Non-malignant thyroid diseases after a wide range of radiation exposures

Comorbid Conditions in Persons Exposed to Ionizing Radiation and Veterans of the Soviet-Afghan War: A Cohort Study in Kazakhstan

OBJECTIVES

This study investigated the prevalence and characteristics of comorbid conditions in patients exposed to ionizing radiation and those who were involved in the Soviet-Afghan war.

METHODS

This study analyzed the frequency and spectrum of morbidity and comorbidity in patients over a long-term period (30-35 years) following exposure to ionizing radiation at the Semipalatinsk nuclear test site or the Chornobyl nuclear power plant, and among participants of the Soviet-Afghan war. A cohort study, both prospective and retrospective, was conducted on 675 patients who underwent comprehensive examinations.

RESULTS

Numerical data were analyzed using the Statistica 6 program. The results are presented as the mean±standard deviation, median, and interquartile range (25-75th percentiles). The statistical significance of between-group differences was assessed using the Student t-test and Pearson chi-square test. A p-value of less than 0.05 was considered statistically significant. We found a high prevalence of cardiovascular diseases, including hypertension (55.0%) and cardiac ischemia (32.9%); these rates exceeded the average for this age group in the general population.

CONCLUSIONS

The cumulative impact of causal occupational, environmental, and ultra-high stress factors in the combat zone in participants of the Soviet-Afghan war, along with common conventional factors, contributed to the formation of a specific comorbidity structure. This necessitates a rational approach to identifying early predictors of cardiovascular events and central nervous system disorders, as well as pathognomonic clinical symptoms in this patient cohort. It also underscores the importance of selecting suitable methods and strategies for implementing treatment and prevention measures.

Reduction in Primary Operator Radiation Dose Exposure During Coronary Angioplasty Using Radiation Absorbing Drape

Background Percutaneous coronary intervention (PCI) involves the use of ionizing radiation and is a common procedure in a cardiac catheterization suite. The RADPAD® surgical drape (Worldwide Innovations & Technologies, Inc., Lenexa, KS) has been developed to reduce scatter radiation exposure to primary operators during routine PCI procedures. This study aims to assess the efficacy of RADPAD drapes in reducing radiation dose in the catheterization laboratory. Methods This was a single-center, prospective, observational study that aimed to compare the primary operator dose received with and without the use of a commercially available shield (RADPAD) during PCI. A total of 53 consecutive patients undergoing PCI were randomized in a 1:1 pattern to receive either the RADPAD (study group) or no RADPAD (control group). Standard shielding and personal protective equipment were used. Radiation exposure to the primary operator, total fluoroscopy time, number of cine acquisitions, and air kerma were recorded for each procedure. A one-way ANOVA calculator, including the Tukey honestly significant difference (HSD) test, was used to compare the mean values of radiation exposure. Scatterplot analysis and linear regression slopes of dose relative to air kerma were performed. All shields were reused once only. Results The study compared radiation exposure during PCI procedures between patients who received radiation attenuation devices (RADPAD) and those who did not. The RADPAD group had 30 patients, while the NO RADPAD group had 23 patients. There was a significant difference in the number of coronary angiography and single/multi-vessel PCI procedures between the two groups. There was no significant difference in procedural time or air kerma dose between the groups, but the RADPAD group had a significantly lower radiation dose (mean dose of 3.679 mrem) compared to the NO RADPAD group (mean dose of 8.12 mrem) (p < 0.00001). The primary operator dose per unit of air kerma was also significantly lower in the RADPAD group. Overall, the use of RADPAD resulted in a significant reduction in radiation exposure during PCI procedures. Conclusion The present study provides further evidence for the efficacy of using radiation-absorbing drapes (RADPAD) in reducing primary operator radiation dose exposure during coronary angioplasty. The equipment for radiation dose reduction of patients also reduces the radiation dose of medical staff. Therefore, the use of RADPAD is recommended as a safe and effective measure for reducing operator radiation dose exposure during coronary angioplasty.

Analysis of factors associated with abnormal thyroid function among medical staff in radiotherapy departments

Objective

To understand abnormal thyroid function and its associated factors among medical staff in radiotherapy departments.

Methods

Data related to medical staff in radiotherapy departments who met the inclusion and exclusion criteria were analyzed from September to December 2022 in Shenyang, Liaoning Province, including basic personal and lifestyle habits, work information, and scores on the Depression Self-Assessment Scale, Perception Stress Scale, and the Generalized Anxiety Scale. Data analysis was performed using the χ2 test and binary logistic regression.

Results

Among 484 medical staff in the radiotherapy department, 147 (30.4%) had abnormal thyroid function. Binary logistic regression analysis showed that age, years of work, smoking, occupational exposure, smoking, late-night snacking habits, depression, and stress perception were factors associated with abnormal thyroid function among medical staff in radiotherapy departments; on the other hand, physical exercise was a protective factor.

Conclusion

The positive rate of thyroid dysfunction among medical personnel in the radiology department is relatively high. It is necessary to strengthen health education and awareness among relevant practitioners and improve the coverage of occupational disease prevention and control education.

Educational Experience of Interventional Cardiology Fellows in the United States and Canada

BACKGROUND

The COVID-19 pandemic and iodinated contrast shortage may have affected interventional cardiology (IC) fellowship training.

OBJECTIVES

The aim of this study was to investigate the educational experience of first-year IC fellows in the United States and Canada.

METHODS

A 59-question online survey was conducted among 2021-2022 first-year IC fellows in the United States and Canada.

RESULTS

Of the 360 IC fellows invited to participate, 111 (31%) responded; 95% were from the United States, and 79% were men. Participants were mostly from university programs (70%), spent 61 to 70 hours/week in the hospital, and had an annual percutaneous coronary intervention case number of <200 (5%), 200 to 249 (8%), 250 to 349 (33%), 350 to 499 (39%), 500 to 699 (12%), or ≥700 (3%). For femoral access, a micropuncture needle was used regularly by 89% and ultrasound-guided puncture by 81%, and 43% used vascular closure devices in most cases (>80%). Intravascular ultrasound was performed and interpreted very comfortably by 62% and optical coherence tomography (OCT) by 32%, and 20% did not have access to OCT. Approximately one-third felt very comfortable performing various atherectomy techniques. Covered stents, fat embolization, and coil embolization were used very comfortably by 14%, 4%, and 3%, respectively. Embolic protection devices were used very comfortably by 11% to 24% of IC fellows. Almost one-quarter of fellows (24%) were warned about their high radiation exposure. Eighty-four percent considered IC fellowship somewhat or very stressful, and 16% reported inadequate psychological support.

CONCLUSIONS

This survey highlights opportunities for improvement with regard to the use of intravascular imaging, atherectomy techniques, complication prevention and management strategies, radiation awareness and mitigation, and psychological support.

Evaluation of a new acrylic-lead shielding device for peripheral dose reduction during cone-beam computed tomography

Objective

To clarify the peripheral dose changes, especially in the eye lens and thyroid gland regions, using an acrylic-lead shield in cone-beam computed tomography (CBCT).

Methods

The acrylic-lead shield consists of system walls and a system mat. The radiophotoluminescence glass dosemeter was set on the eye lens and thyroid gland regions on the RANDO phantom. The system mat was laid under the RANDO phantom ranging from the top of the head to the shoulders, and then, the system walls shielded the phantom's head. Additionally, the phantom was covered anteriorly with a band that had the same shielding ability as the system mat to cover the thyroid gland region. Protocols for CBCT imaging of the thoracic or pelvic region in clinical practice were used. The measurement was performed with and without the acrylic-lead shield.

Results

The dose to the eye lens region was reduced by 45% using the system wall. Conversely, the dose to the thyroid gland was unchanged. The use of the system mat reduced the dose to the thyroid gland region by 47%, and the dose to the eye lens was reduced by 22%. The dose to the eye lens region decreased to the background level using the system walls and mat.

Conclusion

The newly proposed device using an acrylic-lead shield reduced the peripheral dose in CBCT imaging.

Advances in knowledge

Attention is focused on managing peripheral dose in image-guided radiation therapy. The peripheral dose reduction using the acrylic-lead shield is a new proposal in radiotherapy that has never been studied.

The Iodine Rush: Over- or Under-Iodination Risk in the Prophylactic Use of Iodine for Thyroid Blocking in the Event of a Nuclear Disaster

Iodine is an essential element for the production of thyroid hormones (THs). Both deficient and excess iodine intakes may precipitate in adverse thyroidal events. Radioactive iodine (RI) is a common byproduct of nuclear fission processes. During nuclear emergencies RI may be released in a plume, or cloud, contaminating the environment. If inhaled or ingested, it may lead to internal radiation exposure and the uptake of RI mainly by the thyroid gland that absorbs stable iodine (SI) and RI in the same way. A dose of radiation delivered to the thyroid gland is a main risk factor for the thyroid cancer development. The SI prophylaxis helps prevent childhood thyroid cancer. The thyroid gland saturation with prophylactic SI ingestion, reduces the internal exposure of the thyroid by blocking the uptake of RI and inhibiting iodide organification. However, negative impact of inadequate SI intake must be considered. We provide an overview on the recommended iodine intake and the impact of SI and RI on thyroid in children and adolescents, discussing the benefits and adverse effects of the prophylactic SI for thyroid blocking during a nuclear accident. The use of SI for protection against RI may be recommended in cases of radiological or nuclear emergencies, moreover the administration of iodine for prophylactic purposes should be cautious. Benefits and risks should also be considered according to age. Adverse effects from iodine administration cannot be excluded. Precise indications are mandatory to use the iodine for thyroid blocking. Due to this natural adaption mechanism it's possible to tolerate large doses of iodine without clinical effects, however, a prolonged assumption of the iodine when not needed can be dangerous and may precipitate in severe thyroidal and non-thyroidal negative effects.

High-dose radiation exposure and hypothyroidism: aetiology, prevention and replacement therapy

Without any doubt, high dose radiation exposure can induce hypothyroidism. However, there are open questions related to the mechanisms of its induction, corresponding dose thresholds and possible countermeasures. Therefore, this review addresses the aetiology, prevention and therapy of radiation induced hypothyroidism. External beam radiotherapy with several 10 Gy to the head and neck region and radioiodine therapy with several 100 Gy thyroid absorbed dose can destroy the thyroid gland and can induce autoantibodies against thyroid tissue. According to recent literature, clinical hypothyroidism is observed at threshold doses of ∼10 Gy after external beam radiotherapy and of ∼50 Gy after radioiodine therapy, children being more sensitive than adults. In children and adolescents exposed by the Chernobyl accident with mean thyroid absorbed doses of 500-800 mGy, subclinical hypothyroidism has been detected in 3%-6% of the cases with significant correlation to thyroid absorbed doses above 2.5 Gy. In case of nuclear emergencies, iodine thyroid blocking (ITB) is the method of choice to keep thyroid absorbed doses low. Large doses of stable iodine affect two different steps of internalization of radioiodine (transport and organification); perchlorate affecting the transport only may be an alternative to iodine. Administered before radioiodine incorporation, the effect of 100 mg iodide or more is still about 90% after 1 days, 80% after 2 days, and 50% or less after 3 days. If administered (too) late after exposure to radioiodine, the theoretically expected protective effect of ITB is about 50% after 6 h, 25% after 12 h, and about 6% after 24 h. In case of repeated or continuous exposure, repeated administration of 50 mg of iodide daily is indicated. If radiation-induced hypothyroidism cannot be avoided, thyroid hormone replacement therapy with individualized dosing and regular monitoring in order to maintain thyroid-stimulating hormone levels within the normal range ensures normal life expectancy.

Low dose ionizing radiation effects on the immune system

Ionizing radiation interacts with the immune system in many ways with a multiplicity that mirrors the complexity of the immune system itself: namely the need to maintain a delicate balance between different compartments, cells and soluble factors that work collectively to protect, maintain, and restore tissue function in the face of severe challenges including radiation damage. The cytotoxic effects of high dose radiation are less relevant after low dose exposure, where subtle quantitative and functional effects predominate that may go unnoticed until late after exposure or after a second challenge reveals or exacerbates the effects. For example, low doses may permanently alter immune fitness and therefore accelerate immune senescence and pave the way for a wide spectrum of possible pathophysiological events, including early-onset of age-related degenerative disorders and cancer. By contrast, the so called low dose radiation therapy displays beneficial, anti-inflammatory and pain relieving properties in chronic inflammatory and degenerative diseases. In this review, epidemiological, clinical and experimental data regarding the effects of low-dose radiation on the homeostasis and functional integrity of immune cells will be discussed, as will be the role of immune-mediated mechanisms in the systemic manifestation of localized exposures such as inflammatory reactions. The central conclusion is that ionizing radiation fundamentally and durably reshapes the immune system. Further, the importance of discovery of immunological pathways for modifying radiation resilience amongst other research directions in this field is implied.

Hypothyroidism after radiation exposure: brief narrative review

The thyroid gland is among the organs at the greatest risk of cancer from ionizing radiation. Epidemiological evidence from survivors of radiation therapy, atomic bombing, and the Chernobyl reactor accident, clearly shows that radiation exposure in childhood can cause thyroid cancer and benign thyroid nodules. Radiation exposure also may induce hypothyroidism and autoimmune reactions against the thyroid, but these effects are less well-documented. The literature includes only a few, methodologically weak animal studies regarding genetic/molecular mechanisms underlying hypothyroidism and thyroid autoimmunity after radiation exposure. Rather, evidence about radiation-induced hypothyroidism and thyroid autoimmunity derives mainly from follow-up studies in patients treated with external beam radiotherapy (EBRT) or iodine-131, and from epidemiological studies in the atomic bombing or nuclear accident survivors. Historically, hypothyroidism after external irradiation of the thyroid in adulthood was considered not to develop below a 10-20 Gy dose threshold. Newer data suggest a 10 Gy threshold after EBRT. By contrast, data from patients after iodine-131 "internal radiation therapy" of Graves´ disease indicate that hypothyroidism rarely occurs below thyroid doses of 50 Gy. Studies in children affected by the Chernobyl accident indicate that the dose threshold for hypothyroidism may be considerably lower, 3-5 Gy, aligning with observations in A-bomb survivors exposed as children. The reasons for these dose differences in radiosensitivity are not fully understood. Other important questions about the development of hypothyroidism after radiation exposure e.g., in utero, about the interaction between autoimmunity and hypofunction, and about the different effects of internal and external irradiation still must be answered.

Update of hypothyroidism and its management in Unani medicine

Hypothyroidism is a clinical syndrome caused by thyroid hormone deficiency due to reduced production, deranged distribution, or lack of effects of thyroid hormone. The prevalence of hypothyroidism in developed countries is around 4-5%, whereas it is about 11% in India, only 2% in the UK, and 4·6% in the USA. It is more common in women than in men. Hypothyroidism has multiple etiologies and manifestations. The most common clinical manifestations are weight gain, loss of hair, cold intolerance, lethargy, constipation, dry skin, and change in voice. The signs and symptoms of hypothyroidism differ with age, gender, severity of condition, and some other factors. The diagnosis is based on clinical history, physical examination and serum level of FT3, FT4, and thyroid-stimulating hormone, imaging studies, procedures, and histological findings. The treatment of choice for hypothyroidism is levothyroxine, however; in this review article, we have discussed the epidemiology, etiology, clinical sign and symptoms, diagnosis, complications, and management of hypothyroidism in modern medicine and a comparative treatment by the Unani system of medicine (USM). In the USM, the main emphasis of the principle of treatment (Usool-e-Ilaj) is to correct the abnormal constitution (Su-e-Mizaj) and alter the six prerequisites for existence (Asbab-e-Sitta Zarooriya) to restore normal health. It is a packaged treatment, that is, different components of treatment are given as a package form which includes different drugs, dosages form, and regimens.

Herbal preparations in the management of hypothyroidism in Unani medicine

Hypothyroidism is the most common thyroid disorder, affects women more frequently, and incidence increases with age. The prevalence of hypothyroidism in developed countries is around 4-5%, whereas, in India, it is about 11%. The common symptoms of hypothyroidism in adults are weight gain, fatigue, lethargy, cold intolerance, constipation, change in voice, and dry skin. It can affect all systems of the body. Diagnosis is mainly based on clinical history and laboratory investigations. Untreated hypothyroidism increases morbidity and mortality. In conventional medicine, the treatment of choice is Levothyroxine, whereas in Unani System of Medicine, pharmacotherapy consists of single and compound drugs. Single drugs are selected as per the constitution (Mizaj) of drugs as opposed to the abnormal constitution (Su-e-Mizaj) of disease and its pathology. Some drugs increase the basal metabolic rate whereas some evacuate the morbid material from the body by the action of purgation. The drugs are used either in a single form or as a prescription of more than one drug in the form of decoction (Joshandah), infusion (Kheshandah), or powder (Safoof). This review aims at providing comprehensive information regarding various drugs used in Unani system of medicine that is used in the management of thyroid dysfunction.

Effect of chemoradiation on the size of the thyroid gland

We aimed to evaluate changes in thyroid gland size during the treatment of malignancies outside the head and neck with chemotherapy and/or external beam radiation. We performed a retrospective review of records of adult patients treated at our institution with external beam radiation to the chest and/or chemotherapy with taxanes, alkylating agents, and/or a topoisomerase II inhibitor. Neck and chest computed tomography (CT) images were used to calculate thyroid gland volume before and after therapy, using Vitrea^® software or the volumetric ellipsoid method. Thirty-seven patients were included. After treatment, there was a significant reduction in thyroid gland volume of 14.0% (P < 0.01) using Vitrea and 17.1% (P < 0.05) using the volumetric ellipsoid method. Exposure to radiation or chemotherapy was not found to be associated with the degree of thyroid gland reduction, nor was the number of days between CT scans or the stage of the malignancy being treated. Finally, the degree of thyroid gland size reduction did not predict mortality. Our results showed that the treatment of malignancies outside the head and neck with chemotherapy and/or external beam radiation results in a reduction in thyroid gland size. The impact on thyroid gland function remains unknown.

Herbal preparations in the management of hypothyroidism in Unani medicine

Hypothyroidism is the most common thyroid disorder, affects women more frequently, and incidence increases with age. The prevalence of hypothyroidism in developed countries is around 4-5%, whereas, in India, it is about 11%. The common symptoms of hypothyroidism in adults are weight gain, fatigue, lethargy, cold intolerance, constipation, change in voice, and dry skin. It can affect all systems of the body. Diagnosis is mainly based on clinical history and laboratory investigations. Untreated hypothyroidism increases morbidity and mortality. In conventional medicine, the treatment of choice is Levothyroxine, whereas in Unani System of Medicine, pharmacotherapy consists of single and compound drugs. Single drugs are selected as per the constitution (Mizaj) of drugs as opposed to the abnormal constitution (Su-e-Mizaj) of disease and its pathology. Some drugs increase the basal metabolic rate whereas some evacuate the morbid material from the body by the action of purgation. The drugs are used either in a single form or as a prescription of more than one drug in the form of decoction (Joshandah), infusion (Kheshandah), or powder (Safoof). This review aims at providing comprehensive information regarding various drugs used in Unani system of medicine that is used in the management of thyroid dysfunction.

COVERING THE PATIENT'S ARM SUPPORT IN LEAD REDUCED THE RADIATION DOSE RATE TO THE CARDIOLOGISTS DURING PERCUTANEOUS CORONARY INTERVENTIONS: A PHANTOM STUDY

The aim of the study was to estimate organ dose rate reduction to a female anthropomorphic phantom, which simulated the cardiologist, during percutaneous coronary interventions (PCI) when the patient's arm support was covered with 0.4-mm lead foil. Organ dose rates were determined using five radiation detectors inserted into the left eye, left thyroid, left breast, left liver lobe and uterus of the phantom. A male anthropomorphic phantom was placed on the examination table of an angiography system. Heart images of the patient phantom were acquired under 10 gantry angulations typical for PCI. The lead-covered arm support did not interfere with any of the cardiac images. The median organ dose rate reductions to the left eye, left thyroid, left breast, left liver lobe and uterus were 7.8, 36.0, 28.8, 35.7 and 33.5%, respectively. The lead-covered arm support substantially reduced scattered radiation to the female cardiologist without interfering with clinical environments.

Impact of Computed Tomography Scans on the Risk of Thyroid Disease in Minor Head Injury Patients: A Population-Based Retrospective Cohort Study

We investigated the association between head computed tomography (CT) scans and the risk of noncancer thyroid diseases in patients with minor head injury in a Taiwanese healthcare setting. For this retrospective population-based cohort study, the 2009–2013 Longitudinal Health Insurance Database was used to include patients with a minor head injury at admission or emergency visit between 2009 and 2013. Multivariate analysis with a multiple Cox regression model was applied to analyze the data. According to whether a CT scan was conducted within 14 days of admission, patients were divided into a CT scan group (n = 14,041) or a non-CT scan group (n = 34,684). No increased incidence of thyroid diseases was observed in the CT scan group regardless of the number of CT scans performed. The incidence rate ratio for one scan was 1.10 (95% confidence interval: 0.94–1.29) and for two or more scans was 1.09 (95% confidence interval: 0.93–1.28). In conclusion, this population-based cohort study showed that a head CT scan is not associated with increased risk of thyroid disease in patients with minor head injury. The short-term adverse effects on the thyroid could be mild when a regular CT scan is appropriately performed.

Hyperthyroidism After Radiation Therapy for Childhood Cancer: A Report from the Childhood Cancer Survivor Study

PURPOSE

The association of hyperthyroidism with exposure to ionizing radiation is poorly understood. This study addresses the risk of hyperthyroidism in relation to incidental therapeutic radiation dose to the thyroid and pituitary glands in a large cohort of survivors of childhood cancer.

METHODS AND MATERIALS

Using the Childhood Cancer Survivor Study's cohort of 5-year survivors of childhood cancer diagnosed at hospitals in the United States and Canada between 1970 and 1986, the occurrence of hyperthyroidism through 2009 was ascertained among 12,183 survivors who responded to serial questionnaires. Radiation doses to the thyroid and pituitary glands were estimated from radiation therapy records, and chemotherapy exposures were abstracted from medical records. Binary outcome regression was used to estimate prevalence odds ratios (ORs) for hyperthyroidism at 5 years from diagnosis of childhood cancer and Poisson regression to estimate incidence rate ratios (RRs) after the first 5 years.

RESULTS

Survivors reported 179 cases of hyperthyroidism, of which 148 were diagnosed 5 or more years after their cancer diagnosis. The cumulative proportion of survivors diagnosed with hyperthyroidism by 30 years after the cancer diagnosis was 2.5% (95% confidence interval [CI], 2.0%-2.9%) among those who received radiation therapy. A linear relation adequately described the thyroid radiation dose response for prevalence of self-reported hyperthyroidism 5 years after cancer diagnosis (excess OR/Gy, 0.24; 95% CI, 0.06-0.95) and incidence rate thereafter (excess RR/Gy, 0.06; 95% CI, 0.03-0.14) over the dose range of 0 to 63 Gy. Neither radiation dose to the pituitary gland nor chemotherapy was associated significantly with hyperthyroidism. Radiation-associated risk remained elevated >25 years after exposure.

CONCLUSIONS

Risk of hyperthyroidism after radiation therapy during childhood is positively associated with external radiation dose to the thyroid gland, with radiation-related excess risk persisting for >25 years. Neither radiation dose to the pituitary gland nor chemotherapy exposures were associated with hyperthyroidism among childhood cancer survivors through early adulthood.

Clinical Diagnostic Evaluation of Thyroid Nodules

The presence of a thyroid nodule may be recognized by the patient or the clinician on palpation of the neck or it may be an incidental finding during an imaging study for some other indication. The method of detection is less important, however, than distinguishing benign lesions from more aggressive neoplasms. This article outlines the diagnostic algorithm for the evaluation of thyroid nodules including biochemical testing, imaging, and, when appropriate, fine-needle aspiration. In addition, the authors review the natural history of benign nodules, follow-up strategies, and indications for repeat aspiration.

Radiotherapy for childhood cancer and subsequent thyroid cancer risk: a systematic review

Most of the pooled analyses and reviews reported an association between radiotherapy for childhood cancer and an increased thyroid cancer risk. Up to now this article presents the first systematic literature review on this association combined with a critical assessment of the methodological quality of the included articles. PubMed and Web of Science databases were searched for relevant articles until May 2016. We included peer-reviewed cohort and case-control studies that investigated an association between radiotherapy for childhood cancer and the occurrence of subsequent thyroid cancer. A systematic overview is presented for the included studies. We identified 17 retrospective cohort studies, and four nested case-control studies, representing 100,818 subjects. The age range at first cancer diagnosis was 0-25.2 years. Considerable variability was found regarding study sizes, study design, treatment strategies, dose information, and follow-up periods. 20 of the 21 identified studies showed increased thyroid cancer risks associated with childhood radiation exposure. The large majority showed an increased relative risk or odds ratio confirming the association between radiotherapy and thyroid cancer although the variation in results was large. Additionally to a pooled analysis that has been published recently, we systematically included 17 further studies, which allowed us to cover information from countries that were not covered by large-scale childhood cancer survivor studies. The methodological limitations of existing studies and inconsistencies in findings across studies yielded a large study heterogeneity, which made a detailed comparison of study results difficult. There is a need to strengthen standardisation for reporting.

Hypothyroidism after Radiation Therapy for Childhood Cancer: A Report from the Childhood Cancer Survivor Study

While thyroid cancer risks from exposure to ionizing radiation early in life are well characterized quantitatively, the association of radiation with nonmalignant, functional thyroid disorders has been less studied. Here, we report on a risk analysis study of hypothyroidism with radiation dose to the thyroid gland and the hypothalamic-pituitary axis among survivors of childhood cancer. Utilizing data from the Childhood Cancer Survivor Study, a cohort of 14,364 five-year survivors of childhood cancer diagnosed at 26 hospitals in the U.S. and Canada between 1970 and 1986 and followed through 2009, the occurrence of hypothyroidism was ascertained among 12,015 survivors through serial questionnaires. Radiation doses to the thyroid gland and pituitary gland were estimated from radiotherapy records. Binary outcome regression was used to estimate prevalence odds ratios for hypothyroidism at five years from diagnosis of childhood cancer and Poisson regression to model incidence rate ratios (RR) after the first five years. A total of 1,193 cases of hypothyroidism were observed, 777 (65%) of which occurred five or more years after cancer diagnosis. The cumulative proportion affected with hypothyroidism (prevalence at five years after cancer diagnosis plus incidence through 30 years after cancer diagnosis) was highest among five-year survivors of Hodgkin lymphoma (32.3%; 95% CI: 29.5-34.9) and cancers of the central nervous system (17.7%; 95% CI: 15.2-20.4). The incidence rate was significantly associated with radiation dose to the thyroid and pituitary. The joint association of hypothyroidism with thyroid and pituitary dose was sub-additive for pituitary doses greater than 16 Gy. In particular, a very strong thyroid radiation dose dependence at low-to-moderate pituitary/hypothalamic doses was diminished at high pituitary doses. Radiation-related risks were higher in males than females and inversely associated with age at exposure and time since exposure but remained elevated more than 25 years after exposure. Our findings indicated that hypothyroidism was significantly associated with treatment with bleomycin (RR = 3.4; 95% CI: 1.6-7.3) and the alkylating agents cyclohexyl-chloroethyl-nitrosourea (CCNU) (RR = 3.0; 95% CI: 1.5-5.3) and cyclophosphamide (RR = 1.3; 95% CI: 1.0-1.8), with a significant dose response for CCNU ( P < 0.01). The risk of hypothyroidism among childhood cancer survivors treated with radiation depends both on direct, dose-dependent radiation-induced damage to the thyroid gland and on dose-dependent indirect effects secondary to irradiation of the hypothalamic-pituitary axis. The dose-response relationship for each site depends on dose to the other. Radiation-related risk persists for more than 25 years after treatment. Treatment with certain chemotherapy agents may increase the risk of hypothyroidism.

Radiation-related thyroid autoimmunity and dysfunction

The thyroid gland is vulnerable not only to external radiation but also to internal radiation, because the thyroid cells can incorporate radioactive iodine when synthesizing thyroid hormones. Since radiation-induction of thyroid neoplasia, including thyroid cancer, is well recognized, the data on radiation-related thyroid autoimmunity and dysfunction are summarized and reviewed. High-dose irradiation, irrespective of being external or internal, is strongly associated with a risk of hypothyroidism (with the prevalence ranging from 2.4% to 31%) and of Graves' hyperthyroidism (with the prevalence being up to 5%). It is easy to understand that high-dose irradiation induces hypothyroidism with some frequency, because high-dose irradiation destroys the thyroid gland. On the other hand, the basis for development of hyperthyroidism is mechanistically unclear, and it is merely speculative that autoantigens may be released from damaged thyroid glands and recognized by the immune system, leading to the development of anti-thyrotropin receptor antibodies and Graves' hyperthyroidism in subjects who are immunologically predisposed to this ailment. In contrast, the data on moderate to low-dose irradiation on thyroid autoimmunity and dysfunction are inconsistent. Although it is difficult to draw a definitive conclusion, some data may suggest a transient effect of moderate- to low-dose irradiation on hypothyroidism and autoimmune thyroiditis, implying that the effect, if it exists, is reversible. Finally, no report has shown a statistically significant increase in the prevalence of moderate- to low-dose irradiation-induced Graves' hyperthyroidism.

Thyroid neoplasia risk is increased nearly 30 years after the Chernobyl accident

To evaluate risk of thyroid neoplasia nearly 30 years following exposure to radioactive iodine (I-131) from the 1986 Chernobyl nuclear accident, we conducted a fifth cycle of thyroid screening of the Ukrainian-American cohort during 2012-2015, following four previous screening cycles started in 1998. We identified 47 thyroid cancers (TC) and 33 follicular adenomas (FA) among 10,073 individuals who were <18 years at the time of the accident and had a mean I-131 dose of 0.62 Gy. We found a significant I-131 dose response for both TC and FA, with an excess odd ratio per Gy of 1.36 (95% CI: 0.39-4.15) and 2.03 (95% CI: 0.55-6.69), respectively. The excess risk of malignant and benign thyroid neoplasia persists nearly three decades after exposure and underscores the importance of continued follow-up of this cohort to characterize long-term pattern of I-131 risk.

Treatment with Myo-Inositol and Selenium Ensures Euthyroidism in Patients with Autoimmune Thyroiditis

Clinical evidences have highlighted the efficacy of myo-inositol and selenium in the treatment of autoimmune thyroiditis. Aim of this study was to further analyze the role of myo-inositol plus selenium (Myo-Ins-Se) in restoring a normal thyroid function of Hashimoto's patients with subclinical hypothyroidism. Eighty-six patients with Hashimoto's thyroiditis having thyroid-stimulating hormone (TSH) levels between 3 and 6 mIU/L, elevated serum antithyroid peroxidase (TPOAb) and/or antithyroglobulin (TgAb), and normal free thyroxine (fT4) and free triiodothyronine (fT3) levels were enrolled in the study: one hyperthyroid subject with TSH about 0.14 μU/ml was included in this trial as a single case. Patients were assigned to receive Myo-Ins-Se. TSH, TPOAb, and TgAb levels were significantly decreased in patients treated with combined Myo-Ins-Se after 6 months of treatment. In addition, a significant fT3 and fT4 increase, along with an amelioration of their quality of life, was observed. Remarkably, TSH values of the hyperthyroid patient increased from 0.14 μU/ml up to 1.02 μU/ml, showing a complete restoration of TSH values at a normal range. In conclusion, the administration of Myo-Ins-Se is significantly effective in decreasing TSH, TPOAb, and TgAb levels, as well as enhancing thyroid hormones and personal wellbeing, therefore restoring euthyroidism in patients diagnosed with autoimmune thyroiditis.

The effects of iodine blocking on thyroid cancer, hypothyroidism and benign thyroid nodules following nuclear accidents: a systematic review

A potential radiation protection method to reduce the risk of adverse health outcomes in the case of accidental radioactive iodine release is the administration of potassium iodide (KI). Although KI administration is recommended by WHO's Guidelines for Iodine Prophylaxis following Nuclear Accidents, a systematic review of the scientific evidence for the guidelines is lacking. Therefore, this study aims to systematically review the effects of KI administration in the case of accidental radioactive iodine release on thyroid cancer, hypothyroidism and benign thyroid nodules. We applied standard systematic review methodology for a search of the literature, selection of eligible studies, data extraction, assessment of risk of bias, assessment of heterogeneity, data synthesis, and the assessment of the quality of the evidence. We searched MEDLINE (via PubMed) and EMBASE. We found one cross-sectional study, one analytic cohort study and two case-control studies relating to our question. The number of participants ranged from 886-12 514. Two studies were conducted in children and two other studies in children and adults. It was not possible to conduct a meta-analysis. We identified low to very low-quality evidence that KI administration after a nuclear accident resulted in a reduction of the risk of thyroid cancer in children; however, the KI administration and dose was not well described in the studies. None of the studies investigated the effects of KI administration in the case of a nuclear accident on hypothyroidism and benign thyroid nodules. Low to very low-quality evidence suggests that KI intake following a nuclear accident may reduce the risk of thyroid cancer in children. No conclusions can be drawn about the effectiveness of KI intake with respect to the prevention of hypothyroidism and benign thyroid nodules.

Measurement of Thyroid Dose by TLD arising from Radiotherapy of Breast Cancer Patients from Supraclavicular Field

BACKGROUND

Breast cancer is the most frequently diagnosed cancer and the leading global cause of cancer death among women worldwide. Radiotherapy plays a significant role in treatment of breast cancer and reduces locoregional recurrence and eventually improves survival. The treatment fields applied for breast cancer treatment include: tangential, axillary, supraclavicular and internal mammary fields.

OBJECTIVE

In the present study, due to the presence of sensitive organ such as thyroid inside the supraclavicular field, thyroid dose and its effective factors were investigated.

MATERIALS AND METHODS

Thyroid dose of 31 female patients of breast cancer with involved supraclavicular lymph nodes which had undergone radiotherapy were measured. For each patient, three TLD-100 chips were placed on their thyroid gland surface, and thyroid doses of patients were measured. The variables of the study include shield shape, the time of patient's setup, the technologists' experience and qualification. Finally, the results were analyzed by ANOVA test using SPSS 11.5 software.

RESULTS

The average age of the patients was 46±10 years. The average of thyroid dose of the patients was 140±45 mGy (ranged 288.2 and 80.8) in single fraction. There was a significant relationship between the thyroid dose and shield shape. There was also a significant relationship between the thyroid dose and the patient's setup time.

CONCLUSION

Beside organ at risk such as thyroid which is in the supraclavicular field, thyroid dose possibility should be reduced. For solving this problem, an appropriate shield shape, the appropriate time of the patient's setup, etc. could be considered.

Ionizing radiation exposure in interventional cardiology: current radiation protection practice of invasive cardiology operators in Lithuania

Ionizing radiation management is among the most important safety issues in interventional cardiology. Multiple radiation protection measures allow the minimization of x-ray exposure during interventional procedures. Our purpose was to assess the utilization and effectiveness of radiation protection and optimization techniques among interventional cardiologists in Lithuania. Interventional cardiologists of five cardiac centres were interviewed by anonymized questionnaire, addressing personal use of protective garments, shielding, table/detector positioning, frame rate (FR), resolution, field of view adjustment and collimation. Effective patient doses were compared between operators who work with and without x-ray optimization. Thirty one (68.9%) out of 45 Lithuanian interventional cardiologists participated in the survey. Protective aprons were universally used, but not the thyroid collars; 35.5% (n  =  11) operators use protective eyewear and 12.9% (n  =  4) wear radio-protective caps; 83.9% (n  =  26) use overhanging shields, 58.1% (n  =  18)-portable barriers; 12.9% (n  =  4)-abdominal patient's shielding; 35.5% (n  =  11) work at a high table position; 87.1% (n  =  27) keep an image intensifier/receiver close to the patient; 58.1% (n  =  18) reduce the fluoroscopy FR; 6.5% (n  =  2) reduce the fluoro image detail resolution; 83.9% (n  =  26) use a 'store fluoro' option; 41.9% (N  =  13) reduce magnification for catheter transit; 51.6% (n  =  16) limit image magnification; and 35.5% (n  =  11) use image collimation. Median effective patient doses were significantly lower with x-ray optimization techniques in both diagnostic and therapeutic interventions. Many of the ionizing radiation exposure reduction tools and techniques are underused by a considerable proportion of interventional cardiology operators. The application of basic radiation protection tools and techniques effectively reduces ionizing radiation exposure and should be routinely used in practice.

Morphological Changes Induced by Bipolar Radiofrequency Ablation in Thyroid Nodules - a Preclinical Ex Vivo Investigation

Introduction: Recently, radiofrequency ablation (RFA) has been increasingly used for the treatment of thyroid nodules. However, immediate morphological changes associated with bipolar devices are poorly shown. Aims: To present the results of analysis of gross and microscopic alterations in human thyroid tissue induced by RFA delivered through the application of the original patented device. Materials and methods: In total, there were 37 surgically removed thyroid glands in females aged 32-67 at presentation: 16 nodules were follicular adenoma (labelled as 'parenchymal' solid benign nodules) and adenomatous colloid goitre was represented by 21 cases. The thyroid gland was routinely processed and the nodules were sliced into two parts - one was a subject for histological routine processing according to the principles that universally apply in surgical pathology, the other one was used for the RFA procedure. Results: No significant difference in size reduction between parenchymal and colloid nodules was revealed (p>0.1, t-test) straight after the treatment. In addition, RFA equally effectively induced necrosis in follicular adenoma and adenomatous colloid goitre (p>0.1, analysis of variance test). As expected, tumour size correlated with size reduction (the smaller the size of the nodule, the greater percentage of the nodule volume that was ablated): r=-0.48 (p<0.0001). Conclusion: The results make it possible to move from ex vivo experiments to clinical practice.

30 years After the Chernobyl Nuclear Accident: Time for Reflection and Re-evaluation of Current Disaster Preparedness Plans

It has been 30 years since the worst accident in the history of the nuclear era occurred at the Chernobyl power plant in Ukraine close to densely populated urban areas. To date, epidemiological studies reported increased long-term risks of leukemia, cardiovascular diseases, and cataracts among cleanup workers and of thyroid cancer and non-malignant diseases in those exposed as children and adolescents. Mental health effects were the most significant public health consequence of the accident in the three most contaminated countries of Ukraine, Belarus, and the Russian Federation. Timely and clear communication with affected populations emerged as one of the main lessons in the aftermath of the Chernobyl nuclear accident.

Evaluation of thyroid antibodies and benign disease prevalence among young adults exposed to (131)I more than 25 years after the accident at the Chernobyl Nuclear Power Plant

Background. The Chernobyl Nuclear Power Plant (CNPP) accident exposed a large number of inhabitants to internal ¹³¹I radiation. The associations between internal ¹³¹I exposure and thyroid autoimmunity and benign thyroid diseases remain controversial in the population living in the contaminated area around the CNNP. In this study, we evaluate the association of ¹³¹I with benign thyroid diseases. Methods. We compared the prevalence of Anti-Thyroid Autoantibodies (ATAs), thyroid function, and prevalence of thyroid ultrasound finding outcomes in 300 residents of the contaminated area of Ukraine who were 0–5 years of age at the time of the CNPP accident (group 1) and 300 sex-matched residents who were born after the accident (group 2). Results. We did not find any differences of the prevalence of Antithyroglobulin Antibodies (TGAb) positive, Antithyroid Peroxidase Antibodies (TPOAb) positive, and TGAb and/or TPOAb positive between the study groups. (11.7% vs 10.3%; p = 0.602, 17.3% vs 13.0%; p = 0.136, 21.0% vs 17.3%; p = 0.254, respectively); after adjusting for age and sex, the prevalence was not associated with the ¹³¹I exposure status in the study groups. The prevalence of subclinical and overt hypothyroidism cases was not significantly different (p = 0.093 and p = 0.320) in the two groups, nor was the prevalence of goiter (p = 0.482). On the other hand, the prevalence of nodules was significantly higher in group 1 (p = 0.003), though not significantly so after adjustment for age and sex. Discussion. Working 26–27 years after the CNNP accident, we found no increased prevalence of ATAs or benign thyroid diseases in young adults exposed to ¹³¹I fallout during early childhood in the contaminated area of Ukraine. Long-term follow-up is needed to clarify the effects of radiation exposure on autoimmunity reaction in the thyroid.

Risk of thyroid follicular adenoma among children and adolescents in Belarus exposed to iodine-131 after the Chornobyl accident

Several studies reported an increased risk of thyroid cancer in children and adolescents exposed to radioactive iodines, chiefly iodine-131 ((131)I), after the 1986 Chornobyl (Ukrainian spelling) nuclear power plant accident. The risk of benign thyroid tumors following such radiation exposure is much less well known. We have previously reported a novel finding of significantly increased risk of thyroid follicular adenoma in a screening study of children and adolescents exposed to the Chornobyl fallout in Ukraine. To verify this finding, we analyzed baseline screening data from a cohort of 11,613 individuals aged ≤18 years at the time of the accident in Belarus (mean age at screening = 21 years). All participants had individual (131)I doses estimated from thyroid radioactivity measurements and were screened according to a standardized protocol. We found a significant linear dose response for 38 pathologically confirmed follicular adenoma cases. The excess odds ratio per gray of 2.22 (95% confidence interval: 0.41, 13.1) was similar in males and females but decreased significantly with increasing age at exposure (P < 0.01), with the highest radiation risks estimated for those exposed at <2 years of age. Follicular adenoma radiation risks were not significantly modified by most indicators of past and current iodine deficiency. The present study confirms the (131)I-associated increases in risk of follicular adenoma in the Ukrainian population and adds new evidence on the risk increasing with decreasing age at exposure.

Phototherapeutic Effect of Low-Level Laser on Thyroid Gland of Gamma-Irradiated Rats

One inescapable feature of life on the earth is exposure to ionizing radiation. The thyroid gland is one of the most sensitive organs to gamma-radiation and endocrine disrupters. Low-level laser therapy (LLLT) has been used to stimulate tissue repair, and reduce inflammation. The aim of this study was to gauge the value of using Helium-Neon laser to repair the damaged tissues of thyroid gland after gamma-irradiation. Albino rats were used in this study (144 rats), divided into control, gamma, laser, and gamma plus laser-irradiated groups, each group was divided into six subgroups according to time of treatment (total six sessions). Rats were irradiated once with gamma radiation (6 Gy), and an external dose of laser (Wavelength 632.8 nm, 12 mW, CW, Illuminated area 5.73 cm(2), 2.1 mW cm(-2) 120 s, 1.4 J, 0.252 J cm(-2)) twice weekly localized on thyroid region of the neck, for a total of six sessions. Animals were sacrificed after each session. Analysis included thyroid function, oxidative stress markers, liver function and blood picture. Results revealed improvement in thyroid function, liver function and antioxidant levels, and the blood cells count after LLLT.

Non-cancer morbidity among Estonian Chernobyl cleanup workers: a register-based cohort study

OBJECTIVE

To examine non-cancer morbidity in the Estonian Chernobyl cleanup workers cohort compared with the population sample with special attention to radiation-related diseases and mental health disorders.

DESIGN

Register-based cohort study.

SETTING

Estonia.

PARTICIPANTS

An exposed cohort of 3680 men (cleanup workers) and an unexposed cohort of 7631 men (population sample) were followed from 2004 to 2012 through the Population Registry and Health Insurance Fund database.

METHODS

Morbidity in the exposed cohort compared with the unexposed controls was estimated in terms of rate ratio (RR) with 95% CIs using Poisson regression models.

RESULTS

Elevated morbidity in the exposed cohort was found for diseases of the nervous system, digestive system, musculoskeletal system, ischaemic heart disease and for external causes. The most salient excess risk was observed for thyroid diseases (RR=1.69; 95% CI 1.38 to 2.07), intentional self-harm (RR=1.47; 95% CI 1.04 to 2.09) and selected alcohol-related diagnoses (RR=1.25; 95% CI 1.12 to 1.39). No increase in morbidity for stress reactions, depression, headaches or sleep disorders was detected.

CONCLUSIONS

No obvious excess morbidity consistent with biological effects of radiation was seen in the exposed cohort, with the possible exception of benign thyroid diseases. Increased alcohol-induced morbidity may reflect alcohol abuse, and could underlie some of the higher morbidity rates. Mental disorders in the exposed cohort were probably under-reported. The future challenge will be to study mental and physical comorbidities in the Chernobyl cleanup workers cohort.

Incidence of thyroid cancer surrounding Three Mile Island nuclear facility: the 30-year follow-up

OBJECTIVES/HYPOTHESIS

Original data reported a potential increased incidence of thyroid cancer surrounding the Three Mile Island (TMI) nuclear facility. A causal link to the accident, however, was indeterminate. Our objective was to determine if data 30 years later will change original conclusions, explore thyroid cancer incidence rates near nuclear power plants, and better understand effects of chronic low level radiation.

STUDY DESIGN

Retrospective cross-sectional study.

METHODS

Retrospective data for specific Pennsylvania counties were provided by the Pennsylvania Cancer Registry Dataset for thyroid cancer using the Epidemiological Query and Mapping System search engine. Our study examines thyroid cancer incidence from 1985 through 2009 analyzed by year, county, and age.

RESULTS

Thirty years after the TMI accident, an increased incidence of thyroid cancer is seen in counties south of TMI and in high-risk age groups. The average incidence rates from 1990 through 2009 were greater than expected in York, Lancaster, Adams, and Chester Counties.

CONCLUSIONS

Thyroid cancer incidence since the TMI accident was greater than expected in the counties analyzed when compared to local and national population growth. This supports a link to chronic low level radiation exposure and thyroid cancer development. Despite these findings, a direct correlation to the accident remains uncertain as incidence rates may coincide with other factors, and original data were limited.

Discriminating gene expression signature of radiation-induced thyroid tumors after either external exposure or internal contamination

Both external radiation exposure and internal radionuclide contamination are well known risk factors in the development of thyroid epithelial tumors. The identification of specific molecular markers deregulated in radiation-induced thyroid tumors is important for the etiological diagnosis since neither histological features nor genetic alterations can discriminate between sporadic and radiation-induced tumors. Identification of highly discriminating markers in radiation-induced tumors is challenging as it relies on the ability to identify marker deregulation which is associated with a cellular stress that occurred many years before in the thyroid cells. The existence of such a signature is still controversial, as it was not found in several studies while a highly discriminating signature was found in both post-radiotherapy and post-Chernobyl series in other studies. Overall, published studies searching for radiation-induced thyroid tumor specificities, using transcriptomic, proteomic and comparative genomic hybridization approaches, and bearing in mind the analytical constraints required to analyze such small series of tumors, suggest that such a molecular signature could be found. In comparison with sporadic tumors, we highlight molecular similarities and specificities in tumors occurring after high-dose external radiation exposure, such as radiotherapy, and in post-Chernobyl tumors that occurred after internal 131I contamination. We discuss the relevance of signature extrapolation from series of tumors developing after high and low doses in the identification of tumors induced at very low doses of radiation.

Durable donor engraftment after radioimmunotherapy using α-emitter astatine-211-labeled anti-CD45 antibody for conditioning in allogeneic hematopoietic cell transplantation

To reduce toxicity associated with external γ-beam radiation, we investigated radioimmunotherapy with an anti-CD45 mAb labeled with the α-emitter, astatine-211 ((211)At), as a conditioning regimen in dog leukocyte antigen-identical hematopoietic cell transplantation (HCT). Dose-finding studies in 6 dogs treated with 100 to 618 μCi/kg (211)At-labeled anti-CD45 mAb (0.5 mg/kg) without HCT rescue demonstrated dose-dependent myelosuppression with subsequent autologous recovery, and transient liver toxicity in dogs treated with (211)At doses less than or equal to 405 μCi/kg. Higher doses of (211)At induced clinical liver failure. Subsequently, 8 dogs were conditioned with 155 to 625 μCi/kg (211)At-labeled anti-CD45 mAb (0.5 mg/kg) before HCT with dog leukocyte antigen-identical bone marrow followed by a short course of cyclosporine and mycophenolate mofetil immunosuppression. Neutropenia (1-146 cells/μL), lymphopenia (0-270 cells/μL), and thrombocytopenia (1500-6560 platelets/μL) with prompt recovery was observed. Seven dogs had long-term donor mononuclear cell chimerism (19%-58%), whereas 1 dog treated with the lowest (211)At dose (155 μCi/kg) had low donor mononuclear cell chimerism (5%). At the end of follow-up (18-53 weeks), only transient liver toxicity and no renal toxicity had been observed. In conclusion, conditioning with (211)At-labeled anti-CD45 mAb is safe and efficacious and provides a platform for future clinical trials of nonmyeloablative transplantation with radioimmunotherapy-based conditioning.

Hypothyroidism among former workers of a nuclear weapons facility

BACKGROUND

Ionizing radiation alters thyroid function, and workers at a nuclear weapons facility may be exposed to above environmental levels of radiation.

METHODS

Hypothyroid status was determined for 622 former workers of a nuclear weapons facility located in Texas, using a combination of measured thyroid stimulating hormone (TSH) levels and thyroid medication history, as part of an on-going health surveillance program. We classified 916 unique job titles into 35 job categories.

RESULTS

According to the most stringent TSH definition used in this study (0.3-3.0 IU/ml), 174 (28.0%) former workers were considered to be hypothyroid; of these 66 (41.8%) were females and 108 (23.3%) were males. In logistic regression analysis adjusted for age, gender, and smoking status, only having worked as a material handler (n = 18) exhibited an elevated risk of developing hypothyroidism compared to other jobs (OR 3.88, 95% CI 1.43-11.07). This is one of the jobs with suspected exposure to radiation. No excess risk of hypothyroidism was observed for any of the other job categories.

CONCLUSIONS

There is suggestive evidence that only material handlers at this nuclear weapons facility may have elevated risk of hypothyroidism; further evaluation of thyroid health in this population is warranted.