Serum concentration of thyroid hormones in abnormal and euthyroid ranges and breast cancer risk: A cohort study

Protective effect of higher free thyroxine levels within the reference range on biliary tract cancer risk: a multivariable mendelian randomization and mediation analysis

Background

Hepatobiliary cancer (HBC), including hepatocellular carcinoma (HCC) and biliary tract cancer (BTC), is currently one of the malignant tumors that mainly cause human death. Many HBCs are diagnosed in the late stage, which increases the disease burden, indicating that effective prevention strategies and identification of risk factors are urgent. Many studies have reported the role of thyroid hormones on HBC. Our research aims to assess the causal effects and investigate the mediation effects between thyroid function and HBC.

Methods

Utilizing the Mendelian randomization (MR) approach, the study employs single nucleotide polymorphisms (SNPs) as instrumental variables (IVs) to explore causal links between thyroid function [free thyroxine (FT4), thyroid stimulating hormone (TSH), hyperthyroidism and hypothyroidism] and HBC. Data were sourced from the ThyroidOmic consortium and FinnGen consortium. The analysis included univariable and multivariable MR analysis, followed by mediation analysis.

Results

The study found a significant causal association between high FT4 levels and the reduced risk of BTC, but not HCC. However, TSH, hyperthyroidism and hypothyroidism had no causal associations with the risk of HBC. Notably, we also demonstrated that only higher FT4 levels with the reference range (FT4-RR) could reduce the risk of BTC because this protective effect no longer existed under the conditions of hyperthyroidism or hypothyroidism. Finally, we found that the protective effect of FT4-RR on BTC was mediated partially by decreasing the risk of metabolic syndrome (MetS) and reducing the waist circumference (WC).

Conclusion

The findings suggest that higher FT4-RR may have a protective effect against BTC, which is partially mediated by decreased risk of MetS and a reduction in WC. This study highlights the potential role of FT4 in the pathogenesis of BTC and underscores that MetS and WC may play mediation effects as two mediators in this process.

Prevalence of cancer in patients with hypothyroidism: Analysis using big data tools

OBJECTIVE

To evaluate the frequency of different types of cancer in patients diagnosed with hypothyroidism using big data methodology on the Savana Manager platform.

METHODS

An observational, retrospective study was carried out using electronic medical record (EMR) data from the Hospital Universitario Puerta de Hierro Majadahonda (Madrid). Information from the EMRs was extracted using artificial intelligence techniques and analysed using the Savana Manager v3.0 software. Searches were performed using the term "hypothyroidism" and the terms corresponding to the tumours analysed.

RESULTS

Of a total population of 506,749 patients, 23,570 (4.7%) were diagnosed with hypothyroidism. Patients with this diagnosis had a significantly higher frequency of cancer than that found in non-hypothyroid subjects (OR 2.09, 95% confidence interval [CI] 2.01-2.17). This higher frequency was found both in women (OR 1.99, 95% CI 1.90-2.08) and in men (OR 2.83, 95% CI 2.63-3.05). However, this higher frequency of cancer was not observed in hypothyroid patients older than 60 years (OR 0.97, 95% CI 0.92-1.02). Although the frequency of most of the neoplasms studied individually was higher in the population with hypothyroidism, we observed that hypothyroid patients over 60 years of age had a significant decrease in the frequency of prostate, lung, colorectal, and liver cancer.

CONCLUSION

Data from this hospital cohort suggest that there is a significant association between the diagnosis of hypothyroidism and cancer. However, this association is less evident in hypothyroid patients older than 60 years.

The clinical and genetic features in patients coexisting primary breast and thyroid cancers

Background

We attempted to examine the clinical characteristics in patients with breast cancer (BC) and thyroid cancer (TC); explore the potential mechanisms of tumorigenesis and progression.

Methods

Using the Surveillance, Epidemiology, and End Result Program-9 (SEER-9) database, a retrospective study (1975-2017) was conducted on patients with BC and TC. We identified the common differentially expressed genes involved in BC and TC using the Gene Expression Omnibus database (GEO). Immunohistochemical staining (IHC) was performed to verify the expression of the hit gene in patients with co-occurrence of BC and TC. Using The Cancer Genome Atlas (TCGA) database, the relationship between gene expression and clinicopathological characters was determined. Gene set enrichment analysis (GSEA) was used to identify the pathways enriched in BC and TC.

Results

BC patients had a higher predisposition to develop TC (standardized incidence ratio, SIR: 1.29) and vice-versa (SIR: 1.12). Most of these patients were differentiated thyroid carcinoma (DTC) and hormone receptor (HR) - positive BC. The mRNA expression of COMP (Cartilage oligomeric matrix protein) was significantly overexpressed in BC and TC by analyzing the GEO database. The protein expression of COMP was increased in both BC and TC tissues obtained from the same patients validated by IHC. COMP was correlated with worse OS in BC (stage II-IV) and TC; it was the independent factor for prognosis of BC. GSEA indicated that the estrogen response and epithelial-mesenchymal transition (EMT) pathways were significantly enriched in both TC- and BC- COMP overexpressed groups.

Conclusion

The co-occurrence risk of BC and TC in the same individual is higher than in the general population. Overexpression of COMP could promote oncogenesis and progression in patients with BC and TC through estrogen signaling and EMT pathways.

The effect of thyroid dysfunction on breast cancer risk: an updated meta-analysis

In a previous systematic review and meta-analysis of studies reporting associations between hyper-/hypothyroidism and breast cancer incidence published through 29 January 2019, we identified a higher risk with diagnosed hyperthyroidism compared to euthyroidism, but no association with diagnosed hypothyroidism. This 2-year updated meta-analysis aims to investigate the role of menopause in this association and the dose-response relationship with blood levels of thyroid-stimulating hormone (TSH) and thyroid hormones. After the exclusion of studies with only mortality follow-up, with thyroid dysfunction evaluated as a cancer biomarker or after prior breast cancer diagnosis, we reviewed 25 studies that were published up to 01 December 2021 and identified in MEDLINE, the COCHRANE library, Embase, or Web of Science; of these, 9 were included in the previous meta-analysis. Risk estimates from 22 of the 25 studies were included in the meta-analysis and pooled using random-effects models. Compared to euthyroidism, hyperthyroidism and hypothyroidism diagnoses were associated with higher (pooled risk ratio (RR): 1.12, 95% CI: 1.06-1.18, 3829 exposed cases) and lower risks (RR = 0.93, 95% CI: 0.86-1.00, 5632 exposed cases) of breast cancer, respectively. The increased risk after hyperthyroidism was greater among postmenopausal women (RR = 1.19, 95% CI 1.09-1.30) and the decreased risk after hypothyroidism was more pronounced among premenopausal women (RR = 0.69, 95% CI 0.53-0.89). Among women with no prior history of thyroid disease, every 1 mIU/L increase in TSH level was associated with a 0.8% (95% CI > 0-1.5%) lower risk of breast cancer. In conclusion, this meta-analysis supports an association between thyroid hormone levels and breast cancer risk, which could be modified by menopausal status.

Exposure to Novel Brominated Flame Retardants and Organophosphate Esters and Associations with Thyroid Cancer Risk: A Case-Control Study in Eastern China

Novel brominated flame retardant (NBFR) and organophosphate ester (OPE) exposure may engender adverse effects on human health. However, present epidemiological information regarding the effects of such exposure is limited and controversial. In this case-control study, 481 serum samples were collected from patients with thyroid cancer (n = 242) and healthy controls (n = 239) in Shandong Province, eastern China. The levels of NBFRs and OPEs, thyroid hormones, and serum lipid parameters were measured in all the participants. Pentabromotoluene, 2,3-dibromopropyl 2,4,6 tribromophenyl ether, decabromodiphenylethane (DBDPE), tris (2-chloroethyl) phosphate (TCEP), and triphenyl phosphate (TPP) were widely detected (detection frequency > 60%) in all the participants. A significantly high risk association was found between exposure of NBFRs and OPEs (namely 1,2,3,4,5-pentabromobenzene, DBDPE, tri-n-propyl phosphate, tri[(2R)-1-chloro-2-propyl] phosphate, tris (1,3-dichloro-2-propyl) phosphate, and tris (2-butoxyethyl) phosphate) and thyroid cancer in both males and females. In the females of the control group, TCEP levels exhibited a significantly positive association with thyroid-stimulating hormone and a negative association with triiodothyronine (T3), free triiodothyronine (FT3), and free thyroxine (FT4) levels. Weighted quantile sum regression evaluated the mixed effects of the compounds on thyroid hormones levels and thyroid cancer. As a result, TPP accounted for the majority of the T3, thyroxine, and FT3 amounts. Our results suggest that NBFR and OPE exposure contributes to alterations in thyroid function, thereby increasing thyroid cancer risk.

Links between Breast and Thyroid Cancer: Hormones, Genetic Susceptibility and Medical Interventions

Breast and thyroid glands are two common sites of female malignancies. Since the late 19th century, physicians have found that the cancers in either thyroid or mammary gland might increase the risk of second primary cancers in the other site. From then on, many observational clinical studies have confirmed the hypothesis and more than one theory has been developed to explain the phenomenon. Since the two glands both have secretory functions and are regulated by the hypothalamic-pituitary axis, they may share some common oncogenic molecular pathways. However, other risks factors, including medical interventions and hormones, are also observed to play a role. This article aims to provide a comprehensive review of the associations between the two cancers. The putative mechanisms, such as hormone alteration, autoimmune attack, genetic predisposition and other life-related factors are reviewed and discussed. Medical interventions, such as chemotherapy and radiotherapy, can also increase the risk of second primary cancers. This review will provide novel insights into the research designs, clinical managements and treatments of thyroid and breast cancer patients.

Thyroid hormones act as modulators of inflammation through their nuclear receptors

Reciprocal crosstalk between endocrine and immune systems has been well-documented both in physiological and pathological conditions, although the connection between the immune system and thyroid hormones (THs) remains largely unclear. Inflammation and infection are two important processes modulated by the immune system, which have profound effects on both central and peripheral THs metabolism. Conversely, optimal levels of THs are necessary for the maintenance of immune function and response. Although some effects of THs are mediated by their binding to cell membrane integrin receptors, triggering a non-genomic response, most of the actions of these hormones involve their binding to specific nuclear thyroid receptors (TRs), which generate a genomic response by modulating the activity of a great variety of transcription factors. In this special review on THs role in health and disease, we highlight the relevance of these hormones in the molecular mechanisms linked to inflammation upon their binding to specific nuclear receptors. In particular, we focus on THs effects on different signaling pathways involved in the inflammation associated with various infectious and/or pathological processes, emphasizing those mediated by NF-kB, p38MAPK and JAK/STAT. The findings showed in this review suggest new opportunities to improve current therapeutic strategies for the treatment of inflammation associated with several infections and/or diseases, such as cancer, sepsis or Covid-19 infection.

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.

Thyroid Diseases and Breast Cancer

Epidemiological studies aimed at defining the association of thyroid diseases with extra-thyroidal malignancies (EM) have aroused considerable interest in the possibility of revealing common genetic and environmental factors underlying disease etiology and progression. Over the years, multiple lines of evidence indicated a significant relationship between thyroid carcinomas and other primary EM, especially breast cancer. For the latter, a prominent association was also found with benign thyroid diseases. In particular, a meta-analysis revealed an increased risk of breast cancer in patients with autoimmune thyroiditis, and our recent work demonstrated that the odds ratio (OR) for breast cancer was raised in both thyroid autoantibody-positive and -negative patients. However, the OR was significantly lower for thyroid autoantibody-positive patients compared to the negative ones. This is in agreement with findings showing that the development of thyroid autoimmunity in cancer patients receiving immunotherapy is associated with better outcome and supports clinical evidence that breast cancer patients with thyroid autoimmunity have longer disease-free interval and overall survival. These results seem to suggest that factors other than oncologic treatments may play a role in the initiation and progression of a second primary malignancy. The molecular links between thyroid autoimmunity and breast cancer remain, however, unidentified, and different hypotheses have been proposed. Here, we will review the epidemiological, clinical, and experimental data relating thyroid diseases and breast cancer, as well as the possible hormonal and molecular mechanisms underlying such associations.

Insulin resistance and the development of breast cancer in premenopausal women: the Kangbuk Samsung Health Study

PURPOSE

Research on the role of insulin resistance (IR) in breast cancer risk in premenopausal women is scarce. We aimed to investigate the relationship between IR and the development of breast cancer in premenopausal women.

METHODS

We analyzed the prospective association of IR and incident breast cancer in premenopausal women without breast cancer at baseline using a subsample of the Kangbuk Samsung Health Study.

RESULTS

Among 134,488 Korean premenopausal women, 696 women developed incident breast cancers during a median follow-up of 4.34 years. After adjustment for dense breast and other potential confounders, HR (95% CI) for incident breast cancer comparing HOMA-IR quintiles 2, 3, 4, and 5 to the first quintile was 0.91 (0.71-1.17), 0.89 (0.69-1.15), 0.75 (0.57-0.98), and 0.87 (0.65-1.16), respectively (P for trend = 0.117), while HR (95% CI) comparing insulin quintiles 2, 3, 4, and 5 to the first quintile was 1.02 (0.80-1.30), 0.90 (0.69-1.16), 0.72 (0.54-0.96), and 0.96 (0.72-1.28), respectively (P for trend = 0.151). This pattern did not significantly differ by obesity. These results were attenuated and no longer significant in time-dependent analyses where updated status of insulin and other covariates over time were treated as time-varying covariates.

CONCLUSION

Our findings do not support the positive relationship of IR with the development of breast cancer in premenopausal women, unlike in postmenopausal women. Thus, the role of IR as a risk factor for breast cancer may differ by menopausal status.

Organophosphate and Organohalogen Flame-Retardant Exposure and Thyroid Hormone Disruption in a Cross-Sectional Study of Female Firefighters and Office Workers from San Francisco

Occupational exposures to flame retardants (FRs), a class of suspected endocrine-disrupting compounds, are of health concern for firefighters. We sought to characterize exposure to FR compounds and evaluate their association with thyroid hormone levels, a biomarker of early effect, in female firefighters and office workers in San Francisco. In a cross-sectional study, we measured replacement organophosphate and organohalogen FRs in spot urine samples from firefighters (N = 86) and office workers (N = 84), as well as total thyroxine (T4) and thyroid-stimulating hormone in plasma for 84 firefighters and 81 office workers. Median bis(1,3-dichloro-2-propyl)phosphate (BDCPP) levels were 5 times higher in firefighters than office workers. Among firefighters, a doubling of BDCPP was associated with a 2.88% decrease (95% confidence interval -5.28, -0.42) in T4. We did not observe significant associations between FRs and T4 among office workers. In the full group, intermediate body mass index and a college education were associated with higher FR levels. The inverse association observed between FRs and T4 coupled with the lack of studies on women workers and evidence of adverse health effects from FR exposure─including endocrine disruption and breast cancer risk─warrant further research on occupational exposures and identification of opportunities for exposure reduction.

Correlation Analysis of Breast and Thyroid Nodules: A Cross-Sectional Study

Objective

Based on physical examination, to explore the relationship between breast mass (BM) and thyroid nodule (TN) prevalence, and to further explore other related factors that affect the occurrence of BM and TN.

Methods

From January 1, 2018, to January 1, 2021, 12,538 female subjects received breast and thyroid ultrasound examinations at the same time in the health examination center of the Affiliated Hospital of North Sichuan Medical College. Univariate analysis and multivariate logistic analysis were used to screen the relevant factors affecting TN and BM, and propensity score matching was used to further verify the results of the relationship between breast and thyroid.

Results

A total of 4975 (39.7%) of the included subjects have BM and a total of 6315 (50.4%) have TN,2557 (20.4%) had both BM and TN. The logistic regression results show that patients with TN are more likely to suffer from BM [OR = 1.185, 95% CI (1.099-1.278), p<0.0001]. In addition, age, free T4, HDL, height, BMI, systolic blood pressure, diastolic blood pressure, and albumin are independent factors affecting the occurrence of BM; patients with BM are more likely to have TN [OR = 1.180, 95% CI (1.094-1.272), p<0.0001], and age, free T3, free T4, AST, ALT, albumin, height, and BMI are independent influencing factors on the occurrence of TN. The result of propensity score matching confirmed the relationship between BM and TN.

Conclusion

There is a bidirectional pathogenic relationship between BM and TN, women with BM are at increased risk of TN, and women with TN are more likely to have BM. Thyroid hormone is not only related to the occurrence of TN but also affects the occurrence of BM.

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.

LINC00894 Enhances the Progression of Breast Cancer by Sponging miR-429 to Regulate ZEB1 Expression

PURPOSE

Long non-coding RNAs (lncRNAs) are known to regulate tumorigenesis. Although breast cancer tissues show a high expression of LINC00894, its specific biological role in breast cancer progression is still unknown. In this study, lncRNA microarray was used to analyze the lncRNA expression in breast cancer tissues, and LINC00894 was selected for further analysis.

MATERIALS AND METHODS

Expression of LINC00894 in 45 pairs of breast cancer tissues and normal tissues obtained from patients with breast cancer was assessed by quantitative reverse transcription-PCR, while proliferation and invasion of breast cancer cells were assessed using a Cell Counting Kit-8 (CCK-8), EdU assay, colony formation experiment, and transwell assays. A dual-luciferase reporter gene assay and bioinformatics analysis were employed to detect potential targets of LINC00894. Additionally, RNA Binding Protein Immunoprecipitation (RIP) and Western blot assays were utilized to clarify its interaction and roles in the regulation of breast cancer progression.

RESULTS

High expression of LINC00894 was observed in breast cancer cells, and its overexpression significantly expedited cell proliferation and invasion. Moreover, LINC00894 positively regulated the expression of ZEB1 by competitively binding to miR-429.

CONCLUSION

Taken together, these results suggest that LINC00894 competitively binds to miR-429 to mediate ZEB1 expression; consequently, it is implicated to play a role in the progression of breast cancer.

Is There an Ideal Diet to Protect against Iodine Deficiency?

Iodine deficiency is a global issue and affects around 2 billion people worldwide, with pregnant women as a high-risk group. Iodine-deficiency prevention began in the 20th century and started with global salt iodination programmes, which aimed to improve the iodine intake status globally. Although it resulted in the effective eradication of the endemic goitre, it seems that salt iodination did not resolve all the issues. Currently, it is recommended to limit the consumption of salt, which is the main source of iodine, as a preventive measure of non-communicable diseases, such as hypertension or cancer the prevalence of which is increasing. In spite of the fact that there are other sources of iodine, such as fish, seafood, dairy products, water, and vegetables, the high consumption of processed food with a high content of unionised salt, alternative diets or limited salt intake can still lead to iodine deficiency. Thus, iodine deficiency remains a relevant issue, with new, preventive solutions necessary. However, it appears that there is no diet which would fully cover the iodine requirements, and iodine food supplementation is still required.

Thyroid hormones in diabetes, cancer, and aging

Thyroid function is central in the control of physiological and pathophysiological processes. Studies in animal models and human research have determined that thyroid hormones modulate cellular processes relevant for aging and for the majority of age‐related diseases. While several studies have associated mild reductions on thyroid hormone function with exceptional longevity in animals and humans, alterations in thyroid hormones are serious medical conditions associated with unhealthy aging and premature death. Moreover, both hyperthyroidism and hypothyroidism have been associated with the development of certain types of diabetes and cancers, indicating a great complexity of the molecular mechanisms controlled by thyroid hormones. In this review, we describe the latest findings in thyroid hormone research in the field of aging, diabetes, and cancer, with a special focus on hepatocellular carcinomas. While aging studies indicate that the direct modulation of thyroid hormones is not a viable strategy to promote healthy aging or longevity and the development of thyromimetics is challenging due to inefficacy and potential toxicity, we argue that interventions based on the use of modulators of thyroid hormone function might provide therapeutic benefit in certain types of diabetes and cancers.

Causal associations of thyroid function and dysfunction with overall, breast and thyroid cancer: A two-sample Mendelian randomization study

Whether thyroid dysfunction plays a causal role in the development of cancer remains inconclusive. We conducted a two-sample Mendelian randomization study to investigate the associations between genetic predisposition to thyroid dysfunction and 22 site-specific cancers. Single-nucleotide polymorphisms associated with four traits of thyroid function were selected from a genome-wide association meta-analysis with up to 72,167 European-descent individuals. Summary-level data for breast cancer and 21 other cancers were extracted from the Breast Cancer Association Consortium (122,977 breast cancer cases and 105,974 controls) and UK Biobank (367,643 individuals). For breast cancer, a meta-analysis was performed using data from both sources. Genetically predicted thyroid dysfunction was associated with breast cancer, with similar patterns of associations in the Breast Cancer Association Consortium and UK Biobank. The combined odds ratios of breast cancer were 0.94 (0.91-0.98; p = 0.007) per genetically predicted one standard deviation increase in TSH levels, 0.96 (0.91-1.00; p = 0.053) for genetic predisposition to hypothyroidism, 1.04 (1.01-1.07; p = 0.005) for genetic predisposition to hyperthyroidism and 1.07 (1.02-1.12; p = 0.003) per genetically predicted one standard deviation increase in free thyroxine levels. Genetically predicted TSH levels and hypothyroidism were inversely with thyroid cancer; the odds ratios were 0.47 (0.30-0.73; p = 0.001) and 0.70 (0.51-0.98; p = 0.038), respectively. Our study provides evidence of a causal association between thyroid dysfunction and breast cancer (mainly ER-positive tumors) risk. The role of TSH and hypothyroidism for thyroid cancer and the associations between thyroid dysfunction and other cancers need further exploration.

Higher thyroid hormone levels and cancer

PURPOSE

This narrative review aims to summarize the relationship between hyperthyroidism, upper reference range thyroid hormone (TH) levels, and cancer, and to address the clinical management of hyperthyroidism in cancer patients.

METHODS

A comprehensive search was performed by an independent reviewer through Google Scholar and PubMed Electronic databases. All searches were restricted to English language manuscripts published between 2000 and 2020.

RESULTS

Numerous in vitro, in vivo, and population-based studies suggest cancer-stimulating effect of triiodothyronine and thyroxin. THs are presented as mediators for tumor growth, proliferation, and progression. Many population and case-control studies suggest an increased risk of several solid but also hematologic malignancies in relation to hyperthyroidism and upper normal range TH levels. However, results are not unambiguous. In this review, we will summarize population and case-control studies that investigated the relationship between hyperthyroidism, upper reference range TH levels, lower thyrotropin (TSH) levels, lower reference range TSH levels with cancer risk, cancer prognosis, and cancer outcome. The vast majority of evidence suggests an association between clinical and subclinical hyperthyroidism with the risk of developing several types of cancer. Furthermore, hyperthyroidism is also linked with a poorer cancer prognosis. In this review, we will also discuss the diagnosis of hyperthyroidism in patients with pre-existing cancer and cover the management of hyperthyroidism in cancer patients, with special attention on the role of nuclear medicine.

CONCLUSIONS

It is crucial to emphasize the importance of the rapid establishment of euthyroidism, and consequently, the importance of radioiodine therapy, as the therapy of choice in most cancer patients. We want to show that in this day and age there still is a high relevance for I-131 to achieve a permanent solution and thus likely reduce the risk of adverse influence of hyperthyroidism on the occurrence of new and course of existing cancer cases.

Hyperthyroidism is associated with breast cancer risk and mammographic and genetic risk predictors

BACKGROUND

Despite the biological link between thyroid hormones and breast cancer cell proliferation shown in experimental studies, little is known about the association between hyperthyroidism and breast cancer, as well as its association with the most common mammographic and genetic risk predictors for breast cancer.

METHODS

This study estimates the incidence rate ratios (IRRs) of breast cancer among women diagnosed with hyperthyroidism, compared to those who are not, using two cohorts: a Swedish national cohort of the general female population (n = 3,793,492, 2002-2011) and the Karolinska Mammography Project for Risk Prediction of Breast Cancer (KARMA, n = 69,598, 2002-2017). We used logistic regression to estimate the odds ratios (ORs) of hyperthyroidism according to the mammographic and genetic risk predictors for breast cancer.

RESULTS

An increased risk of breast cancer was observed in patients in the national cohort with hyperthyroidism (IRR = 1.23, 95% CI = 1.12-1.36), particularly for toxic nodular goiter (IRR = 1.38, 95% CI = 1.16-1.63). Hyperthyroidism was associated with higher body mass index, early age at first birth, and lower breastfeeding duration. Higher mammographic density was observed in women with toxic nodular goiter, compared to women without hyperthyroidism. Additionally, among genotyped women without breast cancer in the KARMA cohort (N = 11,991), hyperthyroidism was associated with a high polygenic risk score (PRS) for breast cancer overall (OR = 1.98, 95% CI = 1.09-3.60) and for estrogen receptor-positive specific PRS (OR = 1.90, 95% CI = 1.04-3.43).

CONCLUSION

Hyperthyroidism is associated with an increased risk of breast cancer, particularly for patients with toxic nodular goiter. The association could be explained by higher mammographic density among these women, as well as pleiotropic genetic variants determining shared hormonal/endocrine factors leading to the pathology of both diseases.

Mammographic breast density, its changes, and breast cancer risk in premenopausal and postmenopausal women

BACKGROUND

The risk of breast cancer related to changes in breast density over time, including its regression and persistence, remains controversial. The authors investigated the relationship between breast density and its changes over time with the development of breast cancer in premenopausal and postmenopausal women.

METHODS

The current cohort study included 74,249 middle-aged Korean women (aged ≥35 years) who were free of breast cancer at baseline and who underwent repeated screening mammograms. Mammographic breast density was categorized according to the American College of Radiology Breast Imaging Reporting and Data System (BI-RADS). A dense breast was defined as heterogeneously dense or extremely dense, and changes in dense breasts between baseline and subsequent follow-up were classified as none, developed, regressed, or persistent dense breast.

RESULTS

During a median follow-up of 6.1 years (interquartile range, 4.1-8.8 years), a total of 803 incident breast cancers were identified. Baseline breast density was found to be positively associated with incident breast cancer in a dose-response manner, and this association did not significantly differ by menopausal status. The multivariable-adjusted hazard ratios (HRs) for breast cancer comparing "heterogeneously dense" and "extremely dense" categories with the nondense category were 1.96 (95% confidence interval [95% CI], 1.40-2.75) and 2.86 (95% CI, 2.04-4.01), respectively. With respect to changes in dense breasts over time, multivariable-adjusted HRs for breast cancer comparing persistent dense breast with none were 2.37 (95% CI, 1.34-4.21) in premenopausal women and 3.61 (95% CI, 1.78-7.30) in postmenopausal women.

CONCLUSIONS

Both baseline dense breasts and their persistence over time were found to be strongly associated with an increased risk of incident breast cancer in premenopausal and postmenopausal women.

LAY SUMMARY

Both baseline breast density and its changes over time were found to be independently associated with the risk of breast cancer in both premenopausal and postmenopausal women. The risk of incident breast cancer increased in women with persistent dense breasts, whereas the breast cancer risk decreased as dense breasts regressed. The findings of the current study support that both dense breasts at baseline and their persistence over time are independent risk factors for developing breast cancer.

Does hypothyroidism increase the risk of breast cancer: evidence from a meta-analysis

PURPOSE

At present, the relationship between hypothyroidism and the risk of breast cancer is still inconclusive. This meta-analysis was used to systematically assess the relationship between hypothyroidism and breast cancer risk, and to assess whether thyroid hormone replacement therapy can increase breast cancer risk.

METHODS

The relevant articles about hypothyroidism and the risk of breast cancer were obtained on the electronic database platform. Relevant data were extracted, and odd ratios (OR) with corresponding 95% confidence intervals (CI) were merged using Stata SE 12.0 software.

RESULTS

A total of 19 related studies were included in the meta-analysis, including 6 cohort studies and 13 case-control studies. The results show that hypothyroidism was not related to the risk of breast cancer (odd ratios = 0.90, 95% CI 0.77-1.03). In the European subgroup, we observed that patients with hypothyroidism have a lower risk of breast cancer(odd ratios = 0.93, 95% CI 0.88-0.99). Furthermore, no significant correlation was observed between thyroid hormone replacement therapy and the risk of breast cancer. (odd ratios = 0.87, 95% CI 0.65-1.09).

CONCLUSION

Hypothyroidism may reduce the risk of breast cancer in the European population, and no significant correlation was observed between hypothyroidism and breast cancer risk in non-European populations. Due to the limited number of studies included, more large-scale, high-quality, long-term prospective cohort studies are needed.

Association Between Breast and Thyroid Lesions: A Cross-Sectional Study Based on Ultrasonography Screening in China

Introduction: Prior research has shown an association between breast and thyroid cancers, although their relationship is unclear. In China, asymptomatic women undergoing regular health checkups usually undergo breast and thyroid ultrasonography screening. The present cross-sectional ultrasound-based study estimated the prevalence of breast masses (BM) and thyroid nodules (TN) and their relationship among a population-based cohort of Chinese women. Methods: This study included 34,184 consecutive asymptomatic Chinese women who underwent both breast and thyroid ultrasound evaluation during one health care examination. Detected lesions were assigned into categories of different malignant risks according to the Breast and Thyroid Imaging Reporting and Data System (BI-/TI-RADS). Binomial logistic regression was used to determine the association between occurrence of BM and TN, and multinomial logistic regression was used to analyze the correlation of BM and TN in different BI-/TI-RADS categories. Associations between BM and TN, as well as anthropometric and biochemical markers, were also explored. Results: Of those enrolled, 6371 (18.6%) had BM, 12,153 (35.6%) had TN, and 2279 (6.7%) had both. After adjusting for age, body mass index (BMI), and height, females with TN had a higher risk of BM (odds ratio [OR] = 1.151, 95% confidence interval [CI 1.081-1.225], p < 0.0001) than those with normal thyroids, and females with BM had a higher risk of TN (OR = 1.165 [CI 1.096-1.238], p < 0.0001) than those without BM. Women with a TN >10 mm (OR = 1.249 [CI 1.104-1.413], p = 0.0004) and those with a TN ≤10 mm (OR = 1.134 [CI 1.062-1.211], p = 0.0002) were at higher risk of BM compared with those with normal thyroids. As RADS categories increased, so did the correlation between BM and TN. The increased risk of TN was associated with a higher BMI, height, systolic blood pressure, and a lower plasma albumin level. The increased risk of BM was associated with a lower BMI, plasma albumin levels, and higher height. Conclusions: A high prevalence of BM and TN was detected by ultrasonography screening in this cohort of Chinese women. These lesions occurred frequently and simultaneously, particularly in women with lesions in higher RADS categories.

Abnormal and Euthyroid Ranges of Thyroid Hormones in Serum and Liver Cancer Mortality: A Cohort Study

BACKGROUND

This study aimed to evaluate the relationship of serum thyrotropin (TSH) and thyroid hormone concentration with liver cancer mortality.

METHODS

A cohort of 517,996 Korean adults, who did not have liver cancer at baseline and attended a health screening including free thyroxine (FT4) and TSH, were followed for up to 16 years. High and low TSH and FT4 were defined as those above the upper bound of reference interval and those below the lower bound of reference interval of their corresponding reference intervals, respectively. Mortality information was ascertained through National Death Records. The adjusted HR (aHR) with 95% confidence interval (CI) were estimated using a Cox proportional hazard model.

RESULTS

During a median follow-up of 8.1 years, 376 deaths from liver cancer were identified. Subjects with low FT4 levels were associated with an elevated risk of liver cancer mortality with a corresponding multivariable aHR 2.25 (95% CI: 1.62-3.12) compared with those with normal FT4 levels. Within the euthyroid range, there was also a dose-dependent inverse relationship between FT4 level and liver cancer mortality (P < 0.001). Levels of TSH and free T3 had no significant association with liver cancer mortality.

CONCLUSIONS

The risk of liver cancer mortality increased as FT4 level decreased, both within the normal and abnormal ranges of thyroid function.

IMPACT

Thyroid function within the abnormal and normal ranges might affect liver cancer mortality. Further study is warranted to elucidate the role of thyroid hormone in development of liver cancer including the underlying biological mechanism.