Hyperthyroidism, Hypothyroidism, and Cause-Specific Mortality in a Large Cohort of Women

Towards Personalized TSH Reference Ranges: A Genetic and Population-Based Approach in Three Independent Cohorts

Background: Serum thyroid-stimulating hormone (TSH) measurement is the diagnostic cornerstone for primary thyroid dysfunction. There is high inter-individual but limited intra-individual variation in TSH concentrations, largely due to genetic factors. The currently used wide population-based reference intervals may lead to inappropriate management decisions. Methods: A polygenic score (PGS) including 59 genetic variants was used to calculate genetically determined TSH reference ranges in a thyroid disease-free cohort (n = 6,834). Its effect on reclassification of diagnoses was investigated when compared to using population-based reference ranges. Next, results were validated in a second independent population-based thyroid disease-free cohort (n = 3,800). Potential clinical implications were assessed in a third independent population-based cohort including individuals without thyroid disease (n = 26,321) as well as individuals on levothyroxine (LT4) treatment (n = 1,132). Results: PGS was a much stronger predictor of individual TSH concentrations than FT4 (total variance in TSH concentrations explained 9.2-11.1% vs. 2.4-2.7%, respectively) or any other nongenetic factor (total variance in TSH concentrations explained 0.2-1.8%). Genetically determined TSH reference ranges differed significantly between PGS quartiles in all cohorts, while the differences in FT4 concentrations were absent or only minor. Up to 24.7-30.1% of individuals, previously classified as having subclinical hypo- and hyperthyroidism when using population-based TSH reference ranges, were reclassified as euthyroid when genetically determined TSH reference ranges were applied. Individuals in the higher PGS quartiles had a higher probability of being prescribed LT4 treatment compared to individuals from the lower PGS quartiles (3.3% in Q1 vs. 5.2% in Q4, Pfor trend =1.7 × 10-8). Conclusions: Individual genetic profiles have the potential to personalize TSH reference ranges, with large effects on reclassification of diagnosis and LT4 prescriptions. As the currently used PGS can only predict approximately 10% of inter-individual variation in TSH concentrations, it should be further improved when more genetic variants determining TSH concentrations are identified in future studies.

Air pollution exposure, accelerated biological aging, and increased thyroid dysfunction risk: Evidence from a nationwide prospective study

BACKGROUND

Long-term air pollution exposure is a major health concern, yet its associations with thyroid dysfunction (hyperthyroidism and hypothyroidism) and biological aging remain unclear. We aimed to determine the association of long-term air pollution exposure with thyroid dysfunction and to investigate the potential roles of biological aging.

METHODS

A prospective cohort study was conducted on 432,340 participants with available data on air pollutants including particulate matter (PM2.5, PM10, and PM2.5-10), nitrogen dioxide (NO2), and nitric oxide (NO) from the UK Biobank. An air pollution score was calculated using principal component analysis to reflect joint exposure to these pollutants. Biological aging was assessed using the Klemera-Doubal method biological age and the phenotypic age algorithms. The associations of individual and joint air pollutants with thyroid dysfunction were estimated using the Cox proportional hazards regression model. The roles of biological aging were explored using interaction and mediation analyses.

RESULTS

During a median follow-up of 12.41 years, 1,721 (0.40 %) and 9,296 (2.15 %) participants developed hyperthyroidism and hypothyroidism, respectively. All air pollutants were observed to be significantly associated with an increased risk of incident hypothyroidism, while PM2.5, PM10, and NO2 were observed to be significantly associated with an increased risk of incident hyperthyroidism. The hazard ratios (HRs) for hyperthyroidism and hypothyroidism were 1.15 (95 % confidence interval: 1.00-1.32) and 1.15 (1.08-1.22) for individuals in the highest quartile compared with those in the lowest quartile of air pollution score, respectively. Additionally, we noticed that individuals with higher pollutant levels and biologically older generally had a higher risk of incident thyroid dysfunction. Moreover, accelerated biological aging partially mediated 1.9 %-9.4 % of air pollution-associated thyroid dysfunction.

CONCLUSIONS

Despite the possible underestimation of incident thyroid dysfunction, long-term air pollution exposure may increase the risk of incident thyroid dysfunction, particularly in biologically older participants, with biological aging potentially involved in the mechanisms.

Thyroid dysfunction after immune checkpoint inhibitors in a single-centre UK pan-cancer cohort: A retrospective study

PURPOSE

This study investigated thyroid dysfunction with immune checkpoint inhibitors (ICIs) in terms of proportions affected, risk factors, thyroid sequelae, and overall survival (OS).

METHODS

Among patients with normal baseline free T4 (fT4) and thyroid stimulating hormone (TSH) receiving ICIs at a large cancer centre, proportions of hyperthyroidism/hypothyroidism were determined (any, subclinical [normal fT4, abnormal TSH], overt [abnormal fT4, abnormal TSH], isolated hyperthyroxinaemia/hypothyroxinaemia and secondary) with onset times and subsequent thyroid statuses. Associations of overt dysfunction with OS were estimated using Cox regression and methods robust to immortal time bias (time-dependent Cox regression and 3- and 6-month landmark analyses). Associations of baseline variables with overt hyperthyroidism and hypothyroidism were estimated using Fine and Gray regression.

RESULTS

Of 1349 patients, 34.2% developed hyperthyroidism (10.3% overt), including 54.9% receiving combination ICIs, while 28.2% developed hypothyroidism (overt 9.3%, secondary 0.5%). A third of overt hypothyroidism cases occurred without preceding hyperthyroidism. Subclinical thyroid dysfunction returned directly to normal in up to half. Overt hyperthyroidism progressed to overt hypothyroidism in 55.4% (median 1.6 months). Melanoma treatment in the adjuvant vs. advanced setting caused more overt hyperthyroidism (12.1% vs. 7.5%) and overt hypothyroidism (14.5% vs. 9.7%). Baseline eGFR < 60 mL/min/1.73 m2 (HR=1.68, 1.07-2.63) was associated with overt hyperthyroidism and sex (HR=0.60, 0.42-0.87) and TSH (4th vs. 1st quartile HR=1.87, 1.10-3.19) with overt hypothyroidism. Overt dysfunction was associated with OS in the Cox analysis (HR=0.65, 0.50-0.85, median follow-up 22.2 months) but not in the time-dependent Cox (HR=0.79, 0.60-1.03) or landmark analyses (3-month HR=0.74, 0.51-1.07; 6-month HR=0.91, 0.66-1.24).

CONCLUSION

Thyroid dysfunction affects up to half of patients receiving ICIs. The association with OS is unclear after considering immortal time bias. The clinical courses include recovery, thyrotoxicosis and de novo overt hypothyroidism. Adjuvant treatment for melanoma, where longer-term harms are of concern, causes more frequent/aggressive dysfunction.

Thyroid Hormones and Diabetes in Euthyroid Hispanic/Latino Adults of Diverse Backgrounds: HCHS/SOL

Context

Previous studies have demonstrated associations of endogenous thyroid hormones with diabetes; less is known about stages of diabetes development at which they are operative, mechanisms of associations, and the role of the hypothalamic-pituitary-thyroid axis.

Objective

This study examined associations of thyroid hormones with incident prediabetes and diabetes and with changes in glycemic traits in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL), the largest cohort of Hispanic/Latino adults with diverse backgrounds in the United States.

Methods

The study includes 592 postmenopausal euthyroid women and 868 euthyroid men aged 45 to 74 years without diabetes at baseline participating in the Hispanic Community Health Study/Study of Latinos (HCHS/SOL). Baseline hormones included thyrotropin (TSH), free thyroxine (FT4), total triiodothyronine (T3), and indices calculated from thyroid hormones evaluating pituitary sensitivity to thyroid hormone. Transitions to diabetes and prediabetes, and changes in glycemic traits determined at the 6-year follow-up visit, were examined using multivariable Poisson and linear regressions.

Results

Among women, T3 (incident rate ratio [IRR] = 1.65; 95% CI, 1.22-2.24; P = .001) and TSH (IRR = 2.09; 95% CI, 1.01-4.33; P = .047) were positively, while FT4 (IRR = 0.59; 95% CI, 0.39-0.88; P = .011) was inversely, associated with transition from prediabetes to diabetes. Among men, the T3/FT4 ratio was positively associated with transition from normoglycemia to prediabetes but not from prediabetes to diabetes. Indices measuring sensitivity of the pituitary to thyroid hormone suggested increased sensitivity in men who transitioned from prediabetes to diabetes.

Conclusion

Positive associations in women of T3 and TSH and inverse associations of FT4, as well as inverse associations of thyroid indices in men with transition from prediabetes to diabetes, but not from normoglycemia to diabetes, suggest decreased pituitary sensitivity to thyroid hormones in women and increased sensitivity in men later in the development of diabetes.

Matched analysis of circulating selenium with the breast cancer selenotranscriptome: a multicentre prospective study

INTRODUCTION

Low serum selenium and altered tumour RNA expression of certain selenoproteins are associated with a poor breast cancer prognosis. Selenoprotein expression stringently depends on selenium availability, hence circulating selenium may interact with tumour selenoprotein expression. However, there is no matched analysis to date.

METHODS

This study included 1453 patients with newly diagnosed breast cancer from the multicentric prospective Sweden Cancerome Analysis Network - Breast study. Total serum selenium, selenoprotein P and glutathione peroxidase 3 were analysed at time of diagnosis. Bulk RNA-sequencing was conducted in matched tumour tissues. Fully adjusted Cox regression models with an interaction term were employed to detect dose-dependent interactions of circulating selenium with the associations of tumour selenoprotein mRNA expression and mortality.

RESULTS

237 deaths were recorded within ~ 9 years follow-up. All three serum selenium biomarkers correlated positively (p < 0.001). All selenoproteins except for GPX6 were expressed in tumour tissues. Single cell RNA-sequencing revealed a heterogeneous expression pattern in the tumour microenvironment. Circulating selenium correlated positively with tumour SELENOW and SELENON expression (p < 0.001). In fully adjusted models, the associations of DIO1, DIO3 and SELENOM with mortality were dose-dependently modified by serum selenium (p < 0.001, p = 0.020, p = 0.038, respectively). With increasing selenium, DIO1 and SELENOM associated with lower, whereas DIO3 expression associated with higher mortality. Association of DIO1 with lower mortality was only apparent in patients with high selenium [above median (70.36 µg/L)], and the HR (95%CI) for one-unit increase in log(FPKM + 1) was 0.70 (0.50-0.98).

CONCLUSIONS

This first unbiased analysis of serum selenium with the breast cancer selenotranscriptome identified an effect-modification of selenium on the associations of DIO1, SELENOM, and DIO3 with prognosis. Selenium substitution in patients with DIO1-expressing tumours merits consideration to improve survival.

Hyperthyroidism: aetiology, pathogenesis, diagnosis, management, complications, and prognosis

Hyperthyroidism is a common condition with a global prevalence of 0·2-1·3%. When clinical suspicion of hyperthyroidism arises, it should be confirmed by biochemical tests (eg, low TSH, high free thyroxine [FT4], or high free tri-iodothyonine [FT3]). If hyperthyroidism is confirmed by biochemical tests, a nosological diagnosis should be done to find out which disease is causing the hyperthyroidism. Helpful tools are TSH-receptor antibodies, thyroid peroxidase antibodies, thyroid ultrasonography, and scintigraphy. Hyperthyroidism is mostly caused by Graves' hyperthyroidism (70%) or toxic nodular goitre (16%). Hyperthyroidism can also be caused by subacute granulomatous thyroiditis (3%) and drugs (9%) such as amiodarone, tyrosine kinase inhibitors, and immune checkpoint inhibitors. Disease-specific recommendations are given. Currently, Graves' hyperthyroidism is preferably treated with antithyroid drugs. However, recurrence of hyperthyroidism after a 12-18 month course of antithyroid drugs occurs in approximately 50% of patients. Being younger than 40 years, having FT4 concentrations that are 40 pmol/L or higher, having TSH-binding inhibitory immunoglobulins that are higher than 6 U/L, and having a goitre size that is equivalent to or larger than WHO grade 2 before the start of treatment with antithyroid drugs increase risk of recurrence. Long-term treatment with antithyroid drugs (ie, 5-10 years of treatment) is feasible and associated with fewer recurrences (15%) than short-term treatment (ie, 12-18 months of treatment). Toxic nodular goitre is mostly treated with radioiodine (131I) or thyroidectomy and is rarely treated with radiofrequency ablation. Destructive thyrotoxicosis is usually mild and transient, requiring steroids only in severe cases. Specific attention is given to patients with hyperthyroidism who are pregnant, have COVID-19, or have other complications (eg, atrial fibrillation, thyrotoxic periodic paralysis, and thyroid storm). Hyperthyroidism is associated with increased mortality. Prognosis might be improved by rapid and sustained control of hyperthyroidism. Innovative new treatments are expected for Graves' disease, by targeting B cells or TSH receptors.

Clinical presentation and prognosis of COVID-19 in older adults with hypothyroidism: data from the GeroCovid observational study

BACKGROUND

The prevalence of hypothyroidism among older patients hospitalized for COVID-19 and its association with mortality is unclear. This study aims to investigate the prevalence of hypothyroidism in older COVID-19 inpatients and verify if this comorbidity is associated with a specific pattern of onset symptoms and a worse prognosis.

METHODS

COVID-19 inpatients aged ≥ 60 years, participating in the GeroCovid acute wards cohort, were included. The history of hypothyroidism was derived from medical records and the use of thyroid hormones. Sociodemographic data, comorbidities, symptoms/signs at the disease onset and inflammatory markers at ward admission were compared between people with vs without history of hypothyroidism. The association between hypothyroidism and in-hospital mortality was tested through Cox regression.

RESULTS

Of the 1245 patients included, 8.5% had a history of hypothyroidism. These patients were more likely to present arterial hypertension and obesity compared with those without an history of hypothyroidism. Concerning COVID-19 clinical presentation, patients with hypothyroidism had less frequently low oxygen saturation and anorexia but reported muscle pain and loss of smell more commonly than those without hypothyroidism. Among the inflammatory markers, patients with hypothyroidism had higher lymphocytes values. At Cox regression, hypothyroidism was associated with reduced in-hospital mortality only in the univariable model (HR = 0.66, 95% CI 0.45-0.96, p = 0.03); conversely, no significant result were observed after adjusting for potential confounders (HR = 0.69, 95% CI 0.47-1.03, p = 0.07).

CONCLUSIONS

Hypothyroidism does not seem to substantially influence the prognosis of COVID-19 in older people, although it may be associated with peculiar clinical and biochemical features at the disease onset.

Shared genetics and causal relationships between migraine and thyroid function traits

BACKGROUND

Epidemiological studies have reported a comorbid relationship between migraine and thyroid dysfunction.

METHODS

We investigated the genetic relationship between migraine and thyroid function traits using genome-wide association study (GWAS) data.

RESULTS

We found a significant genetic correlation (r_g) with migraine for hypothyroidism (r_g = 0.0608), secondary hypothyroidism (r_g = 0.195), free thyroxine (fT4) (r_g = 0.0772), and hyperthyroidism (r_g = -0.1046), but not thyroid stimulating hormone (TSH). Pairwise GWAS analysis revealed two shared loci with TSH and 11 shared loci with fT4. Cross-trait GWAS meta-analysis of migraine identified novel genome-wide significant loci: 17 with hypothyroidism, one with hyperthyroidism, five with secondary hypothyroidism, eight with TSH, and 15 with fT4. Of the genes at these loci, six (RERE, TGFB2, APLF, SLC9B1, SGTB, BTBD16; migraine + hypothyroidism), three (GADD45A, PFDN1, RSPH6A; migraine + TSH), and three (SSBP3, BRD3, TEF; migraine + fT4) were significant in our gene-based analysis (p_{Fisher's combined P-value} < 2.04 × 10^-6). In addition, causal analyses suggested a negative causal relationship between migraine and hyperthyroidism (p = 8.90 × 10^-3) and a positive causal relationship between migraine and secondary hypothyroidism (p = 1.30 × 10^-3).

CONCLUSION

These findings provide strong evidence for genetic correlation and suggest complex causal relationships between migraine and thyroid traits.

The Clinical Characteristics and Outcomes of COVID-19 Patients with Pre-Existing Thyroid Dysfunction: A Nationwide Study

To which extent the pre-existing hypothyroidism or hyperthyroidism has an impact on coronavirus infection 2019 (COVID-19) outcomes remains unclear. The objective of this study was to evaluate COVID-19 morbidity and mortality in patients with pre-existing thyroid dysfunction. A retrospective cohort of patients with a polymerase chain reaction (PCR)-confirmed COVID-19 infection (n=14 966) from March 11 to May 30, 2020, was established using the database of the Turkish Ministry of Health. We compared the morbidity and mortality rates of COVID-19 patients with pre-existing hypothyroidism (n=8813) and hyperthyroidism (n=1822) to those patients with normal thyroid function (n=4331). Univariate and multivariate regression analyses were performed to identify the factors associated with mortality. Mortality rates were higher in patients with hyperthyroidism (7.7%) and hypothyroidism (4.4%) than those with normal thyroid function (3.4%) (p<0.001 and p=0.008, respectively). Pre-existing hyperthyroidism was significantly associated with an increased risk of mortality (OR 1.54; 95% CI, 1.02-2.33; p=0.042) along with advanced age, male gender, lymphopenia and chronic kidney disease (p<0.001 for all). Although a potential trend was noted, the association between pre-existing hypothyroidism and mortality was not significant (OR 1.36; 95% CI, 0.99-1.86; p=0.055). In conclusion, this study showed an association between pre-existing hyperthyroidism with higher COVID-19 mortality. A potential trend towards increased mortality was also observed for hypothyroidism. The risk was more pronounced in patients with hyperthyroidism.

Cancer and Mortality Risks of Graves' Disease in South Korea Based on National Data from 2010 to 2019

Purpose

This study aimed to investigate Graves' disease (GD) associated cancer and mortality risk using a Korean population-based study.

Patients and Methods

We included 6435 patients with GD using the Korean National Health Insurance Service-National Sample Cohort database from 2010 to 2019. Data concerning such patients were compared in a 1:5 ratio with age- and sex-matched non-GD group (n=32,175). Eighteen subdivided types of cancer and cancers-in-total were analyzed. In addition to the mortality analysis, subgroup analyses were performed according to age and sex.

Results

After adjustment, the hazard ratio (HR) of the GD group for cancer-in-total was 1.07 (95% confidence interval [CI], 0.91-1.27), showing no difference when compared to the non-GD group. However, among different types of cancer, the thyroid cancer risk of the GD group was higher than that of the non-GD group (HR=1.70; 95% CI, 1.20-2.39). When subdivided by age and sex, the thyroid cancer risk of the GD group in males aged 20-39 years was higher than that of the non-GD group (HR=7.00; 95% CI, 1.48-33.12). The mortality risk of the GD group was not different from that of the non-GD group (HR=0.86; 95% CI, 0.70-1.05).

Conclusion

In South Korea, patients with GD had a higher risk of thyroid cancer than the non-GD group. In particular, males aged 20-39 years with GD were more likely to have thyroid cancer than the non-GD group.

Hypothyroidism predicts worsened prognosis in patients undergoing percutaneous coronary intervention

Background

The link between thyroid dysfunction and cardiovascular disease is well established. Hypothyroidism has been significantly associated with increased risk of dyslipidemia, atherosclerosis and heart failure. However, little is known regarding its effect on patients undergoing percutaneous coronary intervention (PCI).

Aim

The aim of study was to examine the impact of concomitant hypothyroidism on mortality and major adverse cardiac event (MACE) in patients undergoing PCI.

Methods

The Rabin Medical Center PCI registry includes all consecutive patients who have undergone PCI between 2004 and 2020. We identified patients with prior diagnosis of hypothyroidism, and compared rates of mortality and MACE (comprising death, myocardial infarction, target vessel revascularization and/or coronary bypass surgery).

Results

Among 28,274 patients, 1,922 (6.8%) were found to have hypothryoidism. These patients were older (70.3 ± 10.4 vs. 66.0 ± 11.8 y.o, P &lt; 0.001) and more likely to be women (34.2% vs. 26.1%, P &lt; 0.001). They had a higher prevalence of atrial fibrillation (10.8% vs. 7.7%, P &lt; 0.001), chronic renal dysfunction (25.1% vs. 18.7%, P = 0.04) and dementia (2.9% vs. 1.8%, P = 0.004). PCI was performed on ACS setting in 52–54% of patients in both groups (p = 0.569). Unadjusted 5-year rates of all-cause mortality (26.9% vs. 20.3%, P &lt; 0.001) and MACE (40.3% vs. 29.4%, P &lt; 0.001) were higher for hypothyroid patients. A propensity match score was able to form 672 matched pairs of HT and control patients, showing similar results. Moreover, following multivariate analysis, TSH as a continuous parameter was associated with a higher risk of mortality and MACE (HR, 1.06 per additional 1 mIU/L; CI, 1.02–1.11; P &lt; 0.001 and HR, 1.07; CI, 1.02–1.12; P &lt; 0.001, respectively) at 5-year follow up.

Conclusion

In our study, hypothyroidism confers worse outcomes in patients undergoing PCI. Further research is needed to establish effective ways to mitigate this augmented 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.

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.

Is there an association between thyroid function tests and 18F FDG PET/CT parameters in untreated cancer patients?

Objectives: We aimed to investigate the association between the extent of disease, 18F FDG PET/CT parameters (SUVmax and the highest SUVmax) and thyroid function tests (TFT) (TSH, FT4, FT3, FT3/FT4 ratio, AntiTG, and AntiTPO) in untreated cancer patients. Material and Method: One hundred and seventy-nine patients who underwent FDG PET/CT for metabolic characterization and staging in our clinic between May 2020 and November 2020 were included in the study. Patients were divided into two groups as malignant and benign according to histopathology findings. Thyroid function tests were ordered from all patients at the time of PET/CT imaging. The association between the presence of local lymph node metastasis, distant metastases and thyroid function tests as well as the association between PET/CT parameters and thyroid function tests in benign and malignant groups were statistically analyzed. Results: Thyroid function tests did not exhibit a significant difference between patients with malignant and benign disease (p> 0.05). Univariate logistic regression analysis revealed that age, FT4 value, and the FT3/F4 ratio were significant parameters in predicting distant metastases. These parameters were also significant in predicting mortality. Multivariate logistic regression analysis showed that age was an independent prognostic factor predicting mortality. Conclusion: Thyroid function tests are not decisive in differentiating malignant and benign lesions. While no statistically significant correlation was observed between thyroid function tests and PET/CT parameters, univariate analyses revealed that especially FT4 and FT3/FT4 ratio were significant in predicting disease extent and mortality in malignant disease. Age was found to be an independent prognostic factor in predicting mortality.

Thyrotropin suppression therapy using levothyroxine does not negatively affect breast cancer prognosis

INTRODUCTION

Breast cancer (BC) and thyroid dysfunction are common in females, yet the relationship between thyroid hormone and BC is unclear. To search for the connection between thyrotropin and BC, we contradistinguished BC patients with or without synchronous second primary thyroid cancer (TC) with surgery using data from the Surveillance, Epidemiology, and End Results (SEER) database. Theoretically, according to the ATA (American Thyroid Association) guidelines, all TC patients were treated with thyrotropin suppressive therapy only from 2010 to 2015.

MATERIALS AND METHODS

Data from BC patients with a synchronous second TC with surgery (BC2TC) and only BC patients (1BC) during 2010-2015 were extracted from the SEER database. Differences in the clinicopathological characteristics between BC2TC and 1BC patients were analyzed by chi-square tests. Comparisons of the disease-specific survival (DSS) and overall survival (OS) curves between these two groups were performed with the log-rank (Mantel-Cox) test.

RESULTS

Within this dataset, we identified 134 BC2TC patients during the period from 2010 to 2015. Significant differences between the BC2TC and 1BC groups were found only for different ages and TNM (tumor-node-metastasis status) stages. There were no significant differences in DSS between the two cohorts (P = 0.060). The same tendencies in OS or DSS were observed for the different age groups and different TNM groups, even the stage I, N0 (without metastases to lymph nodes), and ER (+) (estrogen receptor (ER)-positive) groups.

CONCLUSIONS

There were no remarkable differences in survival between the BC2TC and 1BC groups, and thyrotropin suppression therapy using levothyroxine did not negatively affect BC prognosis.

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.

Low thyroid hormone receptor alpha-2 (THRα-2) tumor expression is associated with unfavorable tumor characteristics and high breast cancer mortality

Background

The active thyroid hormone triiodothyronine (T3) has been found to have an estrogen-like effect on breast cancer cells. Thyroid hormone receptor alpha-2 (THRα-2) acts as an antagonist for triiodothyronine (T3) signaling, and a low expression has been associated with unfavorable tumor characteristics and a higher mortality in breast cancer. However, the evidence are not conclusive. The present study evaluates tumor-specific THRα-2 expression in invasive breast cancers and its association with tumor characteristics and long-term mortality in a large population.

Method

The Malmö Diet and Cancer Study (MDCS), a population-based cohort in Sweden that included 17,035 women from 1991 to 1996, was used. Women diagnosed with breast cancer during 1991–2010 were eligible for inclusion. A tissue micro array was constructed from stored tumor material and stained for THRα-2 using immunohistochemistry. Tumors from 654 patients were scored regarding the intensity and the fraction of cells stained, then dichotomized into low or high expression. Date and cause of death were collected up until 2018-12-31. Tumor- and patient characteristics were available from the MDCS. Missing data was imputed using chained equations. Logistic regression was used to calculate odds ratios (ORs) with 95% confidence intervals (CIs) for low vs high expression of THRα-2 related to specific tumor factors. Mortality was evaluated with Kaplan–Meier curves and Cox regression, rendering hazard ratios (HRs). Analyses were also stratified for estrogen receptor (ER) status.

Results

We found strong evidence of an association between low THRα-2 and unfavorable tumor characteristics, including estrogen receptor negativity: OR 4.04 (95% CI 2.28–7.15) and tumor size > 20–50 mm: OR 2.20 (95% CI 1.39–3.49). We found evidence of increased breast cancer-specific mortality for women with low THRα-2, HR 1.38 (95% CI 0.96–1.99), which remained after adjusting for age at diagnosis, HR 1.48 (95% CI 1.03–2.14), but not after adjusting for relevant prognostic factors, HR 0.98 (95% CI 0.66–1.45). THRα-2 expression in ER-negative tumors had an inverse correlation with overall mortality, HR 0.27 (95% CI 0.11–0.65).

Conclusion

Low tumor-specific THRα-2 expression was in this study associated with prognostically unfavorable tumor characteristics and a higher mortality in breast cancer, but not independent from other prognostic factors.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13058-021-01496-7.

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.

Association between thyroid dysfunction and type 2 diabetes: a meta-analysis of prospective observational studies

BACKGROUND

Diabetes mellitus and thyroid disease are two areas of broad interest in the field of endocrinology and metabolism. Variation of thyroid hormone concentration, even within the normal range, may portend the onset of type 2 diabetes mellitus (T2DM), especially among those with prediabetes. However, current evidence is mixed.

METHODS

Prospective studies which assessed diabetes incidence were identified using a database search of MEDLINE and Embase through May 1, 2021. The Sidik-Jonkman random-effects model and cubic spline model were used to evaluate the associations and dose-response relationships between thyroid function/hormone levels and risk of T2DM and cardiovascular disease (CVD) risk among T2DM patients.

RESULTS

A total of 12 prospective studies were included. We found that high baseline TSH levels were related to a 17% higher risk of T2DM (RR 1.17, 95% CI 1.01, 1.36; I²=78%, P<0.01), compared with normal TSH levels. Low FT3 (RR 1.40, 95% CI 1.09, 1.80; I²=59%, P=0.03) and low FT4 (RR 1.33, 95% CI 1.04, 1.71; I²=62%, P=0.02) levels were significantly associated with risk of T2DM. The cubic spline model indicated a J-shaped relationship with TSH, but inverted-J-shaped relationships with FT3 and FT4. CVD events and all-cause deaths were prospectively evaluated in four studies, but were not associated with abnormal thyroid function.

CONCLUSIONS

Our meta-analysis determined that abnormal thyroid hormone level is associated with an increased risk of T2DM, showing a J-shaped relationship with TSH and inverted-J-shaped relationships with FT3 and FT4.

TRIAL REGISTRATION

Registered number in PROSPERO: CRD42021225695 .

Maternal iodine deficiency: a newborns' overweight risk factor? A prospective study

OBJECTIVES

Childhood obesity and iodine deficiency are global public health concerns. Whether maternal iodine status mediates overweight in infancy has yet to be explored. We aimed to assess the relationship between maternal iodine status and infant birth weight, including small and large for gestational age (SGA and LGA, respectively).

METHODS

A prospective study was carried out among 134 mother-infant pairs from Israel. Maternal iodine intake and status were estimated via questionnaire and serum thyroglobulin (Tg), respectively. Estimated iodine intake below the Recommended Daily Allowance for iodine sufficiency in pregnancy (220 μg/d) considered Inadequate. Maternal and neonatal thyroid function and anthropometric measurements, as well as maternal thyroid antibodies were also tested.

RESULTS

After screening, 118 participants met the inclusion criteria (distributed trimesters I, II and III: n = 3, n = 21, and n = 94, respectively). There was a negative association of iodine intake with Tg values among the study population. Maternal median Tg value was higher than the sufficiency cutoff (16.5 vs 13 µg/L), indicating insufficient iodine status. No SGA cases were found. Inadequate iodine intake was associated with maternal isolated hypothyroxinemia (OR = 3.4; 95% CI 1.2, 9.9) and higher birthweight (including macrosomia and LGA) rates. A suggestive association of elevated Tg with a greater risk of LGA was observed. Offsprings' birth weight percentiles were associated with Tg values in pregnant women with suggestive sufficient iodine status (n = 62, R² = 0.11, p < 0.05).

CONCLUSIONS

Iodine status during pregnancy can be associated with newborn anthropometric index. Maternal inadequate iodine intake may alter fetal growth and might increase the risk of LGA among newborns. These initial findings support the need to further study the impact of iodine deficiency on newborns overweight in Israel and elsewhere.

Prediction of Genetic Factors of Hyperthyroidism Based on Gene Interaction Network

The number of hyperthyroidism patients is increasing these years. As a disease that can lead to cardiovascular disease, it brings great potential health risks to humans. Since hyperthyroidism can induce the occurrence of many diseases, studying its genetic factors will promote the early diagnosis and treatment of hyperthyroidism and its related diseases. Previous studies have used genome-wide association analysis (GWAS) to identify genes related to hyperthyroidism. However, these studies only identify significant sites related to the disease from a statistical point of view and ignore the complex regulation relationship between genes. In addition, mutation is not the only genetic factor of causing hyperthyroidism. Identifying hyperthyroidism-related genes from gene interactions would help researchers discover the disease mechanism. In this paper, we purposed a novel machine learning method for identifying hyperthyroidism-related genes based on gene interaction network. The method, which is called “RW-RVM,” is a combination of Random Walk (RW) and Relevance Vector Machines (RVM). RW was implemented to encode the gene interaction network. The features of genes were the regulation relationship between genes and non-coding RNAs. Finally, multiple RVMs were applied to identify hyperthyroidism-related genes. The result of 10-cross validation shows that the area under the receiver operating characteristic curve (AUC) of our method reached 0.9, and area under the precision-recall curve (AUPR) was 0.87. Seventy-eight novel genes were found to be related to hyperthyroidism. We investigated two genes of these novel genes with existing literature, which proved the accuracy of our result and method.

Trends in thyroid function testing, neck ultrasound, thyroid fine needle aspiration, and thyroidectomies in North-eastern Italy

PURPOSE

Evidence of an increased diagnostic pressure on thyroid has emerged over the past decades. This study aimed to provide estimates of a wide spectrum of surveillance indicators for thyroid dysfunctions and diseases in Italy.

METHODS

A population-based study was conducted in North-eastern Italy, including 11.7 million residents (20% of the total Italian population). Prescriptions for TSH testing, neck ultrasound or thyroid fine needle aspiration (FNA), surgical procedures, and drugs for hypo- or hyperthyroidism were extracted from regional health databases. Proportions and rates of selected examinations were calculated from 2010 to 2017, overall and by sex, calendar years, age, and region.

RESULTS

Between 2010 and 2017 in North-eastern Italy, 24.5% of women and 9.8% of men received at least one TSH test yearly. In 2017, 7.1% of women and 1.5% of men were prescribed drugs for thyroid dysfunction, 94.6% of whom for hypothyroidism. Neck ultrasound examinations were performed yearly in 6.9% of women and 4.6% of men, with a nearly two-fold variation between areas. Thyroid FNA and thyroidectomies were three-fold more frequent in women (394 and 85 per 100,000) than in men (128 and 29 per 100,000) with a marked variation between areas. Both procedures decreased consistently after 2013.

CONCLUSIONS

The results of this population-based study describe recent variations over time and between surrounding areas of indicators of 'diagnostic pressure' on thyroid in North-eastern Italy. These results emphasize the need to harmonize practices and to reduce some procedures (e.g., neck ultrasound and total thyroidectomies) in certain areas.

Association of Thyroid Function with Suicidal Behavior: A Systematic Review and Meta-Analysis

Thyroid disease is a very common condition that influences the entire human body, including cognitive function and mental health. As a result, thyroid disease has been associated with multiple neuropsychiatric conditions. However, the relationship between thyroid dysfunction and suicide is still controversial. We conducted a systematic review and meta-analysis to describe the association of thyroid function with suicidal behavior in adults. We searched four data bases (MEDLINE, EMBASE, PsycINFO, and Scopus) from their inception to 20 July 2018. Studies that reported mean values and standard deviation (SD) of thyroid hormone levels [Thyroid-stimulating hormone (TSH), free thyroxine (FT4), free triiodothyronine (FT3), total thyroxine (TT4), and total triiodothyronine (TT3)] in patients with suicidal behavior compared with controls were included in this meta-analysis. The abstracts and papers retrieved with our search strategies were reviewed independently and in duplicate by four reviewers for assessment of inclusion criteria and data extraction, as well as for evaluation of risk of bias. Random-effects models were used in this meta-analysis to establish the mean difference on thyroid function tests between groups. Overall, 2278 articles were identified, and 13 studies met the inclusion criteria. These studies involved 2807 participants, including 826 participants identified with suicidal behavior. We found that patients with suicide behavior had lower levels of FT3 (−0.20 pg/mL; p = 0.02) and TT4 (−0.23 µg/dL; p = 0.045) compared to controls. We found no differences in either TSH, FT4, or TT3 levels among groups. With our search strategy, we did not identify studies with a comparison of overt/subclinical thyroid disease prevalence between patients with and without suicide behavior. The studies included in this meta-analysis had a low-to-moderate risk of bias. In the available literature, the evidence regarding the association of thyroid disorders and suicidal behavior is limited. We found that patients with suicidal behavior have significantly lower mean FT3 and TT4 levels when compared to patients without suicidal behavior. The clinical implications and pathophysiologic mechanisms of these differences remain unknown and further research is needed.

Modulating Thyroid Hormone Levels in Adult Mice: Impact on Behavior and Compensatory Brain Changes

Thyroid hormone (TH) perturbation is a common medical problem. Because of substantial public health impact, prior researchers have studied hyper- and hypothyroidism in animal models. Although most prior research focused on in utero and/or developmental effects, changes in circulating TH levels are commonly seen in elderly individuals: approximately 20% of persons older than 80 years have clinically impactful hypothyroidism and up to 5% have clinical hyperthyroidism, with women being more often affected than men. TH disease model methodology in mice have varied but usually focus on a single sex, and the impact(s) of TH perturbation on the adult brain are not well understood. We administered thyroxine to middle-aged (13 to 14 months) male and female mice to model hyperthyroidism and TH-lowering drugs propylthiouracil (PTU) and methimazole, to induce hypothyroidism. These pharmacological agents are used commonly in adult humans. Circulating TH-level changes were observed when thyroxine was dosed at 20 µg/mL in drinking water for two weeks. By contrast, PTU and methimazole did not elicit a consistent reproducible effect until two months of treatment. No substantial changes in TH levels were detected in brain tissues of treated animals; however, pronounced changes in gene expression, specifically for TH-processing transcripts, were observed following the treatment with thyroxine. Our study indicated a robust compensatory mechanism by which the brain tissue/cells minimize the TH fluctuation in CNS by altering gene expression. Neurobehavioral changes were related to the TH perturbation and suggested potential associations between cognitive status and hyper- and hypothyroidism.

The Prevalence Role of Monocyte Chemoattractant Protein-1 in Hashimoto's Thyroiditis via Various Stimuli Mechanisms

Hashimoto's thyroiditis (HT) is an autoimmune disease occurred at any age especially in the 30 and 50 years of patient, with time thyroid gland is lost its function, as the lymphocytes produce inflammatory cytokines, have a direct effect on the thyroid gland function. The monocyte chemoattractant protein (MCP) produced by the podocyte and monocyte in response to these stimuli and has a role in the feedback based on thyroid hormones therefore MCP is increased secretion depending on thyroid hormones; also it's increased with enlargement of adipocyte tissue, i.e., in patients with high body mass index (BMI), there is a relationship between Hashimoto's disease and obesity, that has an effect on the thyroid gland function. Obesity have important role on thyrostimulated hormones (TSHs), as it has a great effect on metabolism and expansion of the thyroid gland; researchers have previously found that obese individuals have higher serum TSH levels. The results of the study have reported that MCP 1, TSH, and BMI levels were highly significant increased in sera of G2 compared with G1, while T3 and T4 levels were highly significant decreased in sera of G2 compared with G1 in referring to G1: Healthy control group while G2: HT patients.

MorbiNet Study: Hypothyroidism Comorbidity Networks in the Adult General Population

PURPOSE

Multimorbidity impacts quality of life. We constructed hypothyroidism comorbidity networks to identify positive and negative associations with other prevalent diseases.

METHODS

We analyzed data of 285 342 patients with hypothyroidism from 3 135 948 adults with multimorbidity in a population-based study in Catalonia, Spain, (period: 2006-2017). We constructed hypothyroidism comorbidity networks using logistic regression models, adjusted by age and sex, and for men and women separately. We considered relevant associations those with odds ratios (OR) >1.2 or <0.8 and P value < 1e-5 to identify coexistence greater (or smaller) than the expected by the prevalence of diseases. Multivariate models considering comorbidities were used to further adjust OR values.

RESULTS

The conditions associated included larynx cancer (adjusted OR: 2.48), congenital anomalies (2.26), thyroid cancer (2.13), hyperthyroidism (1.66), vitamin B12/folate deficiency anemia (1.57), and goiter (1.56). The network restricted to men had more connections (mental, cardiovascular, and neurological) and stronger associations with thyroid cancer (7.26 vs 2.55), congenital anomalies (5.11 vs 2.13), hyperthyroidism (4.46 vs 1.69), larynx cancer (3.55 vs 1.67), and goiter (3.94 vs 1.64). After adjustment for comorbidities, OR values were more similar in men and women. The strongest negative associations after adjusting for comorbidities were with HIV/AIDS (OR: 0.71) and tobacco abuse (0.77).

CONCLUSIONS

Networks show direct and indirect hypothyroidism multimorbidity associations. The strongest connections were thyroid and larynx cancer, congenital anomalies, hyperthyroidism, anemia, and goiter. Negative associations included HIV/AIDS and tobacco abuse. The network restricted to men had more and stronger associations, but not after adjusting for comorbidities, suggesting important indirect interactions.

Possible role of hypothyroidism in the prognosis of COVID-19

In patients with COVID‐19, certain medical conditions could result in poorer clinical outcomes. However, the prognostic role of hypothyroidism in COVID‐19 is still unknown. In the present retrospective study, we estimated the prevalence of hypothyroidism in COVID‐19 admitted patients in Tehran, Iran. Among 390 COVID‐19 admitted patients, 21 hypothyroid cases (5.4%) were found, in which nearly 90% were aged 50 years and older. Regarding the effect of hypothyroidism on COVID‐19 mortality, 60 (15.3%) of total patients and 4 (19%) of hypothyroid patients died, and no significant difference was found between the two groups.

The Association of Overt and Subclinical Hyperthyroidism with the Risk of Cardiovascular Events and Cardiovascular Mortality: Meta-Analysis and Systematic Review of Cohort Studies

BACKGROUND

Whether hyperthyroidism is an independent risk factor for cardiovascular events remains controversial. We aimed to evaluate the association of overt and subclinical hyperthyroidism with the risk of ischemic heart disease (IHD), stroke, heart failure, and cardiovascular mortality.

METHODS

Studies regarding the association between hyperthyroidism and cardiovascular events were searched on PubMed and Embase databases. The cardiovascular disease (CVD) risk was classified as high and low, based on pre-existing diseases, including history of coronary, cerebral, or peripheral artery disease; heart failure; atrial fibrillation; diabetes mellitus; or chronic kidney disease.

RESULTS

Thirty-seven cohort studies were included in this meta-analysis. The pooled hazard ratio for subjects with overt hyperthyroidism compared with the control group was 1.11 (95% confidence interval [CI], 1.03 to 1.19) for IHD, 1.35 (95% CI, 1.03 to 1.75) for stroke, and 1.20 (95% CI, 1.00 to 1.46) for cardiovascular mortality. For subjects with subclinical hyperthyroidism, the pooled hazard ratio was 1.24 (95% CI, 1.07 to 1.45) for IHD, when compared with the control group. Subgroup analysis by CVD risk showed that the risk of stroke in overt hyperthyroidism was increased in the low CVD risk group; however, these association was not observed in the high CVD risk group. Similarly, the risk of IHD in subjects with subclinical hyperthyroidism was significantly increased in the low CVD risk group.

CONCLUSION

Overt hyperthyroidism is associated with increased risk of IHD, stroke, and cardiovascular mortality, and subclinical hyperthyroidism is associated with increased risk of IHD. These associations were particularly observed in the low risk CVD group without underlying CVD.

Associations of Thyroid Hormones and Resting Heart Rate in Patients Referred to Coronary Angiography

Resting heart rate (RHR) is associated with increased risk of cardiovascular morbidity and mortality. Thyroid hormones exert several effects on the cardiovascular system, but the relation between thyroid function and RHR remains to be further established. We evaluated whether measures of thyroid hormone status are associated with RHR in patients referred to coronary angiography. Thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroxin (FT4), and RHR were determined in 2795 participants of the Ludwigshafen Risk and Cardiovascular Health (LURIC) Study. Median (25th to 75th percentile) serum concentrations were 1.25 (0.76-1.92) mU/l for TSH, 4.8 (4.2-5.3) pmol/l for FT3 and 17.1 (15.4-19.0) pmol/l for FT4, and mean (±standard deviation) RHR was 68.8 (±11.7) beats/min. Comparing the highest versus the lowest quartile, RHR (beats/min) was significantly higher in the fourth FT4 quartile [3.48, 95% confidence interval (CI): 2.23-4.73; p <0.001] and in the fourth FT3 quartile (2.30, 95% CI: 1.06-3.55; p <0.001), but there was no significant difference for TSH quartiles. In multiple linear regression analyses adjusting for various potential confounders, FT3 and FT4 were significant predictors of RHR (p <0.001 for both). In subgroups restricted to TSH, FT3, and FT4 values within the reference range, both FT3 and FT4 remained significant predictors of RHR (p <0.001 for all). In conclusion, in patients referred to coronary angiography, FT3 and FT4 but not TSH were positively associated with RHR. The relationship between free thyroid hormones and RHR warrants further investigations regarding its diagnostic and therapeutic implications.

Epidemiology of thyroid disorders in the Lifelines Cohort Study (the Netherlands)

BACKGROUND

Thyroid hormone plays a pivotal role in human metabolism. In epidemiologic studies, adequate registration of thyroid disorders is warranted. We examined the prevalence of thyroid disorders, reported thyroid medication use, thyroid hormone levels, and validity of thyroid data obtained from questionnaires in the Lifelines Cohort Study.

METHODS

We evaluated baseline data of all 152180 subjects (aged 18-93 years) of the Lifelines Cohort Study. At baseline, participants were asked about previous thyroid surgery and current and previous thyroid hormone use. At follow-up (n = 136776, after median 43 months), incident thyroid disorders could be reported in an open, non-structured question. Data on baseline thyroid hormone measurements (TSH, FT4 and FT3) were available in a subset of 39935 participants.

RESULTS

Of the 152180 participants, mean (±SD) age was 44.6±13.1 years and 58.5% were female. Thyroid medication was used by 4790 participants (3.1%); the majority (98.2%) used levothyroxine, and 88% were females. 59.3% of levothyroxine users had normal TSH levels. The prevalence of abnormal TSH levels in those not using thyroid medication was 10.8%; 9.4% had a mildly elevated (4.01-10.0 mIU/L), 0.7% had suppressed (<0.40 mIU/L), while 0.7% had elevated (>10.0 mIU/L) TSH levels. Over 98% of subjects with TSH between 4 and 10 mIU/L had normal FT4. Open text questions allowing to report previous thyroid surgery and incident thyroid disorders proved not to be reliable and severely underestimated the true incidence and prevalence of thyroid disorders.

CONCLUSIONS

Undetected thyroid disorders were prevalent in the general population, whereas the prevalence of thyroid medication use was 3.1%. Less than 60% of individuals using levothyroxine had a normal TSH level. The large group of individuals with subclinical hypothyroidism (9.4%) offers an excellent possibility to prospectively follow the natural course of this disorder. Both structured questions as well as linking to G.P.'s and pharmacists' data are necessary to improve the completeness and reliability of Lifelines' data on thyroid disorders.

Clinical significance of Saussurea Costus in thyroid treatment

Saussurea costus (S. costus) belongs to family of Asteraceae and is one of the therapeutic plants extensively used as a traditional medicine in Saudi Arabia. Constituents of this plant have the potential to be developed as bioactive molecules. Among Arabs, the prevalence of thyroid disorders ranges from 6.18 % to 47.34% and hypothyroidism has been reported to be the most prevalent. Although there is no natural treatment that can directly replace thyroid hormones, their role as an alternate treatment or as an add-on to available thyroid treatment has been explored. Flavanoids and antioxidant properties of S. costus may be an important mechanism involved in supporting its medicinal use. Current data on the possible role of S. costus in thyroid disorders is lacking and the available evidence is inconclusive. This review deal with the current understanding of use and myth regarding the use of this medicinal plant in thyroid disease.

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.

A comparison of thyroidal protection by stable iodine or perchlorate in the case of acute or prolonged radioiodine exposure

In the case of a nuclear power plant accident, repetitive/prolonged radioiodine release may occur. Radioiodine accumulates in the thyroid and by irradiation enhances the risk of cancer. Large doses of non-radioactive iodine may protect the thyroid by inhibiting radioiodine uptake into the gland (iodine blockade). Protection is based on a competition at the active carrier site in the cellular membrane and the Wolff-Chaikoff effect, the latter being, however, only transient (24-48 h). Perchlorate may alternatively provide protection by a carrier competition mechanism only. Perchlorate has, however, a stronger affinity to the carrier than iodide. Based on an established biokinetic-dosimetric model developed to study iodine blockade, and after its extension to describe perchlorate pharmacokinetics and the inhibition of iodine transport through the carrier, we computed the protective efficacies that can be achieved by stable iodine or perchlorate in the case of an acute or prolonged radioiodine exposure. In the case of acute radioiodine exposure, perchlorate is less potent than stable iodine considering its ED50. A dose of 100 mg stable iodine has roughly the same protective efficacy as 1000 mg perchlorate. For prolonged exposures, single doses of protective agents, whether stable iodine or perchlorate, offer substantially lower protection than after acute radioiodine exposure, and thus repetitive administrations seem necessary. In case of prolonged exposure, the higher affinity of perchlorate for the carrier in combination with the fading Wolff-Chaikoff effect of iodine confers perchlorate a higher protective efficacy compared to stable iodine. Taking into account the frequency and seriousness of adverse effects, iodine and perchlorate at equieffective dosages seem to be alternatives in case of short-term acute radioiodine exposure, whereas preference should be given to perchlorate in view of its higher protective efficacy in the case of longer lasting radioiodine exposures.

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.

Association Between Exposure to Ambient Air Pollution and Thyroid Function in Korean Adults

CONTEXT

Although a significant relationship has been reported between air pollution and thyroid function in limited samples or regions, few studies have addressed this association in the general population.

OBJECTIVE

Using a nationwide sample of Korean adults, we investigated the association between exposure to air pollution and thyroid function, and whether this association differed between subgroups stratified according to age or body mass index (BMI).

METHODS

We included 4704 adults in the final analysis and used each person's annual average exposure to 4 air pollutants, namely, particulate matter with an aerodynamic diameter less than or equal to 10 μm (PM10), nitrogen dioxide (NO2), sulfur dioxide, and carbon monoxide (CO). We measured serum thyrotropin (TSH) and free thyroxine (FT4) concentrations as indicators of thyroid function according to age and BMI.

RESULTS

The annual average exposure to NO2 and CO was significantly associated with an elevated TSH and reduced FT4 concentration after adjusting for possible confounding factors (all P < .05). In men, in addition to these 2 pollutants, PM10 exposure was positively associated with TSH level (P = .03). Age-stratified analysis showed stronger effects of NO2 and CO exposure in older than in younger adults. Exposure to these air pollutants was related to serum TSH and FT4 concentrations in people with overweight or obesity but not in those of normal weight.

CONCLUSIONS

This study provides the first evidence that air pollution exposure is linked to thyroid function in the general population and that this association may be stronger in older or overweight or obese adults.

Thyroid Hormone in Hepatocellular Carcinoma: Cancer Risk, Growth Regulation, and Anticancer Drug Resistance

Thyroid hormone (TH) and its receptor (TR) are involved in differentiation, metabolic process, and growth regulation in hepatocellular carcinoma (HCC). The TH/TR complexes are ligand-dependent transcriptional factors, functioning through binding to thyroid hormone response elements (TREs) upstream of the target genes. To date, deciphering the biological effects of TH in cancer progression remains challenging. Several lines of evidence suggest a growth inhibitory effect of TH in liver cancer. Mutation and aberrant expression of TRs are highly correlated with several types of cancers including HCC. Several reports show that TH inhibits cell growth in liver cancer through regulation of cell-cycle-related genes and non-coding RNAs. A case–control study indicates that hypothyroidism is associated with an increased risk of HCC. Moreover, TH/TR suppresses hepatocarcinogenesis via selective autophagy. Conversely, other groups have indicated that TH promotes cancer cell proliferation. In vitro and in vivo experiments show that TH/TR enhances cancer cell migration and invasion, anticancer drug resistance, angiogenesis, and cancer stem cell self-renewal. Adding to the complexity of this issue, non-genomic effects of TH mediated by integrin receptor on cell surface can also modulate several biological functions. Accumulating evidence indicate that regulations by genomic and non-genomic effects of TH overlap. Taken together, these observations suggest that the functions of TH depend largely on cell context, and TH/TR plays a duel role in cancer progression. Therefore, understanding the maze of biological effects of TH has become a necessity when attempting to develop effective therapeutic and preventive strategies in liver cancer.

The Impact of Obesity on Thyroid Autoimmunity and Dysfunction: A Systematic Review and Meta-Analysis

Background: To help inform decision making in the clinical setting, we carried out a systematic review and meta-analysis to estimate the association of thyroid disease risks with obesity.

Methods: Pubmed, Embase, Web of Science, Cochrane database and Google Scholar electronic databases were searched from inception to October 31, 2018 without language restrictions to explore the relationship between thyroid disorders and obesity. The relative risk (RR) or odds risk (OR) for thyroid disorders were pooled using the SPSS and STATA software.

Results: A total of 22 studies were included in the study. (1) Meta-analysis showed that obesity was significantly associated with an increased risk of hypothyroidism (RR = 1.86, 95% CI 1.63–2.11, P < 0.001). Meta-analyses after stratification further showed that obese population had increased risks of overt hypothyroidism (RR = 3.21, 95% CI 2.12–4.86, P < 0.001) and subclinical hypothyroidism (RR = 1.70, 95% CI 1.42–2.03, P < 0.001). (2) Further meta-analysis also showed obesity was clearly associated with Hashimoto's thyroiditis (RR = 1.91, 95% CI 1.10–3.32, P = 0.022), but not with Graves' disease. (3) In the meta-analysis of antibodies, obesity was correlated with positive thyroid peroxidase antibody (TPOAb) (RR = 1.93, 95% CI 1.31–2.85, P = 0.001), but not with positive thyroglobulin antibody (TGAb).

Conclusions: Obesity was significantly related to hypothyroidism, HT, and TPOAb, implying that prevention of obesity is crucial for thyroid disorders.

Systematic Review Registration: PROSPERO: CRD42018096897.

Radiosensitivity-related postirradiation hypothyroidism in Graves' disease patients

PURPOSE

The cumulative incidence of hypothyroidism, in ¹³¹I-treated patients with hyperthyroidism caused by Graves' disease, has been gradually increasing each year. Meanwhile, the role of the genes that control radiation sensitivity (GCRS) involved in ¹³¹I therapy is yet to be defined. The main purpose of the present study is to find GCRS that could indicate hypothyroidism in Graves' disease patients treated with ¹³¹I.

METHODS

Thyroid tissue was collected from 59 patients who were diagnosed with Graves' disease. GCRS (including Bcl-2, NF-κB, Survivin, Ku-70, Tob1, EGFR, Egr-1, TP-53, BRCA-1, and ATM) mRNA levels were analyzed with qRT-PCR before radioiodine therapy. Patients were followed up and then grouped by end-point outcomes. The association of the variation of target genes with susceptibility to hypothyroidism was analyzed.

RESULTS

Altogether 44 patients were enrolled, including 11 men and 33 women with an average age of 44.79 ± 12.94 years. Based on their clinical outcomes after at least 2-year follow-up, 59% (26/44) patients were evaluated as hypothyroid, while the remaining 41% (18/44) patients were non-hypothyroid, including 18% (8/44) with persistent hyperthyroidism. The hypothyroid group showed significantly lower Ku-70 mRNA expression levels than the non-hypothyroid group (p = 0.022), whereas no significance was detected regarding other target genes (p > 0.1). Multivariate analysis showed that Ku-70 was significantly correlated with hypothyroidism after ¹³¹I treatment (p = 0.033).

CONCLUSIONS

The opposing changes in mRNA expression levels of Ku-70 in patients with hypothyroidism indicate its potential as a prognostic marker for hypothyroidism induced by ¹³¹I treatment.

Death by unnatural causes, mainly suicide, is increased in patients with Hashimoto's thyroiditis. A nationwide Danish register study

PURPOSE

Hashimoto's thyroiditis (HT) is associated with excess psychiatric in addition to reduced quality of life. However, little is known about risk of unnatural manners of death in HT. We investigated the risk of death by accidents, suicide, violence/homicide, and unknown causes in patients with HT, compared to a matched control population.

METHODS

Register study covering all adult Danes diagnosed with HT during 1995-2012. In total, 111,565 HT cases were identified and matched for age and sex with four euthyroid controls. The hazard ratios (HR) for mortality were calculated using Cox regression analyses, adjusted for pre-existing morbidity. Median follow-up time was 5.9 years (range 0-17.5).

RESULTS

Compared to controls, HT patients had an increased frequency of death by suicide (0.10% vs 0.07%, p < 0.001) and unknown manners (0.05% vs 0.02%, p < 0.001). There were no significant differences between controls and HT patients in risk of death by accidents (0.36% vs 0.37%, p = 0.384) or violence (0.004% vs 0.005%, p = 0.749). After adjustment for pre-existing somatic and psychiatric morbidity HT patients still had an increased risk of suicide and death by unknown causes, whereas risk of death caused by accidents was reduced.

CONCLUSIONS

Mortality due to suicide and unknown causes, but not accidents and violence, was increased in HT. This indicates that HT may have a significant role in the pathophysiological mechanisms of suicidal behavior. This suggests that physicians caring for HT patients should be vigilant when facing expressions of suicidal ideation or signs and symptoms of self-harm as a first step towards prevention.

Association of Radioactive Iodine Treatment With Cancer Mortality in Patients With Hyperthyroidism

IMPORTANCE

Radioactive iodine (RAI) has been used extensively to treat hyperthyroidism since the 1940s. Although widely considered a safe and effective therapy, RAI has been associated with elevated risks of total and site-specific cancer death among patients with hyperthyroidism.

OBJECTIVE

To determine whether greater organ- or tissue-absorbed doses from RAI treatment are associated with overall and site-specific cancer mortality in patients with hyperthyroidism.

DESIGN, SETTING, AND PARTICIPANTS

This cohort study is a 24-year extension of the multicenter Cooperative Thyrotoxicosis Therapy Follow-up Study, which has followed up US and UK patients diagnosed and treated for hyperthyroidism for nearly 7 decades, beginning in 1946. Patients were traced using records from the National Death Index, Social Security Administration, and other resources. After exclusions, 18 805 patients who were treated with RAI and had no history of cancer at the time of the first treatment were eligible for the current analysis. Excess relative risks (ERRs) per 100-mGy dose to the organ or tissue were calculated using multivariable-adjusted linear dose-response models and were converted to relative risks (RR = 1 + ERR). The current analyses were conducted from April 28, 2017, to January 30, 2019.

EXPOSURES

Mean total administered activity of sodium iodide I 131 was 375 MBq for patients with Graves disease and 653 MBq for patients with toxic nodular goiter. Mean organ or tissue dose estimates ranged from 20 to 99 mGy (colon or rectum, ovary, uterus, prostate, bladder, and brain/central nervous system), to 100 to 400 mGy (pancreas, kidney, liver, stomach, female breast, lung, oral mucosa, and marrow), to 1.6 Gy (esophagus), and to 130 Gy (thyroid gland).

MAIN OUTCOMES AND MEASURES

Site-specific and all solid-cancer mortality.

RESULTS

A total of 18 805 patients were included in the study cohort, and the mean (SD) entry age was 49 (14) years. Most patients were women (14 671 [78.0%]), and most had a Graves disease diagnosis (17 615 [93.7%]). Statistically significant positive associations were observed for all solid cancer mortality (n = 1984; RR at 100-mGy dose to the stomach = 1.06; 95% CI, 1.02-1.10; P = .002), including female breast cancer (n = 291; RR at 100-mGy dose to the breast = 1.12; 95% CI, 1.003-1.32; P = .04) and all other solid cancers combined (n = 1693; RR at 100-mGy dose to the stomach = 1.05; 95% CI, 1.01-1.10; P = .01). The 100-mGy dose to the stomach and breast corresponded to a mean (SD) administered activity of 243 (35) MBq and 266 (58) MBq in patients with Graves disease. For every 1000 patients with hyperthyroidism receiving typical doses to the stomach (150 to 250 mGy), an estimated lifetime excess of 19 (95% CI, 3-40) to 32 (95% CI, 5-66) solid cancer deaths could occur.

CONCLUSIONS AND RELEVANCE

In RAI-treated patients with hyperthyroidism, greater organ-absorbed doses appeared to be modestly positively associated with risk of death from solid cancer, including breast cancer. Additional studies are needed of the risks and advantages of all major treatment options available to patients with hyperthyroidism.

Prevalence of Undiagnosed Hypothyroidism in Europe: A Systematic Review and Meta-Analysis

BACKGROUND

Patients with undiagnosed hypothyroidism are not treated for the disease and are at high risk of developing serious complications, with major impact on public health. There is a need to systematically review the available evidence on this topic.

OBJECTIVE

To identify the prevalence of undiagnosed hypothyroidism in Europe.

METHODS

A systematic review of the literature (Medline, EMBASE, and Cochrane Central) was performed to identify epidemiological studies on the prevalence of undiagnosed hypothyroidism among European populations published between January 2008 and April 2018. The Newcastle-Ottawa Scale was used to assess the methodological quality of the included studies. Random-effects meta-analyses were performed to pool estimates of proportions (with 95% confidence intervals [CIs]) of undiagnosed (1) subclinical, (2) overt, and (3) total hypothyroidism.

RESULTS

The search returned 15,565 citations (4,526 duplicates). Twenty papers were included in the study. Fourteen and 6 studies were of good and moderate methodological quality, respectively. The results of the meta-analyses were as follows for the prevalence of undiagnosed hypothyroidism: subclinical, 4.11% (95% CI 3.05-5.31%, I2 = 99.32%); overt, 0.65% (95% CI 0.38-0.99%, I2 = 96.67%); and total, 4.70% (95% CI 2.98-6.79%, I2 = 99.53%). According to the sensitivity analysis, the prevalence of hypothyroidism tends to be higher in female patients, in those aged ≥65 years, among studies with lower sample sizes, in those with thyroid-stimulating hormone levels <4.5 mIU/L, and in Eastern and Southern Europe.

CONCLUSIONS

The current evidence suggests that a considerable proportion of the European population has hypothyroidism, particularly subclinical hypothyroidism, which is undiagnosed. This issue deserves further investigation because of possible deleterious consequences for public health.

Thyroid Cancer Benefits the Prognosis of Ovarian Cancer: A SEER-Based Study

INTRODUCTION

To explore the effect of a second thyroid cancer (TC) on ovarian cancer (OC) patient survival, we compared OC patients with or without a second primary TC using data from the Surveillance, Epidemiology, and End Results (SEER) database.

METHODS

Data for OC only, female TC only and OC patients with a second TC (OC2TC) from two periods, 2000-2014 and 1980-1994, were extracted from the SEER database. Differences in clinicopathological and treatment characteristics were analysed using the chi-square test. Cox regression analyses were used to identify risk factors associated with OC survival. Disease-specific survival (DSS) and overall survival (OS) curves were compared using the log-rank test.

RESULTS

There were 109 OC2TC patients from 2000 to 2014, and significant differences (P < 0.001) in the mean age at OC diagnosis, TNM stage and surgical history were found between OC and OC2TC patients. Several factors, including age, grade, TNM stage, histological type and surgical history, influenced OC survival (P < 0.001). OC2TC patients showed better survival than OC patients from 2000 to 2014, regardless of age, TNM stage or surgical history. However, this superiority was not significant in cases from 1980 to 1994 (P = 0.222 for OS).

CONCLUSION

Survival was better with OC2TC than with OC from 2000 to 2014 rather than 1980-1994, suggesting that TC improved the survival of OC patients from 2000 to 2014.

L-thyroxine malabsorption due to calcium carbonate impairs blood pressure, total cholesterolemia, and fasting glycemia

PURPOSE

Calcium carbonate was previously shown to interfere with L-thyroxine absorption. To estimate the magnitude of tablet L-thyroxine malabsorption caused by calcium carbonate, with resulting increase in serum thyrotropin (TSH), we performed a cohort study in a referral care center.

METHODS

Fifty postmenopausal hypothyroid L-thyroxine-treated women (age 71.7 ± 5.1 years) who added calcium supplementation (600-1000 mg/day) were considered. They were taking L-thyroxine 45-60 min before breakfast (setting 1). After 4.4 ± 2.0 years from initiation of L-thyroxine therapy, they took calcium supplemaentation within 2 h after L-thyroxine taking (setting 2) for 2.3 ± 1.1 years. Hence, we recommended postponing calcium intake 6-8 h after L-thyroxine (setting 3). We evaluated TSH levels, the prevalence of women with elevated TSH (>4.12 mU/L), total cholesterolemia, fasting glycemia, blood pressure, and the prevalence of hypercholesterolemia, hyperglycemia, and hypertension.

RESULTS

TSH levels were 3.33 ± 1.93 mU/L versus 1.93 ± 0.51 or 2.16 ± 0.54 comparing setting 2 with setting 1 or 3 (P < 0.001, both). In setting 2, 18% women had elevated TSH versus none in setting 1 or 3 (P < 0.01). Total cholesterolemia, fasting glycemia, systolic, and diastolic blood pressure were also significantly higher in setting 2 compared to settings 1 and 3. For every 1.0 mU/L increase within the TSH range of 0.85-6.9 mU/L, total cholesterolemia, glycemia, systolic, and diastolic blood pressure increased by 12.1, 3.12 mg/dL, 2.31, and 2.0 mmHg, respectively.

CONCLUSIONS

Monitoring of hypothyroid patients who ingest medications that decrease L-thyroxine absorption should not be restricted to solely measuring serum TSH.

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

The impact of variations in serum thyroid hormone concentration within the euthyroid range on breast cancer risk remains unclear. We investigated the effect of serum thyrotropin (TSH) and thyroid hormone concentration on breast cancer risk. This cohort study involved 62,546 Korean women, aged ≥40 years, who were free of breast cancer at baseline and underwent health examination with determination of free thyroxine (FT4) and TSH. A parametric proportional hazard model was used to estimate the adjusted hazard ratio (aHR) and 95% confidence interval (CI). During a median follow-up of 4.8 years (interquartile range: 2.8-7.3 years), 834 incident breast cancers were identified. Compared to normal FT4 level, abnormally high serum FT4 level was associated with an increased risk of incident breast cancer with a corresponding multivariable aHR (95% CI) of 1.98 (1.02-3.83). This association tended to be stronger in postmenopausal women than in premenopausal women. Within the euthyroid range, the highest TSH tertile was associated with a lower risk of breast cancer than the lowest TSH tertile with a corresponding aHR (95% CI) of 0.68 (0.55-0.84). In contrast, highest FT4 tertile was associated with a higher risk of breast cancer than the lowest FT4 tertile. Abnormally high FT4 as well as higher FT4 within the euthyroid range were positively associated with breast cancer risk, while higher TSH concentration within the euthyroid range was negatively associated with breast cancer risk. Our findings indicate that thyroid function within both the abnormal and euthyroid ranges may contribute to the development of breast cancer.

Hypothyroidism and the risk of breast cancer recurrence and all-cause mortality - a Danish population-based study

Background

Hypothyroidism may occur as a late effect of breast cancer-directed treatment, particularly after radiotherapy, but little is known whether hypothyroidism affects the prognosis after breast cancer. We investigated the association between hypothyroidism and breast cancer recurrence, and all-cause mortality.

Methods

In this population-based cohort study, we used national medical registries to identify all Danish women 35 years or older diagnosed with stage I–III, operable breast cancer between 1996 and 2009. Hypothyroidism was defined as hospital diagnoses ascertained via diagnostic codes, or as prescriptions for levothyroxine. Two analytic models were used: (i) hypothyroidism present at the time of the breast cancer diagnosis (prevalent) and (ii) hypothyroidism diagnosed during follow-up as a time-varying exposure lagged by 1 year (incident). Breast cancer recurrence was defined as any local, regional, or distant recurrence or contralateral breast cancer. All-cause mortality included death from any cause in any setting. We used Cox regression models accounting for competing risks to compute adjusted hazard ratios (HRs) and 95% confidence intervals (CIs) of breast cancer recurrence and all-cause mortality.

Results

The study cohort included 35,463 women with breast cancer with 212,641 person-years of follow-up. At diagnosis, 1272 women had hypothyroidism and 859 women developed hypothyroidism during follow-up. In total, 5810 patients developed recurrent breast cancer. Neither prevalent nor incident hypothyroidism was associated with breast cancer recurrence (adjusted HR_prevalent 1.01, 95% CI 0.87–1.19; adjusted HR_incident 0.93, 95% CI 0.75–1.16, respectively). Furthermore, no differences were seen for all-cause mortality for prevalent or incident hypothyroidism (adjusted HR_prevalent 1.02, 95% CI 0.92–1.14, and HR_incident 1.08, 95% CI 0.95–1.23, respectively). Stratification by menopausal status, oestrogen receptor status, chemotherapy, or radiotherapy did not alter the estimates.

Conclusions

Hypothyroidism present at diagnosis or during follow-up was not associated with breast cancer recurrence or all-cause mortality in women with breast cancer. Our findings provide reassurance to patients and their physicians that hypothyroidism is unlikely to impact on the clinical course of breast cancer or survival.

Electronic supplementary material

The online version of this article (10.1186/s13058-019-1122-3) contains supplementary material, which is available to authorized users.