The impact of environmental factors and contaminants on thyroid function and disease from fetal to adult life: current evidence and future directions.

The thyroid gland regulates most of the physiological processes. Environmental factors, including climate change, pollution, nutritional changes, and exposure to chemicals, have been recognized to impact thyroid function and health. Thyroid disorders and cancer have increased in the last decade, the latter increasing by 1.1% annually, suggesting that environmental contaminants must play a role. This narrative review explores current knowledge on the relationships among environmental factors and thyroid gland anatomy and function, reporting recent data, mechanisms, and gaps through which environmental factors act. Global warming changes thyroid function, and living in both iodine-poor areas and volcanic regions can represent a threat to thyroid function and can favor cancers because of low iodine intake and exposure to heavy metals and radon. Areas with high nitrate and nitrite concentrations in water and soil also negatively affect thyroid function. Air pollution, particularly particulate matter in outdoor air, can worsen thyroid function and can be carcinogenic. Environmental exposure to endocrine-disrupting chemicals can alter thyroid function in many ways, as some chemicals can mimic and/or disrupt thyroid hormone synthesis, release, and action on target tissues, such as bisphenols, phthalates, perchlorate, and per- and poly-fluoroalkyl substances. When discussing diet and nutrition, there is recent evidence of microbiome-associated changes, and an elevated consumption of animal fat would be associated with an increased production of thyroid autoantibodies. There is some evidence of negative effects of microplastics. Finally, infectious diseases can significantly affect thyroid function; recently, lessons have been learned from the SARS-CoV-2 pandemic. Understanding how environmental factors and contaminants influence thyroid function is crucial for developing preventive strategies and policies to guarantee appropriate development and healthy metabolism in the new generations and for preventing thyroid disease and cancer in adults and the elderly. However, there are many gaps in understanding that warrant further research.

Adverse Effects on the Thyroid of Chinese Pregnant Women Exposed to Long-Term Iodine Excess: Optimal and Safe Tolerable Upper Intake Levels of Iodine.

Ensuring optimal iodine nutrition in pregnant women is a global public health concern. However, there is no direct data on safe tolerable upper intake levels (ULs) for pregnant women. A cross-sectional study was performed to determine the ULs of pregnant women. A total of 744 pregnant women were enrolled in this study. The median (IQR) urinary iodine concentration (UIC) in pregnant women was 150.2 (87.6, 268.0) µg/L, and the urinary iodine excretion (UIE) over 24 h was 204.2 (116.0, 387.0) µg/day. Compared with those with a UIE figure of between 150-250 µg/day, the reference group, the prevalence of thyroid dysfunction was 5.7 times higher (95%CI: 1.7, 19.2) in pregnant women with a UIE figure of between 450-550 µg/day, and 3.9 times higher (95%CI: 1.5, 10.3) in pregnant women with a UIE figure of ≥550 µg/day. Compared with an estimated iodine intake (EII) of between 100-200 µg/day, the reference group, the prevalence of thyroid dysfunction was 4.3 times higher (95%CI: 1.3, 14.4) in pregnant women with a UIE figure of between 500-600 µg/day, and 3.6 times higher (95%CI: 1.5, 8.9) in pregnant women with UIE of ≥600 µg/day. In general, our cross-sectional study found that excessive iodine intake during pregnancy appears to directly increase the risk of thyroid dysfunction. Avoiding chronic iodine intakes of 500 µg/day or higher or having a UIE figure of ≥450 µg/day is recommended for pregnant women in China.

Characteristics and clinical course of thyroid abnormalities arisen in long term survivors of childhood cancer.

BACKGROUND: Thyroid abnormality is a common late effect seen in childhood cancer survivors (CCSs). We analyzed the prevalence and risk factors of thyroid abnormalities based on diagnoses and treatment modalities in CCSs. METHODS: The medical records of 257 CCSs who were diagnosed with cancer less than 20 year of age were retrospectively reviewed. The median age was 11.8 years (0.1-19.8). The median follow-up period after completion of therapy was 9.6 years (5.0-19.5). RESULTS: Of 257 subjects, thyroid abnormalities were identified in 107 (41.6%). Sixty-five out of 257 (25.3%) had subclinical hypothyroidism, and 16 (6.2%) developed central hypothyroidism. Five CCSs (1.9%) had primary overt hypothyroidism. Five (1.9%) and 6 (2.3%) CCSs were diagnosed with autoimmune thyroiditis and thyroid cancer, respectively. Among the different diagnostic groups, thyroid abnormalities were frequent in the brain tumor or Hodgkin disease or nasopharyngeal cancer groups. CCSs who received irradiation directly or near hypothalamus-pituitary-thyroid (HPT) axis had more thyroid abnormalities compared to the rest CCSs (P < 0.0001). CCSs who were treated with SCT had an increased prevalence of thyroid abnormalities (60.5%) compared to the other CCSs (37.9%) (P = 0.0069). Forty-five (42%) of 107 subjects with thyroid abnormalities had normalized thyroid hormone levels at the last follow-up. Irradiation directly or near HPT axis were thought to be a predicting factor of persistent subclinical hypothyroidism. CONCLUSIONS: Subclinical hypothyroidism was common in CCSs. CCSs with irradiation directly or near HPT axis were at risk for persistent thyroid dysfunction.

Adverse perinatal conditions and the developmental origins of thyroid dysfunction-Lessons from Animal Models.

PURPOSE: Nutritional, hormonal, and environmental status during development can predispose the individual to obesity and endocrine diseases later in life, an association known as metabolic programming. In general, weight loss or gain are seen in thyroid disorders, and thyroid function can be affected by body adiposity. In addition, hyper- and hypothyroidism can be related to metabolic programming. Our aim was to gather evidence that regardless of the type or critical window of metabolic imprinting, offspring exposed to certain adverse perinatal conditions have a higher risk of developing thyroid dysfunction. METHODS: We reviewed literature data that relate insults occurring during pregnancy and/or lactation to short- and long-term offspring thyroid dysfunction in animal models. RESULTS: Few studies have addressed the hypothalamic-pituitary-thyroid axis and thyroid dysfunction related to metabolic programming. The literature shows that under- and overnutrition, exposure to endocrine disruptors, early weaning, maternal thyroid disease and maternal high-fat diet can induce alterations in offspring thyroid function in a sex-dependent manner. CONCLUSION: Based on the few available data, mainly in rodent models, we can conclude that diet, hormones, and environmental contaminants are related to the developmental origins of later thyroid dysfunction by interrupting the normal maturation of the thyroid gland.

The Interactive Effects of Severe Vitamin D Deficiency and Iodine Nutrition Status on the Risk of Thyroid Disorder in Pregnant Women.

Thyroid dysfunction is associated with both vitamin D deficiency and iodine; however, it is unclear whether they interact. This study aimed to investigate whether and to what extent the interactions between vitamin D and iodine contribute to the risk of thyroid disorder. Participants (n = 4280) were chosen using multistage, stratified random sampling from Shanghai. Fasting blood was drawn for the 25(OH)D and thyroid parameter tests. Spot urine samples were gathered to test for urine iodine. To evaluate the interactive effects of vitamin D and iodine, crossover analysis was carried out. Pregnant women with a high urinary iodine concentration (UIC) and severe vitamin D deficiency had a significantly higher risk of thyrotropin receptor antibody (TrAb) positivity (odds ratio = 2.62, 95% confidence interval (CI): 1.32, 5.22) in the first trimester. Severe vitamin D deficiency and high UIC interacted positively for the risk of TrAb positivity (relative excess risk due to interaction = 1.910, 95%CI: 0.054, 3.766; attributable proportion = 0.700, 95%CI: 0.367, 1.03). Severe vitamin D deficiency combined with excess iodine could increase the risk of TrAb positivity in pregnant women in the first trimester.

Iron: Not Just a Passive Bystander in AITD.

Autoimmune thyroid disease (AITD) is the most prevalent autoimmune disease all over the world and the most frequent cause of hypothyroidism in areas of iodine sufficiency. The pathogenesis of AITD is multifactorial and depends on complex interactions between genetic and environmental factors, with epigenetics being the crucial link. Iron deficiency (ID) can reduce the activities of thyroid peroxidase and 5'-deiodinase, inhibit binding of triiodothyronine to its nuclear receptor, and cause slower utilization of T3 from the serum pool. Moreover, ID can disturb the functioning of the immune system, increasing the risk of autoimmune disorders. ID can be responsible for residual symptoms that may persist in patients with AITD, even if their thyrometabolic status has been controlled. The human lifestyle in the 21st century is inevitably associated with exposure to chemical compounds, pathogens, and stress, which implies an increased risk of autoimmune disorders and thyroid dysfunction. To summarize, in our paper we discuss how iron deficiency can impair the functions of the immune system, cause epigenetic changes in human DNA, and potentiate tissue damage by chemicals acting as thyroid disruptors.

Thyroid Dysfunction from Treatments for Solid Organ Cancers.

In recent years, cancer care has been transformed by immune-based and targeted treatments. Although these treatments are effective against various solid organ malignancies, multiple adverse effects can occur, including thyroid dysfunction. In this review, the authors consider treatments for solid organ cancers that affect the thyroid, focusing on immune checkpoint inhibitors, kinase inhibitors, and radioactive iodine-conjugated treatments (I-131-metaiodobenzylguanidine). They discuss the mechanisms causing thyroid dysfunction, provide a framework for their diagnosis and management, and explore the association of thyroid dysfunction from these agents with patient survival.

Thyroid function disorders and secondary cancer following haematopoietic stem cell transplantation in pediatrics: State of the art and practical recommendations for a risk-based follow-up.

Thyroid disorders (TD) represent a remarkable share of all the late morbidities experienced following pediatric haematopoietic stem cell transplantation (HSCT), with long-term reported occurrence often exceeding 70%. In addition, the data collected on wide cohorts of survivors assessed longitudinally outlined a progressive increase in the cumulative incidence of TD as far as 30 years following transplantation. Accordingly, a life-long monitoring of thyroid health is warranted among patients exposed to HSCT in childhood, in order to early detect TD and undertake a prompt dedicated treatment. Although several national and international consortia have provided recommendations for the early detection of thyroid disorders among childhood cancer survivors exposed to radiotherapy and alkylating agents, no guidelines specifically and thoroughly focused on HSCT-related TD have been published to date. As stem cell transplantation has become the standard-of-care in a growing body of non-oncological conditions, this urge has become pivotal. To highlight the challenging issues specifically involving this cohort of patients and to provide clinicians with the proposal of a practical follow-up protocol, we reviewed published literature in the light of the shared experience of a multidisciplinary team of pediatric oncologists, transplantologists, pathologists and endocrinologists involved in the long-term care of HSCT survivors. As a final result, we hereby present the proposals of a practical and customized risk-based approach to tailor thyroid health follow-up based on HSCT-related detrimental factors.

Risk of thyroid disorders in adult and childhood Hodgkin lymphoma survivors 40 years after treatment.

Thyroid abnormalities are well reported following childhood treatment for Hodgkin Lymphoma (HL). Limited information exists for adult patients and after modern treatments. We analyzed risks of thyroid disorders in 237 female participants treated at the Royal Marsden Hospital 1970-2015. Multivariable analyses of risk according to treatment and time-related factors, survival analyses, and Cox regression modeling were undertaken. Overall, 33.8% of patients reported thyroid disorders (hypothyroidism 30.0% and thyroid nodules 6.8%). Cumulative prevalence was 42.9% by 40 years follow-up. Risks were greatest after supradiaphragmatic radiotherapy (RR = 5.0, p < 0.001), and increasing dose (RR = 1.03/Gy, p < 0.001). There was no association with a chemotherapy agent. Risks of thyroid disease were as raised following adult as childhood treatment. There was no trend in risk by decade of supradiaphragmatic radiotherapy treatment. Risks of thyroid disease after supradiaphragmatic radiotherapy are as great after adult as childhood treatment and persist after more recent treatment periods.

Association Between Serum Cystatin C and Thyroid Diseases: A Systematic Review and Meta-Analysis.

Background: Cystatin C (CysC) is often used to diagnose and monitor renal diseases. Although some studies have investigated the association between serum CysC levels and thyroid diseases, their reported results were inconsistent. Therefore, the relationship between CysC levels and thyroid diseases remains controversial. Aim: This meta-analysis aimed to statistically evaluate serum CysC levels in patients with thyroid diseases. Methods: A literature search was conducted using the PubMed, Web of Science, Embase, EBSCO, and Wiley Online Library databases. The following search terms were used for the title or abstract: "Cystatin C" or "CysC" in combination with the terms "thyroid disease", "thyroid function", "hypothyroidism", or "hyperthyroidism". The results of the systematic analysis were presented as standardized mean differences (SMDs) with corresponding 95% confidence intervals (CIs). Results: Eleven articles (1,265 cases and 894 controls) were included in the meta-analysis. The results of the meta-analysis showed that the serum CysC levels of patients with hyperthyroidism were significantly higher than those of the controls (SMD: 1.79, 95% CI [1.34, 2.25]), and the serum CysC levels of patients with hypothyroidism were significantly lower than those of the controls (SMD -0.59, 95% CI [-0.82, -0.36]). Moreover, the treatment of thyroid diseases significantly affected serum CysC levels. Conclusions: To the best of our knowledge, this meta-analysis is the first to evaluate serum CysC levels in patients with thyroid diseases. Our findings suggest that thyroid function affects serum CysC levels and that serum CysC may be an effective marker for monitoring thyroid diseases. Systematic Review Registration: PROSPERO [https://www.crd.york.ac.uk/PROSPERO/display_record.php?RecordID=258022], identifier CRD42021258022].

THYROID DISEASE IN THE LATE OBSERVATION PERIOD UPON CHEMO AND RADIOTHERAPY IN CHILDREN/SURVIVORS OF ACUTE LYMPHOBLASTIC LEUKEMIA. / KhVOROBY ShchYTOPODIBNOÏ ZALOZY PISLIa KhIMIO TA PROMENEVOÏ TERAPIÏ U DITEI, IaKI PERENESLY GOSTRU LIMFOBLASTNU LEIKEMIIu, U VIDDALENOMU PERIODI SPOSTEREZhENNIa.

OBJECTIVE: to assess the thyroid disease in the late observation period in children who had received chemo- andradiotherapy for the acute lymphoblastic leukemia (ALL) taking into account gender, age period and disease sub-type. MATERIALS AND METHODS: The incidence and nature of thyroid disease (hypothyroidism, thyroiditis, and thyroid can-cer) were studied in children-survivors of acute lymphoblastic leukemia (ALL) being in remission from 6 to 25 years.The distribution of patients by leukemia subtypes was as follows: «common¼ - 67.4 %, pre-B - 23.9 %, pro-B andT-cell - 4.3 %. Children had been receiving chemo- and radiotherapy according to the protocol. Regarding the ageof patients at the time of ALL diagnosis the prepubertal, pubertal and postpubertal periods were taken into account.The endocrine diseases in family history, body weight at birth, serum content of free thyroxine, pituitary thyroid-stimulating hormone, cortisol, iron, ferritin and thyroperoxidase antibodies were evaluated and assayed. RESULTS: Thyroid disease in children was emerging in the first 2-3 years after the ALL treatment with an incidenceof 22.8 % (hypothyroidism - 14.1 %, autoimmune thyroiditis - 7.6 %, papillary cancer - 1.1 %). Seven children inthis group had received radiotherapy (12-18 Gy doses) on the central nervous system (CNS). No correlation wasfound between the radiation exposure event itself, radiation dose to the CNS and thyroid disease in the long-termfollow-up period. Thyroid cancer had developed in a child 11 years upon chemo- and radiotherapy. Hypothyroidismwas more often diagnosed in the patients of prepubertal age (rs = 0.49). There were endocrine diseases in thefamily history in about a half of children, being significantly higher than in the general sample (р < 0.05). The bodyweight at birth of a child who had later developed hypothyroidism was less than in children having got thyroiditis(rs = 0.57). CONCLUSIONS: Disorders in endocrine regulation and of thyroid in particular can affect the prognosis of blood can-cer course in the long-term follow-up in children, especially in prepubertal age, which requires systematic supervi-sion by hematologist and endocrinologist.

Characterisation of the onset and severity of adrenal and thyroid dysfunction associated with CTLA4-related hypophysitis.

CONTEXT: The use of the CTLA4 inhibitor, ipilimumab, has proven efficacious in the treatment of melanoma, renal carcinoma and non-small cell lung cancer; however, it is associated with frequent immune-related adverse events (irAE). Ipilimumab-induced hypophysitis (IIH) is a well-recognised and not infrequent endocrine irAE. OBJECTIVE: To investigate the timing of onset and severity of adrenal and thyroid hormone dysfunction around the development of IIH in patients treated for melanoma. DESIGN: Aretrospective review of hormone levels in consecutive adult patients treated with ipilimumab (3 mg/kg) for advanced melanoma as monotherapy or in combination with a PD-1 inhibitor. RESULTS: Of 189 patients, 24 (13%; 13 males; 60.5 ± 12.2 years) presented with IIH at a median of 16.1 (range: 6.7-160) weeks after commencing treatment, occurring in 14 (58%) after the fourth infusion. At the presentation of IIH, corticotroph deficiency was characterised by an acute and severe decrease in cortisol levels to ≤83 nmol/L (≤3 µg/dL) in all patients, often only days after a previously recorded normal cortisol level. Free thyroxine (fT4) levels were observed to decline from 12 weeks prior to the onset of cortisol insufficiency, with the recovery of thyroid hormone levels by 12 weeks after the presentation of IIH. A median fall in fT4 level of 20% was observed at a median of 3 weeks (IQR: 1.5-6 weeks) prior to the diagnosis of IIH. CONCLUSION: IIH is characterised by an acute severe decline in cortisol levels to ≤83 nmol/L at presentation. A fall in fT4 can herald the development of ACTH deficiency and can be a valuable early indicator of IIH.

The association between BMI, smoking, drinking and thyroid disease: a cross-sectional study in Wuhan, China.

BACKGROUND: There is no clear conclusion on the relationship between thyroid disease and obesity and lifestyle factors such as smoking and drinking. In this study, we analysed the association of body mass index (BMI), smoking and drinking with subclinical hypothyroidism (SHO) and thyroid nodules (TNs) with the results of a cross-sectional survey of urban residents in central China and discussed the potential mechanism linking these predictive factors and the two diseases. METHODS: This study included 1279 participants who were recruited from a Chinese community in 2011 and 2012. A questionnaire, laboratory examination and ultrasound diagnosis were conducted on these participants. Binary logistic regression analysis was used to analyse these factors. RESULTS: Overweight (BMI ≥ 25 kg/m2) was closely related to SHO and TNs in univariate and multivariate logistic regression analyses. Smoking had a protective effect on SHO and TNs, while drinking had a protective effect on TNs in univariate logistic regression and multivariate logistic regression with some covariates, but there was no significant difference between smoking and drinking and the two kinds of thyroid diseases in multivariate logistic regression analysis with all the covariates. In subgroup analysis, BMI ≥ 25 kg/m2 was significantly associated with SHO in people with positive thyroid antibodies (odds ratio (OR) = 2.221, 95 % confidence interval (CI): 1.168-4.184, P = 0.015) and smokers (OR = 2.179, 95 % CI: 1.041-4.561, P = 0.039). BMI ≥ 25 kg/m2 was significantly associated with TNs in people over 60 years old (OR = 2.069, 95 % CI: 1.149-3.724, P = 0.015) and drinkers (OR = 3.065, 95 % CI: 1.413-6.648, P = 0.005). Drinking alcohol had a protective effect on TNs in smokers (OR = 0.456, 95 % CI: 0.240-0.865, P = 0.016) and people with BMI ≥ 25 kg/m2 (OR = 0.467, 95 % CI: 0.236-0.925, P = 0.029). No significant association was found between smoking and the two thyroid diseases in different subgroups. CONCLUSIONS: Obesity is a risk factor for both TNs and SHO, especially in elderly individuals and people with positive thyroid autoantibodies. Obesity and metabolic syndrome may be more associated with TNs than SHO. Smoking may have a protective effect on thyroid disease, while drinking may have a protective effect only on TNs.

Serum thyroid-stimulating hormone receptor antibody levels and thyroid dysfunction after hysterosalpingography: a case-control study.

OBJECTIVE: Hysterosalpingography (HSG) performed with an iodine contrast media can cause thyroid dysfunction, including thyrotoxicosis and hypothyroidism. We investigated the association between the serum levels of thyroid-stimulating hormone receptor antibody (TRAb), an indicator of Graves' disease, and abnormal thyroid function after performing HSG. METHODS: The screening of TRAb was conducted in 362 patients who first visited the Tawara IVF Clinic between April and September 2018. The association between TRAb levels and the effects of HSG examinations on thyroid function were evaluated. RESULTS: Of the 362 patients, 2 (0.55%) had high levels (>2.0 IU/L) of TRAb, whereas 18 (5.0%) had intermediate TRAb levels, ranging from 0.3 to 1.9 IU/L. Of the 98 women (including 7 of the 18 women with TRAb level 0.3-1.9 IU/L, and 91 of the 342 women with TRAb level <0.3 IU/L) who had undergone HSG, two women developed overt thyrotoxicosis after HSG, and the frequency was significantly higher (p = .0044) in the group with intermediate levels of TRAb (28.6%, 2 of 7) than that in the group with low TRAb levels (<0.3 IU/L; 0.0%, 0 of 91). CONCLUSIONS: These findings indicate that increased serum levels of TRAb are significantly associated with the development of thyrotoxicosis after HSG.

Vitamin D and thyroid disorders: a systematic review and Meta-analysis of observational studies.

BACKGROUND: The contribution of vitamin D to thyroid disorders has received paramount attention; however, results are mixed. Hence, we designed a systematic review and meta-analysis to obtain a definitive conclusion. METHODS: The search included PubMed, ISI Web of Science, Scopus, and Google Scholar databases up to March 2021 to collect available papers reporting the relationship between serum levels of vitamin D and thyroid disorders. The pooled effect was reported as weighted mean difference (WMD) and 95% confidence interval (CI). RESULTS: Out of 6123 datasets, 42 were eligible to get into this systematic review and meta-analysis. Serum vitamin D was markedly lower in autoimmune thyroid diseases (AITD) (WMD - 3.1 ng/dl; 95% CI, - 5.57 to - 0.66; P = 0.013; I2 = 99.9%), Hashimoto's thyroiditis (HT) (WMD - 6.05 ng/dl; 95% CI, - 8.35 to - 3.75; P < 0.001; I2 = 91.0%) and hypothyroidism patients (WMD - 13.43 ng/dl; 95% CI, - 26.04 to - 0.81; P = 0.03; I2 = 99.5%), but not in subjects with Graves' disease (GD) (WMD - 4.14 ng/dl; 95% CI, - 8.46 to 0.17; P = 0.06; I2 = 97.5%). CONCLUSIONS: Our findings suggested lower vitamin D levels in patients with hypothyroidism, AITD, and HT compared to healthy subjects. However, the link between serum vitamin D and GD was only significant among subjects ≥40 years old.

Spontaneous Thyroid Hemorrhage Caused by Langerhans Cell Histiocytosis: A Case Report and Literature Review.

Purpose: Langerhans cell histiocytosis (LCH) is a rare clonal disorder of Langerhans antigen-presenting cells. However, thyroid LCH involvement is relatively rare. We present the first case of spontaneous thyroid hemorrhage due to LCH progression and discuss the clinical features, diagnosis, and treatments of thyroid LCH in a literature review. Methods: Clinical data were collected. Previously published articles on thyroid LCH involvement were reviewed to assess the clinical features, diagnosis, and treatments for thyroid LCH. Results: A 54-year-old female presented with a multi-system LCH, affecting the uterus, liver, pituitary gland, and thyroid gland. Clinical stability was achieved after systemic chemotherapy. After 7 years of regular follow up, the patient complained of a sudden painful neck swelling and progressive dyspnea. Computed Tomography revealed bilateral goiter with hematoma, and the patient was diagnosed with spontaneous thyroid bleeding based on her clinical symptoms and radiological findings. The patient was incubated to relieve airway compromise and partial thyroidectomy was performed for definitive treatment. Pathological evaluation further confirmed the diagnosis of thyroid LCH. The patient recovered well after surgery. Conclusion: Spontaneous thyroid bleeding due to thyroid LCH progression is extremely rare. Treatments for LCH vary depending on the severity of the disease. We suggest that, for patients with multi-system LCH with thyroid lesion, long-term active surveillance of thyroid hormone concentrations, and thyroid gland volume is required. Physicians should be alert of the potentially life-threatening spontaneous thyroid hemorrhage when aggravated diffuse goiter and hypothyroidism appear. Further investigation is required to establish the guidelines for thyroid LCH treatment.