Dietary high-fat lard intake induces thyroid dysfunction and abnormal morphology in rats

LncRNA MALAT1-miR-339-5p-NIS axis is involved in the increased level of thyroid stimulating hormone (TSH) induced by combined exposure of high iodine and hyperlipidemia

Hypothyroidism and subclinical hypothyroidism were both characterized by elevated levels of thyroid stimulating hormone (TSH). Previous studies had found that high iodine or hyperlipidemia alone was associated with increased TSH level. However, their combined effects on TSH have not been elucidated. In this study, combination of high iodine and hyperlipidemia was established through the combined exposure of high-water iodine and high fat diet in Wistar rats. The results showed that combined exposure of high iodine and high fat can induce higher TSH level. The mRNA and protein levels of sodium iodide transporters (NIS) and type 1 deiodinase (D1) in thyroid tissues, which were crucial genes in the synthesis of thyroid hormones, decreased remarkably in combined exposure group. Mechanistically, down-regulated long non-coding RNA (lncRNA) metastasis associated in lung denocarcinoma transcript 1 (MALAT1) may regulate the expression of NIS by increasing miR-339-5p, and regulating D1 by increasing miR-224-5p. Then, the above findings were explored in subjects exposed to high water iodine and hyperlipidemia. The results indicated that in population combined with high iodine and hyperlipidemia, TSH level increased to higher level and lncRNA MALAT1-miR-339-5p-NIS axis was obviously activated. Collectively, this study found that combined exposure of high iodine and hyperlipidemia induced a higher level of TSH, and lncRNA MALAT1-miR-339-5p-NIS axis may play important role.

Lipid Metabolism in Pregnancy Women with Hypothyroidism and Potential Influence on Pregnancy Outcome

Thyroid hormone (TH) is essential for maintaining normal physiological processes during pregnancy, including the metabolism of energy materials in both the mother and fetus and the growth and development of fetal bone and nervous system. TH can act on the liver, fat, and other tissues and organs to participate in lipid synthesis and breakdown through multiple pathways. Consequently, abnormal thyroid function is often accompanied by lipid metabolism disorders. Both clinical and subclinical hypothyroidism, as well as dyslipidemia during pregnancy, have been shown to be associated with an increased risk of multiple adverse pregnancy outcomes. Recently, there has been an increased interest in studying the alteration of lipidomic and hypothyroidism (both clinical and subclinical hypothyroidism) during pregnancy. Studies have suggested that altered lipid molecules might be used as potential biomarker and associated with adverse maternal and neonatal outcome. Thus, we summarized the associations between lipid metabolism and clinical or subclinical hypothyroidism during pregnancy in this review. Then, we discussed the underlying mechanisms of thyroid dysfunction and lipid metabolism. In addition, we reviewed the possible effect of dyslipidemia on pregnancy and neonatal outcome. However, the relationship between hypothyroidism during pregnancy and changes in the lipid profile and how to intervene in the occurrence and development of adverse pregnancy outcomes require further study.

Metabolic syndrome and risk of subclinical hypothyroidism: a systematic review and meta-analysis

Background

Subclinical hypothyroidism (SCH) is a common endocrine subclinical disorder, the main adverse consequences of which are the development of clinical hypothyroidism and the promotion of ischemic heart disease. Metabolic syndrome (MetS) is a collection of metabolic problems. The goal of this meta-analysis was to evaluate the relationship between MetS and SCH.

Methods

Suitable publications were identified using PubMed, Embase, and the Cochrane Library. The meta-analysis included only studies in English that reported odds ratio (OR) data for MetS and SCH. Two researchers combined data using a random-effects model. OR and 95% confidence intervals (CIs) were used to present the results.

Results

MetS was associated with an elevated risk of developing SCH (OR 2.56, 95% CI 1.44-4.55). However, the individual components of MetS were not associated with the risk of SCH. Subgroup analysis revealed that different definitions of MetS had varying effects on SCH. Sensitivity analysis confirmed that our results were robust.

Conclusions

This meta-analysis indicates that patients with MetS have an increased risk of SCH, while there is no significant association between the five individual components of MetS and the risk of SCH.

Systematic review registration

https://www.crd.york.ac.uk/PROSPERO/, identifier CRD42023454415.

Obesity and Obesity-Related Thyroid Dysfunction: Any Potential Role for the Very Low-Calorie Ketogenic Diet (VLCKD)?

PURPOSE OF REVIEW

This review aims to explore in-depth the different aspects of the association between very low-calorie ketogenic diet (VLCKD), obesity and obesity-related thyroid dysfunction.

RECENT FINDINGS

The VLCKD, proposed as a non-pharmacological strategy for the management of certain chronic diseases, is becoming increasingly popular worldwide. Initially used to treat epilepsy, it has been shown to be effective in controlling body weight gain and addressing various pathophysiological conditions. Research has shown that a low-calorie, high-fat diet can affect thyroid hormone levels. Weight loss can also influence thyroid hormone levels. Studies have suggested that long-term use of VLCKD for refractory epilepsy may be related to the development of hypothyroidism, with an effect seen in various populations. In particular, women with obesity following VLCKD tend to have reduced T3 levels. We propose further research to unravel the underlying mechanisms linking VLCKD to obesity and obesity-related thyroid dysfunction.

Edible Offal as a Valuable Source of Nutrients in the Diet-A Review

The global increase in demand for meat leads to substantial quantities of by-products, including edible offal from both wild and domesticated animals raised for diversified consumption products within an agricultural framework. Information on the nutritional value of offal is scattered and limited. This review aims to synthesize scientific publications on the potential of offal as a source of nutrients and bioactive substances in human diets. The literature review included publications available in ISI Web of Science and Google Scholar published between 2014 and 2024. Findings indicate that edible offal is characterized by a nutrient concentration often surpassing that found in skeletal muscle. This review discusses the yield of edible offal and explores factors influencing human consumption. Selected factors affecting the nutritional value of offal of various animals and the importance of individual nutrients in ensuring the proper functioning of the human body were analyzed. The optimal use of offal in processing and catering can significantly benefit aspects of human life, including diet quality, food security, and conservation of natural resources.

A systematic review and meta-analysis investigating the relationship between metabolic syndrome and the incidence of thyroid diseases

PURPOSE

To assess the prospective association between metabolic syndrome (MetS), its components, and incidence of thyroid disorders by conducting a systematic review and meta-analysis.

METHODS

A systematic search was performed in Ovid Medline, Embase.com, and Cochrane CENTRAL from inception to February 22, 2023. Publications from prospective studies were included if they provided data on baseline MetS status or one of its components and assessed the incidence of thyroid disorders over time. A random effects meta-analysis was conducted to calculate the odds ratio (OR) for developing thyroid disorders.

RESULTS

After full-text screening of 2927 articles, seven studies met our inclusion criteria. Two of these studies assessed MetS as an exposure (N = 71,727) and were included in our meta-analysis. The association between MetS at baseline and incidence of overt hypothyroidism at follow-up yielded an OR of 0.78 (95% confidence interval [CI]: 0.52-1.16 for two studies, I2 = 0%). Pooled analysis was not possible for subclinical hypothyroidism, due to large heterogeneity (I2 = 92.3%), nor for hyperthyroidism, as only one study assessed this association. We found evidence of an increased risk of overt (RR: 3.10 (1.56-4.64, I2 = 0%) and subclinical hypothyroidism (RR 1.50 (1.05-1.94), I2 = 0%) in individuals with obesity at baseline. There was a lower odds of developing overt hyperthyroidism in individuals with prediabetes at baseline (OR: 0.68 (0.47-0.98), I2 = 0%).

CONCLUSIONS

We were unable to draw firm conclusions regarding the association between MetS and the incidence of thyroid disorders due to the limited number of available studies and the presence of important heterogeneity in reporting results. However, we did find an association between obesity at baseline and incidence of overt and subclinical hypothyroidism.

Dietary Patterns and Hypothyroidism in U.S. Adult Population

The thyroid gland produces hormones that are essential for various body functions. Hypothyroidism is defined as insufficient thyroid hormone production. Several studies have found associations between specific micronutrients and overall thyroid function; however, the amount of evidence regarding the relationship between dietary patterns and hypothyroidism among the U.S. population is limited. Data from three cycles of National Health and Nutrition Examination Surveys (NHANES), 2007-2008, 2009-2010, and 2011-2012, were used (n = 8317). Subjects with serum thyroid stimulating hormone >4.5 mIU/L or on levothyroxine were considered to have hypothyroidism. Age, sex, race/ethnicity, body mass index, and several lifestyle factors were considered as covariates. Three patterns were extracted using factor analysis. These were labeled as fat-processed grains-sugars-meats (FPSM), oils-nuts-potatoes-low-fat meats (ONPL), and fruits-whole grains-vegetables-dairy (FWVD) patterns. In a weighted multiple logistic regression, FPSM and ONPL were inversely associated with hypothyroidism (OR, 0.75; 95% CI, 0.57-1; p = 0.049 and OR, 0.81; 95% CI, 0.67-0.97; p = 0.025, respectively). However, FWVD demonstrated no association with hypothyroidism (p = 0.63). In conclusion, FPSM and ONPL patterns but not FWVD patterns were associated with hypothyroidism in U.S. adults. Nutrient deficiencies and their interactions may be linked to hypothyroidism.

Relationship between thyroid function and dietary inflammatory index in Hashimoto thyroiditis patients

Inflammation is closely related to the changes of thyroid function in Hashimoto thyroiditis patients. Certain nutrients or dietary habits can alter the levels of autoantibodies in Hashimoto thyroiditis. However, it remains unclear whether dietary inflammation affects thyroid function in patients with Hashimoto thyroiditis. The purpose of this study was to assess the relationship between dietary inflammation and thyroid function in Hashimoto thyroiditis patients using data from the National Health and Nutrition Examination Survey. We employed weighted multivariable linear regression, subgroup analyses, and interaction analysis to explore the relationship between thyroid function and dietary inflammatory index. We found that dietary inflammatory index was positively correlated with TSH and total T4. Interaction analysis found an interaction between urinary iodine concentration and FT3, but subgroup analysis for different levels of urinary iodine concentration did not get statistically significant results. Hashimoto thyroiditis patients with more pro-inflammatory diet habits had higher levels of TSH and TT4. In order to prevent hypothyroidism more effectively in patients with Hashimoto thyroiditis, it is essential to control dietary inflammation. However, it is still necessary to design a better prospective cohort study to verify the causal relationship.

Prevalence and Factors Associated with Subclinical Hypothyroidism in Major Depressive Disorder Patients with Dyslipidemia

Background

Major depressive disorder (MDD) is a common psychiatric disorder with a high prevalence of comorbidity with subclinical hypothyroidism. The aim of this study was to investigate the prevalence and factors influencing the comorbidity of subclinical hypothyroidism in patients with dyslipidemic MDD who were hospitalized for the first time in a Chinese population.

Methods

The study incorporated 708 first-time hospitalized MDD patients, all with dyslipidemia. Data collection encompassed socio-demographic information, blood pressure, fasting blood glucose (FBG), lipid, and thyroid hormone levels. Participants were evaluated using the Hamilton Depression Scale (HAMD), Hamilton Anxiety Scale (HAMA), and Positive Symptom Subscale (PSS).

Results

The prevalence of subclinical hypothyroidism in dyslipidemic MDD patients with the first hospitalization was 39.97%. The course of the disease, age at onset, HAMA score, and low-density lipoprotein cholesterol (LDL-C) were risk factors for subclinical hypothyroidism in dyslipidemic MDD patients. The course of disease, age at onset, HAMA score, HAMD score, FBG, and systolic blood pressure (SBP) levels were observed to influence serum Thyroid Stimulating Hormone (TSH) levels.

Conclusion

MDD patients with dyslipidemia have a high prevalence of subclinical hypothyroidism, and the outcome is associated with anxiety, fasting glucose, and lipids. This study provides a potential biomarker for the identification of co-morbid subclinical hypothyroidism in MDD patients with dyslipidaemia.

Autoimmune Thyroid Disorders: The Mediterranean Diet as a Protective Choice

Autoimmune thyroid diseases are on the rise worldwide, and such a rapid increase is mainly driven by environmental factors related to changed lifestyles in "modern" societies. In this context, diet seems to play a crucial role. An unhealthy high-energy diet, rich in animal fat and proteins, salt and refined sugars (the so-called "Western diet") negatively influences the risk of autoimmunity by altering the immune balance and the gut microbiota composition, enhancing oxidative stress and promoting inflammation. In contrast, the Mediterranean diet represents a unique model of healthy eating, characterized by a high intake of food from vegetable sources, a low consumption of saturated fats in favor of unsaturated fats (mainly, olive oil), a moderate consumption of fish (typically, the small oily fishes) and dairy products, as well as a moderate consumption of wine at meals, and a low intake of meat. Thanks to its nutritional components, the Mediterranean Diet positively influences immune system function, gut microbiota composition, and redox homeostasis, exerting anti-oxidants, anti-inflammatory, and immunomodulatory effects. The present review was aimed at exploring the existing knowledge on the correlations between dietary habits and thyroid autoimmunity, to evaluate the role of the Mediterranean diet as a protective model.

Fructose consumption induces molecular adaptations involving thyroid function and thyroid-related genes in brown adipose tissue in rats

The increasing incidence of metabolic diseases is in part due to the high fructose consumption, a carbohydrate vastly used in industry, with a potent lipogenic capacity. Thyroid hormones (TH) are essential for metabolism regulation and are associated with changes in body weight, energy expenditure, insulin sensitivity, and dyslipidemia. This study aimed to investigate the influence of fructose intake on thyroid function and thyroid-related genes. Male Wistar rats were divided into Control (CT, n=8) and Fructose (FT - 10% in drinking water, n=8) groups for three weeks. The FT group showed higher glycemia and serum triacylglycerol, indicating metabolic disturbances, and increased thyroid mass, accompanied by higher expression of Srebf1c and Lpl, suggesting increased lipid synthesis. The FT group also presented higher expression of Tpo and Dio1 in the thyroid, suggesting activation of the thyroid gland, but with no alterations in serum TH concentrations. Brown adipose tissue (BAT) of the FT group exhibited higher expression of Dio2, Thra, and Thrb, indicating increased T3 intra-tissue bioavailability and signaling. These responses were accompanied by increased BAT mass and higher expression of Adrb3, Pparg, Srebf1c, Fasn, Ppara, and Ucp1, suggesting increased BAT adrenergic sensitivity, lipid synthesis, oxidation, and thermogenesis. Therefore, short-term fructose consumption induced thyroid molecular alterations and increased BAT expression of thyroid hormone-related signaling genes that potentially contributed to higher BAT activity.

Association of thyroid function with abnormal lipid metabolism in young patients with first-episode and drug naïve major depressive disorder

INTRODUCTION

Abnormal lipid metabolism in patients with major depressive disorder (MDD) has received increasing attention. The coexistence of MDD and abnormal thyroid function has been intensively studied. Moreover, thyroid function is closely related to lipid metabolism. The aim of this study was to investigate the relationship between thyroid function and abnormal lipid metabolism in young patients with first-episode and drug naïve (FEDN) MDD.

METHODS

A total of 1,251 outpatients aged 18-44 years with FEDN MDD were enrolled. Demographic data were collected, and lipid and thyroid function levels were measured, including total cholesterol (TC), triglycerides (TG), low-density lipoprotein cholesterol (LDL-C), high-density lipoprotein cholesterol (HDL-C), thyroid stimulating hormone (TSH), free triiodothyronine (FT3), free tetraiodothyronine (FT4), anti-thyroglobulin antibody (TG-Ab), and anti-thyroid peroxidase antibody (TPO-Ab). The Hamilton Rating Scale for Depression (HAMD), Hamilton Anxiety Rating Scale (HAMA), and Positive and Negative Syndrome Scale (PANSS) positive subscale were also assessed for each patient.

RESULTS

Compared with young MDD patients without comorbid lipid metabolism abnormalities, patients with comorbid lipid metabolism abnormalities had higher body mass index (BMI) values, HAMD score, HAMA score, PANSS positive subscale score, TSH levels, TG-Ab levels, and TPO-Ab levels. Binary logistic regression analysis showed that TSH level, HAMD score and BMI were risk factors for abnormal lipid metabolism. TSH levels were an independent risk factor for abnormal lipid metabolism in young MDD patients. Stepwise multiple linear regression showed that both TC and LDL-C levels were positively correlated with TSH levels, HAMD and PANSS positive subscale scores, respectively. HDL-C levels were negatively correlated with TSH levels. TG levels were positively correlated with TSH and TG-Ab levels and HAMD score.

DISCUSSION

Our results show that thyroid function parameters, especially TSH levels, are implicated in abnormal lipid metabolism in young patients with FEDN MDD.

Dyslipidemia Is a Risk Factor for Hypothyroidism in Women: A Longitudinal Cohort Study from South Korea

Background: Hypothyroidism is a risk factor for dyslipidemia. We explored whether dyslipidemia is a risk factor for hypothyroidism. Methods: We performed a retrospective analysis of data from a longitudinal cohort study of South Korean adults who underwent medical examination and ≥4 biochemical assessments of thyroid function. The primary outcome was hypothyroidism (thyrotropin [TSH] >4.2 mU/L), and the secondary outcome was severe subclinical hypothyroidism (SCH; TSH ≥10.0 mU/L and normal free thyroxine [fT4] level) or overt hypothyroidism (OH; total triiodothyronine <80 ng/dL and/or fT4 < 0.93 ng/dL and high TSH values). The association of baseline dyslipidemia status with subsequent hypothyroidism was evaluated using Kaplan-Meier curves with the log-rank test and Cox proportional hazards regression models (for the entire population and respective genders). Subgroup analyses according to age (<40 and ≥40 years) and body-mass index (BMI; <23, 23-25, and ≥25 kg/m²) were performed according to gender. Results: We included 1665 participants. During a median follow-up period of 61.0 months, 24.3% (404/1665) individuals developed hypothyroidism. Among these, 36 participants (2.1%) had severe SCH or OH. Excluding patients with a first abnormal TSH level at last follow-up, 44.5% (126/283) of the patients with hypothyroidism had spontaneous TSH normalization. In respective multivariate analyses, dyslipidemia at baseline was independently associated with development of hypothyroidism in women (adjusted hazard ratio [HR] = 2.05 [1.31-3.19], p = 0.002), but not in men (adjusted HR = 1.00 [0.77-1.30], p = 0.991). In women, the presence of dyslipidemia at baseline was associated with development of severe SCH or OH (adjusted HR = 5.33 [1.41-20.12], p = 0.014). In women, respective associations according to age and BMI were as follows: age <40 years, adjusted HR = 2.90 (1.34-6.26, p = 0.007); age ≥40 years, adjusted HR = 1.85 (1.08-3.14, p = 0.023); BMI <23 kg/m², adjusted HR = 1.68 (0.82-3.43, p = 0.151); BMI = 23-25 kg/m², adjusted HR = 2.17 (0.93-5.07, p = 0.071); and BMI ≥25 kg/m², adjusted HR = 2.82 (1.16-6.86, p = 0.022). Conclusions: In Korean adults, dyslipidemia was associated with development of hypothyroidism in women. Our findings require confirmation.

Mediterranean Diet and Thyroid: An Interesting Alliance

The Mediterranean diet, recognized as being cultural heritage by UNESCO, is mostly plant-based and includes a high consumption of whole-grain, fruit, and vegetables with a moderate consumption of alcohol during meals. Thus, it provides a small amount of saturated fatty acids and a high quantity of antioxidants and fiber. For this reason, it has been considered to have an important role in preventing cardiovascular diseases, chronic kidney diseases, type 2 diabetes mellitus, and cancer, but its relationship with thyroid function and diseases is still under debate. The aim of this review was to search for the possible correlation between the Mediterranean diet and thyroid function, and to critically evaluate the pathophysiological link between selected food intake and thyroid disorders.

Effects of high-fat diet on thyroid autoimmunity in the female rat

BACKGROUND

While contributions of dyslipidemia to autoimmune diseases have been described, its impact on thyroid autoimmunity (TA) is less clear. Programmed cell death 1(PD-1)/PD-ligand 1 (PD-L1) immune checkpoint is crucial in preventing autoimmune attack while its blockade exacerbates TA. We thus unveiled the effect of high-fat diet (HFD) on TA, focusing on the contribution of PD-1/PD-L1.

METHODS

Female Sprague Dawley (SD) rats were randomly fed with a regular diet or HFD (60% calories from fat) for 24 weeks. Then, thyroid ultrasonography was performed and samples were collected for lipid and thyroid-related parameter measure.

RESULTS

HFD rats exhibited hyperlipemia and abnormal biosynthesis of the unsaturated fatty acid in serum detected by lipidomics. These rats displayed a relatively lower echogenicity and increased inflammatory infiltration in thyroid accompanied by rising serum thyroid autoantibody levels and hypothyroidism, mimicking human Hashimoto's thyroiditis. These alterations were concurrent with decreased mRNA and immunostaining of intrathyroidal PD-1 and also serum PD-1 levels but not the PD-L1 expression, suggesting a role of a PD-1 pathway. Meanwhile, the infiltration of B and T cell, a key cellular event inhibited by the PD-1 signals, was enhanced in the thyroid of HFD rats, along with thyroid fibrosis and apoptosis.

CONCLUSIONS

Our data suggest that HFD triggers TA through a mechanism possibly involving downregulation of PD-1-related immunosuppression, providing a novel insight into the link between dyslipidemia and autoimmune toxicities.

Ildr1 gene deletion protects against diet-induced obesity and hyperglycemia

Objective

Immunoglobulin-like Domain-Containing Receptor 1 (ILDR1) is expressed on nutrient sensing cholecystokinin-positive enteroendocrine cells of the gastrointestinal tract and it has the unique ability to induce fat-mediated CCK secretion. However, the role of ILDR1 in CCK-mediated regulation of satiety is unknown. In this study, we examined the effects of ILDR1 on food intake and metabolic activity using mice with genetically-deleted Ildr1.

Methods

The expression of ILDR1 in murine tissues and the measurement of adipocyte cell size were evaluated by light and fluorescence confocal microscopy. The effects of Ildr1 deletion on mouse metabolism were quantitated using CLAMS chambers and by targeted metabolomics assays of multiple tissues. Hormone levels were measured by ELISA. The effects of Ildr1 gene deletion on glucose and insulin levels were determined using in vivo oral glucose tolerance, meal tolerance, and insulin tolerance tests, as well as ex vivo islet perifusion.

Results

ILDR1 is expressed in a wide range of tissues. Analysis of metabolic data revealed that although Ildr1^-/- mice consumed more food than wild-type littermates, they gained less weight on a high fat diet and exhibited increased metabolic activity. Adipocytes in Ildr1^-/- mice were significantly smaller than in wild-type mice fed either low or high fat diets. ILDR1 was expressed in both alpha and beta cells of pancreatic islets. Based on oral glucose and mixed meal tolerance tests, Ildr1^-/- mice were more effective at lowering post-prandial glucose levels, had improved insulin sensitivity, and glucose-regulated insulin secretion was enhanced in mice lacking ILDR1.

Conclusion

Ildr1 loss significantly modified metabolic activity in these mutant mice. While Ildr1 gene deletion increased high fat food intake, it reduced weight gain and improved glucose tolerance. These findings indicate that ILDR1 modulates metabolic responses to feeding in mice.

Metabolic Characteristics of Hashimoto's Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management-An Overview

Hashimoto’s thyroiditis (HT) is the most common autoimmune disease and the leading cause of hypothyroidism, in which damage to the thyroid gland occurs due to the infiltration of lymphocytes. It is characterized by increased levels of antibodies against thyroid peroxidase and thyroglobulin. In this review, we present the metabolic profile, the effectiveness of micronutrient supplementation and the impact of dietary management in patients with HT. For this current literature review, the databases PubMed, Cochrane, Medline and Embase were reviewed from the last ten years until March 2022. This article provides a comprehensive overview of recent randomized controlled trials, meta-analyses, and clinical trials. Many patients with HT, even in the euthyroid state, have excess body weight, metabolic disorders, and reduced quality of life. Due to frequent concomitant nutritional deficiencies, the role of vitamin D, iodine, selenium, magnesium, iron and vitamin B12 is currently debated. Several studies have underlined the benefits of vitamin D and selenium supplementation. There is still no specific diet recommended for patients with HT, but a protective effect of an anti-inflammatory diet rich in vitamins and minerals and low in animal foods has been suggested. There is insufficient evidence to support a gluten-free diet for all HT patients. Pharmacotherapy, along with appropriate nutrition and supplementation, are important elements of medical care for patients with HT. The abovementioned factors may decrease autoantibody levels, improve thyroid function, slow down the inflammatory process, maintain proper body weight, relieve symptoms, and prevent nutritional deficiencies and the development of metabolic disorders in patients with HT.

Safety and toxicologic evaluation of Edible Pongamia Oil: A novel food ingredient

Edible Pongamia Oil (EPO) was evaluated in an acute oral toxicity study, GLP 14-Day and 90-Day repeated dose isocaloric dietary toxicity studies in rats, and in vitro Bacterial Reverse Mutation, and in vivo Mammalian Bone Marrow Chromosome Aberration genotoxicity studies for potential use as a food ingredient. In a non-GLP acute study, an LD₅₀ > 5000 mg/kg was determined. Subacute 14-day repeated dose dietary administration of 0, 5, 10 and 15% oil revealed no adverse changes in clinical pathology, liver histology, body weight or weight gain, food consumption or food efficiency. In a 90-day dietary study fed 0, 2.5, 5.0, 7.5 and 10.0%, no mortalities, clinical or ophthalmologic signs, body weight, body weight gain, food consumption, food efficiency or Functional Observational Battery/Motor Activity changes occurred with EPO consumption, nor were there any adverse changes in hematology, clinical chemistry, coagulation, urinalysis, or thyroid hormone values. There were no adverse macroscopic, estrus cycle, histopathologic or spermatogenesis findings, or absolute or relative organ weight changes related to administration of EPO. The No-Adverse-Effect-Level (NOAEL) was 10% in the diet, the highest dose tested, equivalent to 5163 (male) and 6469 (female) mg/kg/day in rats. No mutagenic or clastogenic genotoxic potential was reported.

Reactivity of the Thyroid System to Short-Term Stress in Wistar Rats with Visceral Obesity and Restricted Social Activity

The obesity problem requires a study of its pathophysiological consequences affecting hormonal regulation and organism’s reactivity to extreme exposures. The study was aimed first to examine the effect of a high-calorie diet and social isolation, as well as their combination for 4 months, on the development of obesity, its metabolic and behavioral sequelae, features of the thyroid status, while at the second stage, to assess the reaction of hormonal indices of the thyroid status to short-term stress in rats. The experiments were carried out on male Wistar rats and at the first stage focused on the effects of a high-calorie diet and social isolation, as well as their combinations for 4 months. At the end of the experiment, behavioral reactions, metabolic syndrome indices, thyroid status, and cortisol levels were evaluated. At the second stage, the animals were exposed to short-term acute stress, and the shifts in the hormonal indices were recorded one hour later versus the initial background. A high-calorie diet led to the development of metabolic syndrome, signs of depression, increased thyroid-stimulating hormone (TSH), thyroxine and triiodothyronine serum levels, as well as iodothyronine deiodinase type 1 (D1) activity, in the rat liver. At the same time, there was a decrease in thyroperoxidase activity and an increase in thyroid levels of triglycerides and malondialdehyde. The physiological response to stress in the control rat group included an increase in cortisol and TSH serum levels, however, against the background of a high-calorie diet, no cortisol release into the bloodstream was recorded. Social isolation did not alter normal reactivity of the adrenal cortex, but reduced TSH release in response to acute stress, since the initial level of this hormone was slightly elevated against the background of chronic social isolation stress. Thus, excessive nutrition and the deficit of social activities in male Wistar rats led to significant changes in the organism’s reactivity to acute stress.

Diosgenin From Dioscorea Nipponica Rhizoma Against Graves’ Disease—On Network Pharmacology and Experimental Evaluation

Dioscorea nipponica rhizoma (DNR) is commonly used for the cure of hyperthyroidism resulting from Graves’ disease (GD) or thyroid nodules. However, its therapeutic mechanism remains unclear. This study aimed to utilize network pharmacology integrated molecular docking and experimental verification to reveal the potential pharmacological mechanism of DNR against GD. First, the active componds of DNR were collected from the HERB database and a literature search was conducted. Then, according to multisource database, the predicted genes of DNR and GD were collected to generate networks. The analysis of protein–protein interaction and GO enrichment and KEGG pathway were employed to discover main mechanisms associated with therapeutic targets. Moreover, molecular docking simulation was applied in order to verify the interactions between the drug and target. Finally, our experiments validated the ameliorated effects of diosgenin, the main component of DNR, in terms of phosphorylation deactivation in IGF-1R, which in turn inhibited the phosphorylation and activation of PI3K-AKT and Rap1-MEK signaling pathways, promoting cell apoptosis and GD remission. Our present study provided a foundation for further investigation of the in-depth mechanisms of diosgenin in GD and will provide new scientific evidence for clinical application.

Food preferences and thyroid hormones in children and adolescents with obesity

BACKGROUND

Thyroid hormones profoundly affect energy metabolism but their interrelation with food preference, which might contribute to childhood obesity development, are much less understood. In this study, we investigated if thyroid hormone levels are associated with specific modulation of food preference and potentially linked to the level of obesity in children and adolescents.

METHODS

Interrelations between food preference and peripheral thyroid activity were examined in a population of 99 non-obese and 101 obese children and adolescents (12.8 ± 3.6 years of age, 111/89 F/M) randomly selected from the patients of the Obesity and Metabolic Disease Out-patient Research Unit at National Institute for Children's Diseases in Bratislava in a period between December 2017 and March 2020.

RESULTS

Children and adolescents with obesity had a lower preference for food rich in high sucrose and high-complex carbohydrates, while the preference for protein and fat-containing food and that for dietary fibers did not differ between obese and nonobese. In adolescents with obesity, free thyroxine (FT4) correlated positively with the preference for a high protein and high fat-rich diet, irrespective of the fatty acid unsaturation level. Moreover, FT4 correlated negatively with the preference for dietary fibers, which has been also exclusively found in obese adolescents. Individuals with obesity with higher FT4 levels had higher systemic levels of AST and ALT than the population with lower FT4. Multiple regression analysis with age, sex, BMI-SDS, and FT4 as covariates revealed that FT4 and male gender are the major predictors of variability in the preference for a diet high in protein, fat, and monounsaturated fatty acids. FT4 was the sole predictor of the preference for a diet containing saturated and polyunsaturated fatty acids as well as for a diet low in fiber.

CONCLUSION

The link between free thyroxin levels and dietary preference for food rich in fat and protein is present exclusively in individuals with obesity. Higher serum FT4 was linked with elevated AST and ALT in children and adolescents with obesity, and FT4 was the best predictor for preference for food rich in fat and low in fiber. This may indicate that FT4 could contribute to the development of childhood obesity and its complications by modulating food preference.

The Association Between Serum Palmitic Acid and Thyroid Function

AIM

Emerging evidence indicates that palmitic acid (PA) can regulate the progression and development of many diseases. However, the studies examining the association between PA and thyroid function remain sparse. We aimed to investigate the association between serum PA (sPA) and thyroid function in the US population.

METHODS

In this retrospective study, a cross-sectional analysis was performed using the data pooled from the database of the National Health and Nutrition Examination Survey (NHANES) from 2011 to 2012. The thyroid parameters investigated were mainly free triiodothyronine (FT3), free thyroxine (FT4), total T3 (TT3), TT4, thyroglobulin (Tg), thyroid-stimulating hormone (TSH), anti-thyroglobulin antibody (TgAb), and anti-thyroperoxidase antibody (TPOAb). The central sensitivity to thyroid function was evaluated by the thyroid feedback quantile-based index (TFQI), thyrotrophin thyroxine resistance index (TT4RI), and thyrotropin index (TSHI). The FT3 to FT4 ratio (FT3/FT4) was employed to evaluate peripheral sensitivity to thyroid hormones. Multiple imputation was applied to handle the missing data, and weighted multivariable linear regression, subgroup, and interaction analyses were then employed to estimate the association between sPA and thyroid parameters.

RESULTS

In the 737 adults, after adjusting covariates, we demonstrated a significant negative association between sPA and FT4 [β = -1.078, 95% confidence interval (CI): -1.729 to -0.427], as well as a positive relationship between sPA and FT3/FT4 ratio (β = 0.073, 95% CI: 0.044 to 0.102). These results did not change on multiple imputations. In the subgroup analyses, the associations were more significant in male and obese subjects.

CONCLUSION

This investigation demonstrated the significant correlation between sPA and thyroid dysfunction, which suggested the close relationship between lipotoxicity and hypothyroidism or subclinical hypothyroidism. Future research is required to confirm these findings.

Differential lipids in pregnant women with subclinical hypothyroidism and their correlation to the pregnancy outcomes

Subclinical hypothyroidism (SCH) has become a prevalent complication in pregnancy. Recent research links SCH to disturbed thyroid lipid profile; however, it is unclear how lipid metabolism disorders contribute to the pathogenesis of SCH during pregnancy. Thus, we used nontargeted lipidomics to identify and compare the lipids and metabolites expressed by pregnant women with SCH and healthy pregnant women. Multivariate analysis revealed 143 lipid molecules differentially expressed between the SCH group and the control group. Based on fold change, 30 differentially expressed lipid metabolites are potential biomarkers. KEGG pathway enrichment analysis showed that the differentially expressed metabolites participate in several pathways, including response to pathogenic Escherichia coli infection, regulation of lipolysis in adipocytes, metabolic pathways, glycerophospholipid metabolism, and fat digestion and absorption pathways. Correlation analyses revealed sphingomyelin (SM) and phosphatidylcholine (PC) positively correlate to tumor necrosis factor-α (TNF-α), C-reactive protein (CRP), and interleukin-6 (IL-6), while phosphatidylglycerol (PG), and phosphatidylinositol (PI) negatively correlate with them. In addition, PG positively correlates to birth weight. Thus, the lipid profile of pregnant women with SCH is significantly different from that of healthy pregnant women. Lipid molecules associated with the differential lipid metabolism, such as SM, phosphatidylethanolamine (PE), and PI, should be further investigated for their roles in the pathogenesis of SCH in pregnancy, as they might be targets for reducing the incidence of adverse pregnancy outcomes.

Obesity and Thyroid Axis

Development of obesity is primarily the result of imbalance between energy intake and energy expenditure. Thyroid hormones influence energy expenditure by regulating cellular respiration and thermogenesis and by determining resting metabolic rate. Triiodothyronine influences lipid turnover in adipocytes and impacts appetite regulation through the central nervous system, mainly the hypothalamus. Thyroid-stimulating hormone may also influence thermogenesis, suppress appetite and regulate lipid storage through lipolysis and lipogenesis control. Subclinical hypothyroidism may induce changes in basal metabolic rate with subsequent increase in BMI, but obesity can also affect thyroid function via several mechanisms such as lipotoxicity and changes in adipokines and inflammatory cytokine secretion. The present study investigated the complex and mutual relationships between the thyroid axis and adiposity.

Beyond classic concepts in thyroid homeostasis: Immune system and microbiota

It has long been known that thyroid hormones have implications for multiple physiological processes and can lead to serious illness when there is an imbalance in its metabolism. The connections between thyroid hormone metabolism and the immune system have been extensively described, as they can participate in inflammation, autoimmunity, or cancer progression. In addition, changes in the normal intestinal microbiota involve the activation of the immune system while triggering different pathophysiological disorders. Recent studies have linked the microbiota and certain bacterial fragments or metabolites to the regulation of thyroid hormones and the general response in the endocrine system. Even if the biology and function of the thyroid gland has attracted more attention due to its pathophysiological importance, there are essential mechanisms and issues related to it that are related to the interplay between the intestinal microbiota and the immune system and must be further investigated. Here we summarize additional information to uncover these relationships, the knowledge of which would help establish new personalized medical strategies.

Molecular Interactions between Dietary Lipids and Bone Tissue during Aging

Age-related bone disorders such as osteoporosis or osteoarthritis are a major public health problem due to the functional disability for millions of people worldwide. Furthermore, fractures are associated with a higher degree of morbidity and mortality in the long term, which generates greater financial and health costs. As the world population becomes older, the incidence of this type of disease increases and this effect seems notably greater in those countries that present a more westernized lifestyle. Thus, increased efforts are directed toward reducing risks that need to focus not only on the prevention of bone diseases, but also on the treatment of persons already afflicted. Evidence is accumulating that dietary lipids play an important role in bone health which results relevant to develop effective interventions for prevent bone diseases or alterations, especially in the elderly segment of the population. This review focuses on evidence about the effects of dietary lipids on bone health and describes possible mechanisms to explain how lipids act on bone metabolism during aging. Little work, however, has been accomplished in humans, so this is a challenge for future research.

Association between different obesity phenotypes and hypothyroidism: a study based on a longitudinal health management cohort

PURPOSE

Obese individuals have an increased risk of hypothyroidism. This study investigated the sex-specific association between obesity phenotypes and the development of hypothyroidism.

METHODS

The study population was derived from a health management cohort in Shandong Provincial Hospital from 2012 to 2016. In total, 9011 baseline euthyroid adults were included and classified into four groups according to obesity phenotype: metabolically healthy nonobese (MHNO), metabolically healthy obese (MHO), metabolically unhealthy nonobese (MUNO), and metabolically unhealthy obese (MUO). The median follow-up time was 1.92 (1.00-2.17) years. Incidence density was evaluated and a generalized estimation equation method was used to investigate the associations between obesity phenotypes and the development of hypothyroidism.

RESULTS

The incidence densities of hypothyroidism in males with a consistent obesity phenotype were 12.19 (8.62-16.76), 15.87 (11.39-21.56), 14.52 (6.74-27.57), and 19.88 (14.06-27.34) per 1000 person-years in the MHNO, MHO, MUNO, and MUO groups, respectively. After adjusting for confounding factors, compared with the MHNO phenotype, the MHO, MUNO, and MUO phenotypes were independent risk factors for developing hypothyroidism in males. In the subgroup analysis, the MHO and MUO phenotypes were independent risk factors for developing hypothyroidism in males under 55 years, while the MUNO phenotype was an independent risk factor in males over 55 years. The MHO, MUNO, and MUO phenotypes were not independent risk factors for hypothyroidism in females.

CONCLUSION

Both obesity and metabolic abnormities are associated with a higher risk of hypothyroidism in males. The underlying mechanism of the sex and age differences in this association needs further investigation.

Statin Use and Benefits of Thyroid Function: A Retrospective Cohort Study

PURPOSE

Previous studies have suggested that cholesterol may influence thyroid function. Since statins are widely used for their cholesterol-lowering effect, we aimed to assess the association between statin use and thyroid function, and also to explore the role of the cholesterol-lowering effect in it.

METHODS

We performed a retrospective cohort study derived from REACTION study. Eligible subjects receiving statin therapy were included in the statin group, and sex-, age-, total cholesterol (TC)-, and thyroid function-matched participants without lipid-lowering therapy were included in the control group. The median follow-up time was three years. Outcomes of thyroid function were evaluated at the end of follow-up. We used multivariable regression models to assess the association between statin use and outcomes of thyroid function, and also performed mediation analyses to explore the role of cholesterol in it.

RESULTS

A total of 5,146 participants were screened, and 201 eligible subjects in the statin group and 201 well-matched subjects in the control group were analyzed. At the end of follow-up, TC and thyroid-stimulating hormone (TSH) levels in the statin group were lower than those in the control group (both p < 0.05), and the percentage of euthyroid subjects was higher in the statin group (88.06% vs. 76.12%, p = 0.002). The incidence rate of subclinical hypothyroidism (SCH) in euthyroid subjects was lower in the statin group (6.29% vs. 14.86%, p = 0.009), and the remission rate among subjects with SCH was higher in the statin group (50.00% vs. 15.38%, p = 0.008). In multivariable regression analyses, statin use was independently associated with lower TSH levels and higher odds to be euthyroid (OR 2.335, p = 0.004) at the end of follow-up. Mediation analyses showed the association between statin use and TSH levels were mediated by TC changes during follow-up.

CONCLUSION

Statin use was associated with benefits of thyroid function, and TC changes serve as a mediator of the association between statin use and TSH levels. Further studies are needed to clarify the possible underlying mechanism.

Thyroid redox imbalance in adult Wistar rats that were exposed to nicotine during breastfeeding

Maternal nicotine exposure causes several consequences in offspring phenotype, such as obesity and thyroid dysfunctions. Nicotine exposure can increase oxidative stress levels, which could lead to thyroid dysfunction. However, the mechanism by which nicotine exposure during breastfeeding leads to thyroid gland dysfunction remains elusive. We aimed to investigate the long-term effects of maternal nicotine exposure on redox homeostasis in thyroid gland, besides other essential steps for thyroid hormone synthesis in rats from both sexes. Lactating Wistar rats were implanted with osmotic minipumps releasing nicotine (NIC, 6 mg/kg/day) or saline (control) from postnatal day 2 to 16. Offspring were analyzed at 180-day-old. NIC males showed lower plasma TSH, T₃ and T₄ while NIC females had higher T₃ and T₄. In thyroid, NIC males had higher sodium-iodide symporter protein expression, whereas NIC females had higher thyroid-stimulating hormone receptor (TSHr) and thyroperoxidase (TPO) protein expression. TPO activity was lower in NIC males. Hydrogen peroxide generation was decreased in NIC males. Activities of superoxide dismutase, catalase and glutathione peroxidase were compromised in NIC animals from both sexes. 4-Hydroxynonenal was higher only in NIC females, while thiol was not affected in NIC animals from both sexes. NIC offspring also had altered expression of sex steroid receptors in thyroid gland. Both sexes showed similar thyroid morphology, with lower follicle and colloid size. Thyroid from female offspring exposed to nicotine during breastfeeding developed oxidative stress, while the male gland seemed to be protected from redox damage. Thyroid dysfunctions seem to be associated with redox imbalance in a sex-dependent manner.

Withdrawing from obesogenic diets: benefits and barriers in the short- and long-term in rodent models

There is accumulating evidence of dietary impact on several metabolic parameters. Unhealthy diets are estimated to be responsible for about 20% of the deaths worldwide. The recommendation is to improve the dietary pattern, aiming to prevent further harm. In this context, we reviewed the benefits and barriers of withdrawing from continuous obesogenic diet intake in the short- and long-term, which were found in rodent models. Although dietary modifications demand a re-establishment of the equilibrium, withdrawing was seen as a homeostatic insult and thus elicited several responses to protect the organism. In the short-term, withdrawal presented stressful and reward destimulating responses. The intake of obesogenic diets presented rewarding and stress destimulating responses. Whereas withdrawing in the long term ameliorated several biological functions and histopathologic features, it was not effective at reestablishing food intake and normalizing feeding behaviors or reward pathways. Altogether, terminating obesogenic diet intake does not immediately extinguish all negative consequences, and it even elicits brain behavioral and metabolic modifications. These modifications can hinder the maintenance of habits' change and prevent reaching the long-term benefits of diet improvement.

Differences in food consumption between patients with Hashimoto's thyroiditis and healthy individuals

Food is considered as important environmental factor that plays a role in development of Hashimoto's thyroiditis (HT). The goal of our study was to identify food groups, assessed by food frequency questionnaire, that differ in consumption frequency between 491 patients with HT and 433 controls. We also analysed association of food groups with the wealth of HT-related clinical traits and symptoms. We found significantly increased consumption of animal fat (OR 1.55, p < 0.0001) and processed meat (OR 1.16, p = 0.0012) in HT cases, whereas controls consumed significantly more frequently red meat (OR 0.80, p < 0.0001), non-alcoholic beverages (OR 0.82, p < 0.0001), whole grains (OR 0.82, p < 0.0001) and plant oil (OR 0.87, p < 0.0001). We also observed association of plant oil consumption with increased triiodothyronine levels in HT patients (β = 0.07, p < 0.0001), and, association of olive oil consumption with decreased systolic blood pressure (β = − 0.16, p = 0.001) in HT patients on levothyroxine (LT4) therapy. Analysis of food consumption between HT patients with and without LT4 therapy suggest that patients do not tend to modify their diet upon HT diagnosis in our population. Our study may be of relevance to nutritionists, nutritional therapists and clinicians involved in developing dietary recommendations for HT patients.

Changes in Thyroid and Glycemic Status and Food Intake in Children with Excess Weight Who Were Submitted for a Multi-Component School Intervention for 16 Months

We investigated if children with excess weight who submitted to two types of intervention at school for 16 months showed improvements in thyroid and glycemic function and food intake. Children (8-11 years) with a body mass index-for-age (BMI/A) of ≥1 Z score were divided into two groups: Treatment 1 (n = 73) involved motivation to adopt healthier lifestyle; Treatment 2 (n = 103) involved performing weekly nutritional education, motivational, and physical activities at school. A semi-quantitative food frequency questionnaire was used. The delta BMI/A were similar after 16 months; Treatment 1 showed higher decrease in thyroid-stimulating hormone (TSH; median (range)): -0.45 (-3.19 to 2.17) and 0.06 (-4.57 to 1.63) mIU/L, p = 0.001), FreeT3 (-0.46 (-2.92 to 1.54) and -0.15 (-2.46 to 1.38) pmol/L, p = 0.038), and FreeT4 -1.41 (-6.18 to 3.47) and -0.90 (-4.89 to 2.96) pmol/L, p = 0.018), followed by decrease in energy intake (7304 (6806 to 7840) and 8267 (7739 to 8832) kJ, Ptreatment = 0.439, Ptime <0.001, interaction group-time p < 0.001), macronutrients and sugar. A positive correlation between FreeT3 and BMI/A, and a negative correlation with FreeT4 and insulin were found at baseline (r 0.212, p < 0.01; r -0.155, p < 0.01, respectively) and follow-up (r 0.222, p < 0.01; r -0.221, p < 0.01). The decrease in overall diet and particularly sugar intake was accompanied by a greater reduction in TSH and FreeT3 in Treatment 1, demonstrating the impact of dietary intake on thyroid function.

Quantitative Analysis of the Proteome and the Succinylome in the Thyroid Tissue of High-Fat Diet-Induced Hypothyroxinemia in Rats

Hypothyroidism is a common disease, and its molecular mechanism still needs further investigation. Lysine succinylation is found to be involved in various metabolic processes associated with hypothyroidism. We performed quantitative analysis on lysine succinylome in thyroids of rats with hypothyroxinemia, which was induced through the administration of a high-fat diet. Overall, 129 differentially expressed proteins were quantified. Downregulated proteins were enriched in the thyroid hormone synthesis and thyroid hormone signaling pathways and were mainly localized in the mitochondria. In addition, 172 lysine succinylation sites on 104 proteins were obviously changed. Decreased succinylated proteins were involved in diverse metabolic pathways and were primarily localized in mitochondria. Finally, the mitochondrial oxygen consumption rates of human normal thyroid epithelial cells were measured to further verify the role of lysine succinylation. The mitochondrial oxygen consumption rates were markedly blunted in the cells treated with palmitic acid (all p < 0.05), and the changes were reversed when the cells were treated with palmitic acid and desuccinylase inhibitor together (all p < 0.05). Thus, we theorize that the thyroid differentially expressed proteins and changed succinylation levels played potential roles in the mitochondria-mediated energy metabolism in the high-fat diet-induced hypothyroxinemia rat model.

Moringa oleifera leaf extract ameliorated high-fat diet-induced obesity, oxidative stress and disrupted metabolic hormones

Background

Obesity is a health problem in many countries, and maintaining a perfect weight is challenging. Moringa oleifera leaf extract (ME) is rich in polyphenols with antioxidant and pharmaceutical potential. The present study investigated the potential protective effect of Moringa oleifera leaf extract against obesity induced from a high-fat diet (HFD), oxidative stress and disruption of metabolic hormones compared to simvastatin (SIM) or their combination.

Results

Rats fed a HFD for 6 weeks exhibited a significant increase in body weight and levels of serum glucose and lipid fractions, verifying an obesity state. There were also higher levels of insulin and leptin and lower gherlin in sera of HFD rats compared to the levels in control rats. Homeostasis model assessment for insulin resistance (HOMA-IR), quantitative insulin sensitivity check index (QUICKI) and the atherogenic index were elevated, indicating the development of insulin resistance and dyslipidaemia in these rats. These changes were accompanied with a significant increase in oxidative stress, as indicated by elevated lipid peroxidation and protein oxidation with low levels of antioxidants in liver. The activities of liver function enzymes, including aspartate amino transferase, alanine amino transferase, alkaline phosphatase and gamma glutamyltransferase, were also significantly increased in serum. Concurrent treatment with 300 mg/kg ME for 6 weeks ameliorated the increase in body weight and improved the levels of glucose, lipid fractions and metabolic hormones, indicating the anti-obesity effect and amelioration of tissue insulin resistance potential of ME. ME treatment also normalized oxidative stress and antioxidants in liver and improved liver function enzymes, indicating the antioxidant potential of ME. The effects of ME were similar to SIM, and the combination of these agents was better than each agent alone.

Conclusion

We propose that ME extract has anti-obesity and antioxidant potential and may be used as a lipid-lowering drug to control weight, obesity and its pathophysiological consequences.

CASE FINDING FOR HYPOTHYROIDISM SHOULD INCLUDE TYPE 2 DIABETES AND METABOLIC SYNDROME PATIENTS: A LATIN AMERICAN THYROID SOCIETY (LATS) POSITION STATEMENT

OBJECTIVE

Latin American Thyroid Society (LATS) Hypothyroidism Clinical Practice Guidelines recommend case finding of hypothyroid patients in multiple and different situations that agree with other Society guidelines. However, the detection of hypothyroidism in type 2 diabetes mellitus (T2DM) or metabolic syndrome (MetS) patients is not mentioned in particular. In the recent years, several basic and epidemiologic studies have appeared showing that a lower thyroid function and MetS/T2DM are associated. Hence, the aim of this review is to manifest the LATS position on the diagnosis of hypothyroidism in both MetS and T2DM patients.

METHODS

A search was made in PubMed using the following terms: "hypothyroidism" AND "diabetes" OR "metabolic syndrome." The most relevant studies describing the prevalence and complications due to hypothyroidism in both MetS and T2DM patients were selected.

RESULTS

The current document reviews new information from studies that have shown that the prevalence of hypothyroidism is higher in T2DM patients (odds ratio [OR], 3.45; 95% confidence interval [CI], 2.5 to 4.7) and that diabetic complications are more prevalent in subclinical hypothyroidism (ScH). The incidence of T2DM is 1.09-fold higher with each doubling of thyroid-stimulating hormone (TSH) mIU/L (95% CI, 1.06 to 1.12), and the incidence of prediabetes increases 15% (hazard ratio, 1.15; 95% CI, 1.04 to 1.26) in patients with TSH >5 mIU/L. Similarly, MetS is more prevalent in ScH compared to euthyroid individuals (OR, 1.31; 95% CI, 1.08 to 1.60).

CONCLUSION

Thyroid function is affected in MetS and T2DM, and hypothyroidism is more common in these patients. Diabetic complications are more frequent in ScH patients. Therefore, LATS now recommends aggressive case finding of hypothyroidism in both MetS and T2DM patients.

ABBREVIATIONS

CI = confidence interval; GLUT4 = glucose transporter 4; HOMA-IR = homeostatic model assessment for insulin resistance; HR = hazard ratio; LATS = Latin American Thyroid Society; MetS = metabolic syndrome; OR = odds ratio; ScH = subclinical hypothyroidism; T2DM = type 2 diabetes mellitus; T3 = triiodothyronine; T4 = thyroxine; TSH = thyroid-stimulating hormone.

ER stress contributes to high-fat diet-induced decrease of thyroglobulin and hypothyroidism

Recent studies revealed the emerging role of excess uptake of lipids in the development of hypothyroidism. However, the underlying mechanism is largely unknown. We investigated the effect of high-fat diet (HFD) on thyroid function and the role of endoplasmic reticulum (ER) in HFD-induced hypothyroidism. Male Sprague-Dawley rats were fed with HFD or control diet for 18 wk. HFD rats showed an impaired thyroid function, with decreased thyroglobulin (Tg) level. We found the ER stress was triggered in HFD rat thyroid glands and palmitate-treated thyrocytes. Luminal swelling of ER in thyroid epithelial cells of HFD rats was also observed. The rate of Tg degradation increased in palmitate-treated thyrocytes. In addition, applying 4-phenyl butyric acid to alleviate ER stress in HFD rats improved the decrease of Tg and thyroid function. Withdrawal of the HFD improved thyroid function . In conclusion, we demonstrate that ER stress mediates the HFD-induced hypothyroidism, probably by impairing the production of Tg, and attenuation of ER stress improves thyroid function. Our study provides the understanding of how HFD induces hypothyroidism.

Sex Dimorphic Responses of the Hypothalamus-Pituitary-Thyroid Axis to Maternal Separation and Palatable Diet

Neonatal stress contributes to the development of obesity and has long-lasting effects on elements of the hypothalamus-pituitary-thyroid (HPT) axis. Given the importance of thyroid hormones in metabolic regulation, we studied the effects of maternal separation and a high-fat/high-carbohydrate diet (HFC), offered from puberty or adulthood, on HPT axis activity of adult male and female Wistar rats. Pups were non-handled (NH) or maternally separated (MS) 3 h/day at postnatal days (Pd) 2-21. In a first experiment, at Pd60, rats had access to chow or an HFC diet (cookies, peanuts, chow) for 1 month. Male and female NH and MS rats that consumed the HFC diet increased their caloric intake, body weight, and serum insulin levels; fat weight increased in all groups except in MS males, and serum leptin concentration increased only in females. Mediobasal hypothalamus (MBH) Pomc expression increased in NH-HFC females and Npy decreased in NH-HFC males. MS males showed insulinemia and hypercortisolemia that was attenuated by the HFC diet. The HPT axis activity response to an HFC diet was sex-specific; expression of MBH thyrotropin-releasing hormone-degrading ectoenzyme (Trhde) increased in NH and MS males; serum TSH concentration decreased in NH males, and T4 increased in NH females. In a second experiment, rats were fed chow or an HFC diet from Pd30 or 60 until Pd160 and exposed to 1 h restraint before sacrifice. Regardless of neonatal stress, age of diet exposition, or sex, the HFC diet increased body and fat weight and serum leptin concentration; it induced insulinemia in males, but in females only in Pd30 rats. The HFC diet's capacity to curtail the hypothalamus-pituitary-adrenal axis response to restraint was impaired in MS males. In restrained rats, expression of Trh in the paraventricular nucleus of the hypothalamus, Dio2 and Trhde in MBH, and serum thyroid hormone concentration were altered differently depending on sex, age of diet exposition, and neonatal stress. In conclusion, metabolic alterations associated to an HFC-diet-induced obesity are affected by sex or time of exposition, while various parameters of the HPT axis activity are additionally altered by MS, pointing to the complex interplay that these developmental influences exert on HPT axis activity in adult rats.

A High-Fat Diet Rich in Saturated and Mono-Unsaturated Fatty Acids Induces Disturbance of Thyroid Lipid Profile and Hypothyroxinemia in Male Rats

SCOPE

Increasing evidence has shown that the disturbance of lipid metabolism might make a possible contribution to the pathogenesis of organ dysfunction, including thyroid, yet it is unknown whether excess intake of dietary fat interferes in thyroid lipid profile. We investigate the effects of dietary fat toward the thyroid lipid profile and thyroid function.

METHODS AND RESULTS

Male Sprague-Dawley rats are fed with high-fat diet (HFD) rich in saturated and mono-unsaturated fatty acids or chow diet for 18 weeks. LC-MS analysis of thyroid shows that total free fatty acids (FFAs) content is significantly higher in HFD rats. The concentration of highly saturated triglycerides significantly increases in HFD rats, whereas the polyunsaturated triglyceride significantly decreases, indicating the decrease in unsaturation in the HFD group. Significant increase of lysophosphatidylcholines (LPC) is observed in HFD rats. Thyroid function tests show hypothyroxinemia (total thyroxine [TT₄ ] and free thyroxine [FT₄ ]) in HFD rats, and elevated thyrotropin (TSH) concentration. The HFD rats also show decreased thyroid uptake of iodine.

CONCLUSION

Excess intake of dietary fat induces disturbance of thyroid lipid profile and hypothyroxinemia, indicating thyroid dysfunction. We speculate that it may provide a new prospect in understanding the pathogenesis of hypothyroidism.

Analysis of the correlation between lipotoxicity and pituitary-thyroid axis hormone levels in men and male rats

Lipotoxicity seriously harms human health, but it is unclear whether lipotoxicity is detrimental to the pituitary. We investigated the correlation between serum triglyceride and pituitary axis hormone levels in epidemiological and animal studies. In the epidemiological study, serum thyroid-stimulating hormone (TSH), follicle-stimulating hormone (FSH) and luteinizing hormone (LH) levels were greater in male patients with isolated hypertriglyceridemia than in controls, whereas adrenocorticotropin (ACTH) levels were lower in the patients with hypertriglyceridemia. Pituitary hormone levels correlated with triglyceride levels, even after adjustment for potential confounders. In the animal study, male rats were fed a high-fat or control diet for 28 weeks. As the duration of high-fat feeding increased, the serum and pituitary triglyceride concentrations increased. At early times, the high-fat diet elevated serum TSH and triiodothyronine. At later times, much higher serum TSH levels coupled with reduced thyroxine were observed in the high-fat group. Serum levels of pituitary-gonadal and pituitary-adrenal axis hormones were not affected by the diet. The mRNA and protein expression of Tshβ were greater in the high-fat group than in the control group, whereas expression of Fshβ, Lhβ and Acth had no difference between the groups. Overall, serum triglyceride levels were associated with pituitary-thyroid axis hormone levels.

Palmitic Acid Downregulates Thyroglobulin (Tg), Sodium Iodide Symporter (NIS), and Thyroperoxidase (TPO) in Human Primary Thyrocytes: A Potential Mechanism by Which Lipotoxicity Affects Thyroid?

Our previous studies suggested that the thyroid might be a target organ affected by lipotoxicity, which might be partially related to the increasing prevalence of subclinical hypothyroidism. However, the underlying molecular mechanism is not yet clearly established. This study aimed to assess the effect of palmitic acid stimulation on thyrocyte function. Upon palmitic acid stimulation, intracellular contents of lipids, as well as the expression and activity of three key molecules in thyroid hormone synthesis (i.e., thyroglobulin, sodium iodide symporter, and thyroperoxidase), were determined in human primary thyrocytes. The contents of BODIPY® FL C16 (the fluorescently labeled palmitic acid analogue) entering into the thyrocytes were gradually increased with time extending. Accordingly, the intracellular accumulation of both triglyceride and free fatty acids increased in dose- and time-dependent manners. The effect of palmitic acid stimulation on thyroid hormone synthesis was then determined. Both the mRNA and protein levels of thyroglobulin, sodium iodide symporter, and thyroperoxidase were decreased following palmitic acid stimulation. Consistently, upon palmitic acid stimulation, the secreted thyroglobulin levels in supernatants, ¹³¹I uptake, and extracellular thyroperoxidase activity were all decreased in a dose-dependent manner. Our results demonstrated that upon palmitic acid stimulation, the expressions of the key molecules (thyroglobulin, sodium iodide symporter, and thyroperoxidase) were reduced and their activities were suppressed, which might lead to impaired thyroid hormone synthesis.

High-fat, simple-carbohydrate diet intake induces hypothalamic-pituitary-thyroid axis dysregulation in C57BL/6J male mice

Given the association between subclinical hypothyroidism and metabolic syndrome, we wanted to explore if high-fat, simple-carbohydrate (HFSC) diet affects hypothalamus-pituitary-thyroid axis. One-month-old male C57BL/6J mice were fed with control (C) and HFSC (T) feed (n = 18 each), respectively, for 5 months. There was a significant increase in triiodothyronine in the T group (13.5%) compared with the age-matched C group by the fifth month. Thyroid-stimulating hormone was significantly higher (1 month: 1.9-fold; 3 months: 2.66-fold; 5 months: 3.5-fold) from the first to fifth months in the T group compared with age-matched C group. Thyrotropin-releasing hormone (TRH) gene expression showed significant decrease (1 month: 83.2%; 5 months: 40.7%) in the T group compared with the age-matched C group. TRHR₁ showed significant decrease in the T group compared with the age-matched C group throughout the study (1 month: 82.8%; 3 months: 45.7%; 5 months: 75.2%). However, TRHR₂ showed dynamic change during the study. Initially there was significant (1 month: 0.104-fold) downregulation, followed by significant upregulation (3 months: 3.6-fold) and downregulation (0.73-fold) by the fifth month in the T group compared with the age-matched C group. There was marked depletion of functional follicular cells and colloid substance in the thyroid glands of the T group by the fifth month compared with the C group. Leptin receptors ObRa (1 month: 48.25%; 5 months: 88%) and ObRb (1 month: 46.9%; 5 months: 63.3%) were significantly downregulated in the T group compared with the age-matched C group in the first and fifth months of feeding the respective diets. The expression of p-STAT3, a transcription factor known to have a role in energy balance, intermediate metabolism, and leptin signalling was seen to decrease significantly (6.25-fold) in the hypothalamus of the T group compared with the age-matched C group. In conclusion, HFSC feed disrupts the hypothalamus-pituitary-thyroid axis in male C57BL/6J mice.

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

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

High Thyroid-stimulating Hormone Levels Increase Proinflammatory and Cardiovascular Markers in Patients with Extreme Obesity

BACKGROUND AND AIMS

Obesity is an important health problem worldwide and many studies have suggested a relationship between obesity and thyroid function, with controversial results. Interestingly, high TSH levels have been involved with the presence of inflammatory state and risk for developing cardiovascular diseases in hypothyroid and obese patients. The aim in this work was to determine the prevalence of hypothyroidism in patients with extreme obesity and to determine whether their TSH levels were related to increased serum levels of inflammatory and cardiovascular markers.

METHODS

A cross-sectional study in 101 patients with extreme obesity (BMI ≥40) was performed. Anthropometric (weight, height and waist circumference) and biochemical (fasting glucose, glycosylated hemoglobin, triglycerides, total cholesterol, LDL-C, HDL-C and insulin) parameters were measured. TSH and FT4 levels as well as clinical exploration for diagnosis of hypothyroidism were carried out. Serum concentration of IL-10, IL-6, adiponectin, resistin, leptin, ICAM-1, VCAM-1 and E-selectin were determined.

RESULTS

A high prevalence for diabetes (37.6%), prediabetes (50.5%), dyslipidemia (74.3%), hypertension (61.4%) and hypothyroidism (48.5%) was observed in patients with extreme obesity. The presence of hypothyroidism increased serum concentration of proinflammatory cytokines IL-6 and leptin and decreased the antiinflammatory cytokine adiponectin. In addition, serum TSH levels showed a correlation for waist circumference, weight, BMI, A1c, insulin, IL-6, leptin, ICAM-1 and E-selectin.

CONCLUSION

There is a high prevalence for hypothyroidism in patients with extreme obesity. High levels of TSH contribute to elevate proinflammatory and cardiovascular risk markers, increasing the risk for development of cardiovascular diseases.

Thyroxine therapy ameliorates serum levels of eicosanoids in Chinese subclinical hypothyroidism patients

AIM

The eicosanoids derived from phospholipids play key roles in inflammation. However, the profiles of serum eicosanoids in subclinical hypothyroidism (SH) patients and the effects of thyroxine replacement therapy (TRT) on these eicosanoids remain unclear. Many studies show that TSH regulates lipid metabolism. As eicosanoids derived from phospholipids play key roles in oxidative stress and immune function and inflammatory process, it was necessary to explore the profiles of serum eicosanoids in SH patients and the effects of thyroxine replacement therapy (TRT) on the eicosanoids.

METHODS

A total of 50 Chinese SH patients and 22 healthy volunteers were recruited. SH patients received TRT (L-T4, 25 and 50 mcg/d for patients with TSH≤10.0 mIU/L and TSH>10.0 mIU/L, respectively) for 3 months. Serum levels of major eicosanoids and cPLA2 were analyzed using LC-MS and clinical biochemical assays.

RESULTS

The serum levels of cPLA2, eicosanoids (8-isoPGF2a, 11-dehydroTXB2 and 12-HETE) and 11-dehydroTXB2/6-Keto-PGF1a were significantly elevated in SH patients. The serum TSH levels were significantly correlated with the levels of cPLA2 (r=+0.65), 11-dehydroTXB2 (r=+0.32) and 11-dehydroTXB2/6-Keto-PGF1a (r=+0.37). After 3-month TRT, the serum levels of TSH, cPLA2 and the above-mentioned eicosanoids in SH patients were significantly decreased.

CONCLUSION

The metabolism of eicosanoids is significantly altered in Chinese SH patients, and TRT can ameliorate the abnormalities of serum eicosanoid levels.

Various Possible Toxicants Involved in Thyroid Dysfunction: A Review

About 300 million people across the world suffer from thyroid gland dysfunction. Environmental factors play an important role in causation of autoimmune thyroid diseases in susceptible individuals. Genetics contributes to 70% of the risk. In order to reduce the risk, we need to understand the association of environmental agents with thyroid dysfunction. These factors are especially relevant for those at increased risk due to positive family history. The ideal study to see the impact of a thyroid toxicant consists of directly measuring the degree of exposure to toxicant in an individual with his thyroid status. Knowledge of various factors influencing thyroid dysfunction can help in interpreting the results of such studies in a better way. This article is an attempt to highlight the various possible toxicants affecting thyroid function so that adequate measures can be undertaken to control excessive exposure in future to reduce the prevalence of thyroid disorders.

Lipotoxicity, a potential risk factor for the increasing prevalence of subclinical hypothyroidism?

CONTEXT

Subclinical hypothyroidism (SCH) is an important public health problem worldwide for its increasing prevalence and potential deleterious effects, whereas its etiology has not been fully elucidated. Lipotoxicity exerts extensive and serious impact on human health, but so far, the potential effect of lipotoxicity on thyroid is unclear.

OBJECTIVE

The objective of the study was to assess the association between serum triglyceride levels and the risk for SCH.

DESIGN, PARTICIPANTS, AND METHODS

We conducted a population-based case-control study. A total of 24 100 subjects with similar and stable iodine nutrition status were recruited from China. Cases of 5033 SCH patients were identified and equal controls were matched by age, gender, and region. Conditional logistic regression was used to analyze the association between serum triglyceride levels and risk for SCH.

RESULTS

Hypertriglyceridemia was associated with an approximately 35% increased risk for SCH in both men (odds ratio 1.325; 95% confidence interval 1.002-1.753) and women (odds ratio 1.397; 95% confidence interval 1.217-1.604), even after adjustment for potential confounders. Notably, the risk for SCH increased progressively following the elevation of serum triglyceride levels. Compared with individuals with serum triglyceride levels less than 0.97 mmol/L, the risk for SCH increased approximately 1.9-fold in men and 1.4-fold in women, respectively, when triglyceride levels were greater than 1.99 mmol/L.

CONCLUSION

Our findings suggested that hypertriglyceridemia was positively associated with the risk for SCH.