Thyroid and aging or the aging thyroid? An evidence-based analysis of the literature

Circadian Gene BMAL1 Regulation of Cellular Senescence in Thyroid Aging

As global aging accelerates, the incidence of thyroid diseases, particularly hypothyroidism, is rising in the elderly. The thyroid-stimulating hormone (TSH) levels increase in healthy elderly populations. However, whether the thyroid undergoes cellular senescence and how this relates to thyroid hormone (TH) synthesis remain unclear. To investigate the molecular and functional characteristics of thyroid aging, we performed scRNA-seq on human thyroids from young, middle-aged, and old groups, identifying thousands of aging-related differentially expressed genes and revealing the early onset of aging in the middle-aged group. As aging progresses, the expression levels of genes related to TH synthesis increase, suggesting that epithelial cells (EPI) adjust their gene expression in response to elevated TSH levels. Additionally, the senescence-associated secretory phenotype (SASP) in EPI cells is progressively enhanced with aging. We identified a subgroup of epithelial cells (CDKN1A_EPI) characterized by reduced functionality and significantly elevated levels of cellular senescence. We found that the core circadian rhythm gene BMAL1 (ARNTL) is downregulated during aging. We further validated this finding using the thyroid-specific Bmal1 knockout mouse model, showing that the downregulation of Bmal1 inhibits the expression of Nfkbia (NF-κB inhibitor alpha), thereby accelerating cellular senescence and impairing hormone synthesis. Finally, through cell line experiments and transcriptome sequencing, we confirmed that BMAL1 knockout leads to decreased NFKBIA expression, promoting thyroid cellular senescence. Our study demonstrates that circadian rhythm disruption accelerates cellular senescence in the thyroid and exacerbates the decline of thyroid function, providing a novel theoretical foundation for understanding thyroid aging mechanisms and maintaining thyroid function stability.

Serum Klotho protein level in patients with thyroid dysfunction

OBJECTIVES

This study focused on determining the new marker Klotho and its correlation with other parameters in thyroid dysfunction.

METHODS

Seventy-seven thyroid dysfunction patients were recruited during the period (from Aug 2024 to Dec 2024) with an age range (33-56) years. The patient group was subdivided into two groups: group I (21) Patients with Hyperthyroidism and group II (56) Patients with Hypothyroidism, for comparison, 30 healthy individuals were included as a control. The protein level Klotho was estimated using ELISA. Biochemical parameters; blood urea, creatinine, and lipid profile were measured spectrophotometrically. T3, T4 and TSH were determined using ELFA kit.

RESULTS

Serum levels of Klotho protein were significantly lower (p-value < 0.001) in group I compared to the control group. There was a significant difference (p < 0.001) in the Klotho protein levels in group II compared with the control group. Klotho protein was negatively correlated to TSH, creatinine concentrations, and age. The AUC was excellent with high diagnostic accuracy in differentiating newly diagnosed thyroid dysfunction from the healthy subject group.

CONCLUSIONS

Serum Klotho levels in patients with thyroid dysfunction significantly decreased, particularly in hypothyroidism patients. These levels are inversely correlated with thyroid-stimulating hormone levels and age.

Possible association between subclinical hypothyroidism and age at menopause in Colombian women

OBJECTIVE

To evaluate the association between subclinical hypothyroidism with early menopause, premature menopause, and last menstrual bleeding before the natural age of menopause.

METHODS

This was a cross-sectional study conducted in 643 postmenopausal women aged 40-69 years. Groups were formed according to last menstrual episode: ≥45 [Natural age at menopause], 40-44 and [Early menopause], <40 [Premature menopause], and <45 [last menstrual episode before the natural age of menopause]. The Zulewski scale was applied to identify manifestations related to hypothyroidism and subclinical hypothyroidism, diagnosed with a serum TSH > 4.5 µIU/mL plus T4-free between 0.7 and 1.9 ng/dL.

RESULTS

It was found that 24.4% had the last menstrual episode before the natural age of menopause, 18.6% had early menopause, and 5.7% had premature menopause. Subclinical hypothyroidism was diagnosed in 4.5% of patients. Among women with subclinical hypothyroidism, there was a higher frequency of early menopause, premature menopause, and last menstrual episode before the natural age of menopause, than in women without subclinical hypothyroidism (p < 0.05). Paresthesia (50%) and dry skin (40.7%) were the most reported hypothyroidism-related manifestations. Early menopause, premature menopause, and last menstrual episode before the natural age of menopause were associated with subclinical hypothyroidism, OR: 3.37 [95% CI: 1.40-8.10], OR: 4.31 [95% CI: 1.24-14.97], and OR: 3.57 [95% CI: 1.57-8.10], respectively.

CONCLUSIONS

The last menstrual episode before the natural age of menopause, early menopause, and premature menopause were significantly associated with a higher chance of subclinical hypothyroidism.

Hypothyroidism after hemithyroidectomy: a systematic review and meta-analysis

BACKGROUND

The incidence of hypothyroidism following hemithyroidectomy and risk factors associated with its occurrence are not completely understood. This systematic review investigated the incidence and risk factors for hypothyroidism, thyroxine supplementation following hemithyroidectomy as well as the course of post-operative hypothyroidism, including the time to hypothyroidism and incidence of transient hypothyroidism.

METHODS

Searches were conducted in MEDLINE, EMBASE, Scopus, and Cochrane library for studies reporting the incidence of hypothyroidism or thyroxine supplementation following hemithyroidectomy.

RESULTS

Sixty-six studies were eligible for inclusion: 36 reported risk factors, and 27 reported post-operative course of hypothyroidism. Median follow-up was 25.2 months. The pooled incidence of hypothyroidism was 29% (95% CI, 25-34%; P<0.001). Transient hypothyroidism occurred in 34% of patients (95% CI, 21-47%; P<0.001). The pooled incidence of thyroxine supplementation was 23% (95% CI, 19-27%; P<0.001), overt hypothyroidism 4% (95% CI, 2-6%, P<0.001). Risk factors for development of hypothyroidism included pre-operative thyroid stimulating hormone (TSH) (WMD, 0.87; 95% CI, 0.75-0.98; P<0.001), TSH ≥ 2 mIU/L (RR, 2.87; 95% CI, 2.43-3.40; P<0.001), female sex (RR, 1.19; 95% CI, 1.08-1.32; P=0.007), age (WMD, 2.29; 95% CI, 1.20-3.38; P<0.001), right sided hemithyroidectomy (RR, 1.35; 95% CI, 1.10-1.65, P=0.003), the presence of autoantibodies anti-TPO (RR, 1.92; 95% CI, 1.49-2.48; P<0.001), anti-Tg (RR, 1.53; 95% CI, 1.40-1.88; P<0.001), and Hashimoto's thyroiditis (RR, 2.05; 95% CI, 1.57-2.68; P=0.001).

CONCLUSION

A significant number of patients will develop hypothyroidism or require thyroxine following hemithyroidectomy. An awareness of patient risk factors and postoperative thyroid function course will assist in counselling patients on their risk profile and guiding management.

Revealing the genetic complexity of hypothyroidism: integrating complementary association methods

Hypothyroidism is a common endocrine disorder whose prevalence increases with age. The disease manifests itself when the thyroid gland fails to produce sufficient thyroid hormones. The disorder includes cases of congenital hypothyroidism (CH), but most cases exhibit hormonal feedback dysregulation and destruction of the thyroid gland by autoantibodies. In this study, we sought to identify causal genes for hypothyroidism in large populations. The study used the UK-Biobank (UKB) database, reporting on 13,687 cases of European ancestry. We used GWAS compilation from Open Targets (OT) and tuned protocols focusing on genes and coding regions, along with complementary association methods of PWAS (proteome-based) and TWAS (transcriptome-based). Comparing summary statistics from numerous GWAS revealed a limited number of variants associated with thyroid development. The proteome-wide association study method identified 77 statistically significant genes, half of which are located within the Chr6-MHC locus and are enriched with autoimmunity-related genes. While coding GWAS and PWAS highlighted the centrality of immune-related genes, OT and transcriptome-wide association study mostly identified genes involved in thyroid developmental programs. We used independent populations from Finland (FinnGen) and the Taiwan cohort to validate the PWAS results. The higher prevalence in females relative to males is substantiated as the polygenic risk score prediction of hypothyroidism relied mostly from the female group genetics. Comparing results from OT, TWAS, and PWAS revealed the complementary facets of hypothyroidism's etiology. This study underscores the significance of synthesizing gene-phenotype association methods for this common, intricate disease. We propose that the integration of established association methods enhances interpretability and clinical utility.

Covariance regression with random forests

Capturing the conditional covariances or correlations among the elements of a multivariate response vector based on covariates is important to various fields including neuroscience, epidemiology and biomedicine. We propose a new method called Covariance Regression with Random Forests (CovRegRF) to estimate the covariance matrix of a multivariate response given a set of covariates, using a random forest framework. Random forest trees are built with a splitting rule specially designed to maximize the difference between the sample covariance matrix estimates of the child nodes. We also propose a significance test for the partial effect of a subset of covariates. We evaluate the performance of the proposed method and significance test through a simulation study which shows that the proposed method provides accurate covariance matrix estimates and that the Type-1 error is well controlled. An application of the proposed method to thyroid disease data is also presented. CovRegRF is implemented in a freely available R package on CRAN.

Normal thyroid volume in subjects evaluated in a primary ambulatory setting in Liguria

BACKGROUND

Ultrasonography (US) is the simplest method of evaluating thyroid volume (TV). The current normal TV in Liguria is not known. The aim of this study was to obtain normative data on TV in Liguria, Italy.

METHODS

From 3552 files of endocrine evaluations registered in a primary outpatient setting, we selected 483 files on euthyroid subjects (383 females and 100 males) with a normal echoic pattern on US. The inclusion criterion was the absence of thyroperoxidase autoantibodies and drugs known to interfere with thyroid hormone secretion or metabolism. TV was calculated by means of US. Anthropometric characteristics, smoking habits and the district where subjects lived were registered.

RESULTS

Less than 50% of patients were not taking any drug. The percentage of obesity was similar in both sexes. TSH levels were similar in males and females. Median TV was 8.0 mL (IQR: 6.7-9.8 mL) in females and 11.8 mL (9.3-15.6 mL) in males (P<0.0001). In females, TV was greater (P=0.01) in smokers than in non-smokers. In both sexes, the right lobe was significantly (P<0.0001) larger in volume than the left. Post-hoc analysis did not show any differences among age-groups in either females or males. In females, but not in males, TV differed significantly (P=0.0002) according to the district of residence. A significant positive correlation was found in both groups between TV and weight, height, BMI and BSA.

CONCLUSIONS

Reference values of TV in the Ligurian population are now available. TV in the general population could be compared with these normative data.

The prevalence of sleep loss and sleep disorders in young and old adults

The ability to sleep declines with age. The National Sleep Foundation, USA has recommended a minimum sleep amount for all ages. Individuals who experience sleep lesser than the recommended amount could be sleep-deprived. Several factors like stress, altered circadian cycle, medical conditions, etc. cause sleep deficiency. Almost 50-60 % of elderly population suffer from sleep disorders such as sleep apnea, restless legs syndrome, REM sleep behavior disorder, etc. Chronic sleep deprivation may further lead to the development of diseases such as Alzheimer's and Parkinson's. This paper reviews the prevalence of sleep disorders and consequences of sleep loss in young and old adults.

Loss of thyroid gland circadian PER2 rhythmicity in aged mice and its potential association with thyroid cancer development

Molecular clocks operate in peripheral tissues, including endocrine glands, and play important regulatory roles in this context. However, potential age-related changes in the expression rhythmicity of clock genes and the effects of these changes on the thyroid gland remain unknown. In the present study, we evaluated the expression rhythmicity of peripheral thyroid clock genes in aged mice using RNA-seq transcriptomic analysis in young (3.5-month) versus aged (20-month) mice. In addition, we determined the cellular effects of silencing of PER2, a major clock gene regulator, in human thyroid cell lines. Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway enrichment analysis revealed that differentially expressed genes (DEGs) in the thyroid glands of aged mice were involved in mitogen-activated protein kinase (MAPK) signaling, chemokine signaling, circadian entrainment, PI3K/AKT signaling, and Apelin signaling. The expression of circadian clock genes Arntl/Bmal1 was significantly downregulated in thyroid glands of aged mice, whereas the expression of genes involved in regulation of cell proliferation, migration, and tumorigenesis was upregulated. Peripheral thyroid clock genes, particularly Per mRNA and PER2 protein, were downregulated in the thyroid glands of aged mice, and circadian oscillation of these genes was declined. Knockdown of the circadian clock gene PER2 in human thyroid follicular cells induced AP-1 activity via JNK MAPK signaling activation, which increased cell proliferation. Furthermore, the aging-related loss of PER2 circadian oscillation activated the AP-1 transcription factor via the JNK MAPK pathway, which could contribute to thyroid hyperplasia, a common age-related condition.

Thyroid disease and hypothyroidism are associated with poor COVID-19 outcomes: A systematic review, meta-analysis, and meta-regression

BACKGROUND AND AIMS

Coronavirus disease (COVID-19) still becomes a global burden that affected people in different groups. The aim of this study was to evaluate the association between thyroid disease and the outcome of COVID-19 patients.

METHOD

This was a meta-analysis study from articles obtained through a systematic literature search to investigate the relationship between thyroid disease and COVID-19 outcomes. Composite poor outcomes comprised of severity, mortality, intensive care unit (ICU) admission, and hospitalization.

RESULTS

A total of 31339 patients from 21 studies included in this study. Thyroid disorder was associated with increased composite poor outcome (risk ratio (RR) 1.87 [95% confidence interval (CI) 1.53, 2.27], p < 0.001; I2 = 84%, p < 0.01), this included higher disease severity (RR 1.92 [1.40, 2.63], p < 0.05; I2 = 86%, p < 0.01), ICU admission (RR 1.61 [1.12, 2.32], p > 0.05; I2 = 32%, p < 0.05), mortality (RR 2.43 [1.44, 4.13], p < 0.05; I2 = 83%, p < 0.01), and hospitalization (RR 1.28 [1.17, 1.39], p < 0.05; I2 = 0%, p < 0.96). Meta-regression analysis indicated that age (p = 0.002) was a significant influence that affects the association. Also, the presence of unspecified thyroid disease (RR 1.91 [1.38, 2.65], p < 0.05; I2 = 81%, p < 0.01) and hypothyroidism (RR 1.90 [1.45, 2.55], p < 0.05; I2 = 85%, p < 0.01) during admission were associated with poor outcomes.

CONCLUSION

Thyroid abnormalities increased the risk of COVID-19 composite poor outcomes and were influenced by the patient's age. Abnormal thyroid and hypothyroidism, but not hyperthyroidism, were associated with poor COVID-19 outcomes.

Thyroid stimulating hormone levels and geriatric syndromes: secondary nested case-control study of the Mexican Health and Aging Study

PURPOSE

To determine the incidence of geriatric syndromes (GS) in community dwelling older adults with subclinical hypothyroidism.

METHODS

This is an analysis from the Mexican Health and Aging Study, of a subsample of 2089 subjects with TSH determination. From this last subsample, we included 1628 individuals with TSH levels in the subclinical range (4.5-10 µU/ml).

RESULTS

The multivariate analysis showed that when comparing data obtained from the 2012 wave with the 2015 wave results, there was a significant incidence of some GS such as falls (OR 1.79, CI 1.16-2.77, p = 0.0116), fatigue (OR 2.17, CI 1.40-3.38, p = 0.0348) and depression (OR 1.70, CI 1.06-2.71, p = 0.0246) among the subclinical hypothyroidism group.

CONCLUSION

This study showed a greater incidence of GS in subjects 50 years and older with sub-clinical hypothyroidism, when compared to those with normal thyroid function.

Deciphering the whale's secrets to have a long life

Whales are marine creatures known for their enormous size and that live in all the oceans on earth. One of the oldest known organisms is bowhead whales, which can survive up to 200 years, and similarly, other species of whales have shown a remarkable long lifespan. In addition to this, whales are highly resistant to cancer, a disease that is strongly related to aging and the accumulation of damage over time. These two characteristics make whales an interesting model to study and that can provide us with a track both to delay aging and to avoid pathologies associated with it, such as cancer. In the present work, we try to analyze different aspects of whales such as metabolism, hematological and biochemical characteristics, and properties of their genome and transcriptome in order to elucidate possible molecular mechanisms that evolution has provided to these aquatic mammals.

Prenatal Phthalates Exposure and Cord Thyroid Hormones: A Birth Cohort Study in Southern Taiwan

BACKGROUND

The regulation of thyroid hormones in the early stages of gestation plays a crucial role in the outcome of a pregnancy. Furthermore, thyroid hormones are fundamental for the fetal development of all organs, including endocrine hormone changes in uterus. Endocrine disrupting chemicals have been shown to have an effect on thyroid hormone homeostasis in newborns, which affects their later development. Few studies have proposed how phthalates could alter thyroid function through several mechanisms and the possible effects on thyroid hormone homeostasis of phthalates on pregnant women. However, the effects of cord blood phthalates and prenatal phthalate exposure on thyroid hormones in newborns remain unclear.

OBJECTIVES

We aim to follow up on our previous established subjects and determine the correlation between phthalate exposure and thyroid hormones in pregnant women and newborns.

MATERIALS AND METHODS

We recruited 61 pregnant women from the Obstetrics and Gynecology Department of a medical hospital in southern Taiwan and followed up. High performance liquid chromatography electrospray ionization tandem mass spectrometry (HPLC-ESI-MS/MS) was used to analyze urine samples for five phthalate metabolites. Serum levels of thyroid hormones were analyzed using electrochemoluminescence immunoassay (ECLIA) method. We used Spearman and Pearson correlation coefficients to evaluate the correlation between each phthalate metabolites in serum and the thyroid hormone levels in fetus and parturient. Finally, multiple logistic regression was used to explore the relationship between hormones and their corresponding phthalate metabolites in cord blood.

RESULTS

High MBP in cord blood was correlated with negative cord serum TSH in newborns (r = -0.25, p < 0.06). By using multiple linear regression after adjusting for potential confounders (gestational and maternal age), cord serum MBP levels showed a negative association with cord serum TSH (β = 0.217, p < 0.05), cord serum T₄ (β = 1.71, p < 0.05) and cord serum T₄ × TSH (β = 42.8, p < 0.05), respectively.

CONCLUSION

We found that levels of cord serum TSH and T₄ in newborns was significantly negatively associated with cord serum MBP levels after adjusting for significant covariate. The fall in TSH in newborns may potentially be delaying their development.

Treatment of subclinical hypothyroidism: assessing when treatment is likely to be beneficial

Introduction: Subclinical hypothyroidism (SCH) is a common condition diagnosed in up to 16% of the population. SCH is diagnosed when serum TSH is high and circulating thyroid hormones are within the reference range. SCH is considered to be a mild form of thyroid failure by some due to the log-linear relationship between TSH and thyroid hormones. Nevertheless, it is unclear whether the treatment of SCH with thyroid hormones is beneficial, and hence, it is not surprising that expert opinions and recommendations from societies differ in their opinions on how best to manage SCH.Areas covered: This article reviews the currently available evidence pertaining to SCH and provides recommendations as to when treatment of SCH should be considered. An electronic search of PubMed from 1970 to 2019 was performed and systematically reviewed studies assessing the effects of treatment in SCH. The main areas that are considered are the effects of treatment on symptoms and quality of life, and important clinical consequences including psychocognitive outcomes and cardiovascular events.Expert opinion: Treatment of SCH with thyroid hormones is debated and the current literature in this area lacks clarity. We provide an evidence-based recommendation for when treatment of SCH with thyroid hormones should be considered.

Prospective role of thyroid disorders in monitoring COVID-19 pandemic

COVID-19 pandemic has affected more than 200 countries and 1.3 million individuals have deceased within eleven months. Intense research on COVID-19 occurrence and prevalence enable us to understand that comorbidities play a crucial role in spread and severity of SARS-CoV-2 infection. Chronic kidney disease, diabetes, respiratory diseases and hypertension are among the various morbidities that are prevalent in symptomatic COVID-19 patients. However, the effect of altered thyroid-driven disorders cannot be ignored. Since thyroid hormone critically coordinate and regulate the major metabolism and biochemical pathways, this review is on the potential role of prevailing thyroid disorders in SARS-CoV-2 infection. Direct link of thyroid hormone with several disorders such as diabetes, vitamin D deficiency, obesity, kidney and liver disorders etc. suggests that the prevailing thyroid conditions may affect SARS-CoV-2 infection. Further, we discuss the oxidative stress-induced aging is associated with the degree of SARS-CoV-2 infection. Importantly, ACE2 protein which facilitates the host-cell entry of SARS-CoV-2 using the spike protein, are highly expressed in individuals with abnormal level of thyroid hormone. Altogether, we report that the malfunction of thyroid hormone synthesis may aggravate SARS-CoV-2 infection and thus monitoring the thyroid hormone may help in understanding the pathogenesis of COVID-19.

Depressive Symptoms are Associated with High Levels of Serum Low-Density Lipoprotein Cholesterol in Older Adults with Type 2 Diabetes Mellitus

Fundamento

O Diabetes Mellitus Tipo 2 (DMT2) é comum nos idosos, que também apresentam um nível elevado de fatores de risco para doenças cardiovasculares (DCVs), tais como dislipidemia. Entretanto, o papel da depressão nos pacientes com DMT2 e sua relação com fatores de risco para DCV são pouco estudados.

Objetivo

O objetivo do presente estudo foi investigar a relação entre sintomas depressivos (SDs) e fatores de risco cardiovascular conhecidos em idosos comunitários portadores de DMT2.

Métodos

Trata-se de um estudo transversal, no qual foram incluídos 85 idosos comunitários com DMT2. Os SDs foram avaliados através da Escala de Depressão Geriátrica de Yesavage, em versão reduzida (GDS-15). Os seguintes fatores de risco cardiovascular foram avaliados: pressão arterial sistólica (PAS) e diastólica (PAD), glicose plasmática em jejum (GPJ), perfil lipídico (triglicerídeos séricos (TG), colesterol total sérico (CT), colesterol sérico de lipoproteína de baixa densidade (LDL-C) e colesterol sérico de lipoproteína de baixa densidade (HDL-C)) e índice de massa corporal (IMC). A análise de regressão múltipla de Poisson foi utilizada para avaliar a associação entre os SDs e cada fator de risco cardiovascular ajustado por sexo, idade, tempo em atividades físicas moderadas e status funcional. O nível de significância adotado para a análise foi de 5%.

Resultados

Dentre todos os fatores de risco analisados, apenas o aumento de LDL-C apresentou uma correlação com níveis elevados de SD (RP=1,005; IC95% 1,002-1,008). Foi observada uma associação significativa entre os níveis de HDL-C (RP=0,99; IC95% 0,98-0,99) e a PAS (RP=1,009; IC95% 1,004-1,014).

Conclusão

Nos idosos com DMT2, a presença de SD foi associada a níveis de LDL-C, HDL-C e PAS, mesmo após o ajuste por sexo, idade, nível de atividade física e capacidade funcional. (Arq Bras Cardiol. 2020; 115(3):462-467)

Relationship between Thyroid and Kidney Function: Analysis from the Korea National Health and Nutrition Examination Survey Between 2013 and 2015

INTRODUCTION

Thyroid function is evaluated by thyroid stimulating hormone (TSH) and free thyroxine (fT4). Although many studies have indicated an intimate relationship between thyroid hormones and kidney functions, reports about the simultaneous evaluation of TSH and fT4 are rare.

OBJECTIVE

We aimed to analyze the association between TSH and kidney function, with emphasis on a potential nonlinear relationship, and identify an independent relationship between fT4 and kidney function.

METHODS

We reviewed the data of 7,061 subjects in the Korea National Health and Nutrition Examination Surveys who were randomly subsampled for thyroid function evaluation between 2013 and 2015. A total of 5,578 subjects were included in the final analysis, after excluding people <18 years old, and those with a short fasting time, abnormal fT4 levels, and thyroid disease or related medications. Creatinine-based estimated glomerular filtration rate (eGFR) was used to define kidney function.

RESULTS

A 1 mmol/L increase of logarithmic TSH was associated with decreased eGFR (β: -1.8; 95% CI -2.3 to -1.2; p < 0.001), according to multivariate linear regression analysis. On the multivariate generalized additive model plot, TSH demonstrated an L-shaped relationship with eGFR, showing a steeper slope for 0-4 mIU/L of TSH. A 1 µg/dL increase of fT4 was also associated with decreased eGFR (β: -7.0; 95% CI -0.94 to -4.7; p < 0.001) on the multivariate linear regression analysis; this association was reversed after adjusting for age. On the mediation analysis, the indirect effect via age and direct effect per 1 µg/dL increase of fT4 on eGFR was 9.9 (8.1 to 11.7, p < 0.001) and -7.1 (-9.3 to -4.8, p < 0.001), respectively.

CONCLUSIONS

Increased TSH was associated with decreased eGFR, particularly in the reference range. The direct effect of increased fT4 was decreased eGFR, which may be affected indirectly by age.

Association of endemic goitre and exceptional longevity in Sardinia: evidence from an ecological study

This study aims to test the hypothesis that a high prevalence of endemic goitre, considered as a proxy measure for subclinically reduced thyroid function in the population, is geographically associated with exceptional longevity. Using historical data available for 377 Sardinian municipalities in the first half of the twentieth century, we performed an ecological study to investigate the geographic distribution of goitre and its spatial association with demographic indicators of population longevity. This analysis was conducted by using both conventional ordinary least square and geographically weighted regression models to take into account spatial autocorrelation and included other longevity-associated factors previously identified in Sardinia. The spatial analysis revealed that the goitre rate (p < 0.0001), the proportion of inhabitants involved in pastoralism (p = 0.016), the terrain inclination (p = 0.008), and the distance from the workplace as a proxy for physical activity (p = 0.023) were consistently associated with population longevity at an aggregated level in the 377 municipalities. Within the limits of an ecological study design, our findings support the existence of a significant association between high goitre prevalence and increased probability to survive into old age. The present study confirms previous results and is consistent with animal studies and epidemiological surveys in other long-lived areas known as Blue Zones. Potential mechanisms underlying this association need to be further investigated.

Biological Aging Parameters Can Be Improved After Autologous Adipose-Derived Stem Cell Injection

Biological aging (BA) is a comprehensive assessment tool for elderly persons. The authors aimed to develop a rat model that can be used to assess BA by evaluating various blood, biochemical, and hormonal parameters and demonstrate that the intravenous administration of autologous adipose-derived stem cells (ADSCs) improves BA. Twelve elderly (aged 20 months) male Sprague-Dawley rats were used in this study and divided into 2 groups: autologous ADSC administration (n = 6) and saline administration (n = 6). The complete blood count, biochemical and hormonal parameters, and antioxidant potential were evaluated before harvesting the rat inguinal fat tissue and intravenous ADSC administration as well as at 1, 3, and 5 weeks after ADSC administration. Adipose-derived stem cells administration regulated blood content, biochemical parameters, renal function, and antioxidant enzymes in elderly rats. Furthermore, changes in several hormonal levels were identified in the ADSC administration group compared with the saline administration group. An assessment model of BA in elderly rats was successfully developed after the intravenous administration of autologous ADSCs. The authors suggest that intravenously injected ADSC treatment may be a valuable method to improve BA.

The Relationship Between Occupational Exposure to Low-dose Ionizing Radiation and Changes in Thyroid Hormones in Hospital Workers

BACKGROUND

The effects of ionized radiation on the thyroid have been extensively studied. However, most studies have focused on high-dose radiation received accidentally or through therapy, and few were on low-dose occupational exposure.

METHODS

Using a retrospective cohort study design, we collected health examination reports from employees who worked on jobs with occupational exposure to radiation at a hospital to evaluate possible changes in the serum thyroid hormones and determine whether there is a dose-response effect. After excluding those with diseases that may affect thyroid function and who were pregnant at any given examination during the study periods we followed the remaining 326 workers for 12 years and evaluated the associations between radiation exposure and changes in serum thyroid hormones using the generalized estimating equation for repeated measures. Data from an external comparison cohort were used to adjust for changes over time.

RESULTS

We observed declines in triiodothyronine (T3) and thyroxine (T4) over the study period, but not in thyroid-stimulating hormone (TSH). In addition, we found negative dose-response relationships between exposure duration and declines in the serum levels of T3 (a change of -0.037 ng/ml/year after adjusting for sex and age at the beginning of follow-up; 95% confidence interval [CI] = -0.042, -0.032 ng/ml/year) and T4 (-0.115 µg/dl/year; 95% CI = -0.140, -0.091 µg/dl/year). We also observed an increase in the TSH level (0.683 µIU/ml/year; 95% CI = 0.151, 1.214 µIU/ml/year) after the ninth year of follow-up.

CONCLUSIONS

We concluded that despite low exposure doses, occupational exposure to ionizing radiation in healthcare workers still may be associated with the declines in the serum levels of T3 and T4.

Metabolic Syndrome, Thyroid Function and Autoimmunity - The PORMETS Study

BACKGROUND

The prevalence of thyroid dysfunction and autoimmunity in the Portuguese population has not yet been estimated. However, the national prevalence of the metabolic syndrome remains high. The association of thyroid pathology with cardiovascular risk has been addressed but is still unclear. Our study aimed to evaluate the prevalence of thyroid dysfunction and autoimmunity and to assess the associations of thyroid-stimulating hormone and thyroid hormones and antibodies with metabolic syndrome, its components, and other possible determinants in a national sample.

MATERIAL AND METHODS

The present study included a subsample of 486 randomly selected participants from a nationwide cross-sectional study sample of 4095 adults. A structured questionnaire was administered on past medical history and socio-demographic and behavioural characteristics. Blood pressure and anthropometric measurements were collected, and the serum lipid profile, glucose, insulin, hs- CRP, TSH, FT4, FT3 and thyroid antibodies were measured.

RESULTS

In our sample, the prevalence of hypothyroidism, hyperthyroidism and undiagnosed dysfunction was 4.9%, 2.5% and 72.2%, respectively. Overall, the prevalence of positivity for the thyroid peroxidase and thyroglobulin antibodies was 11.9% and 15.0%, respectively. A positive association was found between free triiodothyronine and metabolic syndrome (OR: 2.019; 95% CI: 1.196, 3.410). Additionally, thyroid peroxidase antibodies had a negative association with metabolic syndrome (OR: 0.465; 95% CI: 0.236, 0.917) and its triglyceride component (OR: 0.321; 95% CI: 0.124, 0.836).

CONCLUSION

The prevalence of undiagnosed thyroid dysfunction and autoimmunity was high. Thyroid peroxidase antibodies were negatively associated with metabolic syndrome and its triglyceride component, whereas the free triiodothyronine level was positively associated with metabolic syndrome.

Prevalence of thyroid dysfunction in older Chinese patients with type 2 diabetes-A multicenter cross-sectional observational study across China

Type 2 diabetes [T2D] and thyroid dysfunction [TD] often co-occur, have overlapping pathologies, and their risk increases with age. Since 1995, universal salt iodization has been implemented in China to prevent disorders caused by iodine deficiency. However, after two decades of implementation of universal salt iodization, the prevalence of TD in elderly Chinese patients with T2D is not well described and may have been underestimated. We conducted a questionnaire-based survey across 24 endocrinology centers in China between December 2015 and July 2016. Demographic and clinical data from 1677 patients with T2D were obtained and analyzed to examine the prevalence of TD along with T2D in these patients. We assessed TD prevalence according to the four TD subtypes [subclinical hypothyroidism, clinical hypothyroidism, subclinical hyperthyroidism, and clinical hyperthyroidism], TD history, gender, and age. The diagnosis rates were calculated for TD and also for the TD subtype. The number of patients reaching treatment goals for T2D [hemoglobin A1c <7%] and TD [normal free thyroxine and thyroid-stimulating hormone [TSH]] and the incidences of complications and comorbidities were recorded. Among the enrolled patients with T2D [N = 1677], TD was diagnosed in 23.79% [399/1677] out of which 61% (245/399) were previously diagnosed and 38.59% (154/399) were newly diagnosed cases. Subclinical hypothyroidism, clinical hypothyroidism, subclinical hyperthyroidism, and clinical hyperthyroidism were reported in 4.89%, 9.3%, 1.13%, and 3.16% of the total population, respectively. Among patients previously diagnosed with TD, the incidence in women [166/795; 20.88%] was higher than in men [79/882; 8.96%]. The treatment goals for TD and T2D were attained in 39.6% [97/245] and 34.41% [577/1677] of the cases, respectively. Diabetic complications and comorbidities were reported in 99.7% of patients, with peripheral neuropathy being the most common [43.46%] followed by cataract [24.73%]. We had found that the incidences of dyslipidemia, elevated LDL levels, and osteoporosis were significantly higher in patients with TD than those without TD. TD is underdiagnosed in elderly Chinese patients with T2D.

Hypothyroidism in the older population

BACKGROUND

Both overt hypothyroidism as well as minor elevations of serum thyrotropin (TSH) levels associated with thyroid hormones within their respective reference ranges (termed subclinical hypothyroidism) are relatively common in older individuals. There is growing evidence that treatment of subclinical hypothyroidism may not be beneficial, particularly in an older person. These findings are relevant at a time when treatment with thyroid hormones is increasing and more than 10-15% of people aged over 80 years are prescribed levothyroxine replacement therapy.

MAIN BODY

The prevalence of hypothyroidism increases with age. However, the reference range for TSH also rises with age, as the population distribution of TSH concentration progressively rises with age. Furthermore, there is evidence to suggest that minor TSH elevations are not associated with important outcomes such as impaired quality of life, symptoms, cognition, cardiovascular events and mortality in older individuals. There is also evidence that treatment of mild subclinical hypothyroidism may not benefit quality of life and/or symptoms in older people. It is unknown whether treatment targets should be reset depending on the age of the patient. It is likely that some older patients with non-specific symptoms and incidental mild subclinical hypothyroidism may be treated with thyroid hormones and could potentially be harmed as a result. This article reviews the current literature pertaining to hypothyroidism with a special emphasis on the older individual and assesses the risk/benefit impact of contemporary management on outcomes in this age group.

CONCLUSIONS

Current evidence suggests that threshold for treating mild subclinical hypothyroidism in older people should be high. It is reasonable to aim for a higher TSH target in treated older hypothyroid patients as their thyroid hormone requirements may be lower. In addition, age-appropriate TSH reference ranges should be considered in the diagnostic pathway of identifying individuals at risk of developing hypothyroidism. Appropriately designed and powered randomised controlled trials are required to confirm risk/benefit of treatment of subclinical hypothyroidism in older people. Until the results of such RCTs are available to guide clinical management international guidelines should be followed that advocate a conservative policy in the management of mild subclinical hypothyroidism in older individuals.

Heart rate response to graded exercise test of elderly subjects in different ranges of TSH levels

OBJECTIVE

Life expectancy is increasing worldwide and studies have been demonstrating that elevated serum thyroid stimulating hormone (TSH) concentration in elderly is associated with some better health outcomes. This elevation is somewhat physiological as aging. The aim of this study was to investigate the heart rate (HR) response during a graded exercise test and its recovery in healthy elderly, comparing subjects within serum TSH in the lower limit of reference range to those within the TSH in the upper limit.

SUBJECTS AND METHODS

A cross-sectional study was conducted with 86 healthy elderly aged 71.5 ± 5.1 years, with serum TSH between 0.4 - 4.0 mUl/mL. The participants were divided into two groups according to TSH level: < 1.0 mUl/mL (n = 13) and ≥ 1.0 µUI/mL (n = 73). All participants performed an ergometric test on a treadmill. The HR was recorded and analyzed at rest, during exercise and during the three minutes immediately after exercise.

RESULTS

No differences were observed in relation to HR at peak of exercise (TSH < 1.0 µUI/mL: 133.9 ± 22.5 bpm vs. TSH ≥ 1.0 µUI/mL: 132.4 ± 21.3 bpm; p = 0.70) and during the first minute of recovery phase (TSH < 1.0 µUI/mL: 122.3 ± 23.1 bpm vs. TSH ≥ 1.0 µUI/mL: 115.7 ± 18.4 bpm p = 0.33). The groups also presented similar chronotropic index (TSH < 1.0 µUI/mL: 78.1 ± 30.6 vs. TSH ≥ 1.0 µUI/mL: 79.5 ± 26.4; p = 0.74).

CONCLUSION

In this sample studied, there were no difference between lower and upper TSH level concerning HR response during rest, peak of exercise and exercise recovery.

Hypothyroidism as a Predictor of Surgical Outcomes in the Elderly

There is a high prevalence of hypothyroidism in the elderly population, mainly among women. The most important cause is autoimmune thyroiditis, but also iodine deficiency, radioiodine ablation, and surgery may be responsible for hypothyroidism in elderly hospitalized patients. Thyroid-related symptoms are sometimes comparable to physiological manifestations of the aging process, and hypothyroidism may be related with many symptoms which can be present in critical patients, such as cognitive impairment, cardiovascular, gastrointestinal, and hematological alterations, and eventually myxedema coma which is a severe and life-threatening condition in older adults. Adequate thyroid hormone levels are required to achieve optimal outcomes from any kind of surgical intervention. However, only few randomized clinical trials investigated the association between non-thyroidal illness (or low-T3 syndrome), and adverse surgical outcomes, so far. The goal of this review is to discuss the role of thyroid function as a predictor of surgical outcomes in the elderly.

THE ENDOCRINOLOGY OF AGING: A KEY TO LONGEVITY "GREAT EXPECTATIONS"

ABBREVIATIONS

AMP = adenosine monophosphate CETP = cholesteryl ester transfer protein FOXO = Forkhead box O GH = growth hormone HDL = high-density lipoprotein IGF-1 = insulin-like growth factor 1 LDL = low-density lipoprotein miRNA = microRNA mTOR = mammalian target of rapamycin SIRT = sirtuin T4 = thyroxine TSH = thyroid-stimulating hormone "The Moving Finger writes; and, having writ, Moves on: nor all thy Piety nor Wit Shall lure it back to cancel half a Line, Nor all thy Tears wash out a Word of it." Omar Khayyam ( 1 ).

Association between Thyroid Function and Body Mass Index: A 10-Year Follow-Up

BACKGROUND/AIMS

We aimed to evaluate the association between change in thyroid function tests within the euthyroid range and body mass index (BMI) in persons with normal weight at baseline.

METHODS

This study investigated 1,100 normal-weight euthyroid persons in a population-based cohort study, Tehran Thyroid Study. BMI was calculated and serum concentrations of thyrotropin (TSH) and free T4 (FT4) were assayed at baseline and after 10 years of follow-up. We evaluated the relationship between thyroid and obesity based on 2 definitions for outcome: (1) a binary outcome as BMI <25 or ≥25 kg/m2, and (2) a multinomial outcome as normal BMI, overweight, and obese.

RESULTS

A total of 569 women and 531 men, aged 36.3 ± 13.5 years, were included. Modified Poisson regression analysis for binary outcome, after adjustment for age, sex, smoking, and anti-thyroid peroxidase antibody status, revealed a negative association between delta serum FT4 and follow-up BMI (relative risk 0.55 [95% CI 0.37-0.80]) without any significant association between change in serum TSH and follow-up BMI. However, in multinomial logistic regression analysis, we found no relationship between delta serum FT4 or TSH and follow-up BMI categories, for either overweight or obese vs. normal-weight participants.

CONCLUSIONS

In normal-weight euthyroid individuals, changes in serum concentrations of FT4, but not TSH, may contribute to change in body weight.

Inappropriate Suppression of Thyrotropin Concentrations in Young Patients with Thyroid Nodules Including Thyroid Cancer: The Fukushima Health Management Survey

BACKGROUND

Serum thyroid hormone concentration is regulated through the hypothalamic-pituitary-thyroid axis. This study aimed to clarify the relationships between thyroid hormone regulation and ultrasonographic findings in subjects with thyroid nodules detected during thyroid ultrasound examination for the Fukushima Health Management Survey.

METHODS

As of October 31, 2014, a total of 296,253 subjects, who had been living in Fukushima Prefecture at the time of the Fukushima nuclear power plant accident and were aged ≤18 years on March 11, 2011, participated in two concurrent screening programs. In the primary screening, thyroid nodules were detected in 2241 subjects. A secondary confirmatory thyroid ultrasound examination and blood sampling for thyroid function tests were performed on 2004 subjects. The subjects were reassessed and classified into disease-free subjects (Group 1), subjects with cysts only (Group 2), subjects with nodules (Group 3), and subjects with malignancy or suspected malignancy (Group 4). Serum concentrations of free triiodothyronine (fT3), free thyroxine (fT4), thyrotropin (TSH), thyroglobulin, and the fT3/fT4 ratio were classified according to the diagnoses.

RESULTS

Inverse relationships between age and log TSH values (Spearman's correlation r = -0.311, p = 0.015), serum fT3 concentration (r = -0.688, p < 0.001), and the fT3/fT4 ratio (r = -0.520, p < 0.001) were observed in Group 1. When analysis of covariance with Bonferroni post hoc comparisons was used in the four groups, the log TSH values were significantly lower in both Group 3 and Group 4 compared with Group 1 and Group 2 after correcting for age (p < 0.001; Group 1 vs. Group 3, p = 0.016; Group 1 vs. Group 4, p = 0.022; Group 2 vs. Group 3, p = 0.001; Group 2 vs. Group 4, p = 0.008). However, no significant differences were observed between the four groups regarding levels of fT3, fT4, fT3/fT4 ratio, and thyroglobulin (p = 0.304, 0.340, 0.208, and 0.583, respectively).

CONCLUSION

TSH suppression can be present in response to illness, including thyroid nodules, in young subjects. Low TSH levels may be associated with the finding of papillary thyroid cancer as well as with thyroid nodules in children and adolescents.

Anaesthetic Management of a Patient with Thyrotoxicosis for Nonthyroid Surgery with Peripheral Nerve Blockade

Thyrotoxicosis is a hypermetabolic condition caused by an elevation in thyroid hormone levels. The disorder has a variety of causes, manifestations, and therapies. Several clinical features of thyrotoxicosis are due to sympathetic stimulation with increased beta-adrenoreceptor upregulation and sensitization to catecholamine. Anaesthetic management of thyrotoxicosis patients using neuraxial block has been described in literature; however, to our knowledge, there are no reports of peripheral nerve block utilization. Here, we report on the anaesthetic management of a patient with thyroiditis-associated thyrotoxicosis undergoing emergency surgery via a femoral and sciatic nerve block.

Thermogenesis and longevity in mammals. Thyroxin model of accelerated aging

Development of experimental models of life span regulation is an important goal of modern gerontology. We proposed a thyroxin model of accelerated aging. Male Wistar rats at the age of 17 months received thyroxin in drinking water at a concentration of 6 mg/L for 2 months as a model of induced hyperthyroidism (IH). Administration of thyroxin resulted in a decrease in life span and a 2°C increase in body temperature that was accompanied by a 2 fold increase in thyroxin level and a 40% increase in triiodothyronine in blood serum. Induced hyperthyroidism can be used as a model of accelerated aging. We also found that thyroxin administration acts as uncoupler of oxidative phosphorylation as treatment was accompanied by an increase in the generation of superoxide radicals by 50%. Antioxidant enzyme activity remained unchanged (glutathione peroxidase, glutathione reductase mitochondrial) or was reduced (glutathione-S-transferase by 1.7 times) as compared with the control. The activity of glucose-6-transferase was increased by 2.8 times as compared with control, and malate dehydrogenase activity in liver increased by 6.8 times. Induced hyperthyroidism in rats resulted in distinct epigenotype which was accompanied by a decrease in life span.

Prevalence and risk factors of subclinical thyroid disease

Subclinical thyroid disease is defined biochemically by an abnormal thyrotropin (TSH) level and normal serum-free thyroxine level. The prevalence of this condition varies according to the reference range for TSH and geographic or demographic factors. Recently, several studies, including our community-based cohort studies, have reported on the incidence of subclinical thyroid disease in Korea. Using these studies, we reviewed the prevalence and risk factors of subclinical thyroid disease, focusing on subclinical hypothyroidism.