Thyroid antibody status, subclinical hypothyroidism, and the risk of coronary heart disease: an individual participant data analysis

Iodine-Induced Hypothyroidism and Long-Term Risks of Incident Heart Failure

Background Although most individuals can adapt to a large iodine load and remain euthyroid, hypothyroidism can develop after iodine exposure. Hypothyroidism is associated with adverse cardiovascular consequences, including heart failure. This study was performed to investigate the relationships between iodine-induced hypothyroidism and incident heart failure. Methods and Results This cohort study of the US Veterans Health Administration (1998-2021) included adults aged ≥18 years with a serum thyroid-stimulating hormone (thyrotropin) <60 days of iodine contrast administration, and <1 year of a baseline normal serum thyroid-stimulating hormone. Cox proportional hazards regression ascertained risk of incident heart failure following iodine-induced hypothyroidism, adjusting for age, sex, race and ethnicity, body mass index, and history of coronary heart disease, dyslipidemia, diabetes, and hypertension. Of 45 470 veterans (mean±SD age, 61.1±14.1 years; 88% men), 3361 (7.4%) developed iodine-induced hypothyroidism. Heart failure developed in 5685 (12.5%) individuals over a median follow-up of 3.6 years (interquartile range, 1.9-7.2 years). Adjusted for risk factors, iodine-induced hypothyroidism was associated with increased risk of heart failure, compared with those who remained euthyroid after iodine exposure (adjusted hazard ratio [HR], 1.11 [95% CI, 1.01-1.22]). Women were at greater risk than men (adjusted HR: women, 1.65 [95% CI, 1.13-2.40]; men, 1.08 [95% CI, 0.98-1.19]; P for interaction, 0.02). Conclusions In the largest US study of this topic, hypothyroidism following iodine exposure was associated with an increased risk of incident heart failure, particularly in women. These findings support the need for further research to address the clinical significance of this issue, including the possible sex-specific risks of incident heart failure in more diverse data sets and study populations.

Polycystic ovary syndrome and thyroid disorder: a comprehensive narrative review of the literature

Background

Published data on the relationship between polycystic ovary syndrome (PCOS) and thyroid dysfunction are sparse and confusing.

Objective

To comprehensively review data available in the literature regarding the relationship between PCOS and the thyroid function, and its abnormalities.

Methods

Nine main areas of interest were identified and analyzed according to the available evidence: 1) Evaluation of thyroid function for PCOS diagnosis; 2) Epidemiology data on thyroid function/disorders in patients with PCOS, and vice versa; 3) Experimental data supporting the relationship between thyroid function/disorders and PCOS; 4) Effects of thyroid function/disorders on PCOS features, and vice versa; 5) Effect of thyroid alterations on the cardiometabolic risk in women with PCOS; 6) Effect of thyroid abnormalities on reproductive outcomes in women with PCOS; 7) Relationship between thyroid function/abnormalities in patients with PCOS who are undergoing fertility treatment; 8) Effect of treatments for thyroid diseases on PCOS; and 9) Effect of treatments for PCOS on thyroid function. An extensive literature search for specific keywords was performed for articles published from 1970 to March 2023 using PubMed and Web of Science. Data were reported in a narrative fashion.

Results

PCOS is a diagnosis of exclusion for which diagnosis is possible only after excluding disorders that mimic the PCOS phenotype, including thyroid dysfunctions. However, the tests and the cutoff values used for this are not specified. Many experimental and clinical data suggest a relationship between perturbations of the thyroid function and PCOS. Direct and unequivocal evidence on the effects of thyroid function/disorders on PCOS features are lacking. High thyroid-stimulating hormone levels and subclinical hypothyroidism may be associated with significant worsening of several intermediate endpoints of cardiometabolic risk in women with PCOS. Thyroid abnormalities may worsen reproductive outcomes, especially in patients undergoing fertility treatment. To date, there are no data demonstrating the efficacy of thyroid medications on fertility and cardiometabolic risk in women with PCOS. Lifestyle modification changes, metformin, and vitamin D seem to improve thyroid function in the general population.

Conclusion

PCOS and thyroid disorders are closely related, and their coexistence may identify patients with a higher reproductive and metabolic risk. Regular screening for thyroid function and thyroid-specific autoantibodies in women with PCOS, particularly before and during pregnancy, is highly recommended.

Thyroid Hormones and Cardiometabolic Risk Factors in Saudi Women with Polycystic Ovary Syndrome: A Cross-Sectional Study

Objective

The PCOS-thyroid nexus has recently drawn the focus of various investigations due to the prevalence of thyroid problems in PCOS. Additionally, risk factors for cardiovascular disease (CVD) are more prevalent in PCOS women. Therefore, we aim to assess the levels of thyroid hormones in Saudi females with polycystic ovary syndrome (PCOS) and to examine the correlation between cardiometabolic risk factors (CMRFs) and thyroid hormones in PCOS patients.

Methods

A cross-sectional research with 200 PCOS-diagnosed female patients was conducted from April 2018 to April 2020. In addition to other anthropometric and serum biochemical markers, glycemic status, thyroid function test, lipid profiles, homocysteine, and C-reactive protein levels were detected in patients.

Results

In PCOS, hypothyroidism is more common than hyperthyroidism (55 vs 27.5%, p = 0.05). While women with raised TSH (hypothyroidism) had a higher BMI, WC, FBG, and poorer HDL-C (p< 0.05). Significant differences were found in LDL-C, TG, Homocysteine, and CRP levels (all p<0.001 and< 0.05). PCOS women with hypothyroidism at increased risk of CVD, as indicated by AIP (Atherogenic Index of plasma) (0.57±0.42) was found. The elevated TSH levels were favorably linked with TG, Homocysteine, CRP, BMI, AIP, and WC (all p< 0.001, 0.05) but negatively connected with HDL-C and FT4.

Conclusion

A strong relationship between PCOS and thyroid dysfunction was detected since PCOS hypothyroid groups had higher TSH levels and CMRFs. This group's CVD risk was elevated due to CRP, homocysteine, triglycerides, and obesity.

Subclinical hypothyroidism, outcomes and management guidelines: a narrative review and update of recent literature

Subclinical hypothyroidism (SCH) is diagnosed when serum thyroid stimulation hormone (thyrotropin; TSH) levels are above the reference range, accompanied by levels of free thyroxine within its reference range. The management of SCH remains a diagnostic and therapeutic challenge despite many years of research relating to its epidemiology, aetiology, effectiveness of treatment and safety. European Thyroid Association (ETA) guidelines for the management of SCH were published almost a decade ago. This narrative review summarizes the clinical literature relating to SCH and outcomes since the publication of these guidelines. Clinical evidence emerging during the previous decade generally supports the view that SCH is associated with adverse outcomes to an extent that is intermediate between euthyroidism and overt hypothyroidism although evidence that treatment with thyroid hormone replacement is beneficial is lacking. Accordingly, the rationale for the recommendations for intervention in the ETA guidelines based on the age of the patient, level of serum TSH, symptoms and comorbidities remains valid today.

Association of thyroid autoimmunity with the presence and severity of coronary atherosclerosis in patients undergoing coronary angiography

Studies on the association of thyroid autoimmunity with cardiometabolic risk and coronary artery disease (CAD) have produced conflicting results. This study aimed to investigate the relationship of thyroid autoimmune bodies (thyroid peroxidase antibody [TPOAb] and thyroglobulin antibody [TgAb]) with CAD in euthyroid subjects undergoing coronary angiography. A total of 307 subjects who underwent coronary angiography were included. The severity of coronary atherosclerosis was evaluated by using Gensini score. Serum TSH, total T3, total T4, TPOAb, TgAb, lipid levels et al were measured and compared between the groups with and without CAD. Logistic multivariate regression analysis were performed to assess the associations. Levels of thyroid hormones were comparable between the two groups. The positive percentage of anti-Tg antibodies was higher in non-CAD group (15.22% vs 7.91%, χ2 = 3.95, p = .047) while no significant difference was observed for anti-TPO antibodies (19.57% vs 17.21%, χ2 = 0.243, p = .622). The natural log-transformed Gensini score (ln (Gensini score)) was lower in the TgAb+ group (2.94 ± 1.11 vs 2.41 ± 1.18, P = .015). There was no significant difference for ln (Gensini score) between TPOAb- and TPOAb+ group (2.90 ± 1.14 vs 2.85 ± 1.09, P = .782). Logistical regression analysis revealed that positive TgAb was inversely associated with the presence of CAD (OR: 0.387, 95% CI: 0.157-0.952, p = .039) independent of other risk factors. The results showed that TgAb positivity might be an independent protective factor for CAD.

Update on subclinical thyroid dysfunction

Subclinical thyroid dysfunction is defined by serum thyroid-stimulating hormone (TSH) levels either greater or less than the reference range with normal thyroxine (T4) concentrations, and consists of subclinical hypothyroidism (SCH) and subclinical hyperthyroidism (SCHyper). For the proper diagnosis of SCH, it is most important to be able to correctly evaluate the serum TSH levels, which have numerous unique characteristics. We also need to be versed in TSH harmonization, which was recently launched world-wide. In this review, we will attempt to determine the best clinical approaches to the treatment of subclinical thyroid dysfunction based on recent guidelines published from several countries and novel findings of several recent large-scale clinical studies.

Metabolic Characteristics of Hashimoto's Thyroiditis Patients and the Role of Microelements and Diet in the Disease Management-An Overview

Hashimoto’s thyroiditis (HT) is the most common autoimmune disease and the leading cause of hypothyroidism, in which damage to the thyroid gland occurs due to the infiltration of lymphocytes. It is characterized by increased levels of antibodies against thyroid peroxidase and thyroglobulin. In this review, we present the metabolic profile, the effectiveness of micronutrient supplementation and the impact of dietary management in patients with HT. For this current literature review, the databases PubMed, Cochrane, Medline and Embase were reviewed from the last ten years until March 2022. This article provides a comprehensive overview of recent randomized controlled trials, meta-analyses, and clinical trials. Many patients with HT, even in the euthyroid state, have excess body weight, metabolic disorders, and reduced quality of life. Due to frequent concomitant nutritional deficiencies, the role of vitamin D, iodine, selenium, magnesium, iron and vitamin B12 is currently debated. Several studies have underlined the benefits of vitamin D and selenium supplementation. There is still no specific diet recommended for patients with HT, but a protective effect of an anti-inflammatory diet rich in vitamins and minerals and low in animal foods has been suggested. There is insufficient evidence to support a gluten-free diet for all HT patients. Pharmacotherapy, along with appropriate nutrition and supplementation, are important elements of medical care for patients with HT. The abovementioned factors may decrease autoantibody levels, improve thyroid function, slow down the inflammatory process, maintain proper body weight, relieve symptoms, and prevent nutritional deficiencies and the development of metabolic disorders in patients with HT.

The impact of the management strategies for patients with subclinical hypothyroidism on long-term clinical outcomes: An umbrella review

AIM

This umbrella review summarises and compares synthesised evidence on the impact of subclinical hypothyroidism and its management on long-term clinical outcomes.

METHODS

We conducted comprehensive searches on MEDLINE, EMBASE, Scopus, Web of Science, Cochrane Database of Systematic Reviews, JBI Evidence Synthesis, the PROSPERO register, Epistemonikos Database and PDQ Evidence from inception to February and July 2021 using keywords on subclinical hypothyroidism, treatment with levothyroxine, monitoring and primary outcomes (all-cause mortality, cardiovascular events, stroke, frailty fractures and quality of life). Only systematic reviews and meta-analyses on adult patient populations were considered. Study selection, data extraction and quality appraisal using AMSTAR-2 were done independently by two reviewers and discrepancies were resolved through discussion. Overlap across the selected reviews was also assessed, followed by a narrative synthesis of findings.

RESULTS

A total of 763 studies were identified from literature searches; 20 reviews met inclusion criteria. Methodological quality ratings were high (n = 8), moderate (n = 7), and low (n = 5), but no reviews were excluded on this basis. Though there was slight overlap across all reviews, some pairwise comparisons had high corrected covered area scores. Compared to euthyroidism, untreated subclinical hypothyroidism was associated with a higher risk of cardiovascular events or death if Thyroid Stimulating Hormone was above 10mIU/L at baseline. Treatment was associated with a lower risk of death from all causes for patients younger than 70 years and possibly better cognitive and quality of life scores than untreated individuals. Evidence on the risk of strokes and fractures was inconclusive.

CONCLUSION

In the long term, treatment of subclinical hypothyroidism may be beneficial for some patient groups. However, the findings of this review are negatively impacted by the relative sparseness and poor quality of available evidence. Additional large and adequately powered studies are needed to investigate this topic further.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO (CRD42021235172).

Vitamin B12 (Cobalamin) Deficiency in Overt and Subclinical Primary Hypothyroidism

Background:

B12 (cobalamin) deficiency has been reported in hypothyroid patients with variable prevalence rates thus routine screening of hypothyroid patients was recommended by some and discouraged by others. We aimed to assess the prevalence of B12 deficiency among hypothyroid patients and to evaluate for pernicious anemia and celiac disease as etiologies.

Methods:

A total 133 patients were included. Thyroid hormones and thyroid peroxidase (TPO) autoantibodies were measured. Serum B12 was measured and if deficient, intrinsic factor antibodies (IFAB) and tissue transglutaminase (tTG) antibodies were evaluated.

Results:

Our study included 45 patients with overt hypothyroidism (OH), 48 patients with subclinical hypothyroidism (SCH), and 40 patients as controls. Mean age was 34.3 years and 82% were females. TPO antibodies were positive in 73.5% of OH and 51.1% of SCH patients. B12 deficiency was detected in 33.3%, 47.9%, and 37.5% of OH, SCH, and controls, respectively with no significant difference (P = .334). Borderline-to-low B12 level was more prevalent in the OH and the SCH groups compared to controls (68.9%, 85.4%, and 57.5%, respectively; P = .014). Among B12-deficient hypothyroid patients, 7.5% had positive IFAB and 13.3% had positive tTG antibodies. We did not find a significant association of TPO positivity and B12 deficiency (OR, 0.69; 95% CI 0.3-1.57; P = .147).

Conclusion:

We did not find a higher prevalence of B12 deficiency among hypothyroid patients nor an association with TPO positivity. Borderline B12 levels were more prevalent among hypothyroid patients.

Subclinical hypothyroidism in older individuals

Subclinical hypothyroidism, which is defined as a thyroid-stimulating hormone concentration higher than the reference range (generally 4·5 mIU/L or higher) with normal free thyroxine concentrations, is frequently found in older individuals. International guidelines differ in recommendations for management of subclinical hypothyroidism in older individuals. We assessed published data during the past decade on the clinical significance and treatment of subclinical hypothyroidism in individuals aged 65 years and older. Meta-analyses, randomised clinical trials, and cohort studies are discussed in this narrative Review. Studies showed no significantly increased incidence in adverse cardiovascular, musculoskeletal, or cognitive outcomes in individuals aged 65 years or older when serum thyroid-stimulating hormone concentration was 4·5-7·0 mIU/L versus a euthyroid group. Moreover, in older individuals with subclinical hypothyroidism, symptoms of hypothyroidism and cardiac and bone parameters did not improve after levothyroxine treatment. These data suggest that treatment with levothyroxine should be considered for individuals aged 65 years or older with subclinical hypothyroidism when thyroid-stimulating hormone concentration is persistently 7 mIU/L or higher and to not initiate treatment with thyroid-stimulating hormone concentrations of less than 7 mIU/L. Levothyroxine doses should be personalised according to age, comorbidities, and life expectancy.

Determinants and Clinical Implications of Thyroid Peroxidase Antibodies in Middle-Aged and Elderly Individuals: The Rotterdam Study

Background: Thyroid peroxidase antibodies (TPO-Abs) play an important role in autoimmune thyroid disease, but are also prevalent in healthy individuals. However, it is unclear what determinants may influence the occurrence of TPO-Abs in healthy individuals and how TPO-Abs may affect health outcomes in these individuals. We aimed to identify determinants of TPO-Abs in a large, prospective population-based cohort of middle-aged and elderly individuals and to subsequently assess the association between TPO-Abs and risk of overall and cause-specific mortality. Methods: We performed binomial and multinomial logistic regression analyses to obtain odds ratios (ORs) and 95% confidence intervals [95% CIs] for the association of potential determinants based on previous literature with TPO-Ab positivity (>35 kU/L), TPO-Ab detectability (>5 kU/L), and TPO-Ab categories. Cox proportional hazards regression analyses were performed to obtain hazard ratios (HRs) and CIs for the association between TPO-Abs and mortality risk. Results: In 9685 participants (57% women, median baseline age 63.3 years, median follow-up time 10.1 years), we identified female sex (OR = 2.47 [CI 2.13-2.86]) and current smoking (OR = 3.10 [CI 2.66-3.62]) as determinants of TPO-Ab positivity and TPO-Ab detectability, respectively. Higher age (OR = 0.98 [CI 0.97-0.98]) and all categories of alcohol consumption (ORs ranging from 0.71-0.78) were associated with lower odds of TPO-Ab detectability. TPO-Ab detectability was associated with a higher risk of overall (HR = 1.09 [CI 1.01-1.17]), cancer-related (HR = 1.18 [CI 1.01-1.38]), and cardiovascular mortality (HR = 1.21 [CI 1.01-1.45]). Interestingly, this was more prominent in men compared with women (HR for cardiovascular mortality 1.50 vs. 0.99, respectively). Conclusions: In community-dwelling middle-aged and elderly individuals, female sex and current smoking are the most important determinants associated with TPO-Ab levels in the detectable and positive range, whereas alcohol consumption is associated with lower odds of TPO-Abs. The clinical importance of detectable TPO-Ab levels is illustrated by the association with an increased mortality risk, mainly in men. Our results warrant further exploration of the clinical applicability of detectable TPO-Ab levels, potentially as a marker for low-grade inflammation. The Rotterdam Study has been entered into the Netherlands National Trial Register (NTR; www.trialregister.nl) and into the WHO International Clinical Trials Registry Platform (ICTRP; www.who.int/ictrp/network/primary/en/) under shared catalogue number NTR6831.

Incidence of thyroid diseases: Results from the Brazilian Longitudinal Study of Adult Health (ELSA-Brasil)

OBJECTIVE

To evaluate incidence of subclinical and overt hyperthyroidism and hypothyroidism.

METHODS

The Brazilian Longitudinal Study of Adult Health (ELSA-Brasil) is a prospective cohort study of 15,105 civil servants, examined at baseline and over a 4-year follow-up. This analysis included 9,705 participants with normal thyroid function at baseline, follow-up information about thyroid function and with no report of using drugs that may interfere in the thyroid function. Thyroid function was defined by TSH/FT4 levels or routine use of thyroid hormones/anti-thyroid medications. Annual and cumulative (over 4-year) incidence rates were presented as percentages (95% Confidence Intervals).

RESULTS

The incidence of all overt and subclinical thyroid disease was 6.7% (1.73%/year): 0.19% for overt hyperthyroidism (0.048%/year), 0.54% for subclinical hyperthyroidism (0.14%/year), 1.98% for overt hypothyroidism (0.51%/year), and 3.99% for subclinical hypothyroidism (1.03%/year). The incidence of all thyroid diseases was higher in women, when compared to men, with a low women:men ratio (1.36). For Blacks the highest incidence was for overt hyperthyroidism, while for Whites, the highest incidence was for overt hypothyroidism. However, the highest incidence of overt hyperthyroidism was detected in Asian descendants. The presence of antithyroperoxidase antibodies at baseline was associated with higher incidence of overt thyroid diseases.

CONCLUSION

These results showed a high incidence of hypothyroidism, which is compatible with a country with a more-than-adequate iodine intake. The low women:men ratio of the incidence of thyroid dysfunction highlights the importance of the diagnosis of thyroid diseases among men in Brazil.

Women with Subclinical Hypothyroidism are at Higher Prevalence of Metabolic Syndrome and Its Components Compared to Men in an Older Chinese Population

Purpose: This study investigated the impact of sex differences on the relationship of subclinical hypothyroidism (SCH) with the prevalence of metabolic syndrome (MetS) and its components in an older Chinese population.Methods: The study included 1842 older Chinese individuals aged 65 years or older who received annual health checkups. The impact of sex differences on the relationship of SCH with the prevalence of MetS and its components was investigated by multivariate logistic regression analysis. Interaction effect between sex and SCH on the prevalence of MetS and its components were evaluated using a multivariate logistic regression model which includes interaction terms (sex-SCH).Results: The study comprised 1701 (92.3%) individuals with euthyroidism and 141 (7.7%) with SCH. In men, SCH was not associated with MetS or any components of the MetS. In women, the SCH group had higher prevalence of MetS [odds ratio (OR), 1.870; 95% confidence interval (CI), 1.136-3.079], abdominal obesity (OR, 1.693; 95% CI, 1.043-2.748), hypertriglyceridemia (OR, 1.711; 95% CI, 1.054-2.775) and low high-density lipoprotein cholesterol (HDL-C) (OR, 3.039; 95% CI, 1.576-5.861). There was an interaction between sex and SCH in terms of the effect on the prevalence of MetS and its components, including abdominal obesity and hypertriglyceridemia (P < .01 for all), and with a trend for low HDL-C (P = .098).Conclusion: There were sex differences in the correlation of SCH with the prevalence of MetS and its components in the older Chinese population. An interaction effect between sex and SCH on the prevalence of MetS and its components was found.

[Autoimmune thyroid disease]

Autoimmune thyroiditis (AIT) is not only one of the most prevalent human autoimmune diseases, but also the most frequent cause of primary hypothyroidism. It is characterized by lymphocytic infiltration of the thyroid gland with subsequent gradual destruction and fibrous replacement of thyroid tissue. Genetic predisposition, epigenetic modifications and environmental factors are suspected as disease triggers. Signs and symptoms of hypothyroidism include fatigue, bradycardia, constipation and cold intolerance. In subclinical hypothyroidism, symptoms may be absent. The diagnosis of AIT is based on the presence of antibodies against thyroid specific antigens, primarily anti-thyroid peroxidase antibodies and on a sonographically proven reduced echogenicity of the thyroid parenchyma. The diagnosis of concomitant hypothyroidism is primarily based on clinical signs and symptoms as well as measurement of thyroid-stimulating hormone (TSH)-concentration. Subclinical hypothyroidism is characterized by elevated TSH with normal serum free thyroxine (fT₄) and triiodothyronine (fT₃) levels, while in manifest hypothyroidism serum fT₄ and fT₃ levels are reduced. Levothyroxine (LT₄) treatment in subclinical hypothyroidism is a controversy in the scientific literature and should be discussed individually. It not only depends on the level of TSH-elevation, but also on other factors, such as patient age, presence of comorbidities and clinical symptoms of hypothyroidism. In contrast, overt hypothyroidism and subclinical hypothyroidism with a TSH-level > 10 mIU/L is a strong indication for LT₄ administration, aiming at rapid achievement of euthyroidism. In patients with dissatisfaction due to persistence of symptoms despite optimal LT₄-treatment LT₄/T₃-combination therapy should be considered, based on expert opinion.

Subclinical Hypothyroidism: Prevalence, Health Impact, and Treatment Landscape

Subclinical hypothyroidism (sHypo) is defined as normal serum free thyroid hormone levels coexisting with elevated serum thyroid-stimulating hormone (TSH) levels. sHypo is a common condition observed in clinical practice with several unique features. Its diagnosis should be based on an understanding of geographic and demographic differences in biochemical criteria versus a global reference range for TSH that is based on the 95% confidence interval of a healthy population. During the differential diagnosis, it is important to remember that a considerable proportion of sHypo cases are transient and reversible in nature; the focus is better placed on persistent or progressive forms, which mainly result from chronic autoimmune thyroiditis. Despite significant evidence documenting the health impacts of sHypo, the effects of levothyroxine treatment (LT4-Tx) in patients with sHypo remains controversial, especially in patients with grade 1 sHypo and older adults. Existing evidence suggests that it is reasonable to refrain from immediate LT4-Tx in most patients if they are closely monitored, except in women who are pregnant or in progressive cases. Future research is needed to further characterize the risks and benefits of LT4-Tx in different patient cohorts.

Relationship of TSH Levels with Cardiometabolic Risk Factors in US Youth and Reference Percentiles for Thyroid Function

CONTEXT

Thyroid hormones play an important role in metabolic homeostasis, and higher levels have been associated with cardiometabolic risk.

OBJECTIVE

To examine the association of cardiometabolic risk factors with TSH levels in US youth.

METHODS

Cross-sectional study of youth aged 12 to 18 years without known thyroid abnormalities from 5 National Health and Nutrition Examination Survey cycles (n = 2818) representing 15.4 million US children. Subclinical hypothyroidism (SH) was defined as thyrotropin (TSH) levels of 4.5 to 10 mIU/L. Assessed cardiometabolic risk factors include abdominal obesity (waist circumference >90th percentile), hypertriglyceridemia (triglyceride ≥130 mg/dL), low high-density lipoprotein cholesterol (<40 mg/dL), elevated blood pressure (systolic and diastolic blood pressure ≥90th percentile), hyperglycemia (fasting blood glucose ≥100 mg/dL, or known diabetes), insulin resistance (homeostatic model for insulin resistance > 3.16), and elevated alanine transferase (≥ 50 for boys and ≥44 U/L for girls). Age and sex- specific percentiles for thyroid parameters were calculated.

RESULTS

In this cohort of youth (51.3% male), 31.2% had overweight/obesity. The prevalence of SH was 2.0% (95% CI 1.2-3.1). The median TSH levels were higher in youth with overweight/obesity (P < 0.001). Adjusting for age, sex, race/ethnicity, and obesity, youth with TSH in the fourth quantile had higher odds of abdominal obesity (OR 2.53 [1.43-4.46], P = .002), insulin resistance (OR 2.82 [1.42-5.57], P = .003), and ≥2 cardiometabolic risk factors (CMRF) (OR 2.20 [1.23-3.95], P = .009).

CONCLUSION

The prevalence of SH is low in US youth. The higher odds of insulin resistance and cardiometabolic risk factors in youth with TSH levels >75th percentile requires further study.

Relation of Gut Microbes and L-Thyroxine Through Altered Thyroxine Metabolism in Subclinical Hypothyroidism Subjects

Thyroxine metabolism is an important topic of pathogenesis research and treatment schedule of subclinical hypothyroidism (SCH). L-Thyroxine replacement therapy (LRT) is usually recommended for severe SCH patients only. Our previous studies reported that disordered serum lipid of mild SCH people could also benefit from LRT. However, the benefits were different among individuals, as shown by the variations in drug dosage that required to maintain thyroid-stimulating hormone (TSH) stability. Alternative pathways, such as sulfation and glucuronidation of iodothyronine, may play a role in thyroid hormones metabolism in peripheral tissues aside from thyroid. Conjugated thyroxine can be hydrolyzed and reused in tissues including gastrointestinal tract, in which gut microbiota are one of the most attractive physiological components. On this site, the roles of gut microbiota in thyroidal metabolism should be valued. In this study, a cross-sectional study was performed by analyzing 16S rDNA of gut microbiota in mild SCH patients treated with L-thyroxine or not. Subjects were divided by serum lipid level, L-thyroxine treatment, or L-thyroxine dosage, respectively. Relationship between gut microbiome and serum profile, L-thyroxine treatment, and dose were discussed. Other metabolic disorders such as type 2 diabetes and hypertension were also taken into consideration. It turned out that microbiome varied among individuals divided by dose and the increment of L-thyroxine but not by serum lipid profile. Relative abundance of certain species that were associated with thyroxine metabolism were found varied among different L-thyroxine doses although in relatively low abundance. Moreover, serum cholesterol may perform relevance effects with L-thyroxine in shaping microbiome. Our findings suggested that the differences in L-thyroxine dosage required to maintain TSH level stability, as well as the SCH development, which was displayed by the increased L-thyroxine doses in subsequent follow-up, had relationship with gut microbial composition. The reason may due to the differences in thyroxine metabolic capacity in gut. In addition, the metabolic similarity of iodothyronines and bile acid in gut also provides possibilities for the correlation between host's thyroxine and cholesterol levels. This study was registered with ClinicalTrials.gov as number NCT01848171.

Sex differences in subclinical hypothyroidism and associations with metabolic risk factors: a health examination-based study in mainland China

BACKGROUND

The association between subclinical hypothyroidism (SCH) and metabolic risk factors in the general health examination-based population has been widely explored. However, the results have been inconclusive. Additionally, the sex differences in the prevalence of SCH and the association of SCH with metabolic risk factors remain unknown.

METHODS

We conducted this cross-sectional study using data from health examination-based participants between June 2016 and April 2018 in our health examination centre. Sex differences SCH and the association of SCH with metabolic risk factors were explored.

RESULTS

The total prevalence of SCH was 3.40% among the 5319 included participants, and 4.90% among the 2306 female participants, which was much higher than the prevalence of 2.26% among the 3013 male participants (p < 0.05). In males, the difference between participants younger than 60 and aged 60 or older was not significant (p = 0.104); while in females, the difference between participants younger than 40 and participants aged 40 or older was statistically significant (p = 0.023). Multivariate logistic regression analysis demonstrated that age (OR = 0.568, p = 0.004), body-mass index (BMI) (OR = 5.029, p < 0.001) and systolic/diastolic blood pressure (SBP/DBP) (OR = 5.243, p < 0.001) were independent predictors of SCH in females, but no metabolic risk factor was significantly associated with SCH in males. Further analysis revealed that the prevalence was much higher in participants with one or two metabolic risk factors than in those with no above metabolic risk factors regardless of age (p < 0.01).

CONCLUSIONS

Our study demonstrates that high BMI and/or high blood pressure are associated with SCH in female participants, and the prevalence of SCH among women with one or two metabolic risk factors ranges from 7.69-14.81%, which indicates that in such a population, serum concentrations of TSH and FT4 may be routinely screened in mainland China. Certainly, prospective, large-scale studies with long follow-up period are still necessary to further verify our results.

Hematological Indexes Can Be Used to Predict the Incidence of Hypothyroidism in Nasopharyngeal Carcinoma Patients after Radiotherapy

Background

This study explored the relationship between thyroid-associated antibodies, immune cells, and hypothyroidism to establish a predictive model for the incidence of hypothyroidism in patients with nasopharyngeal carcinoma (NPC) after radiotherapy.

Methods

A total of 170 patients with NPC treated at the Cancer Hospital of University of Chinese Academy of Sciences between January 2015 and August 2018 were included. The complete blood count, biochemical, coagulation function, immune cells, and thyroid-associated antibodies tested before radiotherapy were evaluated. A logistic regression model was performed to elucidate which hematological indexes were related to hypothyroidism development. A predictive model for the incidence of hypothyroidism was established. Internal verification of the multifactor model was performed using the tenfold cross-validation method.

Results

The univariate analysis showed that immune cells had no statistically significant differences among the patients with and without hypothyroidism. Sex, N-stage, antithyroid peroxidase antibody (TPO-Ab), antithyroglobulin antibody (TG-Ab), thyroglobulin (TG), and fibrinogen (Fb) were associated with hypothyroidism. Males and early N-stage were protective factors of thyroid function, whereas increases in TPO-Ab, TG-Ab, TG, and Fb counts were associated with an increased rate of hypothyroidism incidence. The multivariate analysis showed that TPO-Ab, TG-Ab, TG, and Fb were independent predictors of hypothyroidism. The comprehensive effect of the significant model, including TPO-Ab, TG-Ab, TG, and Fb counts, represented the optimal method of predicting the incidence of radiation-induced hypothyroidism (AUC = 0.796). Tenfold cross-validation methods were applied for internal validation. The AUCs of the training and testing sets were 0.792 and 0.798, respectively.

Conclusion

A model combining TPO-Ab, TG-Ab, TG, and Fb can be used to screen populations at a high risk of developing hypothyroidism after radiotherapy.

Levothyroxine for the Treatment of Subclinical Hypothyroidism and Cardiovascular Disease

Subclinical hypothyroidism is a biochemical condition defined by elevated serum thyroid-stimulating hormone levels in the setting of normal levels of the peripheral thyroid hormones, thyroxine and triiodothyronine. Thyroid hormones act on the heart through various mechanisms and subclinical hypothyroidism has been associated with risk factors for cardiovascular disease, such as hypertension and dyslipidemia. In addition, evidence from multiple studies supports an association between subclinical hypothyroidism and cardiovascular disease. However, the use of levothyroxine in subclinical hypothyroidism to reduce cardiovascular disease risk is not clearly beneficial. Treatment with levothyroxine may only provide benefit in certain subgroups, such as patients who are younger or at higher risk of cardiovascular disease. At present, most of the international societal guidelines advise that treatment decisions should be individualized based on patient age, degree of serum thyroid-stimulating hormone (TSH) elevation, symptoms, cardiovascular disease (CVD) risk, and other co-morbidities. Further study in this area is recommended.

Thyroid disease and the metabolic syndrome

PURPOSE OF REVIEW

To summarize recent developments in the association of thyroid function with metabolic syndrome (MetS).

RECENT FINDINGS

Although thyroid hormones even within low normal range are associated with various metabolic abnormalities, the risk of MetS remains a controversial issue. Hyperthyroid state might be associated only with insulin resistance and dysglycemia. Autoimmune thyroid diseases may be a potential risk factor for metabolic abnormalities even in those with low normal thyroid function.

SUMMARY

The interrelation between thyroid stimulating hormone, free T3, freeT4 and metabolic parameters is complex and might be affected by age, sex, BMI, insulin resistance, smoking, iodine intake and inflammatory markers.

Hypothyroidism in Context: Where We've Been and Where We're Going

Hypothyroidism affects up to 5% of the general population, with a further estimated 5% being undiagnosed. Over 99% of affected patients suffer from primary hypothyroidism. Worldwide, environmental iodine deficiency is the most common cause of all thyroid disorders, including hypothyroidism, but in areas of iodine sufficiency, Hashimoto’s disease (chronic autoimmune thyroiditis) is the most common cause of thyroid failure. Hypothyroidism is diagnosed biochemically, being overt primary hypothyroidism defined as serum thyroid-stimulating hormone (TSH) concentrations above and thyroxine concentrations below the normal reference range. Symptoms of hypothyroidism are non-specific and include mild to moderate weight gain, fatigue, poor concentration, depression, and menstrual irregularities, while the consequences of untreated or under-treated hypothyroidism include cardiovascular disease and increased mortality. Levothyroxine has long been the main tool for treating hypothyroidism and is one of the world’s most widely prescribed medicines. In adults with overt hypothyroidism, levothyroxine is usually prescribed at a starting dose of 1.6 µg/kg/day, which is then titrated to achieve optimal TSH levels (0.4–4.0 mIU/L), according to the therapeutic target. We here summarise the history of levothyroxine and discuss future issues regarding the optimal treatment of hypothyroidism. Because nearly one-third of patients with treated hypothyroidism still exhibit symptoms, it is important that levothyroxine is used more appropriately to achieve maximum benefit for patients. In order to ensure this, further research should include more accurate assessments of the true prevalence of hypothyroidism in the community, optimisation of the levothyroxine substitution dose, proper duration of treatment, and identification of patients who may benefit from combination therapy with levothyroxine plus levotriiodothyronine.

Funding: Merck.

Plain Language Summary: Plain language summary available for this article.

Hypothyroidism is one of the most common diseases worldwide, and levothyroxine is the usual medication prescribed to manage it. Hypothyroidism occurs when the thyroid gland, located in the neck, does not produce enough thyroid hormone for the body’s requirements. This can result in heart disease, infertility, and poor brain development in children. People with hypothyroidism may have changes in body weight, and feel tired, weak or unhappy, all of which can reduce their quality of life. In underdeveloped parts of the world, the main reason why people develop hypothyroidism is that they not getting enough iodine from food. Thus, many countries try to increase iodine intake by adding iodine to salt. In areas of the world where people ingest enough iodine, the most common cause of hypothyroidism is Hashimoto’s disease. This is an autoimmune disease in which the person’s immune system produces cells and antibodies that attack the thyroid gland. Most people with hypothyroidism will need to take levothyroxine for a long time, perhaps even for the rest of their lives. Levothyroxine replaces the person’s levels of thyroid hormone and makes them feel better, but the dose often needs to be adjusted for the best effect. In addition, many people with hypothyroidism do not know they have it. Research is ongoing to ensure that more people with hypothyroidism are diagnosed and are given effective treatment, and to work out the best way to use levothyroxine so that patients get the best results.

Associations of Elevated Antithyroperoxidase Antibodies with Thyroid Function, Survival, Functioning, and Depressive Symptoms in the Oldest Old: The Leiden 85-plus Study

Background: Elevated levels of antithyroperoxidase antibodies (TPOAbs) have been associated with progression of subclinical thyroid dysfunction, extrathyroidal diseases, and decrease in functional status. However, TPOAb as determinant of future thyroid dysfunction and other clinical outcomes has not been studied well for adults aged 85 years and over. This study aimed to assess associations of TPOAb levels with thyroid function, survival, physical function, disability in activities of daily living (ADL), cognitive function, and depressive symptoms in the oldest old. Methods: Data from a population-based cohort study (Leiden 85-plus Study) of residents of Leiden, the Netherlands, aged 85 and older were used. Baseline serum TPOAb levels were available for 488 participants (82% of the total cohort). We considered levels ≥35 IU/mL as elevated. Thyroid function (thyrotropin [TSH] and free thyroxine) was assessed at age 85 (baseline), 87, and 88 years. Survival, physical function, disability in ADL, cognitive function, and depressive symptoms were assessed from age 85 through 90 years. Results: At baseline, 64 of the 85-year old participants (13.1%) had elevated TPOAb levels. They were more often female, had higher TSH levels, and a higher prevalence of overt or subclinical hypothyroidism than participants with normal TPOAb levels. Over time, elevated TPOAb levels were independently associated with a lower mortality risk (hazard ratio 0.72, [95% confidence interval 0.53-0.99]), but were not associated with changes in thyroid function, nor with physical function, disability in ADL, cognitive function, or depressive symptoms. Conclusions: In community-dwelling oldest old, elevated TPOAb levels are cross-sectionally associated with higher TSH levels. Over time, elevated TPOAb levels are associated with a survival benefit but are not associated with changes in thyroid function, functional status, or depressive symptoms in old age. The added clinical value of TPOAb tests in oldest old persons with thyroid dysfunction is limited.

Subclinical Hypothyroidism: A Review

IMPORTANCE

Subclinical hypothyroidism, defined as an elevated serum thyrotropin (often referred to as thyroid-stimulating hormone, or TSH) level with normal levels of free thyroxine (FT4) affects up to 10% of the adult population.

OBSERVATIONS

Subclinical hypothyroidism is most often caused by autoimmune (Hashimoto) thyroiditis. However, serum thyrotropin levels rise as people without thyroid disease age; serum thyrotropin concentrations may surpass the upper limit of the traditional reference range of 4 to 5 mU/L among elderly patients. This phenomenon has likely led to an overestimation of the true prevalence of subclinical hypothyroidism in persons older than 70 years. In patients who have circulating thyroid peroxidase antibodies, there is a greater risk of progression from subclinical to overt hypothyroidism. Subclinical hypothyroidism may be associated with an increased risk of heart failure, coronary artery disease events, and mortality from coronary heart disease. In addition, middle-aged patients with subclinical hypothyroidism may have cognitive impairment, nonspecific symptoms such as fatigue, and altered mood. In the absence of large randomized trials showing benefit from levothyroxine therapy, the rationale for treatment is based on the potential for decreasing the risk of adverse cardiovascular events and the possibility of preventing progression to overt hypothyroidism. However, levothyroxine therapy may be associated with iatrogenic thyrotoxicosis, especially in elderly patients, and there is no evidence that it is beneficial in persons aged 65 years or older.

CONCLUSIONS AND RELEVANCE

Subclinical hypothyroidism is common and most individuals can be observed without treatment. Treatment might be indicated for patients with subclinical hypothyroidism and serum thyrotropin levels of 10 mU/L or higher or for young and middle-aged individuals with subclinical hypothyroidism and symptoms consistent with mild hypothyroidism.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, the National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in 3 cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in 3 broad areas: (1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; (2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and (3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.

Thyroid and Cardiovascular Disease: Research Agenda for Enhancing Knowledge, Prevention, and Treatment

Thyroid hormones have long been known to have a range of effects on the cardiovascular system. However, significant knowledge gaps exist concerning the precise molecular and biochemical mechanisms governing these effects and the optimal strategies for management of abnormalities in thyroid function in patients with and without preexisting cardiovascular disease. In September 2017, The National Heart, Lung, and Blood Institute convened a Working Group with the goal of developing priorities for future scientific research relating thyroid dysfunction to the progression of cardiovascular disease. The Working Group reviewed and discussed the roles of normal thyroid physiology, the consequences of thyroid dysfunction, and the effects of therapy in three cardiovascular areas: cardiac electrophysiology and arrhythmias, the vasculature and atherosclerosis, and the myocardium and heart failure. This report describes the current state of the field, outlines barriers and challenges to progress, and proposes research opportunities to advance the field, including strategies for leveraging novel approaches using omics and big data. The Working Group recommended research in three broad areas: 1) investigation into the fundamental biology relating thyroid dysfunction to the development of cardiovascular disease and into the identification of novel biomarkers of thyroid hormone action in cardiovascular tissues; 2) studies that define subgroups of patients with thyroid dysfunction amenable to specific preventive strategies and interventional therapies related to cardiovascular disease; and 3) clinical trials focused on improvement in cardiovascular performance and cardiovascular outcomes through treatment with thyroid hormone or thyromimetic drugs.

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.

Thyrotropin aggravates atherosclerosis by promoting macrophage inflammation in plaques

The increased cardiovascular risk in subclinical hypothyroidism has traditionally been attributed to the associated metabolic disorders. This paper, however, revealed that TSH can aggravate atherosclerosis by promoting macrophage inflammation in the plaque, which deepens our understanding of the significance of TSH elevation in subclinical hypothyroidism.

Subclinical hypothyroidism is associated with cardiovascular diseases, yet the underlying mechanism remains largely unknown. Herein, in a common population (n = 1,103), TSH level was found to be independently correlated with both carotid plaque prevalence and intima-media thickness. Consistently, TSH receptor ablation in ApoE^−/− mice attenuated atherogenesis, accompanied by decreased vascular inflammation and macrophage burden in atherosclerotic plaques. These results were also observed in myeloid-specific Tshr-deficient ApoE^−/− mice, which indicated macrophages to be a critical target of the proinflammatory and atherogenic effects of TSH. In vitro experiments further revealed that TSH activated MAPKs (ERK1/2, p38α, and JNK) and IκB/p65 pathways in macrophages and increased inflammatory cytokine production and their recruitment of monocytes. Thus, the present study has elucidated the new mechanisms by which TSH, as an independent risk factor of atherosclerosis, aggravates vascular inflammation and contributes to atherogenesis.

Association of serum thyrotropin levels with coronary artery disease documented by quantitative coronary angiography: a transversal study

OBJECTIVE

The association between coronary artery disease (CAD) and thyroid function remains controversial. We evaluated the thyroid function and graduated well-defined CAD as confirmed by quantitative coronary angiography (CA).

SUBJECTS AND METHODS

We evaluated the serum TSH, free thyroxine, free triiodothyronine and thyroid antibody levels in 300 consecutive patients (age 61.6 ± 9.9 years and 54% were male) undergoing CAD diagnosis as confirmed by CA. Plaques with ≥ 50% stenosis being indicative of obstructive CAD, and patients were divided into groups according to main epicardial coronary arteries with plaques (0, 1, 2, 3). Lipid profiles and a homeostasis model assessment (HOMA-IR) were determined.

RESULTS

Serum median (25% and 75% percentile) TSH levels in patients with group 2 and 3 (2.25; 1.66-3.12 mU/L and 4.99; 4.38-23.60 mU/L, respectively) had significantly higher TSH concentrations (p < 0.0001) than the group 0 (1.82; 1.35-2.51 mU/L). Furthermore, patients of group 3 had higher TSH concentration (p < 0.0001) than those of group 1 (1.60; 0.89-2.68 mU/L). Group 3 were older (64 ± 8.5 vs. 59 ± 9.5, p = 0.001), had more patients with dyslipidemia (84% versus 58%, p < 0.001), male (54% versus 44%, p = 0.01), hypertension (100% versus 86%, p < 0.001), and smoking (61% versus 33%, p < 0.001) than group 0. Multivariate stepwise logistic analysis showed TSH, age, HbA1c, and HOMA-IR were the CAD associated variables.

CONCLUSIONS

In this cohort, elevated TSH levels in the high normal range or above are associated with the presence and severity of CAD besides may represent a weak CAD risk factor.

Global epidemiology of hyperthyroidism and hypothyroidism

Thyroid hormones are essential for growth, neuronal development, reproduction and regulation of energy metabolism. Hypothyroidism and hyperthyroidism are common conditions with potentially devastating health consequences that affect all populations worldwide. Iodine nutrition is a key determinant of thyroid disease risk; however, other factors, such as ageing, smoking status, genetic susceptibility, ethnicity, endocrine disruptors and the advent of novel therapeutics, including immune checkpoint inhibitors, also influence thyroid disease epidemiology. In the developed world, the prevalence of undiagnosed thyroid disease is likely falling owing to widespread thyroid function testing and relatively low thresholds for treatment initiation. However, continued vigilance against iodine deficiency remains essential in developed countries, particularly in Europe. In this report, we review the global incidence and prevalence of hyperthyroidism and hypothyroidism, highlighting geographical differences and the effect of environmental factors, such as iodine supplementation, on these data. We also highlight the pressing need for detailed epidemiological surveys of thyroid dysfunction and iodine status in developing countries.

Prognostic Value of Free Triiodothyronine Level in Patients With Hypertrophic Obstructive Cardiomyopathy

CONTEXT

Thyroid hormone acts as a fundamental regulator in cardiovascular homeostasis in pathophysiological conditions.

OBJECTIVE

This study aims to determine whether thyroid hormone could be an independent predictor of adverse events in patients with hypertrophic obstructive cardiomyopathy (HOCM).

DESIGN, PATIENTS, AND OUTCOME MEASURES

The original cohort consisted of 965 consecutive patients with HOCM who were admitted to Fuwai Hospital from October 2009 to December 2014, and 756 patients completed thyroid function evaluations. Patients were divided into three groups according to free triiodothyronine (FT3) levels: tertile 1 (<2.81 pg/mL, n = 247), tertile 2 (2.81 to 3.11 pg/mL, n = 250), tertile 3 (3.12 to 4.09 pg/mL, n = 259).

RESULTS

In correlation analysis, FT3 showed significantly positive correlation with left ventricular ejection fraction (r = 0.109, P = 0.003). After a median follow-up of 44 months, a total of 45 (6.0%) endpoints (all-cause mortality or cardiac transplantation) occurred with rates of 13.4%, 3.6%, and 1.2% in tertiles 1, 2, and 3, respectively. Univariate Cox analysis established FT3 as a predictor of endpoint [hazard ratio (HR), 0.111; 95% confidence interval (CI), 0.065, 0.189; P < 0.001]. After adjustment for traditional risk factors, the prognostic value of FT3 level was still significant (HR, 0.216; 95% CI, 0.083, 0.559; P = 0.002). Compared with patients in tertile 3, those in tertile 1 were at a much higher risk of endpoint (HR, 4.918; 95% CI, 1.076, 22.485; P = 0.040).

CONCLUSIONS

FT3 correlated with cardiac function and could serve as an independent predictor of all-cause mortality and cardiac transplantation in patients with HOCM. These results suggest that monitoring thyroid function in HOCM patients is necessary.

Subclinical Hypothyroidism and Its Association with Increased Cardiovascular Mortality

Thyroid hormones play an important role in regulating different metabolism functions and multiple organs' performance. Changes in the thyroid hormone axis can lead to profound effects on the stability of vital organs and systems, especially the cardiovascular system. Hypothyroidism is classified according to the clinical presentation as overt and subclinical. There is some evidence supporting the benefits of thyroxine hormone replacement for subclinical hypothyroidism on cardiovascular mortality outcomes. However, the clinical relevance of measuring and treating high thyroid-stimulating hormone (TSH) levels in newly diagnosed heart failure patients with preserved ejection fraction requires further study. In this report, we review the current evidence regarding the prognostic significance of subclinical hypothyroidism in heart failure patients with preserved ejection fraction.

Maternal Thyroid Antibodies Associates With Cardiometabolic Risk Factors in Children at the Age of 16

CONTEXT AND OBJECTIVE

The objective of this study was to determine the effects of maternal thyroid dysfunction or antibodies during pregnancy on the cardiometabolic risk factors in children.

DESIGN, SETTING, AND PARTICIPANTS

This prospective population-based cohort study, Northern Finland Birth Cohort 1986, included all pregnancies within a year in the area. Maternal serum samples were collected before the 20th week of gestation and analyzed for thyrotropin, free T4, thyroid-peroxidase antibodies (TPO-Abs), and thyroglobulin antibodies (Tg-Abs). Cardiometabolic risk factors in children at the age of 16 years were evaluated via blood sampling and clinical examination. Data were available for 3229 to 4176 mother-child pairs.

MAIN OUTCOME MEASURES

Waist circumference, blood pressure, lipids and lipoproteins, and insulin resistance were measured. Odds ratios (ORs) with 95% confidence intervals (CIs) of cardiometabolic risk factors in children with and without mothers with thyroid dysfunction or antibodies were calculated with logistic regression and adjusted for covariates.

RESULTS

Children of TPO-Ab-positive mothers had higher odds of metabolic syndrome (OR, 2.57; 95%, CI 1.26 to 5.25) and waist circumference indicative of metabolic syndrome (OR, 1.69; 95% CI, 1.14 to 2.50). They were also more likely to be overweight or obese (OR, 1.56; 95% CI, 1.04 to 2.34). Maternal thyroid dysfunction or Tg-Ab positivity did not associate with cardiometabolic risk factors in children.

CONCLUSION

Metabolic syndrome, greater waist circumference, and higher body mass index were more prevalent in children of TPO-Ab-positive mothers, indicating an adverse cardiovascular health profile.

Hypothyroidism

Hypothyroidism is a common condition of thyroid hormone deficiency, which is readily diagnosed and managed but potentially fatal in severe cases if untreated. The definition of hypothyroidism is based on statistical reference ranges of the relevant biochemical parameters and is increasingly a matter of debate. Clinical manifestations of hypothyroidism range from life threatening to no signs or symptoms. The most common symptoms in adults are fatigue, lethargy, cold intolerance, weight gain, constipation, change in voice, and dry skin, but clinical presentation can differ with age and sex, among other factors. The standard treatment is thyroid hormone replacement therapy with levothyroxine. However, a substantial proportion of patients who reach biochemical treatment targets have persistent complaints. In this Seminar, we discuss the epidemiology, causes, and symptoms of hypothyroidism; summarise evidence on diagnosis, long-term risk, treatment, and management; and highlight future directions for research.

Thyroid function and ischemic heart disease: a Mendelian randomization study

To clarify the role of thyroid function in ischemic heart disease (IHD) we assessed IHD risk and risk factors according to genetically predicted thyroid stimulating hormone (TSH), free thyroxine (FT4) and thyroid peroxidase antibody (TPOAb) positivity. Separate-sample instrumental variable analysis with genetic instruments (Mendelian randomization) was used in an extensively genotyped case (n = 64,374)-control (n = 130,681) study, CARDIoGRAMplusC4D. Associations with lipids, diabetes and adiposity were assessed using the Global Lipids Genetics Consortium Results (n = 196,475), the DIAbetes Genetics Replication And Meta-analysis case (n = 34,380)-control (n = 114,981) study, and the Genetic Investigation of ANthropometric Traits (body mass index in 152,893 men and 171,977 women, waist-hip ratio in 93,480 men and 116,741 women). Genetically predicted thyroid function was not associated with IHD (odds ratio (OR) per standard deviation for TSH 1.05, 95% confidence interval (CI) 0.97 to 1.12; for FT4 1.01, 95% CI 0.91 to 1.12; for TPOAb positivity 1.10, 95% CI 0.83 to 1.46) or after Bonferroni correction with risk factors, except for an inverse association of FT4 with low-density lipoprotein-cholesterol. The associations were generally robust to sensitivity analyses using a weighted median method and MR Egger. This novel study provides little indication that TSH, FT4 or TPOAb positivity affects IHD, despite potential effects on its risk factors.

Sub-Clinical Hypothyroidism and Its Association With Increased Cardiovascular Mortality: Call for Action

Thyroid hormones play an important role in regulating different functions regarding metabolism and performance in multiple organs. Any change in the thyroid hormones axis can lead to profound effect on the vital organ stability especially the cardiovascular system. Hypothyroidism is classified according to the clinical presentation as overt and subclinical. Currently, there exists a paucity of evidence on the beneficial effects of thyroxine hormone replacement on cardiovascular mortality outcomes in subclinical hypothyroidism. Also, the clinical relevance of measuring and treating supra-normal thyroid-stimulating hormone levels in newly diagnosed heart failure patients with preserved ejection fraction requires further study. Here we review the current evidence regarding the prognostic significance of sub-clinical hypothyroidism in patients with heart failure with preserved ejection fraction.

What is the association of hypothyroidism with risks of cardiovascular events and mortality? A meta-analysis of 55 cohort studies involving 1,898,314 participants

BACKGROUND

Whether hypothyroidism is an independent risk factor for cardiovascular events is still disputed. We aimed to assess the association between hypothyroidism and risks of cardiovascular events and mortality.

METHODS

We searched PubMed and Embase from inception to 29 February 2016. Cohort studies were included with no restriction of hypothyroid states. Priori main outcomes were ischemic heart disease (IHD), cardiac mortality, cardiovascular mortality, and all-cause mortality.

RESULTS

Fifty-five cohort studies involving 1,898,314 participants were identified. Patients with hypothyroidism, compared with euthyroidism, experienced higher risks of IHD (relative risk (RR): 1.13; 95% confidence interval (CI): 1.01-1.26), myocardial infarction (MI) (RR: 1.15; 95% CI: 1.05-1.25), cardiac mortality (RR: 1.96; 95% CI: 1.38-2.80), and all-cause mortality (RR: 1.25; 95% CI: 1.13-1.39); subclinical hypothyroidism (SCH; especially with thyrotropin level ≥10 mIU/L) was also associated with higher risks of IHD and cardiac mortality. Moreover, cardiac patients with hypothyroidism, compared with those with euthyroidism, experienced higher risks of cardiac mortality (RR: 2.22; 95% CI: 1.28-3.83) and all-cause mortality (RR: 1.51; 95% CI: 1.26-1.81).

CONCLUSIONS

Hypothyroidism is a risk factor for IHD and cardiac mortality. Hypothyroidism is associated with higher risks of cardiac mortality and all-cause mortality compared with euthyroidism in the general public or in patients with cardiac disease.

Cardiovascular risk in chronic autoimmune thyroiditis and subclinical hypothyroidism patients. A cluster analysis

BACKGROUND

Subclinical hypothyroidism (SCH) and chronic autoimmune thyroiditis (CAT) are linked to an increased risk of atherosclerosis and coronary heart disease (CHD). The aim of this study was to look for positive markers of CHD and correlations with thyroid blood tests in patients with SCH or CAT, but no symptoms of CHD, so as to identify CHD risk conditions that otherwise would likely be missed.

METHODS

We measured a series of thyroid, clinical-metabolic and cardiovascular parameters in 30 consecutive endocrinology patients enrolled in our ambulatory endocrinological referral center of "Sapienza" University of Rome. (19 with CAT, 11 with SCH) from January 2015 to March 2015. 13 asymptomatic subjects were enrolled as controls. In each patient, we measured a series of 34 thyroid, clinical-metabolic and cardiovascular parameters.

RESULTS

in the statistical analysis of collected data, the oblique principal components clustering procedure (OPC) revealed the presence of an interesting mixed cluster, composed of a thyroid parameter (TPO-Ab), a metabolic parameter (homocysteine level) and a cardiovascular parameter (MAPSE), in which we assessed the relationships between the single components. Our preliminary results indicate that in both groups of patients elevated TPO-Ab, when accompanied by reduced MAPSE and increased IMT and homocysteine values, may be taken to indicate the presence of clinically unrecognized CHD.

CONCLUSIONS

Confirmation of these results in larger series of patients could justify hormone therapy for prevention of CHD in these thyroid patients versus placebo treatment.

Effects of thyroid hormone withdrawal on metabolic and cardiovascular parameters during radioactive iodine therapy in differentiated thyroid cancer

Objective To investigate the cardiometabolic effects of a severe hypothyroid state induced by withdrawal of thyroid hormone replacement before radioactive iodine therapy. Methods Patients with thyroid cancer who were scheduled to receive radioactive iodine ablation were enrolled. Cardiometabolic parameters were measured using blood samples taken immediately before levothyroxine withdrawal, 4 weeks following withdrawal (on radiotherapy day), and 4 weeks following reinstitution of levothyroxine. Results Out of 48 patients (age 49.4 ± 10.5 years; 77.1% [37/48] female), the severe hypothyroid state induced by levothyroxine withdrawal significantly aggravated the majority of lipid parameters, particularly in patients with a greater number of metabolic syndrome components. Fasting plasma glucose levels and homeostatic model assessment values for insulin resistance and β-cell function significantly decreased following levothyroxine withdrawal. Serum high-sensitivity C-reactive protein, fibrinogen and cystatin C levels significantly decreased, and homocysteine levels increased during the severe hypothyroid state. All of these changes were reversed by levothyroxine reinstitution. Conclusions Severe hypothyroid state induced pronounced changes in cardiometabolic parameters. Further studies should identify the long-term effects of changes in these parameters on cardiovascular morbidity and mortality in relation to thyroid disease.

Hormonal Replacement in Hypopituitarism in Adults: An Endocrine Society Clinical Practice Guideline

OBJECTIVE

To formulate clinical practice guidelines for hormonal replacement in hypopituitarism in adults.

PARTICIPANTS

The participants include an Endocrine Society-appointed Task Force of six experts, a methodologist, and a medical writer. The American Association for Clinical Chemistry, the Pituitary Society, and the European Society of Endocrinology co-sponsored this guideline.

EVIDENCE

The Task Force developed this evidence-based guideline using the Grading of Recommendations, Assessment, Development, and Evaluation system to describe the strength of recommendations and the quality of evidence. The Task Force commissioned two systematic reviews and used the best available evidence from other published systematic reviews and individual studies.

CONSENSUS PROCESS

One group meeting, several conference calls, and e-mail communications enabled consensus. Committees and members of the Endocrine Society, the American Association for Clinical Chemistry, the Pituitary Society, and the European Society of Endocrinology reviewed and commented on preliminary drafts of these guidelines.

CONCLUSIONS

Using an evidence-based approach, this guideline addresses important clinical issues regarding the evaluation and management of hypopituitarism in adults, including appropriate biochemical assessments, specific therapeutic decisions to decrease the risk of co-morbidities due to hormonal over-replacement or under-replacement, and managing hypopituitarism during pregnancy, pituitary surgery, and other types of surgeries.

Recent Advances in Autoimmune Thyroid Diseases

Autoimmune thyroid disease (AITD) includes hyperthyroid Graves disease, hypothyroid autoimmune thyroiditis, and subtle subclinical thyroid dysfunctions. AITD is caused by interactions between genetic and environmental predisposing factors and results in autoimmune deterioration. Data on polymorphisms in the AITD susceptibility genes, related environmental factors, and dysregulation of autoimmune processes have accumulated over time. Over the last decade, there has been progress in the clinical field of AITD with respect to the available diagnostic and therapeutic methods as well as clinical consensus. The updated clinical guidelines allow practitioners to identify the most reasonable and current approaches for proper management. In this review, we focus on recent advances in understanding the genetic and environmental pathogenic mechanisms underlying AITD and introduce the updated set of clinical guidelines for AITD management. We also discuss other aspects of the disease such as management of subclinical thyroid dysfunction, use of levothyroxine plus levotriiodothyronine in the treatment of autoimmune hypothyroidism, risk assessment of long-standing antithyroid drug therapy in recurrent Graves' hyperthyroidism, and future research needs.

Subclinical Hypothyroidism - What is Responsible for its Association with Cardiovascular Disease?

Subclinical hypothyroidism (SH) is a common condition, with prevalence estimates ranging from 4–20%, depending on the population demographics. Although epidemiological analysis associates it with an increased risk of cardiovascular disease, clinical practice guidelines express uncertainty about whether to monitor or to treat. As we await large-scale, well-designed randomised clinical trials regarding treatment of SH, a review of pathophysiological considerations may be informative to better understand this disorder.

A Worthy Finding: Decrease in Total Cholesterol and Low-Density Lipoprotein Cholesterol in Treated Mild Subclinical Hypothyroidism

BACKGROUND

Mild subclinical hypothyroidism (SCH) affects a large number of people and is known to be a risk factor for dyslipidemia. However, whether mild SCH patients should be treated with L-thyroxine to improve lipid profiles remains controversial. In addition, it is also unclear whether all mild SCH patients can benefit from L-thyroxine treatment, regardless of basal thyrotropin or lipid levels. This study aimed to assess the effects of L-thyroxine replacement therapy on the lipid profiles of mild SCH patients.

METHODS

This open-label randomized controlled trial was performed in Ningyang County, Shandong Province, China. A total of 378 mild SCH patients with diagnoses confirmed by two thyroid function tests were randomly assigned to either the intervention group (L-thyroxine replacement therapy) or the control group (no treatment). The primary outcome was a change in serum total cholesterol (TC) concentration.

RESULTS

In all, 369 participants completed the 15-month follow-up period. Reduced TC concentrations were more prominent in the intervention group than they were in the control group (-0.41 mmol/L vs. -0.17 mmol/L; p = 0.012), and changes in low-density lipoprotein cholesterol levels exhibited the same trend. Subgroup analyses were performed to assess the effects of L-thyroxine in patients with different thyrotropin or TC levels. When the study population was stratified according to basal thyrotropin concentration, all patients who had received L-thyroxine showed reduced TC levels (p < 0.001). The treatment was similarly beneficial for all patients, regardless of basal TC level. Even for subjects with TC levels <5.18 mmol/L, serum TC concentrations remained unchanged in the intervention group (p = 0.936) but increased by 0.35 mmol/L in the control group (p = 0.004).

CONCLUSIONS

The findings suggest that mild SCH patients could benefit from L-thyroxine treatment to improve lipid profiles, regardless of basal thyrotropin or TC concentrations.

Subclinical hypothyroidism and the risk of metabolic syndrome: A meta-analysis of observational studies

BACKGROUND

Observational studies on the association between subclinical hypothyroidism (SCH) and metabolic syndrome (MetS) have produced inconsistent results. Therefore, we performed a meta-analysis to evaluate the effect of SCH on the risk of MetS.

METHODS

Multiple databases were searched to identify studies on the association between SCH and the risk of MetS, up to February 2015. Relevant information for analysis was extracted. A random-effects model was used to calculate the pooled risk estimates.

RESULTS

9 studies (7 cross-sectional and 2 case-control studies) were included. The pooled odds ratio (OR) for MetS comparing SCH with euthyroid subjects was 1.31 (95%CI: 1.08 to 1.60, p = 0.006, I(2) = 50%). Subgroup analyses by countries revealed a significant association for the studies from Asian (OR = 1.244, 95% CI: 1.030-1.503, I(2) = 25%) other than non-Asian (OR = 1.548, 95% CI: 0.925-2.591, I(2) = 73.5%) countries. A positive association was identified in the IDF subgroup (OR = 1.288, 95% CI: 1.055-1.572, I(2) = 0%), but not in the NCEP-ATP III (OR = 1.351, 95% CI: 0.950-1.923, I(2) = 66.4%), Chinese (OR = 1.430, 95% CI: 0.891-2.294) and Japanese (OR = 1.542, 95% CI: 0.594-4.005, I(2) = 78.3%) subgroup. A certain degree of heterogeneity was observed among studies which cannot be explained by study design, diagnostic criteria and location.

CONCLUSION

Our results demonstrated that SCH was significantly associated with a higher risk of MetS. Well-designed cohort studies were warranted to confirm our findings.

Subclinical thyroid dysfunction and fracture risk: a meta-analysis

IMPORTANCE

Associations between subclinical thyroid dysfunction and fractures are unclear and clinical trials are lacking.

OBJECTIVE

To assess the association of subclinical thyroid dysfunction with hip, nonspine, spine, or any fractures.

DATA SOURCES AND STUDY SELECTION

The databases of MEDLINE and EMBASE (inception to March 26, 2015) were searched without language restrictions for prospective cohort studies with thyroid function data and subsequent fractures.

DATA EXTRACTION

Individual participant data were obtained from 13 prospective cohorts in the United States, Europe, Australia, and Japan. Levels of thyroid function were defined as euthyroidism (thyroid-stimulating hormone [TSH], 0.45-4.49 mIU/L), subclinical hyperthyroidism (TSH <0.45 mIU/L), and subclinical hypothyroidism (TSH ≥4.50-19.99 mIU/L) with normal thyroxine concentrations.

MAIN OUTCOME AND MEASURES

The primary outcome was hip fracture. Any fractures, nonspine fractures, and clinical spine fractures were secondary outcomes.

RESULTS

Among 70,298 participants, 4092 (5.8%) had subclinical hypothyroidism and 2219 (3.2%) had subclinical hyperthyroidism. During 762,401 person-years of follow-up, hip fracture occurred in 2975 participants (4.6%; 12 studies), any fracture in 2528 participants (9.0%; 8 studies), nonspine fracture in 2018 participants (8.4%; 8 studies), and spine fracture in 296 participants (1.3%; 6 studies). In age- and sex-adjusted analyses, the hazard ratio (HR) for subclinical hyperthyroidism vs euthyroidism was 1.36 for hip fracture (95% CI, 1.13-1.64; 146 events in 2082 participants vs 2534 in 56,471); for any fracture, HR was 1.28 (95% CI, 1.06-1.53; 121 events in 888 participants vs 2203 in 25,901); for nonspine fracture, HR was 1.16 (95% CI, 0.95-1.41; 107 events in 946 participants vs 1745 in 21,722); and for spine fracture, HR was 1.51 (95% CI, 0.93-2.45; 17 events in 732 participants vs 255 in 20,328). Lower TSH was associated with higher fracture rates: for TSH of less than 0.10 mIU/L, HR was 1.61 for hip fracture (95% CI, 1.21-2.15; 47 events in 510 participants); for any fracture, HR was 1.98 (95% CI, 1.41-2.78; 44 events in 212 participants); for nonspine fracture, HR was 1.61 (95% CI, 0.96-2.71; 32 events in 185 participants); and for spine fracture, HR was 3.57 (95% CI, 1.88-6.78; 8 events in 162 participants). Risks were similar after adjustment for other fracture risk factors. Endogenous subclinical hyperthyroidism (excluding thyroid medication users) was associated with HRs of 1.52 (95% CI, 1.19-1.93) for hip fracture, 1.42 (95% CI, 1.16-1.74) for any fracture, and 1.74 (95% CI, 1.01-2.99) for spine fracture. No association was found between subclinical hypothyroidism and fracture risk.

CONCLUSIONS AND RELEVANCE

Subclinical hyperthyroidism was associated with an increased risk of hip and other fractures, particularly among those with TSH levels of less than 0.10 mIU/L and those with endogenous subclinical hyperthyroidism. Further study is needed to determine whether treating subclinical hyperthyroidism can prevent fractures.

Cardiovascular Risk in Patients with Subclinical Hypothyroidism

Subclinical hypothyroidism (SCH) has been associated with increased cardiovascular mortality due to adverse effects mainly on lipids and blood pressure (BP). There is evidence that SCH, especially in patients with thyroid-stimulating hormone (TSH) >10mU/l, may increase cardiovascular risk. Some uncertainty exists regarding the association of SCH with BP; however, that the coexistence of SCH with BP and hypercholesterolaemia has a negative cardiovascular impact is beyond doubt. Insulin resistance, by modulating various risk factors including coagulation, may potentially increase cardiovascular risk. Periodic health examinations including screening has been advised in patients >35 years of age, while treatment with thyroxine should be tailored to each patient.