Thyroid disease and increased cardiovascular risk

Visceral Fat Area and Subcutaneous Fat Area Increase in Hyperthyroidism Patients After Treatment-A Single-Group Repeated-Measures Trial

Purpose

There is evidence that long-term vascular risk remains increased in patients with hyperthyroidism even after normalization of thyroid function, and the mechanisms that regulate this risk are unclear. The aim of this study was to assess how visceral fat area and subcutaneous fat area change after hyperthyroidism treatment, and to further explore the relationship between thyroid hormones, abdominal fat area (visceral fat area and subcutaneous fat area), and lipids.

Patients and Methods

50 patients with newly diagnosed Graves' disease were selected. Anthropometric parameters (weight, height, body mass index, waist circumference, neck circumference), laboratory parameters (thyroid hormones, lipid metabolism indices), abdominal fat area (visceral fat area and subcutaneous fat area), and drug dose were collected. Measurements were made at baseline, 6 and 12 months after treatment. We used linear mixed-effects models for analysis.

Results

The results showed that the following indexes changed significantly at different time points: visceral fat area, subcutaneous fat area, free triiodothyronine, free thyroxine, thyroid stimulating hormone, total cholesterol, high-density lipoprotein, low-density lipoprotein, body weight, neck circumference, body mass index, waist circumference, and drug dose (All P<0.001). We found that free triiodothyronine and free thyroxine were significantly negatively associated with abdominal fat area (P<0.01). There was no significant correlation between drug dose and abdominal fat area (P>0.05). Total cholesterol and low-density lipoprotein were significantly positively associated with abdominal fat area (P<0.01). However, high-density lipoprotein (P=0.06) was not correlated with abdominal fat area. Moreover, the results showed a significant negative correlation between thyroid hormones and lipids (P<0.001).

Conclusion

After anti-thyroid medicine treatment, patients had elevated visceral fat area and subcutaneous fat area and altered lipid profiles. These changes may be one of the reasons why metabolic and cardiovascular diseases remain increased after thyroid function is restored.

Thyroid function test variability and cardiovascular morbidity in hyperthyroidism

OBJECTIVE

The variability of thyroid function tests (TFTs) during antithyroid drug (ATD) therapy and its association with adverse health outcomes have not been previously studied. The aim of this study was to evaluate the association of TFT variability and cardiovascular morbidity during ATD therapy.

DESIGN

Retrospective cohort study.

PATIENTS AND MEASUREMENTS

Hyperthyroid patients (n = 394) treated with ATD therapy at Tampere University Hospital between March 2016 and December 2018 were followed up for a median time of 1.5 years (interquartile range 0.8-2.0). The coefficients of variation (CVs) of the follow-up thyroid-stimulating hormone (TSH), free thyroxine (fT4) and free triiodothyronine (fT3) measurements were determined. The associations of TFT variability and baseline clinical factors with cardiovascular disease (CVD) -associated hospital visits were assessed with logistic regression analyses.

RESULTS

In the multivariable analyses, age (odds ratio [OR]: 1.06, 95% confidence interval [CI]: 1.03-1.09), male gender (OR: 2.33, 95% CI: 1.03-5.28) and fT4-CV (OR: 1.02, 95% CI: 1.01-1.04) were independent risk factors for cardiovascular morbidity, whereas baseline positive thyrotropin receptor antibodies (TRAbs) were associated with lower cardiovascular morbidity (OR: 0.29, 95% CI: 0.14-0.61). When the patients with baseline TRAb positivity were studied separately, fT4-CV was associated with cardiovascular morbidity (OR: 1.03, 95% CI: 1.00-1.05).

CONCLUSIONS

During ATD therapy, fT4 variability is associated with an increased cardiovascular morbidity. Although positive TRAbs are associated with a lower cardiovascular morbidity compared with hyperthyroidism with negative autoantibodies, the variability of fT4 is associated with cardiovascular morbidity also in patients with positive TRAbs.

Association of methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) with thyroid dysfunction: A meta-analysis and trial sequential analysis

Recent studies have shown that two common methylenetetrahydrofolate reductase (MTHFR) gene polymorphisms (C677T and A1298C) might correlate with thyroid dysfunction, but the results remain inconsistent. We carried out a meta-analysis aiming to assess the relationship of both polymorphisms with thyroid dysfunction. The PubMed, EMBASE, CNKI (China National Knowledge Infrastructure), CBMdisc (China Biology Medicine disc), WeiPu and Wanfang databases were searched up to September 2021. Case-control and cohort studies on MTHFR polymorphism and thyroid dysfunction were identified. Eight studies from six publications were finally included in our meta-analysis, including 817 patients and 566 controls. After pooled analysis, we found that the MTHFR C677T polymorphism was associated with an increased risk of hypothyroidism (TT vs. CC+CT/recessive model: OR = 2.07, 95% CI: 1.02-4.20, P = 0.04; TT vs. CC/homozygote model: OR = 2.35, 95% CI: 1.13-4.86, P = 0.02), while trial sequential analysis (TSA) revealed that it could be a false positive result. The MTHFR A1298C polymorphism was related to a decreased risk of hypothyroidism (C vs. A/allele model: OR = 0.63, 95% CI: 0.44-0.92, P = 0.02; CC vs. AC+AA/recessive model: OR = 0.42, 95% CI: 0.22-0.79, P = 0.007; CC vs. AA/homozygote model: OR = 0.43, 95% CI: 0.25-0.85, P = 0.02), which was conclusive according to TSA. The results of this meta-analysis suggest that MTHFR A1298C seems to be a protective factor for hypothyroidism, while the MTHFR C677T polymorphism may be a risk factor. However, more well-designed studies with larger sample sizes are needed to obtain more reliable results of the association between the MTHFR C677T polymorphism and hypothyroidism.

Neutrophil-to-lymphocyte Ratio is Associated with LV Diastolic Dysfunction in the Overt Hyperthyroid Patients

BACKGROUND

Recent studies have shown that the neutrophil-to-lymphocyte ratio (NLR) has gradually been identified as a more reliable marker of inflammation, with predictive value for the development of many diseases. However, its association with left ventricular (LV) diastolic dysfunction in overt hyperthyroid patients is unclear. Here, we aimed to explore the relationship between NLR and LV diastolic dysfunction in overt hyperthyroid patients.

METHODS

For this study, we retrospected the consecutive medical files of 350 overt hyperthyroid patients. Their medical data and laboratory findings were recorded. According to the presence or absence of LV diastolic dysfunction, the patients with overt hyperthyroidism were divided into two groups. One group with LV diastolic dysfunction included 104 patients and another group with non-LV diastolic dysfunction included 246 patients. The NLR values between the two groups were compared, and the relationship between NLR levels and the prevalence of LV diastolic dysfunction was also explored.

RESULTS

The NLR value in LV diastolic dysfunction group in the overt hyperthyroid subjects was significantly higher than that in non-LV diastolic dysfunction group [1.100 (0.907-1.580) vs 1.000 (0.761-1.405), P=0.016]. The prevalence of LV diastolic dysfunction in Low- (NLR<0.879), Medium- (0.879< NLR<1.287), and High- (NLR >1.287) NLR level groups were 20.9%, 32.5% and 35.7% respectively. Moreover, increased NLR is associated with increased prevalence of LV diastolic dysfunction, and after adjustment for potential associated factors, NLR remained significantly associated with LV diastolic dysfunction. (OR = 11.753, 95%CI = 1.938-71.267, P = 0.007).

CONCLUSIONS

Our findings demonstrated that the NLR was associated with LV diastolic dysfunction in the overt hyperthyroid patients, and the prevalence of LV diastolic dysfunction may be positively correlated with NLR levels.

Association between haemorrhoids and Graves’ disease: a retrospective cohort study using data from Taiwan’s Longitudinal Health Insurance Database

Objective

To evaluate the relationship between haemorrhoids and Graves’ disease (GD).

Setting

Using the nationwide data from Taiwan’s Longitudinal Health Insurance Database.

Participants

We conducted a retrospective study, stratified patients by International Classification of Diseases, Ninth Revision, Clinical Modification disease code and compared the incidence rate of GD between patients with and without haemorrhoids. The study period was from 2000 to 2010, with exclusion of patients with diagnosed haemorrhoids before 2000 or after 2009, and we analysed the HR of GD in the univariable and multivariable models as well as the cumulative incidence curves of GD by using Kaplan-Meier curves.

Result

This study included 13 165 and 52 660 patients with and without haemorrhoids, respectively. The mean follow-up duration was approximately 6 years. The incidence rate of GD was 1.57 and 1.13 per 1000 person-years in patients with and without haemorrhoids, respectively. The area under the cumulative incidence curve of GD in patients with haemorrhoids was higher than that of patients without haemorrhoids. The risk of GD increased by 1.39 times (95% CI 1.13 to 1.71) in patients with haemorrhoids compared with patients without haemorrhoids. In the subgroup analysis, women with haemorrhoids had a higher risk of GD (adjusted HR 1.44; 95% CI 1.13 to 1.83). Patients with haemorrhoids aged 30–39 years were more likely to develop GD (adjusted HR 1.73; 95% CI 1.18 to 2.55).

Conclusion

The findings of this study indicate that patients with haemorrhoids may have an increased risk of GD compared with other potential confounding factors.

Prognostic role of hypothyroidism and low free-triiodothyronine levels in patients hospitalized with acute heart failure

Low thyroid function has been widely recognized as a potential cause of heart failure (HF), but the evidence about a possible association with in-hospital, all-cause mortality in patients with acute HF (AHF) is not consistent. This study sought to investigate the prevalence and prognostic role of hypothyroidism, overt and subclinical, and of low free-triiodothyronine (fT3) levels in patients hospitalized with AHF. We retrospectively analyzed consecutive 1018 patients who were hospitalized for AHF in a single academic medical center [Fondazione Policlinico A.Gemelli IRCCS, Rome, Italy] between January 1st 2016, and December 31st 2018. Patients were divided into three groups: normal thyroid function (n = 798), subclinical hypothyroidism (n = 105), and overt hypothyroidism (n = 115). The outcome was in-hospital, all-cause mortality. Patients were 81 years of age, 55% were females and nearly two-thirds of the patients were on New York Heart Association functional class III. The three most common cardiovascular comorbidities were coronary artery disease, hypertension, and atrial fibrillation with no differences across the three groups. Overall, 138 patients (14%) died during the hospital stay. The mortality rate was 27% among patients with overt hypothyroid, 17% among those with subclinical hypothyroidism, and 11% among euthyroid patients (p < 0.001). At a multivariate Cox regression model, overt hypothyroidism (HR 2.1, 95% CI 1.4-3.2) and fT3 levels < 1.8 pg/mL (HR 3.4, 95% CI 2.3-5.1) were associated with an increased likelihood of in-hospital death. No association was found with subclinical hypothyroidism. Among patients hospitalized with AHF, overt hypothyroidism and low fT3 levels are independent predictors of all-cause mortality during the hospital stay.

Outcomes of Graves' Disease Patients Following Antithyroid Drugs, Radioactive Iodine, or Thyroidectomy as the First-line Treatment

BACKGROUND

The long-term outcomes of first-line choice among ATD, RAI, and thyroidectomy for GD patients remain unclear.

OBJECTIVE

To compare the long-term morbidity, mortality, relapse, and costs of GD patients receiving first-line treatment.

METHODS

A population-based retrospective cohort of GD patients initiating first-line treatment with ATD, RAI, or thyroidectomy as a first-line primary treatment between 2006 and 2018 from Hong Kong Hospital Authority was analyzed. Risks of all-cause mortality, CVD, AF, psychological disease, diabetes, and hypertension were estimated using Cox proportional hazards regression models. The 10-year healthcare costs, change of comorbidities, and risk of relapse were compared across treatments.

RESULTS

Over a median follow-up of 90 months with 47,470 person-years, 6385 patients (ATD, 74.93%; RAI, 19.95%; thyroidectomy, 5.12%) who received first-line treatment for GD were analyzed. Compared with ATD group, patients who had undergone surgery had significantly lower risks of all-cause mortality [hazard ratio (HR) = 0.363, 95% confidence interval (CI) = 0.332-0.396], CVD (HR = 0.216, 95% CI = 0.195-0.239), AF (HR = 0.103, 95% CI = 0.085-0.124), psychological disease (HR = 0.279, 95% CI = 0.258-0.301), diabetes (HR = 0.341, 95% CI = 0.305-0.381), and hypertension (HR = 0.673, 95% CI = 0.632-0.718). Meanwhile, RAI group was also associated with decreased risks of all-cause mortality (HR = 0.931, 95% CI = 0.882-0.982), CVD (HR = 0.784, 95% CI = 0.742-0.828), AF (HR = 0.622, 95% CI = 0.578-0.67), and psychological disease (HR = 0.895, 95% CI = 0.855-0.937). The relapse rate was 2.41% in surgery, 75.60% in ATD, and 19.53% in RAI group. The surgery group was observed with a significant lower Charlson Comorbidity Index score than the other 2 groups at the tenth-year follow-up. The mean 10-year cumulative healthcare costs in ATD, RAI, and surgery group was US$23915, US$24260, and US$20202, respectively.

CONCLUSIONS

GD patients who received surgery as an initial treatment appeared to have lower chances of all-cause mortality, CVD, AF, psychological disease, diabetes, and hypertension in the long-term when compared to those treated with ATD or RAI. The surgery group had the lowest relapse and direct healthcare costs among the 3 treatment modalities. This long-term cohort study suggested surgery may have a larger role to play as an initial treatment for GD patients.

New Insights in RBM20 Cardiomyopathy

PURPOSE OF REVIEW

This review aims to give an update on recent findings related to the cardiac splicing factor RNA-binding motif protein 20 (RBM20) and RBM20 cardiomyopathy, a form of dilated cardiomyopathy caused by mutations in RBM20.

RECENT FINDINGS

While most research on RBM20 splicing targets has focused on titin (TTN), multiple studies over the last years have shown that other splicing targets of RBM20 including Ca²⁺/calmodulin-dependent kinase IIδ (CAMK2D) might be critically involved in the development of RBM20 cardiomyopathy. In this regard, loss of RBM20 causes an abnormal intracellular calcium handling, which may relate to the arrhythmogenic presentation of RBM20 cardiomyopathy. In addition, RBM20 presents clinically in a highly gender-specific manner, with male patients suffering from an earlier disease onset and a more severe disease progression. Further research on RBM20, and treatment of RBM20 cardiomyopathy, will need to consider both the multitude and relative contribution of the different splicing targets and related pathways, as well as gender differences.

Common carotid pulsatility is deteriorated by autoimmune thyroiditis in children with type 1 diabetes mellitus - A pilot study

Autoimmune thyroiditis (AIT) frequently coexists with type 1 diabetes (DM1) and additionally increases the extent of microcirculatory complications due to DM1. We hypothesized that in pediatric patients with DM1, impairment of macrocirculation could be further augmented by a coexisting autoimmune process. Therefore, we investigated the influence of AIT on large arteries in DM1 pediatric patients. Our group consisted of 19 DM1, 19 DM1 + AIT patients and 29 control subjects. The groups were comparable regarding age and gender. The DM1 and DM1 + AIT patients were matched for age at onset of DM1 and diabetes duration. Macrocirculation was described using pulsatility indices (PIs) determined for common carotid (CCA) and peripheral arteries of upper and lower limbs. CCA resistance index (RI) and ABI were also assessed. Children with DM1 + AIT had only significantly lower CCA_PI and CCA_RI in comparison with controls whereas in the absence of AIT such difference was not found. The diabetes duration and age of onset did not correlate with carotid indices. Total cholesterol level was higher both in DM1 + AIT and DM1 groups than in the control group. For low density lipoproteins cholesterol, a significant difference was found between DM1 + AIT and control groups. Age-independent impact of AIT on CCA_PI was confirmed by multivariate analysis. Common carotid pulsatility is deteriorated by autoimmune thyroiditis independently of age in children with type 1 diabetes mellitus.

Cardioprotective Mechanisms of Hypothyroidism on Ischemia/Reperfusion in Rats and Effects of Carvedilol: Energetic Study

Hypothyroidism is considered a cardiac risk factor, but there is controversial evidence about its effects on coronary disease. The aim of this work was to evaluate the influence of hypothyroidism in rat hearts exposed to 2 degrees of stunning due to ischemia and reperfusion (I/R) as well as the underlying mechanisms. Hypothyroid (HypoT) rats were obtained by drinking 0.02% methimazole during 15 days. Isolated hearts were perfused and introduced in a flow calorimeter to measure contractile performance (P), total heat rate (Ht), and muscle economy (P/Ht). Hearts were exposed to 2 models of I/R, moderate and severe (respectively 20 or 30 minutes I/45 minutes R). Moreover, free cytosolic and mitochondrial calcium changes were measured by confocal fluorometry on cardiomyocytes. Comparison to euthyroid (EuT) hearts was done. Hypothyroidism was cardioprotective, but HypoT hearts were more sensitive than EuT hearts to the preischemic blockade of mitochondrial transporters mNCX and mKATPchannels. Moreover, the postischemic recovery of P and P/Ht in HypoT hearts was strongly reduced by inhibition of the cellular pathways of PI3K/Akt and protein kinase C (PKC), and it was increased by nitric oxide synthase (NOS) inhibition. However, physiological concentrations of adrenaline reduced the cardioprotection of HypoT, but oral treatment with 20 mg/kg/day carvedilol prevented it. Results show that hypothyroidism reduces the mitochondrial Ca2+overload during I/R by mKATPchannel activation and Ca2+extrusion through mNCX, while the PI3K/Akt and PKC pathways are involved in that cardioprotection. Contrarily, NOS activation and adrenaline blunt such cardioprotection, but carvedilol prevented the adrenergic dysfunction. These results would explain why hypothyroidism is a clinical risk factor in angor patients under adrenergic exacerbation but reduced the incidence of acute episodes of coronary syndrome in hospitalized patients. Results suggest that a treatment with carvedilol could be a potential therapeutic agent to prevent cardiac postischemic dysfunction in hypothyroid patients.

Primary therapy of Graves' disease and cardiovascular morbidity and mortality: a linked-record cohort study

BACKGROUND

Graves' disease is routinely treated with antithyroid drugs, radioiodine, or surgery, but whether the choice of initial therapy influences long-term outcomes is uncertain. We evaluated cardiovascular morbidity and mortality according to the method and effectiveness of primary therapy in Graves' disease.

METHODS

In this retrospective cohort study, we identified patients with hyperthyroidism, diagnosed between Jan 1, 1998, and Dec 31, 2013, from a thyroid-stimulating hormone (TSH)-receptor antibody (TRAb) test register in south Wales, UK, and imported their clinical data into the All-Wales Secure Anonymised Information Linkage (SAIL) Databank (Swansea University, Swansea, UK). Patients with Graves' disease, defined by positive TRAb tests, were selected for the study, and their clinical data were linked with outcomes in SAIL. We had no exclusion criteria. Patients were matched by age and sex to a control population (1:4) in the SAIL database. Patients were grouped by treatment within 1 year of diagnosis into the antithyroid drug group, radioiodine with resolved hyperthyroidism group (radioiodine group A), or radioiodine with unresolved hyperthyroidism group (radioiodine group B). We used landmark Kaplan-Meier and Cox regression models to analyse the association of treatment with the primary outcome of all-cause mortality and the secondary outcome of major adverse cardiovascular events (myocardial infarction, heart failure, ischaemic stroke, or death) with the landmark set at 1 year after diagnosis. We analysed the association between outcomes and concentration of TSH using Cox regression and outcomes and free thyroxine (FT4) concentration using restricted cubic-spline regression models.

FINDINGS

We extracted patient-level data on 4189 patients (3414 [81·5%] females and 775 [18·5%] males) with Graves' disease and 16 756 controls (13 656 [81·5%] females and 3100 [18·5%] males). In landmark analyses, 3587 patients were in the antithyroid drug group, 250 were in radioiodine group A, 182 were in radioiodine group B. Patients had increased all-cause mortality compared with controls (hazard ratio [HR] 1·22, 95% CI 1·05-1·42). Compared with patients in the antithyroid drug group, mortality was lower among those in radioiodine group A (HR 0·50, 95% CI 0·29-0·85), but not for those in radioiodine group B (HR 1·51, 95% CI 0·96-2·37). Persistently low TSH concentrations at 1 year after diagnosis were associated with increased mortality independent of treatment method (HR 1·55, 95% CI 1·08-2·24). Spline regressions showed a positive non-linear relationship between FT4 concentrations at 1 year and all-cause mortality.

INTERPRETATION

Regardless of the method of treatment, early and effective control of hyperthyroidism among patients with Graves' disease is associated with improved survival compared with less effective control. Rapid and sustained control of hyperthyroidism should be prioritised in the management of Graves' disease and early definitive treatment with radioiodine should be offered to patients who are unlikely to achieve remission with antithyroid drugs alone.

FUNDING

National Institute for Social Care and Health Research, Wales.

Duration of Hyperthyroidism and Lack of Sufficient Treatment Are Associated with Increased Cardiovascular Risk

BACKGROUND

Cardiovascular disease remains the most prevalent cause of death in hyperthyroidism. However, the impact on cardiovascular events of varying thyroid status and of treatment remains unclarified. The aims of this study were to investigate the association between hyperthyroidism and cardiovascular events in treated and untreated hyperthyroid individuals, as well as exploring the impact of cumulative periods of hyperthyroidism as a proxy for undertreatment on cardiovascular events.

METHOD

This was a case-control study nested within a population-based cohort of individuals attending health services in Funen County, Denmark, in the period from 1995 to 2011. Data on comorbidities and mortality were collected from The Danish National Patient Register and The Danish Register of Causes of Death. Participants were 275,467 individuals with at least one serum thyrotropin (TSH) measurement in the study period. Hyperthyroidism was defined as at least two measurements of decreased serum TSH within six months, separated by at least 14 days. Incident cases of cardiovascular disease (myocardial infarction, atrial fibrillation, heart failure, stroke, and cardiovascular death) were matched with controls. Conditional logistic regression analyses were performed to calculate odds ratios (OR) for exposure to hyperthyroidism, adjusting for preexisting comorbidities.

RESULTS

A total of 20,651 individuals experienced a cardiovascular event (9.5% incidence rate 13.2/1000 person-years [confidence interval (CI) 13.0-13.4]) compared to euthyroid individuals, conditional logistic regression showed increased cardiovascular risk in untreated hyperthyroid patients (OR = 1.25 [CI 1.06-1.48], p = 0.007) but not in treated hyperthyroid patients (OR = 1.04 [CI 0.90-1.22], p = 0.57)]. The OR for cardiovascular events per six months of decreased TSH was 1.09 ([CI 1.05-1.14], p < 0.001) in treated hyperthyroid individuals, and 1.10 ([CI 1.05-1.15], p < 0.001) in untreated hyperthyroid individuals.

CONCLUSIONS

The risk of cardiovascular disease was found to be increased in untreated hyperthyroid patients, and the duration of decreased TSH associated with increasing risk of cardiovascular outcomes in both treated and untreated hyperthyroid individuals. This suggests that increased cardiovascular risk is driven not only by lack of treatment but also by insufficient therapy. The results support timely treatment and careful monitoring of hyperthyroid patients in order to reduce cardiovascular risk.

A Comparison of Doppler Flow Parameters in the Ophthalmic Artery and Central Retinal Artery in Patients With Graves' Disease and Toxic Nodular Goiter

Purpose: Despite unquestionable clinical usefulness of Clinical Activity Score, the evaluating system needs frequent supplementation. One of such diagnostic tools is Doppler imaging that is used for the analysis of flow in the retrobulbar vessels. The improvement of the reliability and sensibility of measurements could make Doppler imaging an everyday clinical tool and improve the efficacy of treatment in patients with active thyroid-associated orbitopathy. However, the systemic influence of hyperthyroidism on the orbital vessels can falsify the assessment of local inflammation severity. Methods: To eliminate the influence of systemic hyperthyroidism on orbital vessels, we compared peak systolic velocity (PSV), end-diastolic velocity (EDV), and resistance index (RI) in the central retinal artery (CRA), and ophthalmic artery (OA) in patients with hyperthyroidism in the course of Graves' disease without any detectable orbital changes, (CAS = 0) and toxic nodular goiter. Results: There were no statistically significant differences between the patients with Graves' disease and toxic nodular goiter in terms of the examined parameters in either of the arteries. However, higher PSV and RI and lower EDV in the CRA as well as higher PSV and EDV and unchanged RI in the OA were found in the patients with Graves' diseases and toxic nodular goiter. Conclusion: Hyperthyroidism and hyperthyroidism-induced hyperkinetic flow have a systemic influence on the orbital vessels, irrespective of the cause of hyperthyreosis. Thus, it is necessary to compare the flow parameters in retrobulbar vessels in Graves' patients with the toxic nodular goiter patients to eliminate the systemic influence of hyperthyroidism on the orbital vessels.

Biphasic dyslipidemia in a patient with painless thyroiditis

In this case study, we followed the thyroid function and serum lipid levels of a patient with painless thyroiditis. Serum lipid levels were decreased during the hyperthyroid phase and elevated during the hypothyroid phase. Both serum lipid levels and thyroid function returned to normative values following a course of thyroid replacement treatment.

Cardiovascular Morbidity and Mortality After Treatment of Hyperthyroidism with Either Radioactive Iodine or Thyroidectomy

BACKGROUND

Hyperthyroid patients remain at an increased risk of cardiovascular diseases (CVDs) after restoring euthyroidism. The impact of the different treatment modalities of hyperthyroidism on future CVD risk remains unclear. The aims of this study were to assess cardiovascular morbidity and mortality in hyperthyroidism before and after treatment, and to compare the effects of two different treatment modalities: radioactive iodine (RAI) and thyroid surgery.

METHODS

A comparative cohort study was conducted among 6148 hyperthyroid patients treated with either RAI or thyroidectomy and 18,432 age- and sex-matched controls. First, hospitalizations due to CVDs prior to the treatment were analyzed. Second, the hazard ratios (HR) for any new hospitalization and mortality due to CVDs after treatment were estimated among all the hyperthyroid patients compared to the age- and sex-matched controls and also in the RAI-treated patients compared to the thyroidectomy-treated patients. The results were adjusted for prevalent CVDs at the time of treatment.

RESULTS

Before treatment for hyperthyroidism, hospitalizations due to all CVDs were more common in the hyperthyroid patients compared to the controls (odds ratio = 1.61 [confidence interval (CI) 1.49-1.73]). During the post-treatment follow-up, hospitalizations due to CVDs remained more frequent among the patients (HR = 1.15 [CI 1.09-1.21]), but there was no difference in CVD mortality (HR = 0.93 [CI 0.84-1.03]). Compared to the patients treated with thyroidectomy, the RAI-treated patients had a higher risk of hospitalization due to all CVDs (HR = 1.17), atrial fibrillation (HR = 1.28), as well as a higher CVD mortality rate (HR = 2.56). Yet, treatment with RAI resulting in hypothyroidism was not associated with increased CVD morbidity compared to thyroidectomy.

CONCLUSIONS

Hyperthyroidism increases the risk of CVD-related hospitalization, and the risk is sustained for up to two decades after treatment with RAI or surgery. Hyperthyroid patients treated with RAI remain at a higher CVD risk compared to patients treated with thyroidectomy. Hypothyroidism during follow-up, however, predicts better cardiovascular outcomes.

Subclinical hypothyroidism and metabolic risk factors association: A health examination-based study in northern Taiwan

Background

Subclinical hypothyroidism (SCH) is defined as elevation in serum thyroid-stimulating hormone (TSH) levels despite normal serum levels of free thyroxine. It remains controversial whether people with SCH have higher total cholesterol and low-density lipoprotein cholesterol levels compared to normal-thyroid subjects. The aim of this study was to assess the metabolic risk factors for SCH.

Methods

Subjects were recruited from the health examination center of Chang Gung Memorial Hospital, Linkou, from January 1, 2010 to December 31, 2011. This was a cross-sectional review of medical records. The subjects were ethnic Taiwanese residents without known thyroid disease at baseline.

Results

A total of 22,324 subjects received annual health examination at Chang Gung Memorial Hospital from 2010 to 2011. Among them, 15,943 subjects were included as the normal thyroid group (NG), and 203 subjects (101 men and 102 women) met the criteria for SCH. The prevalence of metabolic syndrome (MetS) in the NG was 26.2% in men and 18.7% in women, whereas that in the SCH group was 39.6% in men and 29.4% in women. Women in the SCH group showed significantly higher cholesterol, triglyceride, non-high density lipoprotein (HDL) and cholesterol/HDL levels than those in the NG (p < 0.05).

Conclusion

Because SCH is more prevalent in women and the risk increases with age, greater attention to the risk of MetS development is warranted. As for men, regardless of thyroid function, the risk of MetS development with age still warrants attention. Thus, our data suggest that national guidelines for screening for thyroid disease using serum TSH levels in the elderly are mandatory.

Mitochondrial Bioenergetics During Ischemia and Reperfusion

During ischemia and reperfusion (I/R) mitochondria suffer a deficiency to supply the cardiomyocyte with chemical energy, but also contribute to the cytosolic ionic alterations especially of Ca²⁺. Their free calcium concentration ([Ca²⁺]m) mainly depends on mitochondrial entrance through the uniporter (UCam) and extrusion in exchange with Na⁺ (mNCX) driven by the electrochemical gradient (ΔΨm). Cardiac energetic is frequently estimated by the oxygen consumption, which determines metabolism coupled to ATP production and to the maintaining of ΔΨm. Nevertheless, a better estimation of heart energy consumption is the total heat release associated to ATP hydrolysis, metabolism, and binding reactions, which is measurable either in the presence or the absence of oxygenation or perfusion. Consequently, a mechano-calorimetrical approach on isolated hearts gives a tool to evaluate muscle economy. The mitochondrial role during I/R depends on the injury degree. We investigated the role of the mitochondrial Ca²⁺ transporters in the energetic of hearts stunned by a model of no-flow I/R in rat hearts. This chapter explores an integrated view of previous and new results which give evidences to the mitochondrial role in cardiac stunning by ischemia o hypoxia, and the influence of thyroid alterations and cardioprotective strategies, such as cardioplegic solutions (high K-low Ca, pyruvate) and the phytoestrogen genistein in both sex. Rat ventricles were perfused in a flow-calorimeter at either 30 °C or 37 °C to continuously measure the left ventricular pressure (LVP) and total heat rate (Ht). A pharmacological treatment was done before exposing to no-flow I and R. The post-ischemic contractile (PICR as %) and energetical (Ht) recovery and muscle economy (Eco: P/Ht) were determined during stunning. The functional interaction between mitochondria (Mit) and sarcoplasmic reticulum (SR) was evaluated with selective mitochondrial inhibitors in hearts reperfused with Krebs-10 mM caffeine-36 mM Na⁺. The caffeine induced contracture (CIC) was due to SR Ca²⁺ release, while relaxation mainly depends on mitochondrial Ca²⁺ uptake since neither SL-NCX nor SERCA are functional under this media. The ratio of area-under-curves over ischemic values (AUC-ΔHt/AUC-ΔLVP) estimates the energetical consumption (EC) to maintain CIC. Relaxation of CIC was accelerated by inhibition of mNCX or by adding the aerobic substrate pyruvate, while both increased EC. Contrarily, relaxation was slowed by cardioplegia (high K-low Ca Krebs) and by inhibition of UCam. Thus, Mit regulate the cytosolic [Ca²⁺] and SR Ca²⁺ content. Both, hyperthyroidism (HpT) and hypothyroidism (HypoT) reduced the peak of CIC but increased EC, in spite of improving PICR. Both, CIC and PICR in HpT were also sensitive to inhibition of mNCX or UCam, suggesting that Mit contribute to regulate the SR store and Ca²⁺ release. The interaction between mitochondria and SR and the energetic consequences were also analyzed for the effects of genistein in hearts exposed to I/R, and for the hypoxia/reoxygenation process. Our results give evidence about the mitochondrial regulation of both PICR and energetic consumption during stunning, through the Ca²⁺ movement.

Increased Cardiovascular Mortality and Morbidity in Patients Treated for Toxic Nodular Goiter Compared to Graves' Disease and Nontoxic Goiter

BACKGROUND

Previous research has suggested an increased risk of death and cardiovascular disease in patients treated for hyperthyroidism. However, studies on this subject are heterogeneous, often based on old data, or have not considered the impact that treatment for hyperthyroidism might have on cardiovascular risk. It is also unclear whether long-term prognosis differs between Graves' disease and toxic nodular goiter. The aim of this study was to use a very large cohort built on recent data to assess whether improvements in cardiovascular care might have changed the prognosis over time. The study also investigated the impact of different etiologies of hyperthyroidism.

METHODS

This was an observational register study for the period 1976-2012, with subjects followed for a median period of 18.4 years. Study patients were Stockholm residents treated for Graves' disease or toxic nodular goiter with either radioactive iodine or surgery (N = 12,239). This group was compared to Stockholm residents treated for nontoxic goiter (N = 3685), with adjustments made for age, sex, comorbidities, and time of treatment. Comparisons were also made to the general population of Stockholm. Outcomes were assessed in terms of all-cause and cardiovascular mortality as well as cardiovascular morbidity.

RESULTS

The hazard ratios (HR) for all-cause mortality and for cardiovascular mortality were 1.27 [confidence interval (CI) 1.20-1.35] and 1.29 [CI 1.17-1.42], respectively, for hyperthyroid patients compared to those with nontoxic goiter. For cardiovascular morbidity, the HR was 1.12 [CI 1.06-1.18]. Patients aged ≥45 years who were treated for toxic nodular goiter were generally at greater risk than others, and those included from the year 1990 and onwards were at greater risk than those included earlier. Increased all-cause mortality, as well as cardiovascular mortality and morbidity, were also seen in comparisons with the general population.

CONCLUSIONS

This is the first large study to indicate that the long-term risk of death and cardiovascular disease in hyperthyroid subjects is due to the hyperthyroidism itself and not an effect of confounding introduced by its treatment. Much of the excess risk is confined to individuals treated for toxic nodular goiter. Despite advances in cardiovascular care during recent decades, hyperthyroidism is still a diagnosis associated with increased cardiovascular morbidity and mortality.

Excess Mortality in Treated and Untreated Hyperthyroidism Is Related to Cumulative Periods of Low Serum TSH

INTRODUCTION AND AIM

Cumulative time-dependent excess mortality in hyperthyroid patients has been suggested. However, the effect of antithyroid treatment on mortality, especially in subclinical hyperthyroidism, remains unclarified. We investigated the association between hyperthyroidism and mortality in both treated and untreated hyperthyroid individuals.

PATIENTS AND METHODS

Register-based cohort study of 235,547 individuals who had at least one serum thyroid-stimulating hormone (TSH) measurement in the period 1995 to 2011 (7.3 years median follow-up). Hyperthyroidism was defined as at least two measurements of low serum TSH. Mortality rates for treated and untreated hyperthyroid subjects compared with euthyroid controls were calculated using multivariate Cox regression analyses, controlling for age, sex, and comorbidities. Cumulative periods of decreased serum TSH were analyzed as a time-dependent covariate.

RESULTS

Hazard ratio (HR) for mortality was increased in untreated [1.23; 95% confidence interval (CI), 1.12 to 1.37; P < 0.001], but not in treated, hyperthyroid patients. When including cumulative periods of TSH in the Cox regression analyses, HR for mortality per every 6 months of decreased TSH was 1.11 (95% CI, 1.09 to 1.13; P < 0.0001) in untreated hyperthyroid patients (n = 1137) and 1.13 (95% CI, 1.11 to 1.15; P < 0.0001) in treated patients (n = 1656). This corresponds to a 184% and 239% increase in mortality after 5 years of decreased TSH in untreated and treated hyperthyroidism, respectively.

CONCLUSIONS

Mortality is increased in hyperthyroidism. Cumulative periods of decreased TSH increased mortality in both treated and untreated hyperthyroidism, implying that excess mortality may not be driven by lack of therapy, but rather inability to keep patients euthyroid. Meticulous follow-up during treatment to maintain biochemical euthyroidism may be warranted.

Nomogram for radiation-induced hypothyroidism prediction in nasopharyngeal carcinoma after treatment

OBJECTIVE

The aim of this study was to develop a nomogram for radiation-induced hypothyroidism (RHT) prediction.

METHODS

We collected data from 164 patients with nasopharyngeal carcinoma (NPC) in our previous prospective study. Biochemical hypothyroidism was defined as a serum thyroid-stimulating hormone level greater than the normal value. We collected both clinical and dose-volume factors. A univariate Cox regression analysis was performed to identify RHT risk factors. Optimal predictors were selected according to the least absolute shrinkage and selection operator (LASSO). We then selected the Cox regression models that best balanced the prediction performance and practicability to build a nomogram for RHT prediction.

RESULTS

There were 38 (23.2%) patients who developed RHT, and the median follow-up was 24 months. The univariate Cox regression analysis indicated that gender, minimum dose, mean dose (D_mean) and V₂₅-V₆₀ [V_x (%), the percentage of thyroid volume receiving >x Gy] of the thyroid were significantly associated with RHT. The variables of gender, receiving chemotherapy or not (chemo), D_mean and V₅₀ were selected using the LASSO analysis. A nomogram based on a three-variable (gender, chemo and V₅₀) Cox regression model was constructed, and its concordance index was 0.72. Good accordance between prediction and observation was showed by calibration curves in the probability of RHT at 18, 24 and 30 months.

CONCLUSION

This study built a nomogram for RHT in NPC survivors by analyzing both clinical and dose-volume parameters using LASSO. Thus, the individual dose constraint could be achieved in a visual format. Advances in knowledge: This study used LASSO to more accurately address the multicollinear problem between variables. The resulting nomogram will help physicians predict RHT.

Low Urinary Iodine Concentrations Associated with Dyslipidemia in US Adults

Iodine is an essential component of the thyroid hormone which plays crucial roles in healthy thyroid function and lipid metabolism. However, the association between iodine status and dyslipidemia has not been well established at a population level. We aimed to test the hypothesis that the odds of dyslipidemia including elevated total cholesterol, triglycerides, low-density lipoprotein (LDL) cholesterol and apolipoprotein B, and lowered high-density lipoprotein (HDL) cholesterol and HDL/LDL ratio are associated with urinary iodine concentration (UIC) in a population perspective. Data of 2495 US adults (≥20 years) in the National Health and Nutrition Examination Survey 2007–2012 were used in this study. Two subgroups (i.e., UIC below vs. above the 10th percentile) were compared of dyslipidemia as defined based on NCEP ATP III guidelines. The differences between the groups were tested statistically by chi-square test, simple linear regressions, and multiple logistic regressions. Serum lipid concentrations differed significantly between two iodine status groups when sociodemographic and lifestyle covariates were controlled (all, p < 0.05). Those with the lowest decile of UIC were more likely to be at risk for elevated total cholesterol (>200 mg/dL) (adjusted odds ratio (AOR) = 1.51, 95% confidence interval (CI): 1.03–2.23) and elevated LDL cholesterol (>130 mg/dL) (AOR = 1.58, 95% CI: 1.11–2.23) and lowered HDL/LDL ratio (<0.4) (AOR = 1.66, 95% CI: 1.18–2.33), compared to those with UIC above the 10th percentile. In US adults, low UIC was associated with increased odds for dyslipidemia. Findings of the present cross-sectional study with spot urine samples highlight the significant association between UIC and serum lipids at population level, but do not substantiate a causal relationship. Further investigations are warranted to elucidate the causal relationship among iodine intakes, iodine status, and serum lipid profiles.

Thyroid function, as assessed by TSH, and future risk of venous thromboembolism: the Tromsø study

OBJECTIVE

The relationship between thyroid function and the risk of venous thromboembolism (VTE) has not been addressed in population-based cohorts. We investigated the association between TSH levels and the risk of VTE in a general adult population.

DESIGN

Population-based cohort study.

METHODS

TSH was measured in 11 962 subjects aged 25-89 years who participated in Tromsø 4-6 starting in 1994-1995. Incident VTE events were recorded through 31st December 2010. Cox's regression models with TSH as a time-varying covariate were used to calculate hazard ratios (HRs) of VTE by TSH categories (low TSH: <0.05  mU/l; moderately reduced TSH: 0.05-0.19  mU/l; normal TSH: 0.20-4.00  mU/l; moderately elevated TSH: 4.01-5.00  mU/l; and high TSH: >5.00 mU/l) and within the normal range of TSH, modeling TSH as a continuous variable.

RESULTS

There were 289 VTEs during 8.2 years of median follow-up. Subjects with low (prevalence: 0.22%) and high (3.01%) TSH had slightly higher risk estimates for VTE than did subjects with normal TSH (multivariable HRs: 2.16, 95% CI 0.69-6.76 and 1.55, 95% CI 0.87-2.77 respectively), but the CIs were wide. Moreover, there was no association between TSH within the normal range and VTE (HR per 1 mU/l increase: 0.95, 95% CI 0.82-1.11).

CONCLUSION

Serum levels of TSH within the normal range were not associated with a risk of VTE, whereas low and high TSH levels were rare and associated with a moderately higher risk of VTE. The present findings suggest that only a minor proportion of the VTE risk in the population can be attributed to thyroid dysfunction.

An examination of myth: a favorable cardiovascular risk-benefit analysis of high-dose thyroid for affective disorders

INTRODUCTION

High dose thyroid (HDT) is included in major treatment guidelines for the treatment of bipolar disorders. Yet it is seldom used partly based on perceived cardiovascular risks. The cardiovascular risks of HDT are examined.

METHODS

A literature search was conducted for the cardiovascular risks of HDT and for comparisons sake psychiatric medications. Case reports of atrial fibrillation (afib) associated with HDT are reported.

RESULTS

While hyperthyroidism is a significant cardiovascular risk factor causing a 20% premature death rate, HDT treatment does not appear to be of significant cardiovascular risk. HDT differs from hyperthyroidism in significant ways. The sequela of hyperthyroidism are increasingly tied to autoimmune complications which are absent with HDT. Equating hyperthyroidism with HDT is incorrect. The five case reports of HDT treatment associated with afib were potentially caused by other factors. If HDT increases the risks of afib, monitoring for afib would minimizes the risk. Even in overt hyperthyroidism the risk of other arrhythmias are minimal. When compared to many psychiatric medications HDT is as safe or safer.

LIMITATIONS

There are no direct studies of cardiovascular risks of HDT for affective patients. High tolerance of a medication does not necessarily imply lack of risk. The five case reports were spontaneous, other cases may not have been reported.

CONCLUSION

The cardiovascular risks of HDT appear to be low. HDT is at least as safe as or safer than many psychiatric medications. It is effective and well tolerated.

Serum free thyroxine levels are positively associated with arterial stiffness in the SardiNIA study

OBJECTIVE

Thyroid dysfunction may accelerate atherosclerosis. Aortic pulse wave velocity (PWV) is an early index of arterial stiffness and an important risk factor for cardiovascular disease and might therefore be linked to changes in thyroid activity. We investigated the relationship between thyroid function and carotid-femoral PWV, as an index of arterial stiffness.

DESIGN

Cross-sectional cohort study.

PATIENTS

Participants from the SardiNIA study. Those being treated for thyroid diseases were excluded, yielding a sample of 5875 aged 14-102.

MEASUREMENTS

Clinical parameters, blood tests including serum TSH and serum FT4, and carotid-femoral PWV were measured.

RESULTS

After adjusting for confounders, a direct and linear association between FT4 and PWV was shown (multiple regression analysis). The model containing age, mean blood pressure, body mass index, heart rate, FT4, hypertension, diabetes and dyslipidaemia accounted for 55% of the variation in PWV.

CONCLUSIONS

Like several other known risk factors, serum FT4 levels are associated with carotid-femoral PWV, suggesting that high FT4 levels have a detrimental effect on aortic stiffness and may contribute to ageing process of the vascular system. This finding may help to understand the pathogenesis of cardiovascular disease and contribute to improve prevention therapy.

Effects of levothyroxine replacement therapy on parameters of metabolic syndrome and atherosclerosis in hypothyroid patients: a prospective pilot study

The aim of this study was to investigate the effect of levothyroxine (LT4) replacement therapy during three months on some parameters of metabolic syndrome and atherosclerosis in patients with increased thyroid-stimulating hormone (TSH) level. This study included a group of 30 female patients with TSH level >4 mIU/L and 15 matched healthy controls. Intima media complex thickness (IMCT) and peak systolic flow velocity (PSFV) of superficial femoral artery were determined by Color Doppler scan. In hypothyroid subjects, BMI, SBP, DBP, and TSH were significantly increased versus controls and decreased after LT4 administration. FT4 was significantly lower in hypothyroid subjects compared with controls and significantly higher by treatment. TC, Tg, HDL-C, and LDL-C were similar to controls at baseline but TC and LDL-C were significantly decreased by LH4 treatment. IMCT was significantly increased versus controls at baseline and significantly reduced by treatment. PSFV was similar to controls at baseline and significantly decreased on treatment. In this study, we have demonstrated the effects of LT4 replacement therapy during three months of treatment on correction of risk factors of metabolic syndrome and atherosclerosis.

Association of thyroid-stimulating hormone and cardiovascular risk factors

Thyroid hormone plays an important role in regulating the lipid and glucose metabolism. Previously, much attention has been drawn to define the pathophysiological relationship between thyroid dysfunction and the incidence of cardiovascular diseases (CVDs). While the conditions of overt hypothyroidism and subclinical hypothyroidism were both emphasized, the association between CVD risks and the deregulated circulating thyroid-stimulating hormone (TSH) level remains to be elucidated. Nevertheless, multiple TSH-mediated physiological adaptations, including alteration of the serum lipids, body mass index, blood pressure and insulin sensitivity, have led to the difficulty of clearly examining the association between the TSH level and CVD prevalence. The current review aims to 1) summarize the evidence for the role of thyroid dysfunction and TSH abnormality in CVD pathogenesis and 2) explore the possible underlying molecular mechanisms of TSH-mediated cardiovascular pathology in hopes of providing better therapeutic strategies for the patients with deregulated TSH.

Duration of thyroid dysfunction correlates with all-cause mortality. the OPENTHYRO Register Cohort

Introduction and Aim

The association between thyroid dysfunction and mortality is controversial. Moreover, the impact of duration of thyroid dysfunction is unclarified. Our aim was to investigate the correlation between biochemically assessed thyroid function as well as dysfunction duration and mortality.

Methods

Register-based follow-up study of 239,768 individuals with a serum TSH measurement from hospitals and/or general practice in Funen, Denmark. Measurements were performed at a single laboratory from January 1st 1995 to January 1st 2011. Cox regression was used for mortality analyses and Charlson Comorbidity Index (CCI) was used as comorbidity score.

Results

Hazard ratios (HR) with 95% confidence intervals (CI) for mortality with decreased (<0.3 mIU/L) or elevated (>4.0 mIU/L) levels of TSH were 2.22; 2.14–2.30; P<0.0001 and 1.28; 1.22–1.35; P<0.0001, respectively. Adjusting for age, gender, CCI and diagnostic setting attenuated the risk estimates (HR 1.23; 95% CI: 1.19–1.28; P<0.0001, mean follow-up time 7.7 years, and HR 1.07; 95% CI: 1.02–1.13; P = 0.004, mean follow-up time 7.2 years) for decreased and elevated values of TSH, respectively. Mortality risk increased by a factor 1.09; 95% CI: 1.08–1.10; P<0.0001 or by a factor 1.03; 95% CI: 1.02–1.04; P<0.0001 for each six months a patient suffered from decreased or elevated TSH, respectively. Subdividing according to degree of thyroid dysfunction, overt hyperthyroidism (HR_overt 1.12; 95% CI: 1.06–1.19; P<0.0001), subclinical hyperthyroidism (HR_subclinical 1.09; 95% CI: 1.02–1.17; P = 0.02) and overt hypothyroidism (HR_overt 1.57; 95% CI: 1.34–1.83; P<0.0001), but not subclinical hypothyroidism (HR_subclinical 1.03; 95% CI: 0.97–1.09; P = 0.4) were associated with increased mortality.

Conclusions and Relevance

In a large-scale, population-based cohort with long-term follow-up (median 7.4 years), overt and subclinical hyperthyroidism and overt but not subclinical hypothyroidism were associated with increased mortality. Excess mortality with increasing duration of decreased or elevated serum TSH suggests the importance of timely intervention in individuals with thyroid dysfunction.

Serum homocysteine levels are decreased in levothyroxine-treated women with autoimmune thyroiditis

BACKGROUND

Hyperhomocysteinemia is a well-known cardiovascular risk factor and its elevation is established in overt hypothyroidism. Since some authors suggest that chronic autoimmune thyroiditis per se may be considered as a novel risk factor of atherosclerosis independent of thyroid function, the analysis of classical cardiovascular risk factors might be helpful in evaluation the causative relationship. Data concerning the impact of thyroid autoimmunity in euthyroid state on homocysteine (Hcy) level is lacking. The aim of this study was to evaluate Hcy level in context of anti-thyroperoxidase antibodies (TPOAbs) in euthyroidism.

METHODS

It is a case-control study. 31 euthyroid women treated with levothyroxine (L-T4) due to Hashimoto thyroiditis (HT) and 26 females in euthyroidism without L-T4 replacement therapy were enrolled in the study. All women with HT had positive TPOAbs. Forty healthy females negative for TPOAbs comparable for age and body mass index (BMI) participated in the study as controls. Exclusion criteria were a history of any acute or chronic disease, use of any medications (including oral contraceptives and vitamin supplements), smoking, alcoholism.

RESULTS

TPOAbs titers were higher in both groups of HT patients versus the healthy controls. Hcy levels were found to be significantly lower in treated HT patients (Me 11 μmol; IQR 4.2 μmol) as compared with healthy controls (Me 13.35 μmol; IQR 6.34 μmol; p = 0.0179). In contrast, no significant difference was found between non treated HT and control group in Hcy level. The study groups and the controls did not differ in age and BMI. Furthermore, levels of TSH, FT4, TC, LDL, HDL and TAG did not differ between the study group and the control group.

CONCLUSION

The main finding of the study is a decrease in Hcy level in treated HT as compared with healthy controls. Based on our observations one can also assume that correct L-T4 replacement was associated here with a decrease of Hcy. Furthermore, it seems that non treated HT in euthyroidism is not associated with Hcy increase, in contrast to overt hypothyroidism. This may be just another argument against the concepts about the role of "euthyroid HT" in the development of atherosclerosis.

The impact of thyroid autoimmunity on arterial stiffness in postmenopausal patients with fibromyalgia

OBJECTIVE

The exact mechanism of arterial stiffness in fibromyalgia (FM) remains unclear. The present study aimed to evaluate the association between thyroid function and markers of arterial function in postmenopausal FM patients.

METHODS

This study included 163 postmenopausal FM patients without any known cardiovascular diseases and within a normal reference range of thyroid-stimulating hormone (TSH) level. Clinical parameters including the Fibromyalgia Impact Questionnaire (FIQ), the pain visual analogical scale (VAS) and tender point counts were measured. Vascular function was assessed by brachial-ankle pulse wave velocity (baPWV) and flow-mediated dilation (FMD). We evaluated the associations between arterial markers and serum TSH, free thyroxin, as well as serum thyroidperoxidase autoantibody (TPO Ab).

RESULTS

Patients with a high baPWV (≥ 1490 cm/s) showed more positive TPO Ab (65% vs. 10%, P = 0.006) than those with a normal baPWV. Additionally, the baPWV values of patients with positive TPO Ab were significantly different from those with negative TPO Ab. Age, FIQ and TPO Ab were significantly correlated with baPWV and FMD (all P < 0.05). Multiple linear regression analysis revealed that the only significant predictors of baPWV were age, FIQ and the presence of TPO Ab after adjustment for traditional risk factors. A significant association was also found between FMD and positive TPO Ab.

CONCLUSION

Age, functional status and presence of TPO Ab were significantly associated with increased arterial stiffness in postmenopausal FM patients. Given the combined thyroid autoimmunity in FM patients, a re-evaluation of the effects on the vasculature may be necessary.

Relation of hypothyroidism and incident atrial fibrillation (from the Framingham Heart Study)

BACKGROUND

Hyperthyroidism has a well-described association with atrial fibrillation (AF). However, the relation of hypothyroidism to AF has had limited investigation. Hypothyroidism is associated with cardiovascular risk factors, subclinical cardiovascular disease, and overt cardiovascular disease, all of which predispose to AF. We investigated 10-year incidence of AF in a community-dwelling cohort.

METHODS

Among 6,653 Framingham heart Study participants, 5,069 participants, 52% female, with mean age of 57 ± 12 years, were eligible after excluding those with missing thyroid-stimulating hormone (TSH), TSH <0.45 μU/L (hyperthyroid), TSH >19.9 μU/L, or prevalent AF. Thyroid-stimulating hormone was categorized by range (≥0.45 to <4.5, 4.5 to <10.0, 10.0 to ≤19.9 μU/L) and by quartiles. We examined the associations between TSH and 10-year risk of AF using multivariable-adjusted Cox proportional hazards analysis.

RESULTS

Over 10-year follow-up, we observed 277 cases of incident AF. A 1-SD increase in TSH was not associated with increased risk of AF (hazard ratio 1.01, 95% CI 0.90-1.14, P = .83). In categorical analysis, using TSH ≥0.45 to <4.5 μU/L as the referent (equivalent to euthyroid state), we found no significant association between hypothyroidism and 10-year AF risk. Comparing the highest (2.6 < TSH < 19.9 μU/L) to lowest (0.45 < TSH < 1.3 μU/L) quartiles of TSH further did not identify a significant association between TSH levels and 10-year risk of AF.

CONCLUSIONS

In conclusion, we did not identify a significant association between hypothyroidism and 10-year risk of incident AF in a community-based study.

Comparison of mortality in hyperthyroidism during periods of treatment with thionamides and after radioiodine

CONTEXT

Hyperthyroidism is common, but opinions regarding optimal therapy with antithyroid drugs or radioiodine (131-I) differ. There are no randomized trials comparing these options in terms of mortality.

OBJECTIVE

The aim of the study was to determine whether mortality associated with hyperthyroidism varies with treatment administered or other factors.

DESIGN, SETTING, AND PATIENTS

We conducted a prospective observational population-based study of 1036 subjects aged ≥ 40 years presenting to a single specialist clinic from 1989-2003 with a first episode of hyperthyroidism who were followed until June 2012.

INTERVENTIONS

Antithyroid drugs or radioiodine (131-I) were administered.

MAIN OUTCOME MEASURES

We compared causes of death with age-, sex-, and period-specific mortality in England and Wales and used within-cohort analysis of influence of treatment modality, outcome, disease etiology, severity and control, and comorbidities.

RESULTS

In 12 868 person-years of follow-up, 334 died vs 290.6 expected (standardized mortality ratio [SMR], 1.15 [95% confidence interval (CI),1.03-1.28]; P = .01). Increased all-cause mortality largely reflected increased circulatory deaths (SMR, 1.20 [95% CI, 1.01-1.43]; P = .04). All-cause mortality was increased for the person-years accumulated during thionamide treatment (SMR, 1.30 [95% CI, 1.05-1.61]; P = .02) and after 131-I not associated with hypothyroidism (SMR, 1.24 [95% CI, 1.04-1.46]; P = .01) but not during T₄ replacement for 131-I-induced hypothyroidism (SMR, 0.98 [95% CI, 0.82-1.18]; P = .85). Within-cohort analysis comparing mortality during thionamide treatment showed a similar hazard ratio (HR) for all-cause mortality when 131-I did not result in hypothyroidism (HR, 0.95 [95% CI, 0.70-1.29]), but reduced mortality with 131-I-induced hypothyroidism (HR, 0.70 [95% CI, 0.51-0.96]). Reduced mortality associated with hypothyroidism was seen only in those without significant comorbidities and not in those with other serious diseases. Atrial fibrillation at presentation (P = .02) and an increment of 10 pmol/L in serial free T₄ concentration during follow-up (P = .009) were independently associated with mortality.

CONCLUSIONS

Among hyperthyroid subjects aged 40 years or older, mortality was increased during periods of thionamide treatment and after radioiodine not resulting in hypothyroidism, but not during follow-up after radioiodine-induced hypothyroidism. Independent associations of mortality with atrial fibrillation and incomplete biochemical control during treatment indicate potential causative links with poor outcome.

Thyroid dysfunction in the elderly

Thyroid dysfunction is common in the general population, and mild or subclinical forms can be present in more than 10% of individuals aged >80 years. The diagnosis of abnormal thyroid hormone concentrations in people aged >60 years poses a challenge, as the clinical presentation of thyroid dysfunction is usually nonspecific, and ageing is associated with a number of physiological changes that can affect thyroid function test results. Furthermore, the presence of acute or chronic nonthyroidal illnesses and the use of medications that interfere with thyroid function tests are common confounders in the determination of thyroid status in the elderly. Early diagnosis and treatment of overt thyroid dysfunction is crucial in this population in view of the marked effects of abnormal circulating thyroid hormone levels on a number of organ systems, including the heart, the skeleton and the neurological system. The clinical significance of mild thyroid overactivity and underactivity remains uncertain, and the need for treatment of subclinical thyroid dysfunction is much debated. A number of large epidemiological studies have identified associations between mild thyroid dysfunction and short-term as well as long-term adverse outcomes, and a small but increasing number of randomized controlled intervention studies have been reported. Guidelines recommend treatment of thyroid dysfunction on the basis of the degree of abnormal serum TSH concentrations, patient age and associated comorbidities. This Review describes the current evidence on the prevalence, diagnosis, management and long-term consequences of thyroid dysfunction in the elderly.

Graves' disease and toxic nodular goiter are both associated with increased mortality but differ with respect to the cause of death: a Danish population-based register study

BACKGROUND

Hyperthyroidism has been associated with increased all-cause mortality. Whether the underlying cause of hyperthyroidism influences this association is unclear. Our objectives were to explore whether mortality risk and cause of death differ between Graves' disease (GD) and toxic nodular goiter (TNG).

METHODS

This is an observational cohort study, using record-linkage data from nationwide Danish health registers. A total of 1291 subjects with GD and 861 with TNG, treated in a hospital setting, were identified and followed for a mean period of 11 years. Cases were matched 1:4 with nonhyperthyroid controls with respect to age and sex. The hazard ratio (HR) for mortality was calculated using Cox regression analyses. All analyses were adjusted for comorbidity using the Charlson score.

RESULTS

Both GD (HR=1.42 [95% confidence interval (CI) 1.25-1.60]) and TNG (HR=1.22 [CI 1.07-1.40]) were associated with increased all-cause mortality. After stratification for the cause of death, GD was associated with increased mortality due to cardiovascular diseases (HR=1.49 [CI 1.25-1.77]) and lung diseases (HR=1.91 [CI 1.37-2.65]), whereas TNG was associated with increased cancer mortality (HR=1.36 [CI 1.06-1.75]). When analyzing mortality in GD using TNG individuals as controls, there was no significant difference in all-cause mortality between GD and TNG. However, GD was clearly associated with a higher cardiovascular mortality (HR=1.39 [CI 1.10-1.76]) compared to TNG.

CONCLUSION

Both GD and TNG, treated in a hospital setting, are associated with increased all-cause mortality. The causes of death differ between the two phenotypes, with cardiovascular mortality being significantly higher in GD.

Excess mortality in patients diagnosed with hypothyroidism: a nationwide cohort study of singletons and twins

BACKGROUND

Although hypothyroidism is associated with increased morbidity, an association with increased mortality is still debated. Our objective was to investigate, at a nationwide level, whether a diagnosis of hypothyroidism influences mortality.

METHODS

In an observational cohort study from January 1, 1978 until December 31, 2008 using record-linkage data from nationwide Danish health registers, 3587 singletons and 682 twins diagnosed with hypothyroidism were identified. Hypothyroid individuals were matched 1:4 with nonhypothyroid controls with respect to age and gender and followed over a mean period of 5.6 years (range 0-30 years). The hazard ratio (HR) for mortality was calculated using Cox regression analyses. Comorbidity was evaluated using the Charlson score (CS).

RESULTS

In singletons with hypothyroidism, the mortality risk was increased (HR 1.52; 95% confidence interval [CI]: 1.41-1.65). Although the effect attenuated, hypothyroidism remained associated with increased mortality when evaluating subjects with a CS = 0 (HR 1.23; 95% CI: 1.05-1.44). In twin pairs discordant for hypothyroidism, the hypothyroid twin had excess mortality compared with the corresponding euthyroid cotwin (HR 1.40; 95% CI 0.95-2.05). However, after stratifying for zygosity, hypothyroidism was associated with excess mortality in dizygotic twin pairs (HR 1.61; 95% CI 1.00-2.58), whereas the association attenuated in monozygotic pairs (HR 1.06; 95% CI 0.55-2.05).

CONCLUSIONS

Hypothyroidism is associated with an excess mortality of around 50%, which to some degree is explained by comorbidity. In addition, the finding of an association between hypothyroidism and mortality within disease discordant dizygotic but not monozygotic twin pairs indicates that the association between hypothyroidism and mortality is also influenced by genetic confounding.

Record linkage in Scotland and its applications to health research

AIMS AND OBJECTIVES

  This paper will focus on the key concepts behind record linkage and describe how probability matching of Scottish health records can be used for national health research.

BACKGROUND

  Record linkage can bring together two or more records relating to the same individual. This allows information from multiple sources to be joined together to produce richer data sets for research purposes and has wide applicability in public health and epidemiological research. The probability matching techniques underpinning record linkage bring together records on a patient basis using key identifying information on each record. Scotland has a strong track record for performing linkage for research purposes owing to routinely collected and well-maintained national administrative health data sets, the emergence of the Scottish record linkage system and organisations like the Information Services Division of NHS National Services Scotland who centrally hold permanently linked patient-based databases. Design.  A record linkage retrospective population cohort study is described within this paper.

METHODS

  The paper will describe current linkage methodology before discussing typical applications in the setting of Information Services Division and focusing on a particular linkage study investigating rates and risk factors for gastroschisis.

RESULTS

  Conclusions from the gastroschisis study are typical of the types of important findings drawn from analysing linked health data.

CONCLUSIONS

  Scotland's good track record for linking records for health research is evidenced by the high volume of research projects, publications and findings resulting from probability matching of national health data. Relevance to clinical practice.  Record linkage allows information relating to the same person held across different data sources to be brought together. Probabilistic record linkage can overcome data quality issues, producing accurate matches. This allows linked, analysable, patient-based databases, capable of answering complex research questions, to be produced from several data sources with wide applications in the field of health research.

Managing thyroid dysfunction in selected special situations

Managing thyroid dysfunction is simple at first glance, the idea is to bring hormone levels in the euthyroid range, treat with antithyroid drugs, radio-iodine or surgery if toxic and replace with thyroxine or T3 if hypothyroid. Complexities arise when there are coexisting conditions that affect the thyroid or are affected by thyroid dysfunction and this review will deal with the special situations that need care when correcting thyroid hormone levels.

Excess mortality in hyperthyroidism: the influence of preexisting comorbidity and genetic confounding: a danish nationwide register-based cohort study of twins and singletons

CONTEXT

Hyperthyroidism is associated with severe comorbidity, such as stroke, and seems to confer increased mortality. However, it is unknown whether this increased mortality is explained by hyperthyroidism per se, comorbidity, and/or genetic confounding.

OBJECTIVE

The objective of the study was to investigate whether hyperthyroidism is associated with an increased mortality and, if so, whether the association is influenced by comorbidity and/or genetic confounding.

METHODS

This was an observational cohort study using record-linkage data from nationwide Danish health registers. We identified 4850 singletons and 926 twins from same-sex pairs diagnosed with hyperthyroidism. Each case was matched with four controls for age and gender. The Charlson score was calculated from discharge diagnoses on an individual level to measure comorbidity. Cases and controls were followed up for a mean of 10 yr (range 0-31 yr), and the hazard ratio (HR) for mortality was calculated using Cox regression analyses.

RESULTS

In singletons there was a significantly higher mortality in individuals diagnosed with hyperthyroidism than in controls [HR 1.37; 95% confidence interval (CI) 1.30-1.46]. This persisted after adjustment for preexisting comorbidity (HR 1,28; 95% CI 1.21-1.36). In twin pairs discordant for hyperthyroidism (625 pairs), the twin with hyperthyroidism had an increased mortality compared with the corresponding cotwin (HR 1.43; 95% CI 1.09-1.88). However, this was found only in dizygotic pairs (HR 1.80; 95% CI 1.27-2.55) but not in monozygotic pairs (HR 0.95; 95% CI 0.60-1.50).

CONCLUSIONS

Hyperthyroidism is associated with an increased mortality independent of preexisting comorbidity. The study of twin pairs discordant for hyperthyroidism suggests that genetic confounding influences the association between hyperthyroidism and mortality.

How could we improve the increased cardiovascular mortality in patients with overt and subclinical hyperthyroidism?

Over the past five years several meta-analyses have evaluated the cardiovascular mortality in patients with hyperthyroidism. They assessed various studies in which different inclusion criteria were used for the analysis of the cardiovascular mortality. More selective criteria have been used in recent meta-analyses. Only prospective cohort studies were included and only cohorts using second and third generation TSH assays were chosen. In addition, only the studies where the TSH evaluation was repeated during the follow-up were selected. The results of these recent meta-analyses provide evidence that overt and subclinical hyperthyroidism, particularly in patients with undetectable serum TSH, may increase the cardiovascular mortality. However, still today, the results remain inconclusive and not sufficient enough to recommend treatment for patients with low-detectable serum TSH. The high cardiovascular risk and mortality in presence of thyroid hormone excess suggest that this dysfunction is an important health problem and requires guidelines for the treatment of patients at high cardiovascular risk. Rigorous studies are necessary to evaluate the effects of the various causes of hyperthyroidism on the clinical outcomes. Randomized controlled clinical trials are needed to assess the benefits of treatment to improve the cardiovascular mortality and morbidity of mild and overt hyperthyroidism.

Subclinical hyperthyroidism and the risk of cardiovascular events and all-cause mortality: an updated meta-analysis of cohort studies

OBJECTIVES

Whether subclinical hyperthyroidism (SCH) results in poor prognosis remains controversial. Our aim was to evaluate the association between SCH and the risk of cardiovascular disease (CVD), cardiovascular mortality, and all-cause mortality by conducting a meta-analysis of cohort studies.

METHODS

The PubMed and Embase databases were searched through November 2011 to identify studies that met pre-stated inclusion criteria. Relevant information for analysis was extracted. Either a fixed or a random effects model was used to calculate the overall combined risk estimates.

RESULTS

Seventeen cohort studies were included in this meta-analysis. The overall combined relative risks for individuals with SCH compared with the reference group were 1.19 (95% confidence interval (CI): 1.10 to 1.28) for CVD, 1.52 (95% CI: 1.08 to 2.13) for cardiovascular mortality, and 1.25 (95% CI: 1.00 to 1.55) for all-cause mortality. Subgroup analysis by sample source (community or convenience sample) showed that the significant association for cardiovascular and all-cause mortality only existed when pooling studies from convenience samples. Heterogeneity was observed when pooling studies on the association between SCH and cardiovascular and all-cause mortality. Sensitivity analysis showed omission of each individual study did not significantly change the pooled effects. No evidence of publication bias was observed.

CONCLUSIONS

Our findings demonstrated that SCH significantly increased the risk of CVD for the general population and the risk of cardiovascular and all-cause mortality for the individuals with other morbidities.

The metabolic syndrome in thyroid disease: A report from Nigeria

BACKGROUND

The objective of this study was to determine the prevalence of the metabolic syndrome and its components in people with thyroid disorders.

MATERIALS AND METHODS

112 subjects with a history of thyroid disorders were consecutively enrolled for the study. Clinical data were obtained by interviewing the patients and referring to their case folders and prescriptions. The subjects were categorized into three: thyrotoxic, those with hypothyroidism and those with nontoxic goiters, based on clinical parameters and or thyroid function tests. The study subjects were weighed and their anthropometric indices were documented. The laboratory parameters that were analyzed included total cholesterol, high-density and low-density cholesterol and triglyceride. Statistical analysis was performed using Student's t test, one-way analysis of variance (ANOVA) test and chi-square test.

RESULTS

The study subjects were aged between 14 and 76 years, with a mean age of 44.5 years, and the female:male ratio was 97:15. The mean age and anthropometric indices were comparable in subjects with thyrotoxicosis, hypothyroidism and euthyroidism. The overall prevalence of the metabolic syndrome was 28% and the frequency of occurrence of the metabolic syndrome in subjects with thyrotoxicosis, hypothyroidism and nontoxic goiter was 24%, 40% and 42%, respectively. The commonest occurring metabolic syndrome defining criterion was dysglycemia, while hypertension and elevated triglyceride were the least documented of the criteria.

CONCLUSION

Metabolic syndrome occurs in 1 in every 4 persons with thyroid disorders, and as such, routine screening for this cardiovascular risk factor may be of benefit in this group of people, especially in those with hypothyroidism.

A review of the evidence for and against increased mortality in hypothyroidism

The lifetime risk of overt hypothyroidism is around 5%, and this disease is usually preceded by subclinical hypothyroidism, which has an even higher prevalence (estimated to be up to 9%). Hypothyroidism has been linked with cardiac dysfunction, atherosclerosis, hypertension and coagulopathy. Intuitively, this increased morbidity is expected to shorten patients' lifespan, but definitive data are lacking on whether either of these hypothyroid states (particularly overt hypothyroidism) increase mortality. Study findings are inconsistent and, overall, the pooled data do not demonstrate increased mortality in patients with either subclinical or overt hypothyroidism. However, none of the available studies was adequately designed to answer this question. This Review discusses major shortcomings in those studies, such as population dissimilarities, hypothyroid state classification and misclassification, the inclusion of nonthyroidal illness, drug interference from concurrent therapies, serious comorbidities (for example, cardiovascular disease), differences in duration of follow-up and the number of levothyroxine-treated individuals. Taken together, the data exhibit little evidence of systematic bias and no strong scientific proof of increased mortality related to either subclinical or overt hypothyroidism. Future studies, however, should take the above-mentioned shortcomings and potential genetic confounding into consideration.

A critical review and meta-analysis of the association between overt hyperthyroidism and mortality

BACKGROUND

Overt hyperthyroidism has been associated with cardiac arrhythmias, hypercoagulopathy, stroke, and pulmonary embolism, all of which may increase mortality. Some, but not all, studies show an increased mortality in patients with hyperthyroidism. This inconsistency may be due to differences in study design, characteristics of participants, or confounders. In order to test whether hyperthyroidism influences mortality, we performed a critical review and statistical meta-analysis.

METHODS

Based on an electronic PubMed search, using the Medical Subject Heading words such as hyperthyroidism, thyrotoxicosis, and mortality or survival, case-control and cohort studies were selected and reviewed. Using meta-analysis, an overall relative risk (RR) of mortality was calculated.

RESULTS

Eight studies fulfilled the inclusion criteria, six of which showed an increased all-cause mortality; seven studies, including 31,138 patients and 400,000 person years at risk, allowed calculation of mortality in a meta-analysis. Based on this, the RR of overall mortality was 1.21 (95% confidence interval: 1.05-1.38). Analyses including studies considering setting, treatment, and control for co-morbidity did not significantly alter this finding. As the measured heterogeneity (I(2)) ranges from 89.1 to 98.3%, which is much higher than the 50% generally viewed on as a threshold, the statistical heterogeneity is very pronounced in the included studies.

CONCLUSION

In patients diagnosed with hyperthyroidism, mortality is increased by ∼ 20%. Future studies need to address the cause of hyperthyroidism, impact of type of therapy, time dependency, as well as the potential influence of confounding or genetic susceptibility before the question of causality can be answered.

Cardiovascular involvement in patients with different causes of hyperthyroidism

Various clinical disorders can cause hyperthyroidism, the effects of which vary according to the patient's age, severity of clinical presentation and association with other comorbidities. Hyperthyroidism is associated with increased morbidity and mortality from cardiovascular disease, although whether the risk of specific cardiovascular complications is related to the etiology of hyperthyroidism is unknown. This article will focus on patients with Graves disease, toxic adenoma and toxic multinodular goiter, and will compare the cardiovascular risks associated with these diseases. Patients with toxic multinodular goiter have a higher cardiovascular risk than do patients with Graves disease, although cardiovascular complications in both groups are differentially influenced by the patient's age and the cause of hyperthyroidism. Atrial fibrillation, atrial enlargement and congestive heart failure are important cardiac complications of hyperthyroidism and are prevalent in patients aged > or = 60 years with toxic multinodular goiter, particularly in those with underlying cardiac disease. An increased risk of stroke is common in patients > 65 years of age with atrial fibrillation. Graves disease is linked with autoimmune complications, such as cardiac valve involvement, pulmonary arterial hypertension and specific cardiomyopathy. Consequently, the etiology of hyperthyroidism must be established to enable correct treatment of the disease and the cardiovascular complications.

Apolipoprotein E and paraoxonase 1 polymorphisms are associated with lower serum thyroid hormones in postmenopausal women

OBJECTIVE

Autoimmune thyroiditis and overt or subclinical hypothyroidism have been associated with increased prevalence of cardiovascular disease (CVD).

DESIGN

Cross-sectional investigation of the association between gene polymorphisms related to CVD with thyroid function and autoimmunity.

PATIENTS

In total 84 healthy postmenopausal women aged 49-69 years.

MEASUREMENTS

FT3, FT4, anti-TPO and anti-TG were assessed in the sera of participants. The following polymorphisms were assessed from peripheral lymphocyte DNA: Apolipoprotein E E2/E3/E4, paraoxonase 1 A/B, Glycoprotein IIIa leu33pro, MTHFR ala222val, ApoBarg3500gln, plasminogen activator inhibitor 1 4G/5G, cholesterol 7-alpha hydroxylase A204C and cholesterol ester transfer protein B1/B2.

RESULTS

A statistically significant correlation was found between Apolipoprotein E and paraoxonase 1 polymorphisms and serum thyroid hormones: carriers of the E2 or E4 allele of the ApoE gene had lower levels of FT4 (P = 0.0005) than women with the E3/E3 genotype. Carriers of the B allele of paraoxonase 1 gene had lower levels of FT3 compared to women with the wild-type genotype (P = 0.047). A statistically significant positive association (P = 0.049) was also observed between anti-TG antibodies and the presence of the E2 allele of the Apolipoprotein E gene.

CONCLUSIONS

Polymorphisms of apolipoprotein E and paraoxonase 1 are associated with different levels of thyroid hormone and anti-Tg antibody levels in the study population in this pilot study. The mechanism underlying this association remains to be elucidated.