The relationship between liver histology and thyroid function tests in patients with non-alcoholic fatty liver disease (NAFLD)

Thyroid dysfunction in MASLD: Results of a nationwide study

Background & Aims

Thyroid hormones are known to be potent modulators of hepatic metabolism and targeting the thyroid hormone receptor was recently approved as the first treatment for metabolic-associated steatotic liver disease (MASLD); however, the exact relationship between thyroid disorders and biopsy-confirmed MASLD remains unclear.

Methods

We conducted a nationwide matched case-control study leveraging data from the Swedish Epidemiology Strengthened by histoPathology Reports in Sweden (ESPRESSO) cohort, which includes liver biopsy data spanning from 1969 to 2017. We identified 12,172 patients with MASLD and 56,831 matched general-population controls, including 5,478 patients with MASLD with 10,682 sibling controls. Conditional logistic regression was used to calculate odds ratios for hypothyroidism and hyperthyroidism defined through ICD codes or prescription records. Causal inference was examined using Mendelian randomization (MR). Both observational and MR mediation analyses were performed to explore the roles of metabolic features.

Results

Hypothyroidism was associated with 1.68-fold increased odds of MASLD (95% CI 1.36-2.06). The association remained stable in the analysis using siblings as controls. However, in absolute terms, hypothyroidism was uncommon and seen in 2.5% in people with MASLD and in 1.4% of controls. Higher genetically predicted thyroid-stimulating hormone levels and hypothyroidism were linked to increased MASLD risk. Mediation analysis showed that metabolic disorders contributed ∼41% to this risk. Furthermore, there was an inverse association between hyperthyroidism and MASLD (adjusted odds ratio 0.17, 95% CI 0.05-0.56); however, the association did not reach statistical significance in the MR analysis.

Conclusions

The findings suggest that hypothyroidism is associated with a heightened risk of MASLD and that hyperthyroidism is potentially protective against MASLD.

Impact and implications

The approval by the US FDA of resmetirom, a thyroid hormone receptor β-selective agonist for non-cirrhotic metabolic dysfunction-associated steatohepatitis with stage 2-3 fibrosis, highlights the potential role of thyroid dysfunction in metabolic-associated steatotic liver disease (MASLD). This study identified hypothyroidism as a risk factor for MASLD, especially in men and individuals younger than 40 years, with the association peaking at non-cirrhotic fibrosis. Metabolic disorders mediated ∼41% of the hypothyroidism-MASLD association. Hyperthyroidism was potentially inversely associated with MASLD. Despite its low prevalence (2.5% in MASLD cases, 1.4% in controls), the population health impact of hypothyroidism warrants further attention.

Correlation between serum thyroid hormone level and metabolic steatohepatitis: A retrospective study

BACKGROUND

Metabolic steatohepatitis (MASH) is a common liver disease, and its association with serum thyroid hormone levels is unclear. This study aimed to analyze the association between MASH and serum levels of thyroid hormones in patients with normal thyroid function.

METHODS

638 non-alcoholic fatty liver disease patients hospitalized in our hospital from March 2021 to March 2024 were retrospectively selected and divided into MASH (n = 262) and non-MASH (n = 376) groups based on the diagnosis made by expert pathologists. The clinical data of the patients were collected, and multivariate logistic regression analysis was utilized to investigate the association between MASH and serum thyroid hormone levels.

RESULTS

Serum levels of thyroid-stimulating hormone (TSH) and free triiodothyronine (FT3) in the MASH group were significantly higher compared to the non-MASH group, and serum free thyroxine (FT4) levels were lower than those in non-MASH group. The FT3/FT4 ratio in MASH group was higher than that in non-MASH group (P < 0.05). Logistic regression analysis showed that serum levels of TSH, FT3 and FT4 were independent influencing factors for MASH. The area under receiver operating characteristic (ROC) curve of TSH, FT3, FT4 and FT3/FT4 for predicting the occurrence of MASH were 0.944, 0.973, 0.753 and 0.959, respectively.

CONCLUSIONS

Elevated serum levels of TSH, FT3, and the FT3/FT4 ratio, along with decreased serum FT4 levels, were independently associated with an increased risk of MASH.

Thyroid function and hepatic fibrosis/cirrhosis: a two-sample Mendelian randomization study

Background

Evidence on the relationship between thyroid function and hepatic fibrosis/cirrhosis are still unclear, with inconsistent conclusions. This Mendelian randomization (MR) study aimed to investigate the potential causal association between thyroid function and hepatic fibrosis/cirrhosis in order to provide new insights for improving prevention and control strategies for this disease.

Methods

Genome-wide association study (GWAS) data on exposures, which included hyperthyroidism, hypothyroidism, and thyroid-stimulating hormone (TSH), were extracted from the MRC Integrative Epidemiology Unit (MRC-IEU) (https://gwas.mrcieu.ac.uk/), and GWAS data for outcomes, including hepatic fibrosis/cirrhosis and chitinase-3-like protein 1 (CHI3L1), were obtained from the FinnGen consortium (https://www.finngen.fi/fi). Inverse variance weighted (IVW), weighted median, and MR-Egger methods were utilized to examine the causal association between thyroid function and the risk of hepatic fibrosis/cirrhosis. Cochran's Q test was used to assess the heterogeneity of instrumental variables (IVs), while MR-PRESSO and leave-one-out analyses were conducted for sensitivity analysis.

Results

IVW estimates suggested that hypothyroidism had a potential causal association with higher odds of hepatic fibrosis/cirrhosis (OR = 1.247, 95% CI: 1.087-1.431). Leave-one-out results indicated that this potential causal relationship was relatively robust. In addition, we assessed the causal association between hypothyroidism and hepatic fibrosis/cirrhosis before and after removal of outliers with heterogeneity. After removing the outliers, the association was still significant (OR = 1.266, 95% CI: 1.082-1.482, P = 0.0046).

Conclusion

Patients with hypothyroidism may have a higher risk of hepatic fibrosis/cirrhosis, and this finding may provide some references for the early screening and prevention of the disease. However, further studies are needed to explore the specific mechanisms by which hypothyroidism influences hepatic fibrosis/cirrhosis.

Integrative Transcriptomics and Proteomics Analysis Reveals THRSP's Role in Lipid Metabolism

Background/Objectives: Abnormalities in lipid metabolism and endoplasmic reticulum (ER) stress are strongly associated with the development of a multitude of pathological conditions, including nonalcoholic fatty liver disease (NAFLD), diabetes mellitus, and obesity. Previous studies have indicated a potential connection between thyroid hormone responsive (THRSP) and lipid metabolism and that ER stress may participate in the synthesis of key regulators of adipogenesis. However, the specific mechanisms remain to be investigated. Methods: In this study, we explored the roles of THRSP in lipid metabolism by interfering with THRSP gene expression in mouse mesenchymal stem cells, comparing the effects on adipogenesis between control and interfered groups, and by combining transcriptomic and proteomic analysis. Results: Our results showed that the number of lipid droplets was significantly reduced after interfering with THRSP, and the expression levels of key regulators of adipogenesis, such as LPL, FABP4, PLIN1, and CIDEC, were significantly downregulated. Both transcriptomic and proteomic results showed that the differential genes (proteins) were enriched in the processes of lipolytic regulation, ER stress, cholesterol metabolism, sphingolipid metabolism, PPAR signaling pathway, and glycerophospholipid metabolism. The ER stress marker gene, ATF6, was the most significantly downregulated transcription factor. In addition, RT-qPCR validation indicated that the expression levels of PPAR signaling pathway gene SCD1; key genes of lipid droplet generation including LIPE, DGAT1, and AGPAT2; and ER stress marker gene ATF6 were significantly downregulated. Conclusions: These suggest that THRSP is involved in regulating ER stress and the PPAR signaling pathway, which is closely related to lipid synthesis and metabolism. Interfering with the expression of THRSP may be helpful in ameliorating the occurrence of diseases related to abnormalities in lipid metabolism.

A Study of Non-alcoholic Fatty Liver Disease in Patients With Hypothyroidism: A Cross-Sectional Study in a Tertiary Care Hospital

Background Hypothyroidism occurs when the thyroid gland is underactive and fails to produce sufficient thyroid hormones. It can affect multiple organs including the heart, brain, liver, kidneys, and reproductive system, leading to symptoms such as fatigue, cognitive impairment, elevated cholesterol, fluid retention, fatty liver, and menstrual irregularities. Given the higher prevalence of fatty liver disease in patients with hypothyroidism, it is important to evaluate the need for routine screening for fatty liver in these patients. Materials and methods This observational, cross-sectional study was conducted at Dr. D. Y. Patil Medical Hospital, Pune, Maharashtra, India, from October 2022 to June 2024. The study included 60 patients aged over 12 years who were known or recently diagnosed with hypothyroidism. Patients with type 2 diabetes mellitus, pregnant women, or those with chronic liver disease were excluded. Data collected included physical examination findings and laboratory test results. Fatty liver was diagnosed using magnetic resonance elastography. Statistical analysis was performed using IBM SPSS statistics for Windows, version 20 (IBM Corp., Armonk, New York). The statistical significance of parametric data was evaluated using the Chi-square test. A p-value less than 0.05 and a confidence interval of 95% were considered statistically significant. Result The study population had an average age of about 45 years, with most participants aged between 40 and 49 years. The majority of the participants were female, making up over 83% of the group, while males constituted about 17%. The most commonly reported symptom was weight gain, followed by constipation and fatigue. For individuals with fatty liver, the average thyroid-stimulating hormone (TSH) level was notably higher compared to those without fatty liver. Additionally, low-density lipoprotein (LDL) levels were higher in individuals with non-alcoholic fatty liver disease (NAFLD) compared to those without. Both TSH and LDL levels showed a statistically significant association with the occurrence of NAFLD. Conclusion Hypothyroidism was more prevalent in females and in the age group 40-49 years. There was a statistical significance between TSH and the occurrence of NAFLD. In this study, statistical significance was also found between LDL and the occurrence of NAFLD.

Impact of peripheral thyroid hormone balance on liver fat: insights from the NutriAct trial

OBJECTIVE

Hypothyroidism has been proposed as a potential contributor to steatotic liver disease (SLD), but existing data shows conflicting results in euthyroid subjects. Therefore, we investigated the association between thyroid function and intrahepatic lipids (IHLs) during a 36-month randomized controlled trial evaluating a diet known to reduce liver fat.

DESIGN

502 eligible subjects (aged 50-80 years, ≥1 risk factor for unhealthy aging) were randomly assigned to either follow a diet rich in unsaturated fatty acids, plant protein, and fiber (intervention group, IG), or dietary recommendations of the German Nutrition Society (control group, CG).

METHODS

Serum levels of thyroid hormones (THs) as well as IHLs, defined via magnetic resonance spectroscopy, were measured within an euthyroid subgroup without significant alcohol consumption at baseline (n = 332) and after 12 months (n = 243). A ratio of T3/T4 was used to assess whole-body deiodinase activity. Estimates of glucose and lipid metabolism were analyzed.

RESULTS

Only fT3 and T3/T4 ratios showed a significant positive correlation with IHL at baseline. We observed a significant decline in fT3, T3, fT3/fT4 ratio, and T3/T4 ratio in CG and IG after 12 months without significant differences between groups. TSH, fT4, and T4 remained stable. A larger improvement of IHL during dietary intervention was seen in those subjects with a lower decline in T3 concentrations.

CONCLUSIONS

Altered TH balance indicates a possible compensatory upregulation of whole-body TH activity in subjects with increased liver fat. This might be also relevant during the improvement of hepatic steatosis.

Thyroid function, adipokines and mitokines in metabolic dysfunction-associated steatohepatitis: A multi-centre biopsy-based observational study

BACKGROUND AND AIMS

Thyroid axis is currently under investigation as a therapeutic target in metabolic dysfunction-associated steatotic liver disease (MASLD). Thyroid function was examined herein in the full spectrum of disease.

METHODS

Subjects were recruited and had liver biopsies in two Gastroenterology-Hepatology Clinics (Greece and Australia) and one Bariatric-Metabolic Surgery Clinic (Italy). The main working sample was n = 677 subjects with MASLD after excluding subjects with abnormal free thyroxine levels. Participants were classified according to thyroid-stimulating hormone (TSH) standard criteria: Subclinical hyperthyroidism (<0.4 uIU/mL); Euthyroidism with relatively low (0.4 to <2.5 uIU/mL); euthyroidism with relatively high (2.5-4.0 uIU/mL); subclinical hypothyroidism (>4 uIU/mL).

RESULTS

TSH as a continuous variable was positively associated with significant fibrosis (F ≥ 2), metabolic dysfunction-associated steatohepatitis (MASH) and at-risk MASH. Subclinical hypothyroidism was associated with fibrosis F ≥ 2 (odds ratio [OR] = 3.47, 95% confident interval [CI] [1.50, 8.05], p = .02), MASH (OR = 3.44, 95% CI [1.48, 7.98] p = .001) and at-risk MASH (OR = 3.88, 95% CI [1.76, 8.55], p = .001), before and after controlling for adiposity, central obesity, and insulin resistance. When leptin, adiponectin, or growth differentiation factor-15 were examined as moderators, significance was lost. Sex-specific analysis revealed a strong association between TSH and the presence of significant fibrosis among women, eliminated only when adipokines/mitokines were adjusted for. Restricted cubic spline analysis revealed associations between TSH and liver outcomes (p-values < .01) with inflection points for fibrosis F ≥ 2 being 2.49, for MASH being 2.67 and for at-risk MASH being 6.96.

CONCLUSIONS

These observations provide support for studies on the administration of thyroid hormone in MASLD therapeutics for subclinical hypothyroidism and liver-specific thyroid receptor agonists for subjects across the TSH continuum.

Current Therapeutical Approaches Targeting Lipid Metabolism in NAFLD

Nonalcoholic fatty liver disease (NAFLD, including nonalcoholic fatty liver (NAFL) and nonalcoholic steatohepatitis (NASH)) is a high-prevalence disorder, affecting about 1 billion people, which can evolve to more severe conditions like cirrhosis or hepatocellular carcinoma. NAFLD is often concomitant with conditions of the metabolic syndrome, such as central obesity and insulin-resistance, but a specific drug able to revert NAFL and prevent its evolution towards NASH is still lacking. With the liver being a key organ in metabolic processes, the potential therapeutic strategies are many, and range from directly targeting the lipid metabolism to the prevention of tissue inflammation. However, side effects have been reported for the drugs tested up to now. In this review, different approaches to the treatment of NAFLD are presented, including newer therapies and ongoing clinical trials. Particular focus is placed on the reverse cholesterol transport system and on the agonists for nuclear factors like PPAR and FXR, but also drugs initially developed for other conditions such as incretins and thyromimetics along with validated natural compounds that have anti-inflammatory potential. This work provides an overview of the different therapeutic strategies currently being tested for NAFLD, other than, or along with, the recommendation of weight loss.

A qualitative patient interview study to understand the experience of patients with nonalcoholic steatohepatitis

NASH is a potentially progressive form of NAFLD characterized by hepatocyte injury and liver inflammation which can cause fibrosis. Currently, there are limited data on the patient experience of NASH. Our aim was to use both literature review and patient interviews to understand the signs/symptoms and life impacts of NASH fibrosis stages F1-F4 that are important to patients, as well as begin to investigate the applicability of an instrument (ie, questionnaire) that may be used to capture patients' experiences. The literature review identified concepts (signs/symptoms and impacts) related to NASH fibrosis stages F1-F4 and the NASH-specific patient-reported outcome instrument (NASH-CHECK) for reporting patient experience of NASH. Interviews with 22 patients from Canada and the USA with NASH fibrosis stages F1-F4 revealed 27 signs/symptoms and 32 impacts that they felt were important, including fatigue, pain in the abdomen, worry, and frustration. Three concepts reported during patient interviews were not identified in the literature review. No concepts appeared to be exclusive to a specific fibrosis stage or presence/absence of obesity and no linear trends were identified between fibrosis stage or presence/absence of obesity and level of disturbance reported for concepts. The patient interviews supported the concepts included in the NASH-CHECK overall, demonstrating that it could be used to report the patient experience of NASH fibrosis stages F1-F4. Interviews with patients with NASH fibrosis stages F1-F4 revealed patients can self-report and elaborate on signs/symptoms and impacts related to the disease regardless of fibrosis stage. The NASH-CHECK was identified as a suitable instrument that could be used by patients with fibrosis stages F1-F4.

An adipocentric perspective on the development and progression of non-alcoholic fatty liver disease

Alongside the liver, white adipose tissue (WAT) is critical in regulating systemic energy homeostasis. Although each organ has its specialised functions, they must work coordinately to regulate whole-body metabolism. Adipose tissues and the liver are relatively resilient and can adapt to an energy surplus by facilitating triglyceride (TG) storage up to a certain threshold level without significant metabolic disturbances. However, lipid storage in WAT beyond a "personalised" adiposity threshold becomes dysfunctional, leading to metabolic inflexibility, progressive inflammation, and aberrant adipokine secretion. Moreover, the failure of adipose tissue to store and mobilise lipids results in systemic knock-on lipid overload, particularly in the liver. Factors contributing to hepatic lipid overload include lipids released from WAT, dietary fat intake, and enhanced de novo lipogenesis. In contrast, extrahepatic mechanisms counteracting toxic hepatic lipid overload entail coordinated compensation through oxidation of surplus fatty acids in brown adipose tissue and storage of fatty acids as TGs in WAT. Failure of these integrated homeostatic mechanisms leads to quantitative increases and qualitative alterations to the lipidome of the liver. Initially, hepatocytes preferentially accumulate TG species leading to a relatively "benign" non-alcoholic fatty liver. However, with time, inflammatory responses ensue, progressing into more severe conditions such as non-alcoholic steatohepatitis, cirrhosis, and hepatocellular carcinoma, in some individuals (often without an early prognostic clue). Herein, we highlight the pathogenic importance of obesity-induced "adipose tissue failure", resulting in decreased adipose tissue functionality (i.e. fat storage capacity and metabolic flexibility), in the development and progression of NAFL/NASH.

MAFLD: a multisystem disease

Nonalcoholic fatty liver disease (NAFLD), affecting about 25% of general population and more than 50% of dysmetabolic patients, is an emerging cause of chronic liver disease and its complications. Recently, an international consensus of experts proposed to rename this disease as 'Metabolic dysfunction-Associated Fatty Liver Disease' (MAFLD) to focus on the bidirectional interplay between fatty liver and metabolic alterations and to stress the need of assessing fatty liver independently from alcohol consumption and other coexisting causes of liver disease. The peculiarity of NAFLD/MAFLD lies in the presence of a higher risk of not only - as expected - liver-related events but also of extrahepatic events, mostly cardiovascular and cancers. Available evidence suggests that these associations are not only the expression of sharing the same risk factors but shed light about the ability of NAFLD/MAFLD and particularly of its progressive form - nonalcoholic/metabolic dysfunction-associated steatohepatitis - to act as an independent risk factor via promotion of atherogenic dyslipidemia and a proinflammatory, profibrogenic, and procoagulant systemic environment. The present review summarizes available epidemiological and clinical evidence supporting the concept of NAFLD/MAFLD as a multisystemic disease, and highlights potential explanatory mechanisms underlying the association between NAFLD/MAFLD and extrahepatic disorders.

Association between Thyroid Hormones and Non-alcoholic Fatty Liver Disease and Non-alcoholic Steatohepatitis in Obese Individuals Undergoing Bariatric Surgery

Background: Non-alcoholic fatty liver disease (NAFLD), non-alcoholic steatohepatitis (NASH), and hepatic fibrosis have emerged as one of the leading causes of chronic liver disease. The prevalence of the NAFLD spectrum has increased, which can be attributed to the rise in obesity. As NAFLD can ultimately lead to liver cirrhosis, it is imperative to identify modifiable risk factors associated with its onset and progression to provide timely intervention to prevent potentially disastrous consequences. Considering the pivotal role of the endocrine axis in several metabolic pathways such as obesity and insulin resistance, thyroid hormones are crucial in the pathophysiology of NAFLD. The study is focused on the identification of an association between thyroid function and radiographic and histological parameters of NAFLD in patients with severe obesity. Methods: Ninety patients were recruited for this study and underwent initial assessments, including demographic profiles, anthropometric measurements, hepatic biopsy, and basic laboratory tests. Liver stiffness was evaluated using two-dimensional shear wave elastography (2D-SWE) at least 2 weeks before liver biopsy. Results: Among the 90 participants, 80% were women. The mean age was 38.5±11.1 years, and the mean body mass index (BMI) was 45.46±6.26 kg/m2. The mean levels of serum T3 and free T4 in patients with positive histology were not statistically significant compared with patients with negative histology. Furthermore, there was no statistical significance in the mean T3 and free T4 levels between patients diagnosed with hepatic steatosis or fibrosis (on ultrasonography and elastography) and those with negative hepatic imaging. Serum levels of thyroid-stimulating hormone (TSH) were negatively correlated with ultrasonography (P=0.007). Binary logistic regression analysis revealed that none of the thyroid hormones was a predictive factor for liver histology in both adjusted and crude models. Conclusion: The results from our analysis did not suggest an association between thyroid hormones and NAFLD, which is in line with several previously published studies. However, the authors note that there are published data that do propose a link between the two entities. Therefore, well-designed large-scale clinical studies are required to clarify this discrepancy.

Influence of Altered Thyroid Hormone Mechanisms in the Progression of Metabolic Dysfunction Associated with Fatty Liver Disease (MAFLD): A Systematic Review

We performed a systematic review of the mechanisms of thyroid hormones (THs) associated with metabolic dysfunction associated with fatty liver disease (MAFLD). This systematic review was registered under PROSPERO (CRD42022323766). We searched the MEDLINE (via PubMed) and Embase databases from their inception to March 2022. We included studies that assessed thyroid function by measuring the serum level of THs and those involved in MAFLD. We excluded reviews, case reports, editorials, letters, duplicate studies and designed controls. Forty-three studies included MAFLD, eleven analyzed THs, and thirty-two evaluated the mechanisms of THs in MAFLD. Thyroid hormones are essential for healthy growth, development and tissue maintenance. In the liver, THs directly influence the regulation of lipid and carbohydrate metabolism, restoring the homeostatic state of the body. The selected studies showed an association of reduced levels of THs with the development and progression of MAFLD. In parallel, reduced levels of T3 have a negative impact on the activation of co-regulators in the liver, reducing the transcription of genes important in hepatic metabolism. Overall, this is the first review that systematically synthesizes studies focused on the mechanism of THs in the development and progression of MAFLD. The data generated in this systematic review strengthen knowledge of the impact of TH changes on the liver and direct new studies focusing on therapies that use these mechanisms.

The Role of Insulin Resistance in Fueling NAFLD Pathogenesis: From Molecular Mechanisms to Clinical Implications

Non-alcoholic fatty liver disease (NAFLD) represents a predominant hepatopathy that is rapidly becoming the most common cause of hepatocellular carcinoma worldwide. The close association with metabolic syndrome’s extrahepatic components has suggested the nature of the systemic metabolic-related disorder based on the interplay between genetic, nutritional, and environmental factors, creating a complex network of yet-unclarified pathogenetic mechanisms in which the role of insulin resistance (IR) could be crucial. This review detailed the clinical and pathogenetic evidence involved in the NAFLD–IR relationship, presenting both the classic and more innovative models. In particular, we focused on the reciprocal effects of IR, oxidative stress, and systemic inflammation on insulin-sensitivity disruption in critical regions such as the hepatic and the adipose tissue, while considering the impact of genetics/epigenetics on the regulation of IR mechanisms as well as nutrients on specific insulin-related gene expression (nutrigenetics and nutrigenomics). In addition, we discussed the emerging capability of the gut microbiota to interfere with physiological signaling of the hormonal pathways responsible for maintaining metabolic homeostasis and by inducing an abnormal activation of the immune system. The translation of these novel findings into clinical practice could promote the expansion of accurate diagnostic/prognostic stratification tools and tailored pharmacological approaches.

Targeting Thyroid Hormone/Thyroid Hormone Receptor Axis: An Attractive Therapy Strategy in Liver Diseases

Thyroid hormone/thyroid hormone receptor (TH/TR) axis is characterized by TH with the assistance of plasma membrane transporters to combine with TR and mediate biological activities. Growing evidence suggests that TH/TR participates in plenty of hepatic metabolism. Thus, this review focuses on the role of the TH/TR axis in the liver diseases. To be specific, the TH/TR axis may improve metabolic-associated fatty liver disease, hepatitis, liver fibrosis, and liver injury while exacerbating the progression of acute liver failure and alcoholic liver disease. Also, the TH/TR axis has paradoxical roles in hepatocellular carcinoma. The TH/TR axis may be a prospecting target to cure hepatic diseases.

Hypothyroidism and Diabetes-Related Dementia: Focused on Neuronal Dysfunction, Insulin Resistance, and Dyslipidemia

The incidence of dementia is steadily increasing worldwide. The risk factors for dementia are diverse, and include genetic background, environmental factors, sex differences, and vascular abnormalities. Among the subtypes of dementia, diabetes-related dementia is emerging as a complex type of dementia related to metabolic imbalance, due to the increase in the number of patients with metabolic syndrome and dementia worldwide. Thyroid hormones are considered metabolic regulatory hormones and affect various diseases, such as liver failure, obesity, and dementia. Thyroid dysregulation affects various cellular mechanisms and is linked to multiple disease pathologies. In particular, hypothyroidism is considered a critical cause for various neurological problems-such as metabolic disease, depressive symptoms, and dementia-in the central nervous system. Recent studies have demonstrated the relationship between hypothyroidism and brain insulin resistance and dyslipidemia, leading to diabetes-related dementia. Therefore, we reviewed the relationship between hypothyroidism and diabetes-related dementia, with a focus on major features of diabetes-related dementia such as insulin resistance, neuronal dysfunction, and dyslipidemia.

Non-Alcoholic Fatty Liver Disease and Hypothyroidism: Review of Clinical and Experimental Studies

Hypothyroidism is a widespread condition affecting people of different socio-economic background and geographical location. A lot of studies highlight the effect of hypothyroidism on the metabolic processes in various organs, including the liver. On the other hand, liver damage often results in the development of non-alcoholic fatty liver disease; however, the data on the impact of hypothyroidism on liver morphology, which can serve as a direct indicator and marker of liver condition and function, are limited and controversial. In this report, we reviewed the relationship between non-alcoholic fatty liver disease and hypothyroidism with an accent on morphological alteration of the liver discovered in clinical and experimental studies.

Hypothyroidism-Associated Dyslipidemia: Potential Molecular Mechanisms Leading to NAFLD

Thyroid hormones control lipid metabolism by exhibiting specific effects on the liver and adipose tissue in a coordinated manner. Different diseases of the thyroid gland can result in hypothyroidism. Hypothyroidism is frequently associated with dyslipidemia. Hypothyroidism-associated dyslipidemia subsequently results in intrahepatic accumulation of fat, leading to nonalcoholic fatty liver disease (NAFLD), which leads to the development of hepatic insulin resistance. The prevalence of NAFLD in the western world is increasing, and evidence of its association with hypothyroidism is accumulating. Since hypothyroidism has been identified as a modifiable risk factor of NAFLD and recent data provides evidence that selective thyroid hormone receptor β (THR-β) agonists are effective in the treatment of dyslipidemia and NAFLD, interest in potential therapeutic options for NAFLD targeting these receptors is growing. In this review, we summarize current knowledge regarding clinical and molecular data exploring the association of hypothyroidism, dyslipidemia and NAFLD.

TSH Levels as an Independent Risk Factor for NAFLD and Liver Fibrosis in the General Population

Thyroid hormones may be a risk factor for the development of non-alcoholic fatty liver disease (NAFLD) and its progression to liver fibrosis. The aim of this study is to investigate the relationship between thyroid stimulating hormone (TSH) levels, NAFLD, and liver fibrosis in the general population. A descriptive cross-sectional study was performed in subjects aged 18–75 years randomly selected from primary care centers between 2012 and 2016. Each subject underwent clinical evaluation, physical examination, blood tests and transient elastography. Descriptive and multivariate logistic regression analyses were used to identify factors associated with NAFLD and fibrosis. We included 2452 subjects (54 ± 12 years; 61% female). Subjects with TSH ≥ 2.5 μIU/mL were significantly associated with obesity, atherogenic dyslipidemia, metabolic syndrome (MetS), hypertransaminasemia and altered cholesterol and triglycerides. The prevalence of NAFLD and liver fibrosis was significantly higher in subjects with TSH ≥ 2.5 (μIU/mL). We found a 1.5 times increased risk of NAFLD, 1.8 and 2.3 times increased risk of liver fibrosis for cut-off points of ≥8.0 kPa and ≥9.2 kPa, respectively, in subjects with TSH ≥ 2.5 μIU/mL compared with TSH < 2.5 μIU/mL (control group), independent of the presence of MetS. These findings remained significant when stratifying TSH, with values ≥ 10 μIU/mL.