Changes In Thyroid Function Research Articles

Iodine Nutrition and Thyroid Function in Pregnant Women Exposed to Different Iodine Sources.

Pregnant women are more vulnerable to iodine deficiency and iodine excess. The study aimed to assess the changes in iodine nutrition and thyroid function of pregnant women exposed to different iodine sources resulting in various iodine intakes during pregnancy. From 2016 to 2017, 2004 healthy pregnant women aged 20-35years from Shandong and Tianjin, China, were enrolled. Urinary iodine concentration (UIC), drinking water iodine content (WIC), thyroid-stimulating hormone (TSH), free triiodothyronine (FT3), free thyroid hormone (FT4), thyroglobulin (Tg), serum thyroid peroxidase antibody (TPOAb), and thyroglobulin antibody (TgAb) were measured. Pregnant women in both Shandong and Tianjin were iodine sufficient, but the median UIC in pregnant women was significantly higher in Shandong (244μg/L) than thatin Tianjin (159μg/L). No differences were found in UIC over the course of gestation in Shandong. In Tianjin, the UIC decreased during 13-24weeks and stabilized thereafter. Compared with Tianjin, TSH levels were higher and FT3 and FT4 levels were lower in Shandong. Both FT3 and FT4 significantly decreased during pregnancy in Shandong and Tianjin. TSH and Tg increased over the course of gestation in both Shandong and Tianjin. The iodine status of pregnant women in Tianjin and Shandong were sufficient, but different changing patterns in UIC and thyroid function during pregnancy were presented. More attention should be focused on iodine nutrition of pregnant women, even in iodine-sufficient areas.

Iodine Intake is Associated with Thyroid Function in Mild to Moderately Iodine Deficient Pregnant Women.

Background: Studies indicate that mild to moderate iodine deficiency in pregnancy may have a long-term negative impact on child neurodevelopment. These effects are likely mediated via changes in maternal thyroid function, since iodine is essential for the production of thyroid hormones. However, the impact of iodine availability on thyroid function during pregnancy and on thyroid function reference ranges are understudied. The aim of this study was to investigate the association between iodine intake and thyroid function during pregnancy.Design: In a population-based pregnancy cohort including 2910 pregnant women participating in The Norwegian Mother and Child Cohort Study, we explored cross sectional associations of maternal iodine intake measured (1) by a food frequency questionnaire and (2) as iodine concentration in a spot urine sample, with plasma thyroid hormones and antibodies.Results: Biological samples were collected in mean gestational week 18.5 (standard deviation 1.3) and diet was assessed in gestational week 22. Median iodine intake from food was 121 μg/day (interquartile range 90, 160), and 40% reported use of iodine-containing supplements in pregnancy. Median urinary iodine concentration (UIC) was 59 μg/L among those who did not use supplements and 98 μg/L in the women reporting current use at the time of sampling, indicating mild to moderate iodine deficiency in both groups. Iodine intake as measured by the food frequency questionnaire was not associated with the outcome measures, while UIC was inversely associated with FT3 (p = 0.002) and FT4 (p < 0.001). Introduction of an iodine-containing supplement after gestational week 12 was associated with indications of lower thyroid hormone production (lower FT4, p = 0.027, and nonsignificantly lower FT3, p = 0.17). The 2.5th and 97.5th percentiles of TSH, FT4, and FT3 were not significantly different by groups defined by calculated iodine intake or by UIC.Conclusion: The results indicate that mild to moderate iodine deficiency affect thyroid function in pregnancy. However, the differences were small, suggesting that normal reference ranges can be determined based on data also from mildly iodine deficient populations, but this needs to be further studied. Introducing an iodine-containing supplement might temporarily inhibit thyroid hormone production and/or release.

In vitro approaches to risk assess chemical mediated changes in thyroid function

In vitro approaches to risk assess chemical mediated changes in thyroid function

Reference intervals for neonatal thyroid function tests in the first 7 days of life.

Prompt intervention can prevent permanent adverse neurological effects caused by neonatal hypothyroidism. Thyroid function changes rapidly in the first few days of life but well-defined age-specific reference intervals (RIs) for thyroid-stimulating hormone (TSH), free thyroxine (FT4) and free tri-iodothyronine (FT3) are not available to aid interpretation. We developed hour-based RIs using data mining. All TSH, FT4 and FT3 results with date and time of collection from neonates aged <7 days during 2005-2015 were extracted from the Monash Pathology database. Neonates with more than one episode of testing or with known primary hypothyroidism, identified by treating physicians or from medical records, were excluded from the analysis. The date and time of birth were obtained from the medical records. Of the 728 neonates qualifying for the study, 569 had time of birth available. All 569 had TSH, 415 had FT4 and 146 had FT3 results. For age ≤24 h, 25-48 h, 49-72 h, 73-96 h, 97-120 h, 121-144 h and 145-168 h of life, the TSH RIs (2.5th-97.5th) (mIU/L) were 4.1-40.2, 3.2-29.6, 2.6-17.3, 2.2-14.7, 1.8-14.2, 1.4-12.7 and 1.0-8.3, respectively; the FT4 RIs (mean ± 2 standard deviation [SD]) (pmol/L) were 15.3-43.6, 14.7-53.2, 16.5-45.5, 17.8-39.4, 15.3-32.1, 14.5-32.6 and 13.9-30.9, respectively; the FT3 RIs (mean±2 SD) (pmol/L) were 5.0-9.4, 4.1-9.1, 2.8-7.8, 2.9-7.8, 3.5-7.2, 3.4-8.0 and 3.8-7.9, respectively. TSH and FT4 were substantially high in the first 24 h after birth followed by a rapid decline over the subsequent 168 h. Use of hour-based RIs in newborns allows for more accurate identification of neonates who are at risk of hypothyroidism.

Thyroid Function Changes in the Elderly and Their Relationship to Cardiovascular Health: A Mini-Review

Background: Thyroid hormones have significant effects on the cardiovascular systems. In general, hyperthyroidism is associated with an increased risk of dysrhythmias, while hypothyroidism may cause atherosclerosis. Recent large studies have sought to identify aging-associated changes in thyroid function and their relevance to cardiovascular morbidity and mortality in the elderly. Conflicting results have often been published, likely due to the heterogeneity of the studied populations. Objective: This review seeks to briefly summarize the most recent large population studies analyzing thyroid changes with aging and interpreting their effects on cardiovascular health in the elderly. Methods: Selective review of recent literature. Results: The emerging pattern suggests a slight decrease in thyroid function in the elderly leading to slightly higher thyroid stimulating hormone (TSH) levels. However, the incidence of mild hyperthyroidism also increases, especially in populations with historical or current iodine deficiency. Large observational studies suggest that the potential harm from mild hypothyroidism seen in younger population tends to diminish in older subjects, while the harm from mild hyperthyroidism becomes more significant. A markedly increased risk of atrial fibrillation is a well-established consequence of subclinical hyperthyroidism in patients in the sixth decade of life and beyond. Conclusions: The absence of large prospective interventional data does not allow the formulation of strict clinical recommendations, but a higher TSH threshold for treating both subclinical hypothyroidism and subclinical hyperthyroidism in the elderly seems reasonable.

Longitudinal Trajectories of Gestational Thyroid Function: A New Approach to Better Understand Changes in Thyroid Function.

Most studies of thyroid function changes during pregnancy use a cross-sectional design comparing means between groups rather than similarities within groups. Latent class growth analysis (LCGA) is a novel approach to investigate longitudinal changes that provide dynamic understanding of the relationship between thyroid status and advancing pregnancy. Prospective observational study with repeated assessments. General community. Eleven hundred healthy women were included at 12 weeks' gestation. The existence of both free T4 (fT4) and TSH trajectories throughout pregnancy determined by LCGA. LCGA revealed three trajectory classes. Class 1 (n = 1019; 92.4%), a low increasing TSH reference group, had a gradual increase in TSH throughout gestation (from 1.1 to 1.3 IU/L). Class 2 (n = 30; 2.8%), a high increasing TSH group, displayed the largest increase in TSH (from 1.9 to 3.3 IU/L). Class 3 (n = 51; 4.6%), a decreasing TSH group, had the largest fall in TSH (from 3.2 to 2.4 IU/L). Subclinical hypothyroidism at 12 weeks occurred in up to 60% of class 3 women and was accompanied by elevated thyroid peroxidase antibodies (TPO-Ab) titers (50%) and a parental history of thyroid dysfunction (23%). In class 2, 70% of women were nulliparous compared with 46% in class 1 and 49% in class 3. LCGA revealed distinct trajectories of longitudinal changes in fT4 and TSH levels during pregnancy in 7.4% of women. These trajectories were correlated with parity and TPO-Ab status and followed patterns that might reflect differences in pregnancy-specific immune tolerance between nulliparous and multiparous women.

Thyroid function in the etiology of fatigue in breast cancer.

BackgroundCancer related fatigue (CRF), reported in about 90% of breast cancer patients receiving chemotherapy, and has a profound impact on physical function, psychological distress and quality of life. Although several etiological factors such as anemia, depression, chronic inflammation, neurological pathology and alterations in metabolism have been proposed, the mechanisms of CRF are largely unknown.MethodsWe conducted a pilot, prospective, case-control study to estimate the magnitude of change in thyroid function in breast cancer patients from baseline to 24 months, compared to cancer-free, age-matched controls. Secondary objectives were to correlate changes in thyroid function and obesity over time with fatigue symptoms scores in this patient population.ResultsThe proportion of women with breast cancer who developed subclinical or overt hypothyroidism (TSH >4.0 mIU/L) from baseline to year 1 was significantly greater compared to controls (9.6% vs. 5%; p=0.02). Subjects with breast cancer reported significantly worse fatigue symptoms than age-matched controls, as indicated by higher disruption indices (p<0.001 at baseline, p=0.02 at year 1, p=0.09 at year 2). Additionally, a significant interaction effect on disruption index score (p=0.019), general level of activity over time (p=0.006) and normal work activity (p= 0.002) was observed in the subgroup of women with BMI>30.ConclusionScreening breast cancer patients for thyroid function status at baseline and serially post-treatment to evaluate the need for thyroid hormone replacement may provide for a novel strategy for treating chemotherapy-induced fatigue.

Clinical associations of maternal thyroid function with foetal brain development: Epidemiological interpretation and overview of available evidence

Thyroid hormone is an important regulator of early brain development, particularly during early stages of gestation during which foetal thyroid hormone availability depends on the maternal transfer of thyroid hormones. There is a wide range of experimental studies showing that low maternal thyroid hormone availability is associated with suboptimal brain development parameters. While few clinical studies have shown that overt maternal hypothyroidism is associated with lower child IQ, the question whether more subclinical changes in maternal thyroid function could also lead to suboptimal foetal brain development. In this review, we put the latter studies in perspective and discuss their interpretation from an epidemiological and clinical perspective. Furthermore, we extend this discussion to also include future perspective and identify important knowledge gaps in the field.

Serum TSH level stability after 5 years in euthyroid adults at low risk for thyroid dysfunction.

To evaluate changes in thyroid function after 5 years, the interval proposed for new assessment, in initially euthyroid adults. Initially, 1,426 apparently healthy adults considered low risk for thyroid dysfunction, were evaluated by measurement of TSH. After 5 years, 1,215 (85.2%) subjects were reevaluated. After 5 years, four subjects were receiving levothyroxine (L-T4) replacement therapy and 25 others had TSH > 4 mIU/L, only two of them with TSH > 10 mIU/L. All of these subjects had TSH > 3 mIU/L in the initial evaluation. During reassessment, none of the subjects had been or was treated for hyperthyroidism and 22 had TSH < 0.4 mIU/L (none of them < 0.1 mIU/L). Nineteen of these subjects had TSH ≤ 0.6 mIU/L in the initial evaluation. Among the 1,098 subjects with TSH between 0.6 and 3 mIU/L in the initial evaluation, reassessment showed that none of the subjects was using L-T4; only three had TSH > 4 mIU/L (none of them > 10 mIU/L); none had been or was treated for hyperthyroidism, and only three had TSH < 0.4 mIU/L (none of them < 0.1 mIU/L). These results did not differ between men and women or between subjects ≤ 60 and > 60 years. Repeat TSH measurement within an interval of only 5 years would not be cost-effective in adults without known thyroid disease or risk factors for dysfunction who exhibit TSH between 0.6 and 3 mIU/L.

Nitric oxide is involved in the hypothyroidism with significant morphology changes in female Wistar rats induced by chronic exposure to high water iodine from potassium iodate

Epidemiological studies indicated that chronic exposure to high water iodine is associated with primary hypothyroidism (PH) and subclinical hypothyroidism (SCH). However, the mechanism is not well understood. In this study, we explored whether chronic exposure to high water iodine from potassium iodate (KIO3) can induce hypothyroidism in addition to determining if nitric oxide (NO) is involved in the pathogenesis. 96 female Wistar rats were divided into six groups: control, I1000μg/L, I3000μg/L, I6000μg/L, N-nitro-L-arginine methylester (L-NAME) and L-NAME+I6000μg/L. After 3 months, urine iodine concentration, thyroid hormone, NO and nitric oxide synthase (NOS) serum levels were determined. Additionally, thyroid expression of inducible nitric oxide synthase (iNOS) was also investigated. Thyroid morphology was observed under light microscopy and transmission electron microscope. SCH as indicated by elevated serum thyrotropin (TSH) was induced among rats exposed to 3000 μg/L I-, while rats treated with 6000 μg/L I- presented PH characterized by elevated TSH and lowered total thyroxine in serum. Moreover, serum NO, NOS and iNOS expression in the thyroid were significantly increased in I3000μg/L and I6000μg/L groups. Changes in thyroid function and morphology in the L-NAME+I6000μg/L group were extenuated compared to I6000μg/L group. These findings suggested that chronic exposure to high water iodine from KIO3 likely induces hypothyroidism with significant morphology changes in female Wistar rats and NO appears to be involved in the pathogenesis.

Skeletal Effects of Thyroid Hormones

The importance of functional thyroid abnormalities can hardly be overstated as they affect over 5% of the population. Thyroid hormones exert a multitude of effects on the metabolism of both the developing and the adult skeleton. It is thus unsurprising that changes in thyroid function can have a variety of often severe skeletal consequences. In recent years, numerous advances were made in the understanding of this domain. These include for instance the mapping of different pathways mediating genomic and nongenomic actions of thyroid hormones in osteoblasts and osteoclasts, or the investigation of the direct role of thyrotropin in skeletal remodeling. New disease states such as RTHα were recently recognized, and the clinical significance of subclinical thyroid dysfunctions in bone pathology is also better understood. In this current paper, we review the influence of thyroid hormones and different forms of thyroid disorders on bone metabolism with a special focus on practical clinical considerations.

Thyroid And Aging

Review physiologic thyroid function changes with aging and emphasize careful interpretation of tests in the aging population. Literature review. Using age-specific thyroid-stimulating hormone (TSH) reference ranges should minimize or avoid the unnecessary diagnosis of thyroid disease in elderly patients. Subclinical thyroid dysfunction and abnormal TSH with normal thyroid levels may improve with time, so careful monitoring of thyroid function is recommended. Overt thyroid disease should always be treated. Clinical judgement is always warranted to decide how and when to treat subclinical thyroid disease in the elderly. FT4 = free thyroxine; rT3 = reverse triiodothyronine; T3 = triiodothyronine; T4 = thyroxine; TFT = thyroid function test; TSH = thyroid-stimulating hormone.

Resolution of Severe Left Ventricular Dysfunction and Development of Pulmonary Hypertension with Change of Thyroid Function from Hypothyroidism to Hyperthyroidism in a Patient with Thyrotoxicosis: A Case Report

Resolution of Severe Left Ventricular Dysfunction and Development of Pulmonary Hypertension with Change of Thyroid Function from Hypothyroidism to Hyperthyroidism in a Patient with Thyrotoxicosis: A Case Report

Cpitn in Iraqi Females with Thyroid Dysfunction

Background: Changes in thyroid function have significant health consequences onhuman beings. Women's risk of developing thyroid problems is seven times thatof men. The associations between periodontal diseases and thyroid dysfunctionhad received great attention in periodontal literature in last few decades. In theonly few studies that conducted in Iraq, the concentration was primarily directedtoward oral health status and dental treatment needs while the periodontaltreatment needs have been omitted. This omission is definitely due to absence ofimplementation of CPITN in these studies.Aim of the study: to estimate the periodontal health status and periodontal treatmentneed among Iraqi females with thyroid dysfunction.Material and methods: sample of this study consist of 225 adult Iraqi femalesallocated into three comparable groups. Group A (patients with hypothyroidism),Group B (patients with hyperthyroidism) and Group C (control group). CPITN,CAL &amp; TN indices were recorded and the data were analyzed statistically usingSPSS program.Results: generally, healthy women found to have better periodontal health and lessclinical attachment loss compared to those with thyroid dysfunction but theseresults was not significant for all CPITN scores. On the other hand all populationsample were found to need periodontal treatment in different levels.Conclusion: Thyroid dysfunction in its both types (hypothyroidism &amp;hyperthyroidism) has its impact on periodontal health status, but this impact stillin need of more extensive researches to expand our knowledge about this vitalsubject.

Interpretation of thyroid function tests

Thyroid function tests are one of the most common endocrine panels in general practice because a good understanding of when to order them, interpretation of their results and indications for treatment are important for the optimal treatment of thyroid dysfunction. Thyroid-stimulating hormone (TSH) should be the first test to be performed on any patient with suspected thyroid dysfunction and in follow-up of individuals on treatment. It is useful as a first-line test because even small changes in thyroid function are sufficient to cause a significant increase in TSH secretion. Thyroxine levels may be assessed in a patient with hyperthyroidism, to determine the severity of hyperthyroxinemia. Antithyroid peroxidase measurements should be considered while evaluating patients with subclinical hypothyroidism and can facilitate the identification of autoimmune thyroiditis during the evaluation of nodular thyroid disease. The measurement of TSH receptor antibody must be considered when confirmation of Graves' disease is needed and radioactive iodine uptake cannot be done.

The Influence of Abnormal Mother to Infant Thyroid Function, Early Intervention Treatment on the Compensation for Mental Retardation

Objective: To observe the hyperthyroidism and hypothyroidism patients with pregnancy after production, the baby’s thyroid function changes, the baby's mental abnormality, compensation for the children with intellectual disabilities and early intervention after treatment. Methods: In this study, 151 pregnant women with abnormal thyroid function from Department of Endocrinology in Jilin Central Hospital between 2010-2016, these women in the G12 and G24 were measured FT3, FT4, TSH, TPO, TG-ab, the babies at birth, 6 months, 12 months, examine their thyroid function, exercise and intelligence score respectively. Results: Hyperthyroidism group and hypothyroidism group of pregnant women after intervention treatment of G12 and G24, thyroid function tends to normal, there were no significant differences in FT3, FT4 and TSH levels. TSH was significantly increased in the patients with hyperthyroidism group at birth, compared with the other two groups, P < 0.05, the difference was statistically significant. Comparison of the nerve intelligence development and motor scores of the pregnant women in each group MDI and PDI, the levels of MDI and PDI in the hyperthyroidism group were decreased, but the late rise was obvious, there was no significant difference between the groups. There was no significant difference in the development of thyroid and nerve intelligence and motor scores after early intervention in the healthy control group. Conclusion: The abnormal thyroid function of pregnant women can affect the thyroid function of offspring, so that the intelligence development of offspring is affected. Adverse pregnancy was significantly increased, timely intervention treatment of pregnant women with abnormal thyroid function and adjustment of sub generation, the intelligence score and the absolute value of the motor score can be increased, it shows compensative effect on mental retardation in their offspring.

Quality of Life in Patients Treated with Percutaneous Laser Ablation for Non-Functioning Benign Thyroid Nodules: A Prospective Single-Center Study.

ObjectiveWhile many studies have reported that laser ablation (LA) for benign non-fuctioning thyroid nodules is efficacious in reducing nodular volume and neck symptoms, none have described changes in quality of life (QoL). The purpose of this study was to report post-LA changes in QoL in our cohort of patients.Materials and MethodsFourteen patients with benign thyroid nodules were involved in a prospective, single-center study and underwent a single session of LA. We evaluated the following: changes in nodule volume, thyroid function, and autoimmunity; adverse events during and after LA; changes in neck discomfort by means of a visual analogic scale (VAS) at one week and 1, 3, 6, and 12 months; and changes in QoL through the 13-scale Thyroid-specific Patient Reported Outcome (ThyPRO) questionnaire at 1, 3, 6, and 12 months. ThyPRO is a validated questionnaire for thyroid diseases, which consists of 13 scales with multiple-choice answers. They investigate several aspects of life that may be impaired by goiter-related compression symptoms, by esthetic alterations and by hypo- or hyperthyroidism.ResultsNodule volume decrease was −37 ± 23%, −55 ± 22%, −53 ± 25%, −58 ± 25% (p < 0.01 vs. baseline) at the first, third, sixth, and twelfth month, respectively. No hypothyroidism or positivization of autoimmunity was observed. There were no major complications during or after LA. After LA, VAS scores improved significantly from 1 week onwards in 100% of patients, while a significant improvement was seen in the goiter symptoms score after one month, and in the general score and mean values of ThyPRO after six months. Scores on the other ThyPRO scales did not change significantly.ConclusionLaser ablation is safe and effective in reducing nodule volume and neck symptoms; this is confirmed by improvements in the goiter scale, general score, and mean values of ThyPRO and in the VAS score.

Analysis of influencing factor of newly diagnosed thyroid associated ophthalmopathy after radioiodine treatment of Graves disease in short term

Objective To analyze the relevant factor of newly diagnosed thyroid associated ophthalmopathy (TAO) after radioiodine treatment of Graves disease(GD) in short term. Methods A total of 19 patients with GD and TAO in three months after radioiodine treatment were selected as observation group, 64 patients with GD treated by radioiodine in the same period were selected as control group.The thyrotrophic receptor antibody(TRAb), thyroglobulin antibody (TGAb), thyroid peroxidase antibody(TPOAb), tumor necrosis factor alpha (TNF-α) and the changes of thyroid function before and after treatment were compared. Results The base line levels of TPOAb, TRAb and TNF-α had no statistically significant differences between the observation group and the control group, but the ascensional range became bigger after treatment(TPOAb: t=-5.632, P=0.000; TRAb: t=-3.284, P=0.002; TNF-α: t=-3.907, P=0.000). One month later, FT3 level increased in the observation group after treatment, but that had no significant change in the control group (t=9.475, P=0.000). After 3 months, the falling range of thyroid function had no statistically significant difference between the two groups, which suggested that the TAO was not related to hypothyroidism.The thyroid function, thyroid weight (t=0.211, P=0.833), rate of iodine intake (t=1.235, P=0.221), gender (χ2=1.554, P=0.213), age (t=0.154, P=0.878), course of disease before radioiodine treatment (Z=0.761, P=0.447) were irrelevant to the occurrence of TAO. Conclusion The rise of TRAb, TPOAb, TNF-α and thyroid function are related to TAO after radioiodine treatment.Identifying the risk factors to predispose patients with GD to develop TAO can dramatically alter the management of these patients. Key words: Graves′ disease; Thyroid Associated Ophthalmopathy; 131I treatment

Unstable Thyroid Function in Older Adults Is Caused by Alterations in Both Thyroid and Pituitary Physiology and Is Associated with Increased Mortality

Average thyrotropin (TSH) levels are known to be higher in older adults when measured in cross-sectional populations. Possible etiologies include differential survival, neutral aging changes, or increased disease prevalence at older ages. This study aimed to elucidate the mechanisms underlying changing thyroid function during aging, and to determine the association of changes with survival, by analyzing the individual thyroid axis over time. Individual patterns of changing TSH and free thyroxine (fT4) were determined in 640 participants in the Baltimore Longitudinal Study of Aging who had at least three measures of serum TSH and fT4, not on medications, over an average of seven years of follow-up. Participants with changing phenotypes were identified based on quintiles for both slopes. Those with alterations in primary thyroid gland function demonstrated intact negative feedback (rising TSH with declining fT4 or declining TSH with rising fT4). Other participants had a parallel rise or fall of TSH and fT4 levels, consistent with pituitary dysfunction. Predictors of phenotype were analyzed by logistic regression. Differential survival between thyroid aging phenotypes was analyzed using multivariate Cox regression. While the majority of participants at all ages had stable thyroid function, changes were more common among older adults, with 32.3% of those aged >80 years but only 9.5% of those aged <60 years demonstrating thyroid function changes in the highest and lowest quintiles. Regression to the mean accounts for some of the changes, for example increased baseline TSH was associated with a falling TSH pattern (odds ratio = 1.4 [confidence interval 1.1-1.7] per 1 mIU/L). Importantly, changing thyroid function in either the upper or lower quintiles of slope for TSH and fT4 was associated with increased risk of death compared to stable thyroid status (hazard ratio = 5.4 [confidence interval 3.1-9.5]). Changing thyroid hormone function is increasingly common at older ages and is associated with decreased survival. Nonetheless, the tendency for abnormal thyroid function tests to resolve, along with altered pituitary responsiveness underlying some TSH elevations, suggests that an elevated TSH level should be not assumed to represent subclinical hypothyroidism in older adults. Thus, caution is appropriate when determining the need for thyroid hormone supplements in older adults.

Association Between Organophosphate Pesticide Exposure and Thyroid Hormones in Pregnant Women.

Use of organophosphate pesticides (OPs) is widespread in China. Although animal studies suggested that OP exposure could affect thyroid function, little is explored in human populations. We investigated levels of OP exposure in pregnant women and the relationship between OPs and thyroid hormones in Shandong, China. We enrolled 637 pregnant women from April 2011 to December 2013. OP exposure was assessed by a questionnaire administered to the pregnant women in the hospital and by analyses of urinary dialkylphosphate (DAP) metabolites of OPs in pregnant women (n = 413). We measured the concentration of five thyroid hormones in serum samples in pregnant women (n = 325) and analyzed the association between DAP metabolites of OPs and thyroid hormones (n = 325). Median levels of DAP metabolites were 9.81 μg/L for dimethylphosphate (DMP), 0.79 μg/L for dimethylthiophosphate (DMTP), 5.00 μg/L for diethylphosphate (DEP), and 0.78 μg/L for diethylthiophosphate (DETP), which were higher than those reported in developed countries. We found that the total DAP concentration (the sum of DMP, DMTP, DEP, and DETP) in urine was positively associated with free T4 levels (β = 0.137; 95% confidence interval [CI] = 0.012, 0.263) and negatively associated with thyroid-stimulating hormone levels (β = -0.145; 95% CI = -0.242, -0.048). The findings suggest that OP exposure may be associated with changes in thyroid function in pregnant women. Given that urinary OP levels in pregnant women in Shandong were much higher than those reported in developed countries, further studies on the effects of OP exposure on thyroid function in pregnant women in China are warranted.