Role of thyroid hormones in the neoplastic process: an overview

Cytologic hallmarks and differential diagnosis of papillary thyroid carcinoma subtypes

Papillary thyroid carcinoma (PTC) is the most common thyroid malignancy, characterized by a range of subtypes that differ in their cytologic features, clinical behavior, and prognosis. Accurate cytologic evaluation of PTC using fine-needle aspiration is essential but can be challenging due to the morphologic diversity among subtypes. This review focuses on the distinct cytologic characteristics of various PTC subtypes, including the classic type, follicular variant, tall cell, columnar cell, hobnail, diffuse sclerosing, Warthin-like, solid/trabecular, and oncocytic PTCs. Each subtype demonstrates unique nuclear features, architectural patterns, and background elements essential for diagnosis and differentiation from other thyroid lesions. Recognizing these distinct cytologic patterns is essential for identifying aggressive subtypes like tall cell, hobnail, and columnar cell PTCs, which have a higher risk of recurrence, metastasis, and poorer clinical outcomes. Additionally, rare subtypes such as diffuse sclerosing and Warthin-like PTCs present unique cytologic profiles that must be carefully interpreted to avoid diagnostic errors. The review also highlights the cytologic indicators of lymph node metastasis and high-grade features, such as differentiated high-grade thyroid carcinoma. The integration of molecular testing can further refine subtype diagnosis by identifying specific genetic mutations. A thorough understanding of these subtype-specific cytologic features and molecular profiles is vital for accurate diagnosis, risk stratification, and personalized management of PTC patients. Future improvements in diagnostic techniques and standardization are needed to enhance cytologic evaluation and clinical decision-making in thyroid cancer.

Recent advances in liquid chromatography-tandem mass spectrometry for the detection of thyroid hormones and thyroglobulin in clinical samples: A review

Thyroid hormones (THs), including triiodothyronine (T3), thyroxine (T4), and their metabolites, are essential for regulating development, growth, and energy metabolism. Thyroglobulin (Tg) produced by thyroid follicular cells acts as an essential substrate for TH synthesis. The combination of THs with Tg is a widely used serological laboratory test for thyroid function assessment. Early detection and timely intervention are significant for preventing and managing thyroid disease. In recent years, liquid chromatography-tandem mass spectrometry (LC-MS/MS) has emerged as a powerful tool for the precise detection of small molecular analytes and steroid hormones in clinical practice as a result of its high sensitivity and specificity. While LC-MS/MS has been increasingly used for detecting THs and Tg recently, its application in clinical practice is still in its early stages. Recent advances in the assessment of thyroid metabolism using LC-MS/MS in clinical samples published during 2004-2023 were reviewed, with a special focus on the use of this technique for quantifying molecules involved in thyroid diseases.

The selenoenzyme type I iodothyronine deiodinase: a new tumor suppressor in ovarian cancer

The selenoenzyme type I iodothyronine deiodinase (DIO1) catalyzes removal of iodine atoms from thyroid hormones. Although DIO1 action is reported to be disturbed in several malignancies, no work has been conducted in high-grade serous ovarian carcinoma (HGSOC), the most lethal gynecologic cancer. We studied DIO1 expression in HGSOC patients [The Cancer Genome Atlas (TCGA) data and tumor tissues], human cell lines (ES-2 and Kuramochi), normal Chinese hamster ovarian cells (CHO-K1), and normal human fallopian tube cells (FT282 and FT109). To study its functional role, DIO1 was overexpressed, inhibited [by propylthiouracil (PTU)], or knocked down (KD), and cell count, proliferation, apoptosis, cell viability, and proteomics analysis were performed. Lower DIO1 levels were observed in HGSOC compared to normal cells and tissues. TCGA analyses confirmed that low DIO1 mRNA expression correlated with worse survival and therapy resistance in patients. Silencing or inhibiting the enzyme led to enhanced ovarian cancer proliferation, while an opposite effect was shown following DIO1 ectopic expression. Proteomics analysis in DIO1-KD cells revealed global changes in proteins that facilitate tumor metabolism and progression. In conclusion, DIO1 expression and ovarian cancer progression are inversely correlated, highlighting a tumor suppressive role for this enzyme and its potential use as a biomarker in this disease.

Targeting Androgen, Thyroid Hormone, and Vitamin A and D Receptors to Treat Prostate Cancer

The nuclear hormone family of receptors regulates gene expression. The androgen receptor (AR), upon ligand binding and homodimerization, shuttles from the cytosol into the nucleus to activate gene expression. Thyroid hormone receptors (TRs), retinoic acid receptors (RARs), and the vitamin D receptor (VDR) are present in the nucleus bound to chromatin as a heterodimer with the retinoid X receptors (RXRs) and repress gene expression. Ligand binding leads to transcription activation. The hormonal ligands for these receptors play crucial roles to ensure the proper conduct of very many tissues and exert effects on prostate cancer (PCa) cells. Androgens support PCa proliferation and androgen deprivation alone or with chemotherapy is the standard therapy for PCa. RARγ activation and 3,5,3'-triiodo-L-thyronine (T3) stimulation of TRβ support the growth of PCa cells. Ligand stimulation of VDR drives growth arrest, differentiation, and apoptosis of PCa cells. Often these receptors are explored as separate avenues to find treatments for PCa and other cancers. However, there is accumulating evidence to support receptor interactions and crosstalk of regulatory events whereby a better understanding might lead to new combinatorial treatments.

The key roles of thyroid hormone in mitochondrial regulation, at interface of human health and disease

Mitochondria are highly plastic and dynamic organelles long known as the powerhouse of cellular bioenergetics, but also endowed with a critical role in stress responses and homeostasis maintenance, supporting and integrating activities across multifaced cellular processes. As a such, mitochondria dysfunctions are leading causes of a wide range of diseases and pathologies. Thyroid hormones (THs) are endocrine regulators of cellular metabolism, regulating intracellular nutrients fueling of sugars, amino acids and fatty acids. For instance, THs regulate the balance between the anabolism and catabolism of all the macro-molecules, influencing energy homeostasis during different nutritional conditions. Noteworthy, not only most of the TH-dependent metabolic modulations act via the mitochondria, but also THs have been proved to regulate the mitochondrial biosynthesis, dynamics and function. The significance of such an interplay is different in the context of specific tissues and strongly impacts on cellular homeostasis. Thus, a comprehensive understanding of THs-dependent mitochondrial functions and dynamics is required to develop more precise strategies for targeting mitochondrial function. Herein, we describe the mechanisms of TH-dependent metabolic regulation with a focus on mitochondrial action, in different tissue contexts, thus providing new insights for targeted modulation of mitochondrial dynamics.

Risk of Subsequent Primary Cancers in Thyroid Cancer Survivors according to the Dose of Levothyroxine: A Nationwide Cohort Study

BACKGRUOUND

Current research has not investigated the effect of thyroid-stimulating hormone suppression therapy with levothyroxine on the risk for developing subsequent primary cancers (SPCs). This study aimed to investigate the association between levothyroxine dosage and the risk for SPCs in thyroid cancer patients.

METHODS

We conducted a nationwide population-based retrospective cohort study form Korean National Health Insurance database. This cohort included 342,920 thyroid cancer patients between 2004 and 2018. Patients were divided into the non-levothyroxine and the levothyroxine groups, the latter consisting of four dosage subgroups according to quartiles. Cox proportional hazard models were performed to evaluate the risk for SPCs by adjusting for variables including cumulative doses of radioactive iodine (RAI) therapy.

RESULTS

A total of 17,410 SPC cases were observed over a median 7.3 years of follow-up. The high-dose levothyroxine subgroups (Q3 and Q4) had a higher risk for SPC (adjusted hazard ratio [HR], 1.14 and 1.27; 95% confidence interval [CI], 1.05-1.24 and 1.17- 1.37; respectively) compared to the non-levothyroxine group. In particular, the adjusted HR of stomach (1.31), colorectal (1.60), liver and biliary tract (1.95), and pancreatic (2.48) cancers were increased in the Q4 subgroup. We consistently observed a positive association between high levothyroxine dosage per body weight and risk of SPCs, even after adjusting for various confounding variables. Moreover, similar results were identified in the stratified analyses according to thyroidectomy type and RAI therapy, as well as in a subgroup analysis of patients with good adherence.

CONCLUSION

High-dose levothyroxine use was associated with increased risk of SPCs among thyroid cancer patients regardless of RAI therapy.

Autoimmune Thyroid Disease and Differentiated Thyroid Carcinoma: A Review of the Mechanisms That Explain an Intriguing and Exciting Relationship

Autoimmune thyroid disease is a complex and highly frequent disease, where a wide variety of genetic, epigenetic and environmental factors (among others) come together and interact, and is characterized by the presence of two clinical outcomes: hypothyroidism (in Hashimoto's thyroiditis) and hyperthyroidism (in Graves-Basedow disease). For its part, differentiated thyroid carcinoma (mainly papillary carcinoma) is the most common type of cancer affecting the thyroid (and one of the most prevalent worldwide). An important co-occurrence between autoimmune thyroid disease and differentiated thyroid carcinoma has been documented. In this article, studies that have evaluated possible associations and relationships between autoimmune thyroid disease and differentiated thyroid cancer are systematically described and summarized. To date, the underlying mechanism that explains this association is inflammation; however, the characteristics and designs of the studies evaluated do not yet allow a causal relationship between the two entities to be established. These aspects have made it difficult to establish "causality" in the continuum of the pathogenesis between both conditions.

Hypothyroidism and hyperthyroidism related to gynecologic cancers: a nationwide population-based cohort study

The purpose of this study was to assess the risks of hyperthyroidism and hypothyroidism related to gynecological cancers. Population-based retrospective cohort study. We conducted a cohort study using the Taiwan National Health Insurance Research Database to explore hyperthyroidism and hypothyroidism associated with site-specific gynecologic cancers in women from January 1, 2000 to December 31, 2018. The examined gynecologic cancers included endometrial (EC), uterine corpus cancer (UC), and ovarian cancer (OC). The incidence and hazard ratios were quantified using Cox proportional hazards models. The incidence of developing gynecological (Gyn) cancers in the hyperthyroid and hypothyroid women was 0.29 and 0.44 per 1000 person-years, which was 0.86 fold lower and 1.13 fold higher than that in the comparison cohort (p < 0.001). Compared with patients aged 20-40 years, patients in older age groups had a lower and higher risk of developing Gyn cancers (for hyperthyroid, 40-65 years: adjusted hazard ratio (aHR) = 0.82; > 65 years: aHR = 0.94; for hypothyroid, adjusted hazard ratio (aHR) = 1.26; > 65 years: aHR = 1.38). Compared with the non-hypothyroid women and non-hyperthyroid women beyond 6 years of follow-up, hypothyroid and hyperthyroid women showed decreased risk of Gyn cancers. Medication treatment for hyperthyroid and hypothyroid disease did not showed significant association in subgroup analyses (aHR = 0.99 and 0.80, respectively). Our results show that women with hyperthyroidism have a significantly reduced risk of gynecological cancers, whereas women with hypothyroidism have a slightly increased risk of gynecological cancers suggesting an association between thyroid function level and risk of gynecological cancers.

Refining personalized diagnosis, treatment and exploitation of hypothyroidism related to solid nonthyroid cancer

Hypothyroidism in the setting of cancer is a puzzling entity due to the dual role of the thyroid hormones (TH) in cancer – promoting versus inhibitory – and the complexity of the hypothyroidism itself. The present review provides a comprehensive overview of the personalized approach to hypothyroidism in patients with solid nonthyroid cancer, focusing on current challenges, unmet needs and future perspectives. Major electronic databases were searched from January 2011 until March 2022. The milestones of the refinement of such a personalized approach are prompt diagnosis, proper TH replacement and development of interventions and/or pharmaceutical agents to exploit hypothyroidism or, on the contrary, TH replacement as an anticancer strategy. Further elucidation of the dual role of TH in cancer – especially of the interference of TH signaling with the hallmarks of cancer – is anticipated to inform decision-making and optimize patient selection.

Thyroid hormone signaling in the intestinal stem cells and their niche

Several studies emphasized the function of the thyroid hormones in stem cell biology. These hormones act through the nuclear hormone receptor TRs, which are T3-modulated transcription factors. Pioneer work on T3-dependent amphibian metamorphosis showed that the crosstalk between the epithelium and the underlying mesenchyme is absolutely required for intestinal maturation and stem cell emergence. With the recent advances of powerful animal models and 3D-organoid cultures, similar findings have now begun to be described in mammals, where the action of T3 and TRα1 control physiological and cancer-related stem cell biology. In this review, we have summarized recent findings on the multiple functions of T3 and TRα1 in intestinal epithelium stem cells, cancer stem cells and their niche. In particular, we have highlighted the regulation of metabolic functions directly linked to normal and/or cancer stem cell biology. These findings help explain other possible mechanisms by which TRα1 controls stem cell biology, beyond the more classical Wnt and Notch signaling pathways.

The continuum of care of anticancer treatment-induced hypothyroidism in patients with solid non thyroid tumors: time for an intimate collaboration between oncologists and endocrinologists

INTRODUCTION

Hypothyroidism is a common adverse event of various anticancer treatment modalities, constituting a notable paradigm of the integration of the endocrine perspective into precision oncology.

AREAS COVERED

The present narrative review provides a comprehensive and updated overview of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors. A study search was conducted on the following electronic databases: PubMed, Google Scholar, Scopus.com, ClinicalTrials.gov, and European Union Clinical Trials Register from 2011 until August 2021.

EXPERT OPINION

In patients with solid non-thyroid tumors, hypothyroidism is a common adverse event of radiotherapy, high dose interleukin 2 (HD IL-2), interferon alpha (IFN-α), bexarotene, immune checkpoint inhibitors (ICPi), and tyrosine kinase inhibitors (TKIs), while chemotherapy may induce hypothyroidism more often than initially considered. The path forward for the management of anticancer treatment-induced hypothyroidism in patients with solid non-thyroid tumors is an integrated approach grounded on 5 pillars: prevention, vigilance, diagnosis, treatment and monitoring. Current challenges concerning anticancer treatment-induced hypothyroidism await counteraction, namely awareness of the growing list of related anticancer treatments, identification of predictive factors, counteraction of diagnostic pitfalls, tuning of thyroid hormone replacement, and elucidation of its prognostic significance. Close collaboration of oncologists with endocrinologists will provide optimal patient care.

The Clinical Relevance of Hypothyroidism in Patients with Solid Non-Thyroid Cancer: A Tantalizing Conundrum

Hypothyroidism in patients with solid non-thyroid cancer is a tantalizing entity, integrating an intriguing thyroid hormones (THs)-cancer association with the complexity of hypothyroidism itself. The present narrative review provides a comprehensive overview of the clinical relevance of hypothyroidism in solid non-thyroid cancer. Hypothyroidism in patients with solid non-thyroid cancer is reminiscent of hypothyroidism in the general population, yet also poses distinct challenges due to the dual role of THs in cancer: promoting versus inhibitory. Close collaboration between oncologists and endocrinologists will enable the prompt and personalized diagnosis and treatment of hypothyroidism in patients with solid non-thyroid cancer. Clinical data indicate that hypothyroidism is a predictor of a decreased or increased risk of solid non-thyroid cancer and is a prognostic factor of favorable or unfavorable prognosis in solid non-thyroid cancer. However, the impact of hypothyroidism with respect to the risk and/or prognosis of solid non-thyroid cancer is not a consistent finding. To harness hypothyroidism, or THs replacement, as a personalized anticancer strategy for solid non-thyroid cancer, four prerequisites need to be fulfilled, namely: (i) deciphering the dual THs actions in cancer; (ii) identifying interventions in THs status and developing agents that block tumor-promoting THs actions and/or mimic anticancer THs actions; (iii) appropriate patient selection; and (iv) counteracting current methodological limitations.

Comprehensive Analysis of Expression and Prognostic Value of Selenoprotein Genes in Thyroid Cancer

Background: Low selenium levels are associated with an increased incidence and advanced stage of thyroid cancers (THCAs). In response to changes in selenium levels, a hierarchy of selenoprotein biosynthesis allows tissue-specific fine-tuning of the 25 selenoproteins. To determine the role of individual selenoproteins on thyroid carcinogenesis, we carried out a multiomic data mining study. Methods: The expression levels of individual selenoproteins and their correlations with prognosis in THCAs were analyzed using Oncomine, GEPIA, and Kaplan-Meier plotter platforms. Co-expression analyses using the cBioportal database were carried out to identify genes that are correlated with selenoproteins. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichments were performed for genes correlated with selenoproteins that were identified as clinically significant. Results and Discussion: DIO1, GPX3, SELENOO, SELENOP, SELENOS, and SELENOV were significantly downregulated in THCAs and were associated with poor prognoses. Biological processes including negative regulation of growth and angiogenesis were enriched in DIO1-positively and DIO1-negatively correlated genes, respectively. Many biological processes including negative regulation of growth and MAPK cascade were enriched in GPX3-positively and GPX3-negatively correlated genes, respectively. The antitumor effects of SELENOS might be attributed to their protection against endoplasmic reticulum (ER) stress. SELENOO was revealed to be correlated with ER stress, mitochondrial translation, and telomere maintenance. Biological processes of SELENOV-correlated genes were enriched in redox processes and ER calcium ion homeostasis. Moreover, cell adhesion and angiogenesis were also shown to be negatively regulated by SELENOV, providing an antimetastatic effect similar as DIO1. Conclusion: This study explored the distinct roles of the 25 selenoproteins in THCA pathogenesis, providing potential oncosuppressing effects of 6 selenoproteins.

The Intriguing Thyroid Hormones-Lung Cancer Association as Exemplification of the Thyroid Hormones-Cancer Association: Three Decades of Evolving Research

Exemplifying the long-pursued thyroid hormones (TH)-cancer association, the TH-lung cancer association is a compelling, yet elusive, issue. The present narrative review provides background knowledge on the molecular aspects of TH actions, with focus on the contribution of TH to hallmarks of cancer. Then, it provides a comprehensive overview of data pertinent to the TH-lung cancer association garnered over the last three decades and identifies obstacles that need to be overcome to enable harnessing this association in the clinical setting. TH contribute to all hallmarks of cancer through integration of diverse actions, currently classified according to molecular background. Despite the increasingly recognized implication of TH in lung cancer, three pending queries need to be resolved to empower a tailored approach: (1) How to stratify patients with TH-sensitive lung tumors? (2) How is determined whether TH promote or inhibit lung cancer progression? (3) How to mimic the antitumor and/or abrogate the tumor-promoting TH actions in lung cancer? To address these queries, research should prioritize the elucidation of the crosstalk between TH signaling and oncogenic signaling implicated in lung cancer initiation and progression, and the development of efficient, safe, and feasible strategies leveraging this crosstalk in therapeutics.

Targeting the DIO3 enzyme using first-in-class inhibitors effectively suppresses tumor growth: a new paradigm in ovarian cancer treatment

The enzyme iodothyronine deiodinase type 3 (DIO3) contributes to cancer proliferation by inactivating the tumor-suppressive actions of thyroid hormone (T3). We recently established DIO3 involvement in the progression of high-grade serous ovarian cancer (HGSOC). Here we provide a link between high DIO3 expression and lower survival in patients, similar to common disease markers such as Ki67, PAX8, CA-125, and CCNE1. These observations suggest that DIO3 is a logical target for inhibition. Using a DIO3 mimic, we developed original DIO3 inhibitors that contain a core of dibromomaleic anhydride (DBRMD) as scaffold. Two compounds, PBENZ-DBRMD and ITYR-DBRMD, demonstrated attenuated cell counts, induction in apoptosis, and a reduction in cell proliferation in DIO3-positive HGSOC cells (OVCAR3 and KURAMOCHI), but not in DIO3-negative normal ovary cells (CHOK1) and OVCAR3 depleted for DIO3 or its substrate, T3. Potent tumor inhibition with a high safety profile was further established in HGSOC xenograft model, with no effect in DIO3-depleted tumors. The antitumor effects are mediated by downregulation in an array of pro-cancerous proteins, the majority of which known to be repressed by T3. To conclude, using small molecules that specifically target the DIO3 enzyme we present a new treatment paradigm for ovarian cancer and potentially other DIO3-dependent malignancies.

Does Clinical and Biochemical Thyroid Dysfunction Impact on Endometrial Cancer Survival Outcomes? A Prospective Database Study

Endometrial cancer is the commonest gynaecological malignancy in developed countries, and women presenting with high risk or advanced disease have poor outcomes. Thyroid hormones play a key role in cellular metabolism and can influence cancer growth and invasion. Our aim was to evaluate the association between clinical and biochemical thyroid dysfunction and endometrial cancer survival outcomes. This was a prospective cohort study of women treated for endometrial cancer at a specialist centre. Clinical diagnosis of hypothyroidism was based on clinical and biochemical assessment, verified by general practitioner (GP) records. Pre-treatment serum samples were tested for thyrotropin (TSH), thyroid hormones (free T4 and total T3), and thyroid peroxidase antibodies. Kaplan-Meier survival estimates and log-rank tests were used to compare survival between groups, while Cox regression was used for multivariable analysis, adjusting for known confounders and effect modifications. In total, 333 women with median age and body mass index (BMI) of 66 years (interquartile range (IQR) 56, 73) and 33 kg/m2 (IQR 27, 41) respectively were included. A total of 51 (15.3%) women had a diagnosis of hypothyroidism, 39 (11.9%) had biochemical evidence of overt or subclinical hypothyroidism. Median follow-up was 35 months (IQR 21, 45) with 38 (11.7%) relapses and 50 (15.0%) deaths. Women with a diagnosis of hypothyroidism had improved overall survival (adjusted HR = 0.22, 95%CI 0.06-0.74, p = 0.02), cancer-specific survival (adjusted HR = 0.21, 95%CI 0.05-0.98, p = 0.04) and fewer recurrences (adjusted HR = 0.17, 95%CI 0.04-0.77, p = 0.02) than those who did not. Confirmatory studies should explore underlying mechanisms and the potential for therapeutic exploitation.

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Thyroid dysfunction and breast cancer risk among women in the UK Biobank cohort

This study aimed to evaluate the association between thyroid dysfunction and breast cancer risk. We included 239,436 females of the UK Biobank cohort. Information on thyroid dysfunction, personal and family medical history, medications, reproductive factors, lifestyle, and socioeconomic characteristics was retrieved from baseline self-reported data and hospital inpatient databases. Breast cancer diagnoses were identified through population-based registries. We computed Cox models to estimate hazard ratios (HRs) of breast cancer incidence for thyroid dysfunction diagnosis and treatments, and examined potential confounding and effect modification by comorbidities and breast cancer risk factors. In our study, 3,227 (1.3%) and 20,762 (8.7%) women had hyper- and hypothyroidism prior to the baseline. During a median follow-up of 7.1 years, 5,326 (2.2%) women developed breast cancer. Compared to no thyroid dysfunction, there was no association between hypothyroidism and breast cancer risk overall (HR = 0.93, 95% confidence interval (CI): 0.84-1.02, 442 cases), but we found a decreased risk more than 10 years after hypothyroidism diagnosis (HR=0.85, 95%CI 0.74-0.97, 226 cases). There was no association with hyperthyroidism overall (HR=1.08, 95%CI 0.86-1.35, 79 cases) but breast cancer risk was elevated among women with treated hyperthyroidism (HR=1.38, 95%CI: 1.03-1.86, 44 cases) or aged 60 years or more at hyperthyroidism diagnosis (HR=1.74, 95%CI: 1.01-3.00, 113 cases), and 5-10 years after hyperthyroidism diagnosis (HR=1.58, 95%CI: 1.06-2.33, 25 cases). In conclusion, breast cancer risk was reduced long after hypothyroidism diagnosis, but increased among women with treated hyperthyroidism. Future studies are needed to determine whether the higher breast cancer risk observed among treated hyperthyroidism could be explained by hyperthyroidism severity, type of treatment or aetiology.

Involvement of Thyroid Hormones in Brain Development and Cancer

The development and maturation of the mammalian brain are regulated by thyroid hormones (THs). Both hypothyroidism and hyperthyroidism cause serious anomalies in the organization and function of the nervous system. Most importantly, brain development is sensitive to TH supply well before the onset of the fetal thyroid function, and thus depends on the trans-placental transfer of maternal THs during pregnancy. Although the mechanism of action of THs mainly involves direct regulation of gene expression (genomic effects), mediated by nuclear receptors (THRs), it is now clear that THs can elicit cell responses also by binding to plasma membrane sites (non-genomic effects). Genomic and non-genomic effects of THs cooperate in modeling chromatin organization and function, thus controlling proliferation, maturation, and metabolism of the nervous system. However, the complex interplay of THs with their targets has also been suggested to impact cancer proliferation as well as metastatic processes. Herein, after discussing the general mechanisms of action of THs and their physiological effects on the nervous system, we will summarize a collection of data showing that thyroid hormone levels might influence cancer proliferation and invasion.

Incident atrial fibrillation in patients with differentiated thyroid cancer: a meta-analysis

Differentiated thyroid cancer (DTC) represents the most common form of thyroid neoplasms and is becoming increasingly prevalent. Evidence suggests a possible relationship between DTC diagnosis and subsequent atrial fibrillation (AF). If confirmed, this may present an alarming health risk (AF) in an otherwise condition with a relatively good prognosis (DTC). The aim of this systematic review and meta-analysis is to provide for the first time a pooled estimate of AF incidence in DTC patients in comparison to healthy controls. A detailed search in electronic databases, clinical trial registries and grey literature was performed to identify studies reporting the incidence of AF in DTC patients. Newcastle-Ottawa quality assessment scale was used to assess study quality. We used a random effects (RE) generalized linear mixed model (GLMM) in pooling of individual studies and also calculated a prediction interval for the estimate of a new study. Six observational studies met the eligibility criteria, which included totally 187,754 patients with DTC and 199,770 healthy controls. The median follow-up period was 4.3 to 18.8 years; the incidence rate of AF was 4.86 (95% CI, 3.29 to 7.17, I2 = 96%) cases per 1000 person-years, while the incidence rate ratio was 1.54 (95% CI, 1.44 to 1.65, I2 = 0%, 95% PI, 1.33 to 1.78).This is the first meta-analysis to confirm that patients with DTC are at a high risk for developing AF, which may be attributed to a state of iatrogenic hyperthyroidism due to long-term thyrotropin suppression therapy.

Physiological Role and Use of Thyroid Hormone Metabolites - Potential Utility in COVID-19 Patients

Thyroxine and triiodothyronine (T3) are classical thyroid hormones and with relatively well-understood actions. In contrast, the physiological role of thyroid hormone metabolites, also circulating in the blood, is less well characterized. These molecules, namely, reverse triiodothyronine, 3,5-diiodothyronine, 3-iodothyronamine, tetraiodoacetic acid and triiodoacetic acid, mediate both agonistic (thyromimetic) and antagonistic actions additional to the effects of the classical thyroid hormones. Here, we provide an overview of the main factors influencing thyroid hormone action, and then go on to describe the main effects of the metabolites and their potential use in medicine. One section addresses thyroid hormone levels in corona virus disease 19 (COVID-19). It appears that i) the more potently-acting molecules T3 and triiodoacetic acid have shorter half-lives than the less potent antagonists 3-iodothyronamine and tetraiodoacetic acid; ii) reverse T3 and 3,5-diiodothyronine may serve as indicators for metabolic dysregulation and disease, and iii) Nanotetrac may be a promising candidate for treating cancer, and resmetirom and VK2809 for steatohepatitis. Further, the use of L-T3 in the treatment of severely ill COVID-19 patients is critically discussed.

Chemopreventive and Anticancer Property of Selenoproteins in Obese Breast Cancer

Obesity is a significant risk factor for various cancers including breast cancer resulting in an increased risk of recurrence as well as morbidity and mortality. Extensive studies on various pathways have been successful in establishing a biological relationship between obesity and breast cancer. The molecular classification of breast cancer includes five groups each having different responses to treatment. Increased levels of inflammatory cytokines seen in obese conditions drive the pro-proliferative pathways, such as the influx of macrophages, angiogenesis, and antiapoptotic pathways. Increased peripheral aromatization of androgens by aromatase increases the circulating estrogen levels which are also responsible for the association of obesity with breast cancer. Also, increased oxidative stress due to chronic low-grade inflammation in obese women plays an important role in carcinogenesis. Despite the availability of safe and effective treatment options for breast cancer, obese women are at increased risk of adverse outcomes including treatment-related toxicities. In the recent decade, selenium compounds have gained substantial interest as chemopreventive and anticancer agents. The chemical derivatives of selenium include inorganic and organic compounds that exhibit pro-oxidant properties and alter cellular redox homeostasis. They target more than one metabolic pathway by thiol modifications, induction of reactive oxygen species, and chromatin modifications to exert their chemopreventive and anticancer activities. The primary functional effectors of selenium that play a significant role in human homeostasis are selenoproteins like glutathione peroxidase, thioredoxin reductase, iodothyronine deiodinases, and selenoprotein P. Selenoproteins play a significant role in adipose tissue physiology by modulating preadipocyte proliferation and adipogenic differentiation. They correlate negatively with body mass index resulting in increased oxidative stress that may lead to carcinogenesis in obese individuals. Methylseleninic acid effectively suppresses aromatase activation thus reducing the estrogen levels and acting as a breast cancer chemopreventive agent. Adipose-derived inflammatory mediators influence the selenium metabolites and affect the proliferation and metastatic properties of cancer cells. Recently selenium nanoparticles have shown potent anticancer activity which may lead to a major breakthrough in the management of cancers caused due to multiple pathways. In this review, we discuss the possible role of selenoproteins as chemopreventive and an anticancer agent in obese breast cancer.

Exogenous Thyroid Hormone Is Associated with Shortened Survival and Upregulation of High-Risk Gene Expression Profiles in Steroid Receptor-Positive Breast Cancers

PURPOSE

Thyroid disease is a frequent comorbidity in women with breast cancer, and many require thyroid hormone replacement therapy (THRT). We postulated that THRT has a deleterious clinical effect mechanistically through hormonal interactions, nuclear receptor cross-talk, and upregulation of high-risk breast cancer genes.

EXPERIMENTAL DESIGN

Observational studies of patients with lymph node-negative (LN-) breast cancer (n = 820 and n = 160) were performed to test interactions between THRT and clinical, histologic, outcome, and treatment variables. Differences between the two cohorts include but are not limited to patient numbers, decades of treatment, duration of follow-up/treatment, tumor sizes, incidence, and type and dose/regimen of antihormonal and/or chemotherapeutic agents. In vivo and vitro models, in silico databases, and molecular methods were used to study interactions and define mechanisms underlying THRT effects.

RESULTS

THRT significantly and independently reduced disease-free and breast cancer-specific overall survival of only the steroid receptor (SR)-positive (as compared with SR-negative) node-negative patients in both long-term observational studies. Patients with SR+ LN- breast cancer who received THRT and tamoxifen experienced the shortest survival of all treatment groups. A less potent interaction between THRT and aromatase inhibitors was noted in the second patient cohort. Using in vivo and in vitro models, TH administration enhanced estrogen and TH-associated gene expression and proliferation, nuclear colocalization of estrogen receptor and thyroid hormone receptor, and activation of genes used clinically to predict tumor aggression in SR+ breast cancer, including the IGF-IR, WNT, and TGFβ pathways.

CONCLUSIONS

We show clinically significant adverse interactions between THRT, estrogenic, and oncogenic signaling in patients with SR+ LN- breast cancer.

DIO3, the thyroid hormone inactivating enzyme, promotes tumorigenesis and metabolic reprogramming in high grade serous ovarian cancer

High grade serous ovarian cancer (HGSOC) is the most lethal gynecologic malignancy with a need for better understanding the disease pathogenesis. The biologically active thyroid hormone, T3, is considered a tumor suppressor by promoting cell differentiation and mitochondrial respiration. Tumors evolved a strategy to avoid these anticancer actions by expressing the T3 catabolizing enzyme, Deiodinase type 3 (DIO3). This stimulates cancer proliferation and aerobic glycolysis (Warburg effect). We identified DIO3 expression in HGSOC cell lines, tumor tissues from mice and human patients, fallopian tube (FT) premalignant lesion and secretory cells of normal FT, considered the disease site-of-origin. Stable DIO3 knockdown (DIO3-KD) in HGSOC cells led to increased T3 bioavailability and demonstrated induced apoptosis and attenuated proliferation, migration, colony formation, oncogenic signaling, Warburg effect and tumor growth in mice. Proteomics analysis further indicated alterations in an array of cancer-relevant proteins, the majority of which are involved in tumor suppression and metabolism. Collectively this study establishes the functional role of DIO3 in facilitating tumorigenesis and metabolic reprogramming, and proposes this enzyme as a promising target for inhibition in HGSOC.

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

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

Decreased expression of the thyroid hormone-inactivating enzyme type 3 deiodinase is associated with lower survival rates in breast cancer

Thyroid hormones (THs) are critical regulators of cellular processes, while changes in their levels impact all the hallmarks of cancer. Disturbed expression of type 3 deiodinase (DIO3), the main TH-inactivating enzyme, occurs in several human neoplasms and has been associated with adverse outcomes. Here, we investigated the patterns of DIO3 expression and its prognostic significance in breast cancer. DIO3 expression was evaluated by immunohistochemistry in a primary cohort of patients with breast cancer and validated in a second cohort using RNA sequencing data from the TCGA database. DNA methylation data were obtained from the same database. DIO3 expression was present in normal and tumoral breast tissue. Low levels of DIO3 expression were associated with increased mortality in the primary cohort. Accordingly, low DIO3 mRNA levels were associated with an increased risk of death in a multivariate model in the validation cohort. DNA methylation analysis revealed that the DIO3 gene promoter is hypermethylated in tumors when compared to normal tissue. In conclusion, DIO3 is expressed in normal and tumoral breast tissue, while decreased expression relates to poor overall survival in breast cancer patients. Finally, loss of DIO3 expression is associated with hypermethylation of the gene promoter and might have therapeutic implications.

An unusual finding of giant fat-rich retroperitoneal masses in a patient with Graves' disease

We report the case of a 48-year-old man who was unexpectedly found by abdominal ultrasonography to have large retroperitoneal masses accompanied by Graves' disease. Computed tomography and magnetic resonance imaging further demonstrated giant fat-rich soft masses arising within both renal sinuses. Histopathological examination of the mass was performed twice at 5-year intervals, with both examinations indicating fatty tissue cells with chronic fibrous panniculitis. Intravenous pulse therapy and successive oral glucocorticoid therapy were ineffective against Graves' ophthalmopathy or mass lesion. An antithyroid hormone regimen was followed by subtotal thyroid resection, leading to improvements in hyperthyroidism. Mass growth then attenuated slowly as the thyroid hormones returned to normal levels. The long-term follow-up of this patient should carefully monitor the appearance of warning signs such as mass effects.

Stromal iodothyronine deiodinase 2 (DIO2) promotes the growth of intestinal tumors in ApcΔ716 mutant mice

Iodothyronine deiodinase 2 (DIO2) converts the prohormone thyroxine (T4) to bioactive T3 in peripheral tissues and thereby regulates local thyroid hormone (TH) levels. Although epidemiologic studies suggest the contribution of TH to the progression of colorectal cancer (CRC), the role of DIO2 in CRC remains elusive. Here we show that Dio2 is highly expressed in intestinal polyps of ApcΔ716 mice, a mouse model of familial adenomatous polyposis and early stage sporadic CRC. Laser capture microdissection and in situ hybridization analysis show almost exclusive expression of Dio2 in the stroma of ApcΔ716 polyps in the proximity of the COX-2-positive areas. Treatment with iopanoic acid, a deiodinase inhibitor, or chemical thyroidectomy suppresses tumor formation in ApcΔ716 mice, accompanied by reduced tumor cell proliferation and angiogenesis. Dio2 expression in ApcΔ716 polyps is strongly suppressed by treatment with the COX-2 inhibitor meloxicam. Analysis of The Cancer Genome Atlas data shows upregulation of DIO2 in CRC clinical samples and a close association of its expression pattern with the stromal component, consistently with almost exclusive expression of DIO2 in the stroma of human CRC as revealed by in situ hybridization. These results indicate essential roles of stromal DIO2 and thyroid hormone signaling in promoting the growth of intestinal tumors.

Tetrac as an anti-angiogenic agent in cancer

The thyroid hormones T3 and T4 have emerged as pro-angiogenic hormones with important implications for cancer management. Endogenous circulating hormone levels may help stimulate cancer progression and limit the effectiveness of anticancer therapy, though clinical data remain inconclusive. The capacity of thyroid hormones to modulate angiogenesis is mediated through non-canonical mechanisms initiated at the cell surface receptor integrin αvβ3. This integrin is predominantly expressed on tumour cells, proliferating endothelial cells and tumour stroma-associated cells, emphasising its potential relevance in angiogenesis and tumour biology. Thyroid hormone/integrin αvβ3 signalling results in the activation of intracellular pathways that are commonly associated with angiogenesis and are mediated through classical pro-angiogenic molecules such as vascular endothelial growth factor. The naturally occurring T4 analogue tetrac blocks the pro-angiogenic actions of thyroid hormones at the integrin receptor, in addition to agonist-independent anti-angiogenic effects. Tetrac reduces endothelial cell proliferation, migration and tube formation through a reduction in the transcription of vascular growth factors/growth factor receptors, hypoxia-inducible factor-1α, pro-angiogenic cytokines and a number of other pro-angiogenic genes, while at the same time stimulating the expression of endogenous angiogenesis inhibitors. It further modulates vascular growth factor activity by disrupting the crosstalk between integrin αvβ3 and adjacent growth factor receptors. Moreover, tetrac disrupts thyroid hormone-stimulated tumour recruitment, differentiation and the pro-angiogenic signalling of tumour stroma-associated mesenchymal stem cells. Tetrac affects tumour-associated angiogenesis via multiple mechanisms and interferes with other cancer cell survival pathways. In conjunction with its low toxicity and high tissue selectivity, tetrac is a promising candidate for clinical application.

Comparison of Six Automated Immunoassays With Isotope-Diluted Liquid Chromatography-Tandem Mass Spectrometry for Total Thyroxine Measurement

Background

Accurate serum total thyroxine (TT4) measurement is important for thyroid disorder diagnosis and management. We compared the performance of six automated immunoassays with that of isotope-diluted liquid chromatography-tandem mass spectrometry (ID-LC-MS/MS) as the reference method. We also evaluated the correlation of thyroid stimulating hormone (TSH) with TT4 measured by ID-LC-MS/MS and immunoassays.

Methods

Serum was collected from 156 patients between October 2015 and January 2016. TT4 was measured by immunoassays from Abbott (Architect), Siemens (ADVIA Centaur XP), Roche (E601), Beckman-Coulter (Dxi800), Autobio (Autolumo A2000), and Mindray (CL-1000i), and by ID-LC-MS/MS. Results were analyzed using Passing-Bablok regression and Bland-Altman plots. Minimum requirements based on biological variation were as follows: a mean bias of ≤4.5% and total imprecision (CV) of ≤3.7%.

Results

All immunoassays showed a correlation >0.945 with ID-LC-MS/MS; however, the slope of the Passing-Bablok regression line varied from 0.886 (Mindray) to 1.23 (Siemens) and the intercept from −12.8 (Siemens) to 4.61 (Mindray). Only Autobio, Beckman-Coulter, and Roche included the value of one in the 95% confidence interval for slope. The mean bias ranged from −10.8% (Abbott) to 9.0% (Siemens), with the lowest value noted for Roche (3.5%) and the highest for Abbott (−10.8%). Only Abbott and Roche showed within-run and total CV ≤3.7%.

Conclusions

Though all immunoassays correlated strongly with ID-LC-MS/MS, most did not meet the minimum clinical requirement. Laboratories and immunoassay manufacturers must be aware of these limitations.

Non-genomic Actions of Thyroid Hormones Regulate the Growth and Angiogenesis of T Cell Lymphomas

T-cell lymphomas (TCL) are a heterogeneous group of aggressive clinical lymphoproliferative disorders with considerable clinical, morphological, immunophenotypic, and genetic variation, including ~10-15% of all lymphoid neoplasms. Several evidences indicate an important role of the non-neoplastic microenvironment in promoting both tumor growth and dissemination in T cell malignancies. Thus, dysregulation of integrin expression and activity is associated with TCL survival and proliferation. We found that thyroid hormones acting via the integrin αvβ3 receptor are crucial factors in tumor microenvironment (TME) affecting the pathophysiology of TCL cells. Specifically, TH-activated αvβ3 integrin signaling promoted TCL proliferation and induced and an angiogenic program via the up-regulation of the vascular endothelial growth factor (VEGF). This was observed both on different TCL cell lines representing the different subtypes of human hematological malignancy, and in preclinical models of TCL tumors xenotransplanted in immunodeficient mice as well. Moreover, development of solid tumors by inoculation of murine TCLs in syngeneic hyperthyroid mice, showed increased tumor growth along with increased expression of cell cycle regulators. The genomic or pharmacological inhibition of integrin αvβ3 decreased VEGF production, induced TCL cell death and decreased in vivo tumor growth and angiogenesis. Here, we review the non-genomic actions of THs on TCL regulation and their contribution to TCL development and evolution. These actions not only provide novel new insights on the endocrine modulation of TCL, but also provide a potential molecular target for its treatment.

The Role of Thyroid Hormones in Hepatocyte Proliferation and Liver Cancer

Thyroid hormones T3 and T4 (thyroxine) control a wide variety of effects related to development, differentiation, growth and metabolism, through their interaction with nuclear receptors. But thyroid hormones also produce non-genomic effects that typically start at the plasma membrane and are mediated mainly by integrin αvβ3, although other receptors such as TRα and TRβ are also able to elicit non-genomic responses. In the liver, the effects of thyroid hormones appear to be particularly important. The liver is able to regenerate, but it is subject to pathologies that may lead to cancer, such as fibrosis, cirrhosis, and non-alcoholic fatty liver disease. In addition, cancer cells undergo a reprogramming of their metabolism, resulting in drastic changes such as aerobic glycolysis instead of oxidative phosphorylation. As a consequence, the pyruvate kinase isoform M2, the rate-limiting enzyme of glycolysis, is dysregulated, and this is considered an important factor in tumorigenesis. Redox equilibrium is also important, in fact cancer cells give rise to the production of more reactive oxygen species (ROS) than normal cells. This increase may favor the survival and propagation of cancer cells. We evaluate the possible mechanisms involving the plasma membrane receptor integrin αvβ3 that may lead to cancer progression. Studying diseases that affect the liver and their experimental models may help to unravel the cellular pathways mediated by integrin αvβ3 that can lead to liver cancer. Inhibitors of integrin αvβ3 might represent a future therapeutic tool against liver cancer. We also include information on the possible role of exosomes in liver cancer, as well as on recent strategies such as organoids and spheroids, which may provide a new tool for research, drug discovery, and personalized medicine.

Thyroid Hormones and Cancer: A Comprehensive Review of Preclinical and Clinical Studies

Thyroid hormones take major part in normal growth, development and metabolism. Over a century of research has supported a relationship between thyroid hormones and the pathophysiology of various cancer types. In vitro studies as well as research in animal models demonstrated an effect of the thyroid hormones T3 and T4 on cancer proliferation, apoptosis, invasiveness and angiogenesis. Thyroid hormones mediate their effects on the cancer cell through several non-genomic pathways including activation of the plasma membrane receptor integrin αvβ3. Furthermore, cancer development and progression are affected by dysregulation of local bioavailability of thyroid hormones. Case-control and population-based studies provide conflicting results regarding the association between thyroid hormones and cancer. However, a large body of evidence suggests that subclinical and clinical hyperthyroidism increase the risk of several solid malignancies while hypothyroidism may reduce aggressiveness or delay the onset of cancer. Additional support is provided from studies in which dysregulation of the thyroid hormone axis secondary to cancer treatment or thyroid hormone supplementation was shown to affect cancer outcomes. Recent preclinical and clinical studies in various cancer types have further shown promising outcomes following chemical reduction of thyroid hormones or inhibition or their binding to the integrin receptor. This review provides a comprehensive overview of the preclinical and clinical research conducted so far.

Current concepts and challenges to unravel the role of iodothyronine deiodinases in human neoplasias

Thyroid hormones (THs) are essential for the regulation of several metabolic processes and the energy consumption of the organism. Their action is exerted primarily through interaction with nuclear receptors controlling the transcription of thyroid hormone-responsive genes. Proper regulation of TH levels in different tissues is extremely important for the equilibrium between normal cellular proliferation and differentiation. The iodothyronine deiodinases types 1, 2 and 3 are key enzymes that perform activation and inactivation of THs, thus controlling TH homeostasis in a cell-specific manner. As THs seem to exert their effects in all hallmarks of the neoplastic process, dysregulation of deiodinases in the tumoral context can be critical to the neoplastic development. Here, we aim at reviewing the deiodinases expression in different neoplasias and exploit the mechanisms by which they play an essential role in human carcinogenesis. TH modulation by deiodinases and other classical pathways may represent important targets with the potential to oppose the neoplastic process.

Increased expression of the thyroid hormone nuclear receptor TRα1 characterizes intestinal tumors with high Wnt activity

Our previous work demonstrated a key function of the thyroid hormone nuclear receptor TRα1, a T3-modulated transcription factor, in controlling intestinal development and homeostasis via the Wnt and Notch pathways. Importantly, increased expression of TRα1 in the intestinal epithelium in a mutated Apc genetic background (vil-TRα1/Apc^+/1638N mice) accelerated tumorigenesis and contributed to a more aggressive tumor phenotype compared to that of the Apc mutants alone. Therefore, the aim of this study was to determine the relevance of this synergistic effect in human colorectal cancers and to gain insights into the mechanisms involved. We analyzed cohorts of patients by in silico and experimental approaches and observed increased TRα1 expression and a significant correlation between TRα1 levels and Wnt activity. TRα1 loss-of-function and gain-of-function in Caco2 cell lines not only confirmed that TRα1 levels control Wnt activity but also demonstrated the role of TRα1 in regulating cell proliferation and migration. Finally, upon investigation of the molecular mechanisms responsible for the Wnt-TRα1 association, we described the repression by TRα1 of several Wnt inhibitors, including Frzb, Sox17 and Wif1. In conclusion, our results underline an important functional interplay between the thyroid hormone nuclear receptor TRα1 and the canonical Wnt pathway in intestinal cancer initiation and progression. More importantly, we show for the first time that the expression of TRα1 is induced in human colorectal cancers.

Recent Advances in Thyroid Hormone Regulation: Toward a New Paradigm for Optimal Diagnosis and Treatment

In thyroid health, the pituitary hormone thyroid-stimulating hormone (TSH) raises glandular thyroid hormone production to a physiological level and enhances formation and conversion of T4 to the biologically more active T3. Overstimulation is limited by negative feedback control. In equilibrium defining the euthyroid state, the relationship between TSH and FT4 expresses clusters of genetically determined, interlocked TSH-FT4 pairs, which invalidates their statistical correlation within the euthyroid range. Appropriate reactions to internal or external challenges are defined by unique solutions and homeostatic equilibria. Permissible variations in an individual are much more closely constrained than over a population. Current diagnostic definitions of subclinical thyroid dysfunction are laboratory based, and do not concur with treatment recommendations. An appropriate TSH level is a homeostatic concept that cannot be reduced to a fixed range consideration. The control mode may shift from feedback to tracking where TSH becomes positively, rather than inversely related with FT4. This is obvious in pituitary disease and severe non-thyroid illness, but extends to other prevalent conditions including aging, obesity, and levothyroxine (LT4) treatment. Treatment targets must both be individualized and respect altered equilibria on LT4. To avoid amalgamation bias, clinically meaningful stratification is required in epidemiological studies. In conclusion, pituitary TSH cannot be readily interpreted as a sensitive mirror image of thyroid function because the negative TSH-FT4 correlation is frequently broken, even inverted, by common conditions. The interrelationships between TSH and thyroid hormones and the interlocking elements of the control system are individual, dynamic, and adaptive. This demands a paradigm shift of its diagnostic use.