroidism-associated lipid abnormalities may improve metabolic and cardiovascular outcomes.

Lipid Profile Perturbations Associated With Subclinical Hypothyroidism: A Descriptive Study

Background Hypothyroidism is a prevalent endocrine disorder associated with dyslipidemia, which increases cardiovascular risk. Our study aimed to estimate the prevalence of dyslipidemia and subclinical hypothyroidism (SCH) and their correlation in a diverse population. Methods A descriptive cross-sectional retrospective analysis was conducted to assess the prevalence of dyslipidemia in patients with SCH. Data were collected over 19 months from the Clinical Biochemistry Department of a Moroccan university hospital. A total of 447 patients were included based on comprehensive lipid profile and thyroid-stimulating hormone (TSH) assessments, and normal free thyroxine (FT4) levels. Lipid profile and TSH measurements followed standardized procedures using the Cobas Roche® 6000 system (Roche Diagnostics Corporation, Indianapolis, USA). Dyslipidemia and SCH were defined according to established thresholds recommended by reputable organizations. Statistical analyses were performed using SPSS version 23.0 (IBM Corp., Armonk, USA) and Microsoft Excel (Microsoft Corporation, Redmond, USA), with significance set at p < 0.05. Results In the total population (447 individuals), the prevalence of dyslipidemia was approximately 42.05% (N = 188), with hypoHDLemia being most prevalent at approximately 31.31% (N = 140). The prevalence of SCH was approximately 12.75% (N = 57), with women constituting approximately 7.6% and men approximately 5.15%. In the euthyroid group 1 (N = 390), the prevalence of dyslipidemia was approximately 40.76% (159 individuals), while in the hypothyroid group 2 (N = 57), it increased to approximately 50.87% (N = 29). Hypertriglyceridemia was more prevalent in Group 2, with a prevalence of approximately 21.05% (N = 12), compared to Group 1, which had a prevalence of approximately 13.84% (N = 54). Additionally, hypoHDLemia was notably higher in Group 2, with a prevalence of approximately 38.59% (N = 22), compared to Group 1, which had a prevalence of approximately 30.25% ( N = 118). The chi-square test revealed a significant association between SCH and dyslipidemia (χ2 = 1.427, p < 0.05). The calculated odds ratio (OR) of 1.5 (p < 0.05) indicates that individuals with SCH are 1.5 times more likely to have dyslipidemia compared to those without SCH. Conclusion In conclusion, our study provides valuable insights into the prevalence of dyslipidemia and its association with SCH in our patient population. We observed a notable prevalence of dyslipidemia among individuals with SCH, characterized by elevated levels of total cholesterol (TC) and low-density lipoprotein cholesterol (LDL-C). Importantly, while chi-square tests revealed a significant association between SCH and dyslipidemia, logistic regression analyses did not confirm a statistically significant correlation after adjusting for potential confounders.

Genetic insights into repurposing statins for hyperthyroidism prevention: a drug-target Mendelian randomization study

Background

Current therapeutic measures for thyroid dysfunction are limited and often accompanied by adverse effects. The use of lipid-lowering drugs like statins has recently been associated with lower thyroid eye diseases risk.

Objective

To investigate the implications of genetically proxied lipid-lowering drugs on thyroid dysfunction.

Methods

In this drug-target Mendelian randomization (MR) study, we utilized genetic variants within drug target genes associated with low-density lipoprotein (LDL) or triglyceride (TG), derived from a genome-wide association study (GWAS) meta-analysis (N ≤ 188,577), to simulate lifelong drug interventions. Genetic summary statistics for thyroid dysfunction outcomes were retrieved from GWAS datasets of Thyroid Omics Consortium (N ≤ 54,288) and UK Biobank (N = 484,598). Inverse-variance-weighted MR (IVW-MR) method was performed as primary analysis, followed by validation in colocalization analysis. A subsequent two-step MR analysis was conducted to identify biomarkers mediating the identified drug-outcome association.

Results

In IVW-MR analysis, genetic mimicry of 3-hydroxy-3-methylglutarylcoenzyme reductase (HMGCR) inhibitors (e.g. statins) was significantly associated with lower risk of hyperthyroidism in two independent datasets (OR1, 0.417 per 1-mmol/L lower in LDL-C; 95% CI 0.262 to 0.664; P1 = 2.262 × 10-4; OR2 0.996; 95% CI 0.993-0.998; P2 = 0.002). Two-step MR analysis revealed eighteen biomarkers linked to genetic mimicry of HMGCR inhibition, and identified insulin-like growth factor 1 (IGF-1) levels mediating 2.108% of the negative causal relationship between HMGCR inhibition and hyperthyroidism.

Conclusion

This study supports HMGCR inhibition as a promising therapeutic strategy for hyperthyroidism and suggests its underlying mechanisms may extend beyond lipid metabolism. Further investigations through laboratory studies and clinical trials are necessary to confirm and elucidate these findings.

Association of serum lipids and abnormal lipid score with cancer risk: a population-based prospective study

BACKGROUND

Serum lipid levels are associated with cancer risk. However, there still have uncertainties about the single and combined effects of low lipid levels on cancer risk.

METHODS

A prospective cohort study of 33,773 adults in Shanghai between 2016 and 2017 was conducted. Total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), and high-density lipoprotein cholesterol (HDL-C) levels were measured. Cox proportional hazard models were used to assess the association of single and combined lipids with overall, lung, colon, rectal, thyroid gland, stomach, and female breast cancers. The effect of the combination of abnormal lipid score and lifestyle on cancer was also estimated.

RESULTS

A total of 926 incident cancer cases were identified. In the RCS analysis, hazard ratios (HRs) of overall cancer for individuals with TC < 5.18 mmol/L or with LDL-C < 3.40 mmol/L were higher. Low TC was associated with higher colorectal cancer risk (HR [95% CI] = 1.76 [1.09-2.84]) and low HDL-C increased thyroid cancer risk by 90%. Abnormal lipid score was linearly and positively associated with cancer risk, and smokers with high abnormal lipid scores had a higher cancer risk, compared to non-smokers with low abnormal lipid scores (P < 0.05).

CONCLUSIONS

Low TC levels were associated with an increased risk of overall and colorectal cancer. More attention should be paid to participants with high abnormal lipid scores and unhealthy lifestyles who may have a higher risk of developing cancer. Determining the specific and comprehensive lipid combinations that affect tumorigenesis remains a valuable challenge.

Hypothyroidism increases angiotensinogen gene expression associated with vascular smooth muscle cells cholesterol metabolism dysfunction and aorta remodeling in Psammomys obesus

It has been previously shown that clinical cardiovascular manifestations can be caused by mild changes in thyroid function. However, the implication of angiotensinogen (Agt) and vascular smooth muscle cells (VSMCs) dysfunction in the pathophysiology of cardiovascular manifestations in hypothyroidism have not yet been investigated. We induced experimental hypothyroidism in Psammomys obesus by administering carbimazole for five months. At the end of the experiment, the animals were sacrificed and histopathological analysis was performed using Masson's trichrome staining of the aorta and thyroid gland. The expression of the Agt gene and the genes implicated in cholesterol metabolism regulation in the liver and VSMCs was determined by qRT-PCR. Histological observations revealed profound remodeling of the aorta structure in animals with hypothyroidism. In addition, Agt gene expression in the liver was significantly increased. In vitro study, showed that VSMCs from hypothyroid animals overexpressed 3-hydroxy-3-methylglutaryl coenzyme A reductase (Hmgcr) and Acyl CoA:cholesterol acyltransferase (Acat) 1, with failure to increase the efflux pathway genes (ATP-binding cassette subfamily G member (Abcg) 1 and 4). These results suggest that hypothyroidism leads to vascular alterations, including structural remodeling, VSMCs cholesterol metabolism dysfunction, and their switch to a synthetic phenotype, together with hepatic Agt gene overexpression.

Analysis of Subclinical Thyroid Dysfunction and Metabolic Abnormality in 28568 Healthy People

We analyzed the detection rates of metabolic syndrome (MetS) and subclinical thyroid dysfunction, including subclinical hyperthyroidism (SCHyper) and subclinical hypothyroidism (SCH), in healthy people, as well as their relationship. Clinical data were collected from 28,568 healthy individuals who underwent physical examinations. The detection rates of SCHyper, SCH, and MetS, as well as in different genders and ages, were analyzed. The detection rate of SCHyper and SCH in females was significantly higher than that in males (P < 0.001), but that of MetS in males was significantly higher than that in females (P < 0.001). In each age group, the detection rate of SCH in females was higher than that in males (P < 0.001). The detection rate of SCH was significantly different in different age groups (P < 0.001). The detection rates of hyperlipidemia (P < 0.001), obesity (P = 0.004), hypertension (P = 0.009), and hyperglycemia (P < 0.001) in the female SCH group were significantly higher than those in the normal group. The detection rates of hyperlipidemia (P = 0.006), obesity (P = 0.04), and hypertension (P = 0.04) in the male SCH group were higher than those in the normal group. The males with SCHyper were more prone to hyperlipidemia (P = 0.02) and obesity (P = 0.03). In addition, the female SCHyper group was not significantly different from the normal group (P > 0.05). Conclusively, the detection rate of SCHyper and SCH in females is higher than that in males, which increases with age. Attention should be paid to subclinical thyroid dysfunction in elderly people, especially females. Early individualized screening and early intervention should be carried out for people with abnormal metabolism.

The role of the thyroid in polycystic ovary syndrome

Polycystic ovary syndrome (PCOS) is the most common endocrine and metabolic disease in women of childbearing age and can cause metabolic disorder, infertility, and increased anxiety and depression; as a result, it can seriously affect the physical and mental health of fertile women. PCOS is a highly clinically heterogeneous disease with unclear etiology and pathogenesis, which increases the difficulty of treatment. The thyroid gland has complex regulatory effects on metabolism, reproduction, and emotion, and produces hormones that act on almost all cells of the human body. The clinical manifestations of PCOS are similar to some thyroid diseases. Furthermore, some thyroid diseases, such as subclinical hypothyroidism (SCH), not only increase the incidence rate of PCOS, but also exacerbate its associated metabolic abnormalities and reproductive disorders. Interestingly, PCOS also increases the incidence of some thyroid diseases. However, the role of the thyroid in PCOS remains unclear. This review is intended to thoroughly explore the critical role of the thyroid in PCOS by summarizing the comorbidity of PCOS and thyroid diseases and their combined role in metabolic disorders, related metabolic diseases, and reproductive disorders; and by analyzing the potential mechanism through which the thyroid influences the development and progression of PCOS and its symptoms. We hope this review will provide a valuable reference for the role of the thyroid in PCOS.

Association between thyroid function and diabetes peripheral neuropathy in euthyroid type 2 diabetes mellitus patients

Previous studies disclosed that a high thyroid stimulating hormone level is an independent risk factor for diabetes peripheral neuropathy (DPN) in subclinical hypothyroidism (SCH) patients with type 2 diabetes mellitus (T2DM). However, whether thyroid metabolism has an effect on DPN in euthyroid T2DM patients remains unknown. The aim of this study was to identify the association between thyroid function and DPN in euthyroid T2DM patients. A set of 580 euthyroid T2DM patients was enrolled in the current study and stratified into DPN and Non-DPN groups. Mann-Whitney U test was performed to analyze the continuous variables of biochemical and thyroid metabolism indicators, and the Chi-square test was used to compare the categorical variables. Spearman correlation analysis was performed to analyze the relationship between clinical indicators and free thyroxine (FT4). By using the logistic regression analysis, the prevalence of DPN in different thyroid function indicators were evaluated. T2DM patients with DPN had obviously lower levels of aspartate aminotransferase (AST), alpha-hydroxybutyric dehydrogenase (α-HBDH), superoxide dismutase (SOD), calcium (Ca), creatinine (Cr), uric acid (UA), retinol binding protein (RBP), total protein (TP), albumin (ALB), alanine aminotransferase (ALT) and FT4 than the T2DM patients without DPN (P < 0.05). FT4 was associated with TP, prealbumin (PA), ALB, SOD, anion gap (AG), Ca, chlorine (Cl), UA, RBP, apoprotein A (Apo A), apoprotein B (Apo B), apoprotein E (Apo E), and total cholesterol (TC). According to the FT4 quartile, participants were sequentially divided into four groups to compare the prevalence of DPN between each group. The data suggested that the prevalence of DPN in these four groups was 53.79%, 53.28%, 54.97%, 38.10%, respectively. Moreover, compared with quartile 4, patients in quartile 1, 2, 3 all had a significantly higher risk of DPN (P = 0.007, P = 0.011, P = 0.004). The level of FT4 was negatively correlated with the prevalence of DPN in euthyroid T2DM patients.

The Impact of Laparoscopic Sleeve Gastrectomy on Thyroid Functions in Egyptian Patients with Obesity

BACKGROUND

Sleeve gastrectomy (SG) continues to be one of the most popular bariatric procedures all over the world. Thyroid-stimulating hormone (TSH) frequently shows a slight elevation in patients with obesity. The effect of SG on thyroid hormones has been rarely investigated.

AIM OF THE STUDY

This study aimed to assess the short-term effect of SG on thyroid functions in Egyptian patients with morbid obesity and the potential predictors of the postoperative thyroid functions.

PATIENTS AND METHODS

This study included patients undergoing SG at kasr al ainy hospitals. The patients underwent preoperative 3-, 6-, and 12-month postoperative analyses of the thyroid functions and other biochemical markers.

RESULTS

The study included 106 patients who showed significant improvement in thyroid functions at the follow-up assessment. Twelve-month TSH positively correlated with the 12-month measures of LDL and HbA1c. TSH change at 12-month follow-up (TSH) was inversely correlated to 12-month BMI and positively correlated to preoperative TSH and 12-month percentage of total weight loss (TWL%). Univariable linear regression analysis demonstrated that preoperative TSH (p < 0.001), 12-month TWL% (p = 0.042), 12-month HbA1c (p = 0.001), and 12-month LDL (p = 0.049) were significant predictors for the 12-month TSH levels. Multivariable analysis showed that only preoperative TSH levels (p < 0.001) and 12-month HbA1c levels (p = 0.021) could affect the 12-month TSH levels.

CONCLUSION

The current study supports the evidence of thyroid function improvement after sleeve gastrectomy. This improvement was affected by the amount of weight loss after surgery.

Association between sensitivity to thyroid hormones and dyslipidemia in patients with coronary heart disease

BACKGROUND

Thyroid hormones affect lipid metabolism via central and peripheral regulation. However, there have been few studies on the association between thyroid hormone sensitivity and dyslipidemia. We aimed to investigate the association between thyroid hormone sensitivity and dyslipidemia in patients with coronary heart disease (CHD).

METHODS

A total of 31,678 patients with CHD were included in this large multicenter retrospective study. Central thyroid hormone sensitivity was evaluated using the thyroid feedback quantile-based index (TFQI), parametric thyroid feedback quantile-based index (PTFQI), thyroid-stimulating hormone index (TSHI), and thyrotropin thyroxine resistance index (TT4RI); peripheral thyroid hormone sensitivity was assessed by the ratio of free triiodothyronine (FT3)/free thyroxine (FT4). Logistic regression analysis was used to analyze the association between thyroid hormone sensitivity and dyslipidemia.

RESULTS

Among 31,678 participants, 21,648 (68.34%) had dyslipidemia. In the multi-adjusted models, the risk of dyslipidemia was positively correlated with TFQI (odds ratio [OR]: 1.04; 95% confidence interval [CI]: 1.03-1.05), PTFQI (OR: 1.09; 95% CI: 1.06-1.12), TSHI (OR: 1.08; 95% CI: 1.06-1.11), and TT4RI (OR: 1.08; 95% CI: 1.05-1.11). Conversely, the risk of dyslipidemia was negatively correlated with FT3/FT4 (OR: 0.94; 95% CI: 0.92-0.97). In stratified analyses, the association between thyroid hormone sensitivity and dyslipidemia was statistically significant for different sexes, glucose levels, and blood pressure states.

CONCLUSION

There is a significant association between sensitivity to thyroid hormones and dyslipidemia, regardless of sex, glucose level, or blood pressure. Graphical abstract.

Sensitivity to thyroid hormones is associated with advanced fibrosis in euthyroid patients with non-alcoholic fatty liver disease: A cross-sectional study

BACKGROUND AND AIMS

The relationship between thyroid hormone sensitivity and the occurrence of advanced hepatic fibrosis in non-alcoholic fatty liver disease (NAFLD) remains unclear. We aimed to explore the association between sensitivity to thyroid hormones and advanced fibrosis (F3-F4) of NAFLD in patients with biopsy-proven euthyroid NAFLD.

METHODS

In this study, 129 participants with biopsy-proven euthyroid NAFLD were enrolled, all of whom underwent thyroid function tests and liver biopsy. Indicators reflecting the sensitivity to thyroid hormones were also calculated. A logistic regression model was used to evaluate the association between thyroid hormone sensitivity and risk of advanced liver fibrosis.

RESULTS

Among the 129 participants, 40 (31.0%) had advanced fibrosis. Advanced fibrosis was independently associated with TSH, FT3, FT3/FT4, thyrotroph T4 resistance index (TT4RI), TSH index (TSHI), and thyroid feedback quantile-based index (TFQI) (P<0.05), even after adjusting for sex, age, and metabolic factors. The combination of TFQI with age, waist circumference (WC), triglycerides (TGs), and low-density lipoprotein cholesterol (LDL-C) performed best for advanced fibrosis diagnosis.

CONCLUSION

In euthyroid NAFLD patients, higher FT3/FT4, TFQI, TT4RI, and TSHI values were strongly associated with an increased incidence of advanced liver fibrosis. The combination of TFQI with age, WC, TGs, and LDL-C can be used as a predictor for advanced fibrosis in patients with NAFLD.

Association of Subclinical Hypothyroidism with Nonalcoholic Fatty Liver Disease in Patients with Type 2 Diabetes Mellitus: A Cross-Sectional Study

Background

Nonalcoholic fatty liver disease (NAFLD) and type 2 diabetes mellitus (T2DM) are recognized as two common health problems. Metabolic diseases, such as dyslipidemia, obesity, and hypertension are known risk factors for NAFLD. In addition to these risk factors, other risk factors have been recently suggested, such as thyroid dysfunction.

Materials and Methods

In this study, adult patients with T2DM were recruited. Various clinical and biochemical parameters including thyroid function tests, liver function tests, and liver sonography in all participants were assessed and compared between with and without NAFLD groups.

Results

Data from 926 diabetic patients were analyzed; of which, 744 (80.3%) had fatty liver. The prevalence of subclinical hypothyroidism (SCH) in patients with NAFLD was 11.6% and in patients without NAFLD was 6.0% (P = 0.029). Furthermore, the prevalence of overt hypothyroidism was higher in diabetic patients with NAFLD (3.9% vs. 1.6%); this difference was not statistically significant. In univariate logistic regression analysis, hemoglobin A1c (odds ratio [OR]: 8.13); history of insulin consumption (OR: 5.35); duration of diabetes (OR: 2.20); family history of diabetes (OR: 2.85); history of antihypertensive drug use (OR: 2.14) as well as SCH (OR: 2.03) were significant variables for NAFLD. According to the multivariate logistic model, after eliminating the confounding effect of age, sex, and body mass index; the chance of developing NAFLD in patients with SCH was 2.32 times higher than patients without SCH (P = 0.014).

Conclusion

NAFLD is extremely common in patients with T2DM. The relationship between hypothyroidism and NAFLD is independent of other risk factors.

Relationship between the development of hyperlipidemia in hypothyroidism patients

As shown in the previous studies, hypothyroidism (HT) is identified to be closely associated with the elevated plasma levels of total cholesterol (TC), low-density lipoprotein cholesterol (LDL-C), triglyceride (TG), and with the decreased plasma levels of high density lipoprotein cholesterol (HDL-C). On the other hand, the thyroid hormone (TH), which has been considered as a vital hormone produced and released by the thyroid gland, are well-established to regulate the metabolism of plasma TC; whereas other evidence proposed that the thyroid-stimulating hormone (TSH) also regulated the plasma cholesterol metabolism independently of the TH, which further promotes the progression of hyperlipidemia. Nevertheless, the potential mechanism is still not illustrated. It is worth noting that several studies has found that the progression of HT-induced hyperlipidemia might be associated with the down-regulated plasma levels of TH and the up-regulated plasma levels of TSH, revealing that HT could promote hyperlipidemia and its related cardio-metabolic disorders. Otherwise, multiple novel identified plasma proteins, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), angiopoietin-like protein (ANGPTLs), and fibroblast growth factors (FGFs), have also been demonstrated to embrace a vital function in modulating the progression of hyperlipidemia induced by HT. In the present comprehensive review, the recent findings which elucidated the association of HT and the progression of hyperlipidemia were summarized. Furthermore, other results which illustrated the underlying mechanisms by which HT facilitates the progression of hyperlipidemia and its cardio-metabolic disorders are also listed in the current review.

Efficacy evaluation of probiotics combined with prebiotics in patients with clinical hypothyroidism complicated with small intestinal bacterial overgrowth during the second trimester of pregnancy

Objective

To explore the effect of probiotics combined with prebiotics on clinical hypothyroidism during pregnancy combined with small intestinal bacterial overgrowth.

Methods

(1) In total, 441 pregnant women were included in this study. A total of 231 patients with clinical hypothyroidism during the second trimester of pregnancy and 210 normal pregnant women were enrolled in the lactulose methane-hydrogen breath test. The positive rate of intestinal bacterial overgrowth (SIBO), gastrointestinal symptoms, thyroid function and inflammatory factors were compared between the two groups by chi-square test and two independent sample t-test. (2) SIBO-positive patients in the clinical hypothyroidism group during pregnancy (n=112) were treated with probiotics combined with prebiotics based on conventional levothyroxine sodium tablets treatment. The changes in the methane-hydrogen breath test, gastrointestinal symptoms, thyroid function and inflammatory factors were compared before treatment (G0) and 21 days after treatment (G21) by chi-square test and paired sample t test.

Results

(1) The positive rates of SIBO in pregnant women in the clinical hypothyroidism group and control group were 48.5% and 24.8%, respectively. (2) The incidence of abdominal distention and constipation in the clinical hypothyroidism group was significantly higher than that in the control group, and the risk of abdominal distention and constipation in SIBO-positive pregnant women was higher than that in SIBO-negative pregnant women. (3) The serum levels of hypersensitive C-reactive protein (hsCRP), IL-10, IL-6, TNF-α, low-density lipoprotein (LDL), total cholesterol (TC), free fatty acids (FFAs) and apolipoprotein B (ApoB) in the hypothyroidism group during pregnancy were higher than those in the control group. (4) After 21 days of probiotics combined with prebiotics, the incidence of pure methane positivity in the methane-hydrogen breath test in the G21 group was significantly reduced, and the average abundance of hydrogen and methane at each time point in the G21 group was lower than that in the G0 group. (5) The incidence of constipation in the G21 group was significantly lower than before treatment. (6) The levels of serum TSH, hsCRP, IL-6, TNF-α, TC and LDL in pregnant women after probiotics combined with prebiotics were lower than those before treatment.

Conclusion

Probiotics combined with prebiotics are effective in the treatment of pregnant patients with clinical hypothyroidism complicated with SIBO, providing a new idea to treat pregnant patients with clinical hypothyroidism complicated with SIBO.

Nonalcoholic Fatty Liver Disease and Hypothyroidism: What You Need to Know

Non-alcoholic fatty liver disease (NAFLD) represents one of the leading causes of chronic liver disease globally, perhaps because of the drastic increase in prevalence around the world during the last 20 years and continues growing. The disease starts from simple steatosis (NAFL) that can progress to non-alcoholic steatohepatitis (NASH) and, in some patients, progress to cirrhosis and hepatocellular carcinoma (HCC). The pathogenesis and pathophysiology of NAFLD are complex and involve different factors (genetic, metabolic, endocrinopathies, and others). One of the concerns that appeared in recent years is hypothyroidism-induced NAFLD. The pathogenesis is compound and not well understood, and an association between hypothyroidism and NAFLD remains controversial because of insufficient studies that can confirm it. More research is needed to determine the association between hypothyroidism and NAFLD and the underlying mechanisms. In this review, we will discuss a more in-depth analysis of the physiology of thyroid hormones (TH) as well as the pathophysiology of hypothyroidism-induced NAFLD and, based on the recent meta-analyses, the association of thyroid hormones and NAFLD.

Associations of Fine Particulate Matter Constituents with Metabolic Syndrome and the Mediating Role of Apolipoprotein B: A Multicenter Study in Middle-Aged and Elderly Chinese Adults

Fine particulate matter (PM_2.5) was reported to be associated with metabolic syndrome (MetS), but how PM_2.5 constituents affect MetS and the underlying mediators remains unclear. We aimed to investigate the associations of long-term exposure to 24 kinds of PM_2.5 constituents with MetS (defined by five indicators) in middle-aged and elderly adults and to further explore the potential mediating role of apolipoprotein B (ApoB). A multicenter study was conducted by recruiting subjects (n = 2045) in the Beijing-Tianjin-Hebei region from the cohort of Sub-Clinical Outcomes of Polluted Air in China (SCOPA-China Cohort). Relationships among PM_2.5 constituents, serum ApoB levels, and MetS were estimated by multiple logistic/linear regression models. Mediation analysis quantified the role of ApoB in "PM_2.5 constituents-MetS" associations. Results indicated PM_2.5 was significantly related to elevated MetS prevalence. The MetS odds increased after exposure to sulfate (SO₄^2-), calcium ion (Ca²⁺), magnesium ion (Mg²⁺), Si, Zn, Ca, Mn, Ba, Cu, As, Cr, Ni, or Se (odds ratios ranged from 1.103 to 3.025 per interquartile range increase in each constituent). PM_2.5 and some constituents (SO₄^2-, Ca²⁺, Mg²⁺, Ca, and As) were positively related to serum ApoB levels. ApoB mediated 22.10% of the association between PM_2.5 and MetS. Besides, ApoB mediated 24.59%, 50.17%, 12.70%, and 9.63% of the associations of SO₄^2-, Ca²⁺, Ca, and As with MetS, respectively. Our findings suggest that ApoB partially mediates relationships between PM_2.5 constituents and MetS risk in China.

Thyroid Function Before and After Laparoscopic Sleeve Gastrectomy in Patients with Obesity

BACKGROUND

Effect of laparoscopic sleeve gastrectomy (LSG) on thyroid function of patients with obesity remains unclear. The aim of this study was to evaluate the changes in thyroid function before and after LSG in patients with obesity.

METHODS

Data was retrieved from a retrospectively collected database of patients with morbid obesity and normal thyroid function who received LSG. At 12 months after surgery, changes of thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), and intact parathyroid hormone (iPTH) were evaluated. In addition, the correlation between thyroid hormone levels and body mass index (BMI) and other metabolic indicators and anthropometric parameters were analyzed.

RESULTS

Eighty-five patients were included in the study. The concentrations of FT3 (5.7 ± 0.7 vs 5.1 ± 0.6, p < 0.001) and TSH (2.2 ± 1.0 vs 1.9 ± 0.9, p = 0.002) significantly decreased 12 months postsurgery, while mean FT4 levels increased from12.0 ± 1.9 vs 12.4 ± 2.0 pmol/L (p = 0.013). Furthermore, mean iPTH decreased from 53.3 ± 48.3 to 38.7 ± 13.2 pg/mL (p = 0.011). Multiple stepwise regression analysis showed that changes in LDL levels were an independent factor contributing to changes in TSH levels (β = 0.362, p = 0.001). Moreover, TSH did not correlate with BMI.

CONCLUSIONS

In this study, FT3, TSH, and iPTH were decreased in euthyroid patients with obesity after LSG, while FT4 was significantly increased. Changes in TSH were positively correlated with LDL, but no statistically significant correlation was found with BMI. Additionally, FT3, FT4, and iPTH were correlated with VB12, age, and BMI, respectively.

Circulating concentrations of free triiodothyronine are associated with central adiposity and cardiometabolic risk factors in young euthyroid adults

Thyroid dysfunction is associated with classic cardiometabolic risk factors in humans. However, this relationship remains unclear in young euthyroid adults. The present work examines the associations of circulating thyroid hormones (THs) and thyroid-stimulating hormone (TSH) concentrations with body composition and cardiometabolic risk factors in young euthyroid adults. A total of 106 sedentary, euthyroid adults (72 women; 22 ± 2 years old) participated in this cross-sectional study. THs and TSH serum concentrations were determined in fasting conditions (6 h). Body composition (fat mass (FM), lean mass (LM), and visceral adipose tissue (VAT)) was determined by dual-energy X-ray absorptiometry, anthropometric parameters (weight, height, and waist circumference) were measured, and neck adipose tissue mass was quantified through computed tomography (CT) scanning. Cardiometabolic risk factors including fasting glucose and lipid metabolism markers, hepatic phosphatase and transaminases, and blood pressure were also assessed. Free triiodothyronine (FT3) concentration was positively associated with body mass index, LM, VAT, and waist circumference (all P ≤ 0.038). FT3 was also associated with glucose, insulin, HOMA-IR, fatty liver index, and blood pressure (all P < 0.024). All the associations were attenuated when adjusting for sex. In contrast, we found no associations of TSH or free thyroxine with any body composition parameter or cardiometabolic risk factors. In conclusion, FT3 is associated with central adiposity and cardiometabolic risk factors including insulin resistance, fatty liver index, and mean, systolic and diastolic blood pressure in young euthyroid adults. ClinicalTrials.gov identifier: NCT02365129.

Study on endocrine disruption effect of paclobutrazol and uniconazole on the thyroid of male and female rats based on lipidomics

The present study investigated the effects of paclobutrazol and uniconazole on thyroid endocrine system in rats. Lipidomic analysis was performed to obtain the biomarkers of thyroid endocrine disruption induced by paclobutrazol and uniconazole. Network pharmacology was further used to discover potential targets of biomarkers related to drugs and diseases. After paclobutrazol and uniconazole administration, seven and four common biomarkers related to thyroid endocrine disruption for female and male rats were obtained, respectively. Paclobutrazol and uniconazole significantly increased the biomarker levels of PG (12:0/15:0), PS (14:0/16:0), PA (20:1/15:0) and PG (13:0/17:0) in both sexes of rats. Exposure to paclobutrazol additionally caused a significant decrease of PG (22:6/20:2), PE (24:1/18:1) and PE (24:0/18:0) in female rats, while an increase in male rats. Changes of the common biomarkers for paclobutrazol and uniconazole revealed similar endocrine disruption effect, which was higher in the females. Network pharmacology and KEGG pathway analysis indicated that the thyroid endocrine disrupting effects of paclobutrazol and uniconazole may be related to V-akt murine thymoma viral oncogene homolog (Akts), mitogen-activated protein kinase (MAPKs), epidermal growth factor receptor (EGFR), Insulin-like growth factor (IGF-1), IGF-IR and V-Raf murine sarcoma viral oncogene homolog B1 (BRAF). The results demonstrated that paclobutrazol and uniconazole could cause thyroid endocrine disorders in male and female rats, which were sex-specific, thus highlighting the importance of safe and effective application of these plant growth regulators.

Alteration of Serum Proteome in Levo-Thyroxine-Euthyroid Thyroidectomized Patients

The monotherapy with levo-thyroxine (LT4) is the treatment of choice for patients with hypothyroidism after thyroidectomy. However, many athyreotic LT4-treated patients with thyroid hormones in the physiological range experience hypothyroid-like symptoms, showing post-operative, statistically significant lower FT3 levels with respect to that before total thyroidectomy. Since we hypothesized that the lower plasmatic FT3 levels observed in this subgroup could be associated with tissue hypothyroidism, here we compared, by a preliminary proteomic analysis, eight sera of patients with reduced post-surgical FT3 to eight sera from patients with FT3 levels similar to pre-surgery levels, and six healthy controls. Proteomic analysis highlights a different serum protein profile among the considered conditions. By enrichment analysis, differential proteins are involved in coagulation processes (PLMN-1.61, -1.98 in reduced vs. stable FT3, p < 0.02; A1AT fragmentation), complement system activation (CFAH + 1.83, CFAB + 1.5, C1Qb + 1.6, C1S + 7.79 in reduced vs. stable FT3, p < 0.01) and in lipoprotein particles remodeling (APOAI fragmentation; APOAIV + 2.13, p < 0.003), potentially leading to a pro-inflammatory response. This study suggests that LT4 replacement therapy might restore biochemical euthyroid conditions in thyroidectomized patients, but in some cases without re-establishing body tissue euthyroidism. Since our results, this condition is reflected by the serum protein profile.

Thyroid disorders and cardiovascular manifestations: an update

Cardiovascular disease (CVD) remains the leading cause of death worldwide, representing a major health, social, and economic issue. Thyroid disorders are very common and affect >10% of the adult population in total. The aim of this review is to describe the physiologic role of thyroid hormones on cardiovascular system, to present cardiovascular manifestations in patients with thyroid disorders, emphasizing in molecular mechanisms and biochemical pathways, and to summarize current knowledge of treatment options. Thyroid hormone receptors are located both in myocardium and vessels, and changes in their concentrations affect cardiovascular function. Hyperthyroidism or hypothyroidism, both clinical and subclinical, without the indicated therapeutical management, may contribute to the progression of CVD. According to recent studies, even middle changes in thyroid hormones levels increase cardiovascular mortality from 20% to 80%. In more details, thyroid disorders seem to have serious effects on the cardiovascular system via plenty mechanisms, including dyslipidemia, hypertension, systolic and diastolic myocardial dysfunction, as well endothelial dysfunction. On top of clinical thyroid disorders management, current therapeutics focus on younger patients with subclinical hypothyroidism and elderly patients with subclinical hyperthyroidism.

Update on dyslipidemia in hypothyroidism: the mechanism of dyslipidemia in hypothyroidism

Hypothyroidism is often associated with elevated serum levels of total cholesterol, LDL-C and triglycerides. Thyroid hormone (TH) affects the production, clearance and transformation of cholesterol, but current research shows that thyroid-stimulating hormone (TSH) also participates in lipid metabolism independently of TH. Therefore, the mechanism of hypothyroidism-related dyslipidemia is associated with the decrease of TH and the increase of TSH levels. Some newly identified regulatory factors, such as proprotein convertase subtilisin/kexin type 9, angiogenin-like proteins and fibroblast growth factors are the underlying causes of dyslipidemia in hypothyroidism. HDL serum concentration changes were not consistent, and its function was reportedly impaired. The current review focuses on the updated understanding of the mechanism of hypothyroidism-related dyslipidemia.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Improvements in Quality of Life and Thyroid Parameters in Hypothyroid Patients on Ethanol-Free Formula of Liquid Levothyroxine Therapy in Comparison to Tablet LT4 Form: An Observational Study

Levothyroxine (LT4) is a standard therapy in hypothyroidism; however, its bioavailability and therapeutic effects might be affected by many factors. Data shows that therapy with liquid LT4 characterized by quicker pharmacokinetics provides better thyroid hormones control than tablet LT4. We addressed the quality of life (QoL) and efficacy of the new ethanol-free formula of liquid LT4 (Tirosint^®SOL) treatment in 76 euthyroid patients with primary (PH, n = 46) and central hypothyroidism (CH, n = 30), and compared the results to retrospective data on equivalent doses of tablet L-T4 therapy. After 8 weeks of liquid LT4 therapy, we found a significant improvement in QoL in both PH and CH patients. TSH levels were unaltered in PH patients. Free hormone levels (fT4 and fT3) increased in all the patients, with the exception of fT3 in the CH group. SHBG and low-density lipoprotein (LDL) also improved. Liquid LT4 therapy provided a better thyroid hormone profile and improvement in patients' QoL than the tablet form, which was possibly due to the more favorable pharmacokinetics profile resulting in better absorption, as suggested by the increased free thyroid hormone levels. In summary, this is the first study addressing the QoL in hypothyroid patients, including primary and central hypothyroidism, treated with liquid LT4 formula in everyday practice.

Sensitivity to Thyroid Hormone Indices Are Closely Associated With NAFLD

BACKGROUND

Previous studies on the association between thyroid function and non-alcoholic fatty liver disease (NAFLD) have contradicted. Acquired resistance to thyroid hormone theory might provide a reasonable explanation for these contradictions. We aimed to analyze the association between sensitivity to thyroid hormone indices with NAFLD.

METHODS

A total of 4,610 individuals from the health medical center of the First Hospital of China Medical University were included in this study. The previously used thyroid feedback quantile-based index (TFQI_FT4) was calculated. Also, we substituted free triiodothyronine (FT₃) into the TFQI formulas to get the TFQI_FT3 index. NAFLD was defined using abdominal ultrasound.

RESULTS

Study results showed that FT₃/FT₄ and TFQI_FT3 were positively correlated with the triglyceride (TG), total cholesterol (TC), and low-density lipoprotein cholesterol (LDL-C) levels (P<0.05) and negatively correlated with high-density lipoprotein cholesterol (HDL-C) level (P<0.05). In contrast, TFQI_FT4 was positively correlated with HDL-C level (P < 0.05). After adjustment for multiple confounders, FT₃, FT₃/FT₄, and TFQI_FT3 were positively associated with the risks of dyslipidemia and NAFLD (P < 0.05). TFQI_FT3 and FT₃/FT₄ performed better than TFQI_FT4 on ROC analyses for NAFLD prediction, although the diagnostic sensitivity and specificity at the optimal cut-points were low. However, no association was observed between TFQI_FT4 with the risks of dyslipidemia and NAFLD.

CONCLUSION

TFQI_FT3 and FT₃/FT₄ can be used as new indicators for predicting dyslipidemia and NAFLD, although with low sensitivity and specificity at the optimal cut-points, while TFQI_FT4 has insufficient evidence in predicting dyslipidemia and NAFLD.

Treatment of Thyroid Dysfunction and Serum Lipids: A Systematic Review and Meta-analysis

CONTEXT

Hyperthyroidism is associated with low levels of cholesterol and triglycerides, and hypothyroidism is associated with hypercholesterolemia and hypertriglyceridemia.

OBJECTIVE

The aim of this systematic review was to investigate the impact of therapy for overt and subclinical hyper- and hypothyroidism on serum lipids.

DATA SOURCES

We searched MEDLINE, EMBASE, the Cochrane Central Register of Controlled Trials, the Cochrane Database of Systematic Reviews, and Scopus from 1970 through April 5, 2018.

STUDY SELECTION

Pairs of independent reviewers selected randomized and observational studies evaluating lipid parameters in patients undergoing treatment for hyper- or hypothyroidism.

DATA EXTRACTION

Pairs of independent reviewers extracted data and appraised studies.

DATA SYNTHESIS

Treatment of overt hyperthyroidism showed a significant increase in total cholesterol (TC) by 44.50 mg/dL (95% confidence interval [CI]: 37.99, 51.02), low-density lipoprotein cholesterol (LDL-C) by 31.13 mg/dL (95% CI: 24.33, 37.93), high-density lipoprotein cholesterol (HDL-C) by 5.52 mg/dL (95% CI: 1.48, 9.56), apolipoprotein A (Apo A) by 15.6 mg/dL (95% CI: 10.38, 20.81), apolipoprotein B (apo B) by 26.12 mg/dL (95% CI: 22.67, 29.57), and lipoprotein (Lp[a]) by 4.18 mg/dL (95% CI: 1.65, 6.71). There was no significant change in triglyceride (TG) levels. Treatment of subclinical hyperthyroidism did not change any lipid parameters significantly. Levothyroxine therapy in overt hypothyroidism showed a statistically significant decrease in TC by -58.4 mg/dL (95% CI: -64.70, -52.09), LDL-C by -41.11 mg/dL (95% CI: -46.53, -35.69), HDL-C by -4.14 mg/dL (95% CI: -5.67, -2.61), TGs by -7.25 mg/dL (95% CI: -36.63, 17.87), apo A by -12.59 mg/dL (95% CI: -17.98, -7.19), apo B by -33.96 mg/dL (95% CI: 41.14, -26.77), and Lp(a) by -5.6 mg/dL (95% CI: -9.06, -2.14). Levothyroxine therapy in subclinical hypothyroidism showed similar changes but with a smaller magnitude. The studies contained varied population characteristics, severity of thyroid dysfunction, and follow-up duration.

CONCLUSIONS

Treatment of overt but not subclinical hyperthyroidism is associated with worsening of the lipid profile. Levothyroxine therapy in both overt and subclinical hypothyroidism leads to improvement in the lipid profile, with a smaller magnitude of improvement in subclinical hypothyroidism.

Lipid Management in Patients with Endocrine Disorders: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

This guideline will provide the practicing endocrinologist with an approach to the assessment and treatment of dyslipidemia in patients with endocrine diseases, with the objective of preventing cardiovascular (CV) events and triglyceride-induced pancreatitis. The guideline reviews data on dyslipidemia and atherosclerotic cardiovascular disease (ASCVD) risk in patients with endocrine disorders and discusses the evidence for the correction of dyslipidemia by treatment of the endocrine disease. The guideline also addresses whether treatment of the endocrine disease reduces ASCVD risk.

CONCLUSION

This guideline focuses on lipid and lipoprotein abnormalities associated with endocrine diseases, including diabetes mellitus, and whether treatment of the endocrine disorder improves not only the lipid abnormalities, but also CV outcomes. Based on the available evidence, recommendations are made for the assessment and management of dyslipidemia in patients with endocrine diseases.

HDL Cholesterol Efflux Capacity is Impaired in Severe Short-Term Hypothyroidism Despite Increased HDL Cholesterol

CONTEXT

Severe hypothyroidism has profound effects on lipoprotein metabolism including high-density lipoprotein (HDL) cholesterol elevations but effects on HDL function metrics are unknown.

OBJECTIVE

To determine the impact of severe short-term hypothyroidism on HDL particle characteristics, HDL cholesterol efflux capacity (CEC), and HDL antioxidative capacity.

DESIGN

Observational study with variables measured during severe short-term hypothyroidism (median TSH 81 mU/L) and after 20 weeks of thyroid hormone supplementation (median TSH 0.03 mU/L) (Netherlands Trial Registry ID 7228).

SETTING

University hospital setting in The Netherlands.

PATIENTS

Seventeen patients who had undergone a total thyroidectomy for differentiated thyroid carcinoma.

MAIN OUTCOME MEASURES

HDL particle characteristics (nuclear magnetic resonance spectrometry), CEC (human THP-1-derived macrophage foam cells and apolipoprotein B-depleted plasma), and HDL anti-oxidative capacity (inhibition of low-density lipoprotein oxidation).

RESULTS

During hypothyroidism plasma total cholesterol, HDL cholesterol and apolipoprotein A-I were increased (P ≤ 0.001). HDL particle concentration was unchanged, but there was a shift in HDL subclasses toward larger HDL particles (P < 0.001). CEC was decreased (P = 0.035), also when corrected for HDL cholesterol (P < 0.001) or HDL particle concentration (P = 0.011). HDL antioxidative capacity did not change.

CONCLUSION

During severe short-term hypothyroidism CEC, an important antiatherogenic metric of HDL function, is impaired. HDL cholesterol and larger HDL particles are increased but HDL particle concentration is unchanged. Combined, these findings suggest that HDL quality and quantity are not improved, reflecting dysfunctional HDL in hypothyroidism.

The current debate over treatment of subclinical hypothyroidism to prevent cardiovascular complications

BACKGROUND

Subclinical hypothyroidism (SCH) is an asymptomatic condition associated with increased thyroid-stimulating hormone (TSH) >4 mIU/L with normal thyroxine (T4) and triidothyronine (T3) levels. It is more common in older subjects and especially in women with an overall incidence of 10%.

OBJECTIVE

Because the normal TSH levels increase with age up to 7.5 mIU/L in older people, several studies have reported either no benefits whereas others have reported the benefits of treatment. These studies have caused a great debate over the treatment of SCH, especially in older subjects. Therefore, the objective of this study was to review the current evidence over this debate by reviewing the recent literature on the subject to discern whether treatment of SCH is necessary and under what circumstances.

METHODS

To get a better perspective on the current debate over treatment of SCH, a focused Medline search of the English language literature was conducted from 2012 to 2019 using the terms, hypothyroidism, subclinical, dyslipidaemia, cardiovascular disease, heart failure and 38 papers with pertinent information were selected.

RESULTS

The analysis of results from these papers indicated that the normal levels of TSH are increasing with the advancement of age from 4 mIU/L up to 7.5 mIU/L for patients ≥75 years of age. Also, several of reviewed studies have shown no benefits of treatment whereas, others have shown definite benefits of treatment with levothyroxine supplementation on the clinical and metabolic effects of SBH with reductions in CVD, HF and mortality. The treatment is more effective in younger persons and less so in older persons.

CONCLUSIONS

Based on the overall evidence, treatment of SCH is indicated in younger persons with a TSH level >4.0 mIU/L. In older subjects, treatment should be individualised and based on the presence of symptoms, the level of TSH, and initiated at TSH levels ≥10 mIU/L and at low doses to avoid adverse cardiovascular effects from overtreatment.

Postthyroidectomy obesity in a Korean population: does the extent of surgery matter?

Purpose

The purpose of this study was to investigate the prevalence of postthyroidectomy obesity, and the relationship between the extent of thyroidectomy and obesity.

Methods

A survey conducted at an outpatient clinic from June to October 2014 and retrospective charts for patients undergoing thyroidectomy at Konkuk University Medical Centers from June 2009 to December 2013 were reviewed. We compared clinical characteristics and pre- and postoperative obesity-related factors in 227 patients who underwent total thyroidectomy or lobectomy.

Results

Patients included 39 males and 188 females with a mean age of 46.0 ± 11.0 years; the mean follow-up period was 23.9 ± 16.7 months, and 90 of the 227 patients showed postthyroidectomy obesity. In effect of operative extent on postoperative obesity, patients who underwent TT (48.2 years) than those who underwent lobectomy (43.4 years). TT group had longer follow-up and the frequency of menopause was higher than in the lobectomy group. No differences in postthyroidectomy obesity, body weight change, or body mass index (BMI), change among 2 groups. The predictors of postthyroidectomy obesity were older age, female, heavy alcohol consumption (P = 0.029), higher preoperative BMI (P < 0.001), larger postoperative weight gain (P = 0.024), and larger BMI change. However, the extent of thyroidectomy did not affect postthyroidectomy obesity. Preoperative BMI (P < 0.001) and heavy alcohol consumption (P = 0.03) were independent factors of postthyroidectomy obesity.

Conclusion

The extent of thyroidectomy does not affect postthyroidectomy obesity. Preoperative BMI and heavy alcohol consumption are risk factors for postthyroidectomy obesity. Studies are needed to suggest preoperative life style modification to prevent postthyroidectomy obesity.

Severe hypercholesterolemia in a 2-year-old

Routine and selective cholesterol screening of children is an effective tool to help identify those with familial hypercholesterolemia. In children found to have elevated levels of cholesterol, secondary causes should be excluded, including hypothyroidism. Thyroid hormone has multiple effects on the regulation of lipid synthesis, absorption, and metabolism. In this case report, we described a 2-year-old with a history of congenital hypothyroidism who was found to have severe hypercholesterolemia. A detailed medical history and appropriate screening tests are important in determining the underlying cause of elevated low-density lipoprotein cholesterol to help inform clinical decision-making.

Exercise training-induced changes in metabolic syndrome parameters, carotid wall thickness, and thyroid function in middle-aged women with subclinical hypothyroidism

This study analyzed the differences in effects of a 12-week combination of exercise training program with resistance training and aerobic exercises on the risk factors of metabolic syndrome, carotid wall thickness, and thyroid function, between subclinical hypothyroidism patients and obese groups, in middle-aged women. Subjects consisted of either 20 middle-aged women in the subclinical hypothyroidism (SCH) group or 20 obese (body mass indices [BMI], ≥ 25 kg/m²) women without hypothyroidism in the obese (OB) group. The body composition, blood lipid factors, hormones associated with thyroid functions, blood pressure (BP), and carotid intima-media thickness were measured, while physical fitness was ascertained. In the SCH group, waist circumference (WC) and high-density lipoprotein cholesterol values were outside the normal ranges, while WC and systolic BP (SBP) were outside the normal ranges in the OB group. Following the 12-week training program, significantly positive changes occurred in body fat percentage, sit and reach test results, and SBP (p < 0.05) in the SCH group, while in the OB group, significantly positive changes in BMI, WC, sit and reach test results, SBP, and diastolic BP (DBP, p < 0.05) were observed. In addition, both groups showed significant decreases in intima-media thickness of the right carotid bifurcation (p < 0.05). However, in the two groups, the 12-week exercise training program did not have similar significant impact on the hormones related to thyroid functions and blood lipids. Therefore, further research on exercise training that can effectively induce changes in the hormones associated with thyroid functions in patients with subclinical hypothyroidism is necessary.

Hashimoto Thyroiditis and Dyslipidemia in Childhood: A Review

Hashimoto autoimmune thyroiditis (AIT) is the most common cause of acquired hypothyroidism in the pediatric population. Development of AIT is mediated mainly by cellular immune response directed toward thyroid autoantigens, leading to inflammation and impaired function of thyroid gland. Both thyroid dysfunction and inflammation affect the metabolism of plasma lipoproteins. The alterations in lipid profile worsen with the advancement of hypothyroidism, ranging from discrete changes in euthyroid AIT patients, to atherogenic dyslipidemia in the overt hypothyroidism. In this review, characteristics of dyslipidemia in pediatric AIT patients, and the consequences in respect to the risk for cardiovascular disease (CVD) development are discussed. Additionally, benefit of L-thyroxine treatment on serum lipid profile in pediatric AIT patients is addressed. Finally, potential usefulness of novel lipid biomarkers, such as proprotein convertase subtilisin/kexin type 9 (PCSK9), non-cholesterol sterols, low-density lipoprotein particle size and number, and high-density lipoprotein structure and functionality in AIT patients is also covered. Further longitudinal studies are needed in order to elucidate the long-term cardiovascular outcomes of dyslipidemia in pediatric patients with Hashimoto AIT.

Effects of Short-Term Hypothyroidism on the Lipid Transfer to High-Density Lipoprotein and Other Parameters Related to Lipoprotein Metabolism in Patients Submitted to Thyroidectomy for Thyroid Cancer

BACKGROUND

Elevation of low-density lipoprotein (LDL) cholesterol is the hallmark of the dyslipidemia observed in hypothyroidism, but alterations on high-density lipoprotein (HDL) plasma levels and metabolism are less understood. The aim of this study was to explore aspects of HDL metabolism and enzymes that act on HDL after a short period of overt hypothyroidism.

METHODS

Eighteen women (age 44 ± 11 years; body mass index 27.9 ± 5.2 kg/m²) were studied before total thyroidectomy for thyroid cancer, when they were euthyroid, and after thyroidectomy, in overt hypothyroidism for three weeks, following levothyroxine withdrawal for performance of a whole-body scan.

RESULTS

Thyrotropin and free thyroxine confirmed hypothyroidism; low thyroglobulin and radioiodine uptake indicated near absence of thyroid tissue. LDL cholesterol (125 ± 35 vs. 167 ± 40 mg/dL; p = 0.0002), HDL cholesterol (HDL-C; 39 ± 8 vs. 46 ± 10 mg/dL; p = 0.0025), non-HDL-C (149 ± 38 vs. 201 ± 46 mg/dL; p < 0.0001), unesterified cholesterol (53 ± 10 vs. 70 ± 16 mg/dL; p = 0.0003), apolipoprotein (apo) A-I (1.32 ± 0.19 vs. 1.44 ± 0.22 g/L; p < 0.04), and apo B (0.97 ± 0.25 vs. 1.31 ± 0.28 g/L; p < 0.0001) plasma concentrations were all higher in hypothyroidism compared to values in the euthyroid state, but triglycerides and Lp(a) were unchanged. There were no changes in HDL particle size and lipid composition, cholesteryl ester transfer protein and lecithin cholesterol acyltransferase concentrations and in paraoxonase-1 activity. Regarding the in vitro assay to estimate lipid transfer to HDL, there were no changes when comparing the euthyroid to the hypothyroid state, but when adjusted for HDL-C, the unesterified cholesterol (0.14 ± 0.03 vs. 0.11 ± 0.02; p < 0.0001), triglycerides (0.11 ± 0.02 vs. 0.09 ± 0.02; p < 0.0001), phospholipids (0.44 ± 0.09 vs. 0.40 ± 0.07; p = 0.0205), and esterified cholesterol (0.14 ± 0.03 vs. 0.13 ± 0.03; p = 0.0043) transfer to HDL were all diminished in hypothyroidism.

CONCLUSIONS

In short-term hypothyroidism, HDL-C increased, but this did not increase the capacity of the HDL fraction to receive lipids or the activity of paraoxonase-1, the anti-oxidation enzyme associated to HDL.

Biphasic dyslipidemia in a patient with painless thyroiditis

In this case study, we followed the thyroid function and serum lipid levels of a patient with painless thyroiditis. Serum lipid levels were decreased during the hyperthyroid phase and elevated during the hypothyroid phase. Both serum lipid levels and thyroid function returned to normative values following a course of thyroid replacement treatment.

Paediatric fatty liver disease (PeFLD): All is not NAFLD - Pathophysiological insights and approach to management

The recognition of a pattern of steatotic liver injury where histology mimicked alcoholic liver disease, but alcohol consumption was denied, led to the identification of non-alcoholic fatty liver disease (NAFLD). Non-alcoholic fatty liver disease has since become the most common chronic liver disease in adults owing to the global epidemic of obesity. However, in paediatrics, the term NAFLD seems incongruous: alcohol consumption is largely not a factor and inherited metabolic disorders can mimic or co-exist with a diagnosis of NAFLD. The term paediatric fatty liver disease may be more appropriate. In this article, we summarise the known causes of steatosis in children according to their typical, clinical presentation: i) acute liver failure; ii) neonatal or infantile jaundice; iii) hepatomegaly, splenomegaly or hepatosplenomegaly; iv) developmental delay/psychomotor retardation and perhaps most commonly; v) the asymptomatic child with incidental discovery of abnormal liver enzymes. We offer this model as a means to provide pathophysiological insights and an approach to management of the ever more complex subject of fatty liver.