Measurement Of Thyroid Function Research Articles

Seasonal Variation Of Vitamin D And Serum Thyrotropin Levels And Its Relationship In A Euthyroid Caucasian Population

It is unclear whether seasonal variations in vitamin D concentrations affect the hypothalamo-pituitary-thyroid axis. We investigated the seasonal variability of vitamin D and serum thyrotropin (TSH) levels and their interrelationship. Analysis of 401 patients referred with nonspecific symptoms of tiredness who had simultaneous measurements of 25-hydroxyvitamin D3 (25[OH]D3) and thyroid function. Patients were categorized according to the season of blood sampling and their vitamin D status. 25(OH)D3 levels were higher in spring-summer season compared to autumn-winter (47.9 ± 22.2 nmol/L vs. 42.8 ± 21.8 nmol/L; P = .02). Higher median (interquartile range) TSH levels were found in autumn-winter (1.9 [1.2] mU/L vs. 1.8 [1.1] mU/L; P = .10). Across different seasons, 25(OH)D3 levels were observed to be higher in lower quartiles of TSH, and the inverse relationship was maintained uniformly in the higher quartiles of TSH. An independent inverse relationship could be established between 25(OH)D3 levels and TSH by regression analysis across both season groups (autumn-winter: r = -0.0248; P<.00001 and spring-summer: r = -0.0209; P<.00001). We also observed that TSH varied according to 25(OH)D3 status, with higher TSH found in patients with vitamin D insufficiency or deficiency in comparison to patients who had sufficient or optimal levels across different seasons. Our study shows seasonal variability in 25(OH)D3 production and TSH secretion in euthyroid subjects and that an inverse relationship exists between them. Further studies are needed to see if vitamin D replacement would be beneficial in patients with borderline thyroid function abnormalities. 25(OH)D2 = 25-hydroxyvitamin D2; 25(OH)D3 = 25-hydroxyvitamin D3; AITD = autoimmune thyroid disease; FT4 = free thyroxine; TFT = thyroid function test; TSH = thyrotropin; UVB = ultraviolet B.

Increased Admissions Due to Cardiac Complications of Thyrotoxicosis in Māori

As thyrotoxicosis is a risk factor for atrial fibrillation, current guidelines recommend measuring a thyroid-stimulating hormone level in patients with this disorder. Hyperthyroidism may also be associated with other heart diseases including cardiac ischaemia and cardiac failure. Currently, the prevalence of thyrotoxicosis in cardiac admissions in the absence of a rhythm disorder is unknown. The aims of this study were: 1) to calculate the prevalence of admissions for thyrotoxicosis-associated cardiac disease, 2) determine the type of cardiac disease i.e. dysrhythmic, ischaemic or cardiac failure, and 3) to assess whether Māori are over-represented amongst patients admitted to hospital with cardiac complications of thyrotoxicosis. A retrospective review of admissions with both thyrotoxicosis and cardiac disease from 1 January 2005 to 31 December 2012 inclusive. Seventy-two patients were identified as being admitted for a cardiac complication of thyrotoxicosis, giving a mean of nine admissions per year. Dysrhythmia was the cause for admission in 32 patients, ischaemia in 12, cardiac failure in 11 and mixed cardiac disease in 17. Graves' disease and amiodarone-induced were the most common causes of the thyrotoxicosis (25 and 19 cases, respectively). Of the cohort 26 (36.1%) were Māori (compared to 16.8% of all cardiac admissions over the same period). Māori were more likely to present with cardiac failure than non-Māori (57.7% vs. 26.1%, p=0.008 respectively). Māori are over-represented amongst patients admitted with cardiac complications of thyrotoxicosis and more often present with cardiac failure than non-Māori. Measurement of thyroid function should be considered in patients presenting not only with atrial fibrillation but also in patients presenting with cardiac failure, particularly if they are Māori.

High Circulating Free Thyroxine Levels May Increase the Risk of Frailty: The Rotterdam Study.

Thyroid hormones affect metabolism in various tissues, organs, and systems. However, the overall impact of thyroid function on an individual's vulnerability to adverse outcomes remains unclear. To investigate the cross-sectional and prospective association of thyroid function with the frailty index, a well-established measure of overall health. The Rotterdam Study, a population-based, prospective cohort study. Participants with baseline measurements of thyroid function and the frailty index were eligible. The frailty index was measured at baseline and after a median follow-up time of 10.1 years (interquartile range, 5.7 to 10.8 years). A higher frailty index indicated a worse health state. We assessed the association of thyroid function with frailty at baseline, frailty at follow-up, and frailty changes over time, adjusting for age, sex, cohort, smoking, alcohol, and education. We included 9640 participants (mean age, 64.9 years). There was a U-shaped association of thyrotropin (TSH; P < 0.0003) and free thyroxine (FT4; P < 0.0001) with frailty at baseline. There was no association of TSH, but a positive association of FT4 with frailty at follow-up and frailty changes over time (β, 1.22; confidence interval, 0.73 to 1.72 per 1 unit FT4). In this population-based study, participants with low and high thyroid function were more likely to be frail than participants with normal thyroid function. However, only those with higher FT4 levels had an increased risk of becoming more frail over time. The identification of FT4 as a potential marker of health deterioration could have future implications regarding the prediction and prevention of frailty.

Thyroid Function Within the Normal Range, Subclinical Hypothyroidism, and the Risk of Atrial Fibrillation.

Atrial fibrillation (AF) is a highly prevalent disorder leading to heart failure, stroke, and death. Enhanced understanding of modifiable risk factors may yield opportunities for prevention. The risk of AF is increased in subclinical hyperthyroidism, but it is uncertain whether variations in thyroid function within the normal range or subclinical hypothyroidism are also associated with AF. We conducted a systematic review and obtained individual participant data from prospective cohort studies that measured thyroid function at baseline and assessed incident AF. Studies were identified from MEDLINE and EMBASE databases from inception to July 27, 2016. The euthyroid state was defined as thyroid-stimulating hormone (TSH) 0.45 to 4.49 mIU/L, and subclinical hypothyroidism as TSH 4.5 to 19.9 mIU/L with free thyroxine (fT4) levels within reference range. The association of TSH levels in the euthyroid and subclinical hypothyroid range with incident AF was examined by using Cox proportional hazards models. In euthyroid participants, we additionally examined the association between fT4 levels and incident AF. Of 30 085 participants from 11 cohorts (278 955 person-years of follow-up), 1958 (6.5%) had subclinical hypothyroidism and 2574 individuals (8.6%) developed AF during follow-up. TSH at baseline was not significantly associated with incident AF in euthyroid participants or those with subclinical hypothyroidism. Higher fT4 levels at baseline in euthyroid individuals were associated with increased AF risk in age- and sex-adjusted analyses (hazard ratio, 1.45; 95% confidence interval, 1.26-1.66, for the highest quartile versus the lowest quartile of fT4; P for trend ≤0.001 across quartiles). Estimates did not substantially differ after further adjustment for preexisting cardiovascular disease. In euthyroid individuals, higher circulating fT4 levels, but not TSH levels, are associated with increased risk of incident AF.

Triclosan and triclocarban exposure and thyroid function during pregnancy—A randomized intervention

Triclosan and triclocarban (TCs) are broad-spectrum microbicides found in household and personal wash products. We sought to determine whether TC exposure from wash products or urinary triclosan level modified thyroid function during pregnancy or anthropometric measurements at birth. A randomized intervention of wash products with or without TCs, including toothpaste, enrolled pregnant women from 20 weeks’ gestation. Urinary triclosan, TSH, T4 and T3 were assessed at enrollment, 36weeks’ gestation and/or post-delivery; anthropometric measures at birth were ascertained from medical records. 78 and 76 mothers were assigned to the TC-containing and no-TC-containing product arms, respectively. No differences were observed in any thyroid function measure at any time point or in any anthropometric measurement at birth between either exposure arms or lowest and highest urinary triclosan quartile groups. TCs from wash products, primarily liquid and bar soaps, did not affect thyroid function measures during pregnancy or babies’ anthropometric measures at delivery.

The association between subclinical thyroid dysfunction and dementia: The Health, Aging and Body Composition (Health ABC) Study.

Data on the association between subclinical thyroid dysfunction and dementia are limited and conflicting. We aimed to determine whether subclinical thyroid dysfunction was associated with dementia and cognitive decline. Population-based prospective cohort study. Adults aged 70-79years with measured thyroid function, but no dementia at baseline, and Modified Mini-Mental State (3MS) at baseline and follow-up. Primary outcome was incident-adjudicated dementia, based on 3MS, hospital records and dementia drugs. Secondary outcome was change in 3MS. Models were adjusted for age, sex, race, education and baseline 3MS, and then further for cardiovascular risk factors. Among 2558 adults, 85% were euthyroid (TSH 0.45-4.49mIU/L), 2% had subclinical hyperthyroidism with mildly decreased TSH (TSH 0.10-0.44mIU/L), 1% subclinical hyperthyroidism with suppressed TSH (TSH<0.10mIU/L with normal free thyroxine [FT4]) and 12% subclinical hypothyroidism (TSH 4.50-19.99mIU/L with normal FT4). Over 9years, 22% developed dementia. Compared to euthyroidism, risk of dementia was higher in participants with subclinical hyperthyroidism with suppressed TSH (HR 2.38, 95% CI=1.13;5.04), while we found no significant association in those with mildly decreased TSH (HR 0.79, 95% CI=0.45;1.38) or with subclinical hypothyroidism (HR 0.91, 95% CI=0.70;1.19). Participants with subclinical hyperthyroidism with suppressed TSH had a larger decline in 3MS (-3.89, 95% CI=-7.62; -0.15). Among older adults, subclinical hyperthyroidism with a TSH<0.10mIU/L was associated with a higher risk of dementia and a larger cognitive decline, while subclinical hyperthyroidism with mildly decreased TSH or subclinical hypothyroidism were not.

Thyroid Function during Early Life and Dental Development

Children with low levels of thyroid hormones (hypothyroidism) have delayed tooth eruption, enamel hypoplasia, micrognathia, and anterior open bite, whereas children with hyperthyroidism may suffer from accelerated tooth eruption, maxillary, and mandibular osteoporosis. However, it is still unknown whether thyroid function variations within the normal or subclinical range also have an impact on hard dental tissues in healthy children. The objective of this study was, therefore, to investigate the association between thyroid function from the fetal period until early childhood and dental development at school age. This study is embedded in the Generation R Study, a population-based cohort study established in Rotterdam, the Netherlands. Maternal thyroid function (thyroid-stimulating hormone [TSH], free thyroxine [FT4], and thyroid peroxidase antibody [TPOAb] concentrations) was measured during early pregnancy, and thyroid function of the offspring (TSH and FT4) was measured in cord blood at birth and in early childhood (6 y). Dental development was assessed from panoramic radiographs of children of school-going age (9 y). In total, 2,387 to 2,706 subjects were available for the multivariable linear regression analysis, depending on the point in time of thyroid function measurement. There was an inverse association between cord blood and early childhood TSH concentrations with dental development, with a –0.06 lower standard deviation (SD) per 1 mU/L of TSH (95% confidence interval [CI], –0.11 to –0.01) and a –0.06 lower SD per 1 mU/L of TSH (95% CI, –0.11 to 0.00), respectively. There was no association between the maternal thyroid function during pregnancy and the dental development score of the child. However, TPOAb-positive mothers had children with a –0.20 SD (adjusted 95% CI, –0.35 to –0.04) lower dental development score compared with TPOAb-negative mothers. The findings of this study suggest that the thyroid hormone is involved in the maturation of teeth from the early stages of life onward.

Changes in Acid Labile Subunit (ALS) and Insulin-Like Growth Factor 1 (IGF-1) Concentration in Hyperthyroidism before and After Medical Treatment: A Prospective Controlled Study

Background:The relationship of altered thyroid status with GH and components of insulin-like Growth factor (IGF-1) axis is complex and not fully understood. We aimed to evaluate changes in Acid labile subunit (ALS) and IGF-1 in hyperthyroidism, before and after normalization of thyroid status. Methods:Thirty-four hyperthyroid patients matched with 36 normal controls were studied. The patients and controls were assessed at baseline and the patients were followed up prospectively and re-assessed after 6 months of treatment with antithyroid drug (ATD) (carbimazole). On each occasion, blood was collected for measurement of ALS, IGF-1, glucose, insulin, intact proinsulin and thyroid function. Results: Pre-treatment levels of ALS (p=0.012) and IGF-1 (p=0.007) were significantly lower in patients than controls. Five to 10 weeks post-treatment with ATD, all patients were restored to euthyroidism. ALS and IGF-1 levels increased significantly to similar levels of controls after 6 months of ATD. Within the patients, ALS (p=0.049) and IGF-1 (p=0.001) correlated inversely with free T3, whereas, only IGF-1 (p=0.005) correlated inversely with free T4. Conclusion:These results demonstrate that untreated hyperthyroidism is associated with reduction in ALS and IGF-1. Due to the fact that ALS and IGF-1 were related inversely with thyroid status and their concentrations were normalized with euthyroidism, it would be possible to consider their reductions as helpful markers of altered thyroid status, namely hyperthyroidism.

Natural history of mild subclinical hypothyroidism in a middle-aged and elderly Chinese population: a prospective study.

Subclinical hypothyroidism (SCH) has a high global prevalence. Most SCH patients have mild cases (thyrotropin ≤10 mIU/L). Treatment recommendations for mild SCH are controversial, which raises concerns about the natural history of mild SCH. We aimed to clarify the natural history of mild SCH. This is a prospective population-based study. We measured thyroid function in 11,000 participants in the REACTION study and followed 505 newly diagnosed mild SCH patients aged 40-years or older between 2011 and 2014. Logistic regression analysis was used to seek baseline parameters associated with the natural outcomes of mild SCH. Among 505 mild SCH patients, 221 (43.8%) had persistent SCH, 251 (49.7%) reverted to euthyroidism, and 17 (3.4%) progressed to overt hypothyroidism (OH). Patients with higher baseline total cholesterol (TC, between 201.0-240.0 mg/dL or >240.0 mg/dL vs. <201.0 mg/dL, p = 0.048 and 0.006, respectively) or positive thyroid peroxidase antibodies (TPOAb, p = 0.009) had higher risks of progression to OH, while those with higher baseline creatinine (CR, between 0.71-0.80 mg/dL or >0.80 mg/dL vs. ≤0.65 mg/dL, p = 0.031 and 0.004, respectively), higher baseline thyrotropin (≥7 mIU/L, p < 0.001) or older (>60 years vs. ≤50 years, p = 0.012) had lower odds of reverting to euthyroidism. In conclusion, TPOAb and TC seem to be more important predictors of progression to OH than initial thyrotropin, whereas high baseline thyrotropin or CR were negative correlated with reversion to euthyroidism. The prognostic value of TC and CR in mild SCH should be considered.

Hypothyroidism among pediatric patients with type 1 diabetes mellitus, from patients' characteristics to disease severity.

.We performed this study to evaluate the associations of hypothyroidism with clinical severity and the occurrence of diabetic ketoacidosis (DKA) at initial diagnosis among pediatric patients with type 1 diabetes mellitus (T1DM). 330 children with T1DM who referred to Diabetes Clinic were enrolled. The medical records were e valuated and a blood sample was drawn from patients for measuring thyroid function and antibodies, blood glucose, and glycated hemoglobin (HbA1C) levels. Hypothyroidism was detected in 9.6% of children with T1DM and was associated with higher rates of DKA (OR = 3.15, 95%CI = 1.48–6.71) and younger age at initial diagnosis (7.3 ± 3.2 vs. 10.1 ± 2.5, p = 0.04), higher levels of HbA1C upon enrolment (9.8 ± 2.2 vs. 8.8 ± 1.9, p = 0.02) and the requirement for higher insulin doses to control the disease (0.9 ± 0.42 vs. 0.81 ± 0.2, p = 0.03) compared to children with T1DM and normal thyroid function. Additionally children with T1DM and hypothyroidism had significantly higher rates of anti-TPO antibodies (p < 0.001), consanguinity in their parents (p =0.01), and family history of diabetes mellitus (p = 0.02) in their first degree relatives. In conclusion autoimmune hypothyroidism is prevalent among children with T1DM and is associated with a more aggressive disease at initial presentation, poorly controlled T1DM, and requirement for higher Insulin doses for controlling the disease.

Novel Application of Quantitative Single-Photon Emission Computed Tomography/Computed Tomography to Predict Early Response to Methimazole in Graves' Disease

ObjectiveSince Graves' disease (GD) is resistant to antithyroid drugs (ATDs), an accurate quantitative thyroid function measurement is required for the prediction of early responses to ATD. Quantitative parameters derived from the novel technology, single-photon emission computed tomography/computed tomography (SPECT/CT), were investigated for the prediction of achievement of euthyroidism after methimazole (MMI) treatment in GD.Materials and MethodsA total of 36 GD patients (10 males, 26 females; mean age, 45.3 ± 13.8 years) were enrolled for this study, from April 2015 to January 2016. They underwent quantitative thyroid SPECT/CT 20 minutes post-injection of 99mTc-pertechnetate (5 mCi). Association between the time to biochemical euthyroidism after MMI treatment and %uptake, standardized uptake value (SUV), functional thyroid mass (SUVmean × thyroid volume) from the SPECT/CT, and clinical/biochemical variables, were investigated.ResultsGD patients had a significantly greater %uptake (6.9 ± 6.4%) than historical control euthyroid patients (n = 20, 0.8 ± 0.5%, p < 0.001) from the same quantitative SPECT/CT protocol. Euthyroidism was achieved in 14 patients at 156 ± 62 days post-MMI treatment, but 22 patients had still not achieved euthyroidism by the last follow-up time-point (208 ± 80 days). In the univariate Cox regression analysis, the initial MMI dose (p = 0.014), %uptake (p = 0.015), and functional thyroid mass (p = 0.016) were significant predictors of euthyroidism in response to MMI treatment. However, only %uptake remained significant in a multivariate Cox regression analysis (p = 0.034). A %uptake cutoff of 5.0% dichotomized the faster responding versus the slower responding GD patients (p = 0.006).ConclusionA novel parameter of thyroid %uptake from quantitative SPECT/CT is a predictive indicator of an early response to MMI in GD patients.

Thyroid Surgery in a Resource-Limited Setting.

Objective The present study reviews a series of patients who underwent thyroid surgery in Eldoret, Kenya, to demonstrate the feasibility of conducting long-term (>1 year) outcomes research in a resource-limited setting, impact on the quality of life of the recipient population, and inform future humanitarian collaborations. Study Design Case series with chart review. Setting Tertiary public referral hospital in Eldoret, Kenya. Subjects and Methods Twenty-one patients were enrolled during the study period. A retrospective chart review was performed for all adult patients who underwent thyroid surgery during humanitarian trips (2010-2015). Patients were contacted by mobile telephone. Medical history and physical examination, including laryngoscopy, were performed, and the SF-36 was administered (a quality-of-life questionnaire). Laboratory measurements of thyroid function and neck ultrasound were obtained. Results The mean follow-up was 33.6 ± 20.2 months after surgery: 37.5% of subtotal thyroidectomy patients and 15.4% of lobectomy patients were hypothyroid postoperatively according to serologic studies. There were no cases of goiter recurrence or malignancy. All patients reported postoperative symptomatic improvement and collectively showed positive pre- and postoperative score differences on the SF-36. Conclusion Although limited by a small sample size and the retrospective nature, our study demonstrates the feasibility of long-term surgical and quality-of-life outcomes research in a resource-limited setting. The low complication rates suggest minimal adverse effects of performing surgery in this context. Despite a considerable rate of postoperative hypothyroidism, it is in accordance with prior studies and emphasizes the need for individualized, longitudinal, and multidisciplinary care. Quality-of-life score improvements suggest benefit to the recipient population.

Elevated TSH in adults treated for hypothyroidism is associated with increased mortality.

Numerous studies investigated the link between hypothyroidism and mortality, but a definite conclusion is hard to reach as these were limited by a number of factors, including age of participants, comorbidities and single measurement of thyroid function. To evaluate the association between TSH and fT4 levels and mortality in patients with levothyroxine-treated hypothyroidism. Observational data of hospitalized patients (2011-2014). TSH and fT4 levels obtained between at least 30 days after discharge and until death or end of follow-up were collected. Median TSH and fT4 levels were stratified into categories. In total, 611 patients with treated hypothyroidism, aged 60-80 years (72% females, mean age 71 ± 6 years) were included in the study. All-cause mortality up to 66 months after discharge, by TSH and fT4 categories. During follow-up, the average numbers of TSH and fT4 measurements were 5.5 ± 3.8 and 2.5 ± 4.2 per patient respectively. Mortality rates were 28%, 29% and 54% with median TSH of 0.5-2.5, 2.5-5.0 and 5.0-10.0 IU/L respectively. Adjusted hazard ratios for mortality with median TSH between 5.0 and 10.0 IU/L were 2.3 (95% CI: 1.6-3.4) and 2.2 (95% CI: 1.6-3.2) compared with patients with TSH between 0.5-2.5 IU/L and 2.5-5 IU/L respectively. There was no difference in mortality between patients with median fT4 10-15 or 15-20 pmol/L. In treated hypothyroid adult patients and serial measurements of thyroid function tests, median TSH levels of 5-10 IU/L are associated with increased mortality with no effect of fT4 levels. Treatment should aim at achieving euthyroidism to improve survival.

Thyroid function and risk of type 2 diabetes: a population-based prospective cohort study.

BackgroundThe association of thyroid function with risk of type 2 diabetes remains elusive. We aimed to investigate the association of thyroid function with incident diabetes and progression from prediabetes to diabetes in a population-based prospective cohort study.MethodsWe included 8452 participants (mean age 65 years) with thyroid function measurement, defined by thyroid-stimulating hormone (TSH) and free thyroxine (FT4), and longitudinal assessment of diabetes incidence. Cox-models were used to investigate the association of TSH and FT4 with diabetes and progression from prediabetes to diabetes. Multivariable models were adjusted for age, sex, high-density lipoprotein cholesterol, and glucose at baseline, amongst others.ResultsDuring a mean follow-up of 7.9 years, 798 diabetes cases occurred. Higher TSH levels were associated with a higher diabetes risk (hazard ratio [HR] 1.13; 95 % confidence interval [CI], 1.08–1.18, per logTSH), even within the reference range of thyroid function (HR 1.24; 95 % CI, 1.06–1.45). Higher FT4 levels were associated with a lower diabetes risk amongst all participants (HR 0.96; 95 % CI, 0.93–0.99, per 1 pmol/L) and in participants within the reference range of thyroid function (HR 0.96; 95 % CI, 0.92–0.99). The risk of progression from prediabetes to diabetes was higher with low-normal thyroid function (HR 1.32; 95 % CI, 1.06–1.64 for TSH and HR 0.91; 95 % CI, 0.86–0.97 for FT4). Absolute risk of developing diabetes type 2 in participants with prediabetes decreased from 35 % to almost 15 % with higher FT4 levels within the normal range.ConclusionsLow and low-normal thyroid function are risk factors for incident diabetes, especially in individuals with prediabetes. Future studies should investigate whether screening for and treatment of (subclinical) hypothyroidism is beneficial in subjects at risk of developing diabetes.Electronic supplementary materialThe online version of this article (doi:10.1186/s12916-016-0693-4) contains supplementary material, which is available to authorized users.

Thyroid Function Within the Reference Range and the Risk of Stroke: An Individual Participant Data Analysis.

The currently applied reference ranges for thyroid function are under debate. Despite evidence that thyroid function within the reference range is related with several cardiovascular disorders, its association with the risk of stroke has not been evaluated previously. We identified studies through a systematic literature search and the Thyroid Studies Collaboration, a collaboration of prospective cohort studies. Studies measuring baseline TSH, free T4, and stroke outcomes were included, and we collected individual participant data from each study, including thyroid function measurements and incident all stroke (combined fatal and nonfatal) and fatal stroke. The applied reference range for TSH levels was between 0.45 and 4.49 mIU/L. We collected individual participant data on 43 598 adults with TSH within the reference range from 17 cohorts, with a median follow-up of 11.6 years (interquartile range 5.1-13.9), including 449 908 person-years. Age- and sex-adjusted pooled hazard ratio for TSH was 0.78 (95% confidence interval [CI] 0.65-0.95 across the reference range of TSH) for all stroke and 0.83 (95% CI 0.62-1.09) for fatal stroke. For the free T4 analyses, the hazard ratio was 1.08 (95% CI 0.99-1.15 per SD increase) for all stroke and 1.10 (95% CI 1.04-1.19) for fatal stroke. This was independent of cardiovascular risk factors including systolic blood pressure, total cholesterol, smoking, and prevalent diabetes. Higher levels of TSH within the reference range may decrease the risk of stroke, highlighting the need for further research focusing on the clinical consequences associated with differences within the reference range of thyroid function.

Perinatal psychological distress as a potential modifier of the association between prenatal exposure to endocrine-disrupting chemicals (PBDEs, PCBs, and PFASs) and measures of thyroid function during pregnancy and postpartum

Introduction. The rapid thyroid hormone fluctuations of the perinatal period may make pregnant women especially vulnerable to thyroid disruption, increasing their risk of postpartum depression and ...

Association of Serum Thyrotropin with Anthropometric Markers of Obesity in the General Population.

Except from associations study with body weight, there are few longitudinal data regarding the association between thyroid function and anthropometric measurements such as waist circumference, waist-to-hip ratio, or waist-to height ratio. This study aimed to investigate the association of thyrotropin (TSH) at baseline with changes in different anthropometric markers between baseline and follow-up in the general population. Data were used from four population-based longitudinal cohort studies and one population-based cross-sectional study. A total of 16,902 (8204 males) subjects aged 20-95 years from the general population were studied. Body mass index, waist circumference, waist-to-hip ratio, and waist-to-height ratio were measured. Multivariable median regression models were calculated adjusting for the following covariates: age, sex, baseline value of the respective anthropometric marker, smoking status, follow-up-time period, and study site. In cross-sectional analyses, serum TSH within the reference range was positively associated with waist circumference (β = 0.94 cm [confidence interval (CI) 0.56-1.32]) and waist-to-height-ratio (β = 0.029 [CI 0.017-0.042]). These associations were also present for the full range of TSH. In the longitudinal analyses, serum TSH at baseline was inversely associated with a five-year change of all considered anthropometric measures within the prior defined study-specific reference range, as well as in the full range of serum TSH. High TSH serum levels were positively associated with current anthropometric markers, even in the study-specific reference ranges. In contrast, high TSH serum levels were associated with decreased anthropometric markers over a time span of approximately five years. Further research is needed to determine possible clinical implications as well as public health consequences of these findings.

Thyroid Function Characteristics and Determinants: The Rotterdam Study.

Information on determinants and change of thyroid function over time is sparse and conflicting but crucial for clinical interpretation and research. Therefore, our aim was to systematically investigate determinants of thyroid-stimulating hormone (TSH), free thyroxine (FT4) (as markers of thyroid function), their mutual relation (as marker of thyroid function set point) and changes in thyroid function over time. We included 9402 participants from the Rotterdam Study not taking thyroid medication and with available thyroid function measurements. Repeated measurements (6.5-year interval) were available for 1225 participants. The association of selected determinants with TSH, FT4, and their mutual relation (reflecting thyroid function set point) was estimated using linear regression models using restricted cubic splines with three knots. The factors investigated were age, sex, body mass index (BMI), tobacco smoking, alcohol use, thyroperoxidase antibodies (TPOAb), and common genetic factors. Most influential determinants of TSH were age, smoking, genetic determinants, and TPOAb levels (p < 0.001). For FT4, most influential determinants were age, BMI, sex, genetic determinants and TPOAb levels (p < 0.001). Older age, female sex, and increased TPOAb levels were associated with a stronger relation between TSH and FT4. TSH levels did not change over time, irrespective of age. FT4 levels increased over time, most prominently in those older than 65 years of age (mean increase of 4.5 pmol/L). The main factors that influence the relationship between thyroid hormone and molar concentrations of TSH in our population-based cohort study are age, smoking, BMI, TPOAb levels, and common genetic variants. The set point that determines TSH secretion as it relates to negative thyroid hormone feedback is modified by age, sex and TPOAb positivity. FT4 levels increase over time, with a more pronounced increase in the elderly, while TSH values seem stable over time. Our results question the current notion of an increase of TSH with increasing age.

Para-Dichlorobenzene Exposure Is Associated with Thyroid Dysfunction in US Adolescents

To examine the association between exposure to para-dichlorobenzene, measured as urinary concentrations of 2,5-dichlorophenol (2,5-DCP), and thyroid function in US adolescents. A nationally representative subsample of 618 adolescents aged 12-19 years in the 2007-2008 and 2011-2012 National Health and Nutrition Examination Survey was analyzed for the association of urinary 2,5-DCP with serum thyroid function measures using multivariate logistic and general linear regression models. After adjusting for potential confounders, we found a significantly positive association between urinary concentrations of 2,5-DCP and serum levels of thyroid-stimulating hormone and thyroglobulin in adolescents. Furthermore, urinary 2,5-DCP was associated with an increased prevalence of hypothyroidism in the study population. This study demonstrates a potential relationship between para-dichlorobenzene exposure, measured as urinary 2,5-DCP, and thyroid dysfunction in adolescents; however, further studies are needed to confirm our findings and to elucidate mechanisms of action.

Thyroid Function and the Risk of Nonalcoholic Fatty Liver Disease: The Rotterdam Study.

Although thyroid function is associated with several risk factors of nonalcoholic fatty liver disease (NAFLD), its role in NAFLD development remains unclear. We aimed to prospectively investigate the association between variations in thyroid function and NAFLD. The Rotterdam Study, a large population-based, prospective cohort study. Participants with thyroid function measurements at baseline and NAFLD data (ie, at baseline fatty liver index/at follow-up ultrasound) were eligible. Transient elastography was performed to assess the presence of fibrosis in patients with NAFLD, using the liver stiffness measurements more than or equal to 8 kPa as cutoff for clinically relevant fibrosis. The association between thyroid parameters and incident NAFLD was explored by using logistic regression models. A total of 9419 participants (mean age, 64.75 y) were included. The median follow-up time was 10.04 years (interquartile range, 5.70-10.88 y). After adjusting for age, sex, cohort, follow-up time, use of hypolipidemic drugs, and cardiovascular risk factors, higher free T4 levels were associated with a decreased risk of NAFLD (odds ratio, 0.42; 95% confidence interval [CI], 0.28-0.63). In line, higher TSH levels were associated with an increased risk of having clinically relevant fibrosis in NAFLD (odds ratio, 1.49; CI, 1.04-2.15). Compared with euthyroidism, hypothyroidism was associated with a 1.24-fold higher NAFLD risk (CI, 1.01-1.53). Moreover, NAFLD risk decreased gradually from hypothyroidism to hyperthyroidism (P for trend = .003). Lower thyroid function is associated with an increased NAFLD risk. These findings may lead to new avenues regarding NAFLD prevention and treatment.