Secondary thyroid neoplasms in pediatric cancer patients: increased risk with improved survival

Between 1973 and 1983, eight children who had undergone successful multimodal management of malignant tumors developed secondary thyroid neoplasms. The primary tumors were acute lymphocytic leukemia in three, Wilms' tumor in two, and Hodgkin's disease, rhabdomyosarcoma, and ganglioneuroblastoma in one each. During this period, 174 long-term survivors with these five diagnoses were enrolled in our tumor registry, yielding a 4.6% incidence of secondary thyroid neoplasms. All eight patients received both radiation and chemotherapy. The mean radiation dose was 2,700 r with a calculated thyroid dose of 2,140 r (range, 5 to 4,200 r). Age of diagnosis of the primary tumors ranged from 1 to 8 2/12 years (mean, 5 years), and the latent period between treatment and development of the thyroid lesions averaged 6 1/2 years. Thyroid neoplasms presented at an average age of 11 4/12 years. Five patients developed solitary adenomas, one presented with multiple adenomas, and two had follicular carcinoma with regional lymph node metastases. Although thyroid neoplasms are rare in childhood, clinically apparent thyroid tumors have been observed in up to 2.5% of children following radiation exposure (mean follow-up, 24 years). The reported latent period before the development of thyroid neoplasms in irradiated patients is at least 10 years, with the peak incidence occurring 20 to 25 years after exposure. This study documents a 4.6% incidence of subsequent thyroid neoplasms in pediatric cancer patients within a relatively short follow-up period (mean, 11 years). These thyroid tumors occurred at an earlier age (mean, 11.5 years) and with a shorter latent period (mean, 6.5 years) than would be predicted from previous studies.(ABSTRACT TRUNCATED AT 250 WORDS)     

Exposure of the thyroid to radiation during routine orthopaedic procedures

The availability and usage of portable image intensifiers has revolutionised routine orthopaedic practice. Extensive use of fluoroscopy however may result into significant radiation exposure to operating staff. An accumulated dose of 65 microSv per procedure over long exposure has been reported to increase the risk of thyroid cancer. The present prospective study aimed at measuring the scattered dose to the thyroid using an Unfors EDD dosimeter during DHS/IMHS for fractures of the neck of the femur and IM nailing for long bone fractures. In 32 procedures, the dose of 65 microSv was exceeded 13 times; 8 times during DHS/IMHS and 5 times during IMN. The average thyroid dose was 142 microSv during IMN and 55 microSv during DHS. Only 9 of the total 223 (4%) theatre personnel were using a thyroid shield in spite of its availability. These results suggest that the thyroid is frequently exposed to potentially harmful radiation during these procedures. Strict inclusion of a thyroid shield as a part of routine radiation protection is recommended.     

Thyroid neoplasia following radiation therapy for Hodgkin's lymphoma

The question of thyroid neoplasia following high-dose radiation treatment to the neck and mediastinum for malignant neoplasms such as Hodgkin's lymphoma in children and young adults has been raised recently. Five patients, 19 to 39 years old, were operated on for thyroid neoplasms that developed following cervical and mediastinal radiation therapy for Hodgkin's lymphoma. Three patients had papillary carcinomas and two had follicular adenomas. The latency period between radiation exposure and the diagnosis of thyroid neoplasm ranged from eight to 16 years. This limited series provided strong support for the recommendation that children and young adults who are to receive high-dose radiation therapy to the head, neck, and mediastinum should receive suppressive doses of thyroxine prior to radiation therapy in order to suppress thyrotropin (thyroid-stimulating hormone) and then be maintained on a regimen of suppression permanently.     

Occurrence of previous neck radiotherapy among patients with associated non-medullary thyroid carcinoma and parathyroid adenoma or hyperplasia

Sixteen consecutive patients with co-existent non-medullary thyroid carcinoma and parathyroid adenoma or hyperplasia are reported. Ten of these patients had earlier been treated with external radiation in the neck region. The estimated absorbed dose varied between 5 and 23 gray. The diagnosis of thyroid carcinoma and hyperparathyroidism (HPT) was established 36 years (average) after exposure to radiation. The findings are in accordance with the hypothesis that radiation can serve as an etiological factor in the development of associated thyroid carcinoma and HPT.     

Radiation exposure to the orthopaedic surgeon during periacetabular osteotomy

The objective of this study was to directly measure the radiation exposure to the orthopaedic surgeon and to measure dose points to the surgeon’s fingers, thyroid gland, and forehead during intraoperative fluoroscopy in periacetabular osteotomy (PAO). In a series of 23 consecutive periacetabular osteotomy procedures, exposure monitoring was carried out using thermo luminescent dosimeters. The effective dose received by the operating surgeon was 0.008 mSv per operation which adds up to a yearly dose of 0.64 mSv from PAO. The median point equivalent dose (mSv) exposure under PAO was 0.009 for the forehead and thyroid gland, 0.045 for the right index finger, and 0.039 for the left index finger. The effective estimated yearly dose received by the operating surgeon was very low. Wearing a lead collar reduces radiation exposure to the thyroid gland while the lead gloves did not protect the surgeon’s fingers.     

Radiation exposure during anaesthetic practice

With anaesthesia being administered more often outside of theatre in areas such as radiology suites, the occupational risk to anaesthetists from ionizing radiation may have increased. To determine radiation exposure from X-ray sources during normal anaesthetic practice, passive personal radiation monitoring devices were used to record the occupational exposure to radiation of 29 anaesthetists over a one calendar month period. Occupational whole body effective dose was calculated and extrapolated to give an estimated annual radiation exposure. Seven of the 29 anaesthetists recorded a dose that was higher than the minimum detectable limit. Extrapolating to estimate yearly doses, no anaesthetist would have approached the annual occupational dose limits for ionizing radiation. The maximum extrapolated annual whole body effective dose was 2.14 mSv, the Australian Recommendation and National Standard for occupational exposure being less than 20 mSv per year. The anaesthetist with the highest exposure would have exceeded the yearly recommended exposure limit for pregnant women (1 mSv). Even if they had worked all sessions in a radiation exposed environment, this person would not have exceeded the yearly annual occupational dose limits for ionizing radiation for non-pregnant staff provided they had worn a standard protective lead gown. The collar dose for this person was 7.08 mSv which may represent a significant risk to the thyroid if a protective lead collar was not worn. Although anaesthetists' radiation exposure is within acceptable limits, caution should be taken in rostering pregnant staff to anaesthetize where radiation exposure occurs, and all anaesthetists should routinely wear thyroid collars in such areas.     

儿童及青少年甲状腺癌的流行病学及病因特点

甲状腺癌在儿童及青少年中较为少见,其病理学类型以甲状腺乳头状癌（PTC）为主。不同年龄阶段儿童及青少年甲状腺癌的流行病学特点、病理学类型、临床表现及预后存在差异。儿童时期电离辐射暴露是甲状腺癌唯一确定的危险因素,并存在线性的剂量-效应关系。5%～10%的儿童及青少年甲状腺癌病人有甲状腺肿瘤相关疾病的家族史,具有家族性非髓样甲状腺癌家族史的儿童及青少年患癌风险更高。与成人不同,儿童甲状腺癌中RET/PTC基因重排更为常见,可能是电离辐射相关的致癌因素。家族性非髓样甲状腺癌表现出类似低外显率的常染色体疾病或多基因疾病模式,并具有较高的遗传异质性,其中关键的遗传分子改变目前仍不清楚。儿童及青少年中自身免疫性甲状腺疾病与甲状腺癌的共患率呈逐年上升趋势,我国儿童合并桥本甲状腺炎时发生PTC的风险更高。超重和肥胖可能与儿童及青少年期甲状腺癌的发生有关,并且会增加成年后甲状腺癌的患病风险。儿童时期碘缺乏可导致甲状腺功能减退、甲状腺肿、发育异常等诸多问题;当暴露于电离辐射后,碘缺乏地区的儿童成年后具有更高的甲状腺癌发病率。此外,儿童甲状腺癌还受重金属、食品添加剂、环境致癌物等其他环境与营养因素的影响。儿童及青少年时期相关危险因素的暴露甚至会影响成年后的甲状腺癌的发生与疾病预后,但其具体机制仍有待进一步研究和探索。     

The need to protect the thyroid gland during image intensifier use in orthopaedic procedures

The image intensifier has become an essential part of the orthopaedic surgeon's armamentarium. Its increasing use, however, may expose medical staff and theatre personnel to high doses of radiation. The aim of this study was to assess the compliance of surgeons and staff with radiation protection protocols, especially the use of the thyroid shield and to calculate the radiation exposure dose during routine orthopaedic procedures. We carried out this prospective study of 44 consecutive cases at the Rochdale Infirmary. The total dose of radiation and the total number of images taken were found to be more during hip surgery such as dynamic hip screw fixation for intertrochanteric fracture (1,715.5 mGy.cm2) and the intramedullary nailing (4,357.5 mGy.cm2). However the total percentage of the theatre personnel wearing thyroid shield was as low as 4% (14 people out of total 345 people present in theatre in 44 procedures) in spite of its availability. The consistent neglect in the use of the thyroid shield by surgeons and nursing staff present in theatre during fluoroscopically assisted procedures is a matter for concern. The data presented in this study will emphasise the need to wear a thyroid collar during orthopaedic procedures and the need for better guidelines to protect theatre personnel as well as patients from radiation exposure hazards.     

Clinical Features,Treatment, and Long-Term Outcome of Papillary Thyroid Cancer in Children and Adolescents Without Radiation Exposure

Background  

Cancer of the thyroid gland is rare in children and adolescents. A history of neck irradiation is a well-established risk factor for tumor development, and most previous reports focused on cases that were induced by radiation exposure. We present here a retrospective review of the clinical features, treatment, and long-term outcome of children and adolescents with papillary thyroid cancer (PTC) without a history of radiation exposure who were treated at our institution over a period of ~50 years.     

Thyroid carcinoma and hyperparathyroidism after radiation therapy for adolescent acne vulgaris.

Thyroid and parathyroid disease after head and neck irradiation in infancy and childhood is well known. Patients irradiated for facial acne were older and received a comparatively lower dose of radiation. These mitigating factors suggest a decreased incidence of thyroid and parathyroid disease in these patients. Over the past 28 years (1961 through 1989), 347 consecutive patients were operated on for radiation-associated thyroid and/or parathyroid disease. One hundred and ten patients in this group were irradiated for treatment for adolescent facial acne vulgaris. The interval between radiation exposure and thyroidectomy ranged from 7 to 57 years (mean, 30 years). The overall incidence of thyroid carcinoma was 31% (34 of 110 patients). Regional metastases in 10 patients (29%) were treated with modified radical neck dissection. Hyperparathyroidism, detected in 31% (34 of 110 patients) of this population, was treated with sub-total parathyroidectomy in all cases. The association of thyroid carcinoma and hyperparathyroidism after adolescent radiation exposure for acne vulgaris appears to be more than coincidental. The incidence of thyroid and parathyroid disease may be independent of the timing and dosage of radiation treatment. These thyroid and parathyroid tumors may develop decades after the initial radiation exposure.     

High-dose radiation and the emergence of thyroid nodular disease

High-dose radiation (in excess of 2500 rads or centiGray) to the head and neck area is reputedly infrequently associated with the emergence of thyroid nodular disease. Thirty-three patients who underwent high-dose radiation and who developed thyroid nodular disease have been described. Radiation was originally administered for hyperthyroidism in 11 patients, postmastectomy in five, oral cancer in three, Hodgkin's disease in three, facial hirsutism in three, hemangioma in three, cancer of the larynx in one, skin cancer in one, desmoid tumor of the neck in one, Ewing's tumor in one, and pituitary tumor in one. Treatment included radioiodine in 11, external radiation in 21, interstitial radiation in one, and combined radiation in one. Associated head and neck neoplasms included four parathyroid tumors, one osteogenic sarcoma of the maxilla, two basal cell cancers of the facial skin, and one parotid gland carcinoma. The study group consisted of five men and 26 women varying in age from 22 to 75 years, with a duration of latency of effect varying from 1.5 to 50 years. Thyroid disease consisted of 21 cancers, six adenomas, four colloid goiters, and two cases of thyroiditis resulting in four deaths caused by cancer, for a 20% mortality rate. Consideration of radiation beam behavior showed that isodose curve, penumbra effect, back scatter, and special field resulted in the thyroid gland receiving a low dose, namely under 2500 rads. Clinical factors such as an overlooked goiter, coincidental carcinoma, error in presumption of dose, and second primary malignancy were also considerations. True biologic radiation oncogenesis may have been seen in our radioiodine-treated group with hyperthyroidism as well as the group with Hodgkin's disease who underwent mantle irradiation. It is apparent that for whatever reason and by whatever means and by whatever mechanism, high-dose radiation to the head and neck area can result in significant thyroid disease, and patients undergoing such radiation should be followed with this in mind and considered for thyroid feeding on a prophylactic basis.     

Radiation exposure of the hands and thyroid gland during percutaneous wiring of wrist and hand procedures

The aim of this study was to investigate the radiation exposure of the hands and thyroid glands of orthopaedic surgeon and assistant during procedures involving percutaneous wiring of the hand and wrist. The radiation dose to the hand and thyroid glands was prospectively studied from a total of 30 percutaneous hand and wrist procedures. Four thermolucent densitometers were used to measure the radiation exposure. Cases were divided depending on fracture location (ie. wrist, metacarpal, phalangeal) and surgical experience (i.e. Senior House Officer, Registrar, Consultant). Mean radiation exposure in the hand for the surgeon was 0.80 mSv and 0.87 mSv for the assistant. There was a significant difference in the unshielded thyroid group compared to the shielded thyroid group (p < 0.05). The duration and number of exposure decreases with increasing experience. We also found a trend whereas we operate from proximal to distal (wrist to phalangeal), the total direct hand exposure increases. Radiation exposure in the hands and thyroid glands during percutaneous wiring of hand and wrist procedures were within the recommended limit. However, for the junior orthopaedic trainee, the risk of over radiating oneself is higher as the duration and number of exposure increases. We recommended the use of thyroid shield and adherence to the ALARA principle in any fluoroscopic assisted procedures. Routine monitoring of radiation exposure is essential in preventing radiation related disease.     

Association between Residual Thyroid Carcinoma and Diffuse Hepatic Uptake of 131I following Radioiodine Ablation in Postoperative Total Thyroidectomy Patients

In patients with differentiated thyroid cancer (DTC) total or near-total thyroidectomy, postoperative 131I ablation, and thyroid suppression therapy are reported to be associated with fewer recurrences than other treatments. Many patients with DTC after total thyroidectomy and radioablation therapy have diffuse hepatic uptake of radioiodine, and its clinical importance is debated. Some investigators report that diffuse liver uptake correlates with uptake in the thyroid bed or the presence of metastatic thyroid cancer somewhere in the body, whereas others note no such correlation. The purpose of this research was to determine the clinical importance of diffuse hepatic uptake of radioiodine after 131I ablative therapy in patients with DTC. We retrospectively reviewed 141 posttherapy scans done in 118 patients with DTC. Patients had had total thyroidectomy and were hypothyroid when serum thyroglobulin (Tg) levels were obtained, and they were treated with 30 to 200 mCi of 131I. Scans were performed 3 to 21 days after radioablation therapy. Information was collected regarding the patients' age and gender, the interval between the ablation therapy and scan, uptake of radioiodine, serum thyroglobulin level, thyroid-stimulating hormone (TSH) level, thyroglobulin antibodies, TNM classification, mortality, and recurrence. Diffuse liver uptake was classified from 0 to 4 depending on hepatic brightness. Radioiodine scans were done to determine whether there was uptake in the thyroid bed or elsewhere. Statistical analyses included analysis of variance and Kaplan-Meier survival analysis. Diffuse hepatic uptake was observed (grades 1-4) in 96.4% of the patients; thus 3.6% had no hepatic uptake. There was no significant association between liver uptake and the uptake in the thyroid bed, the dose of 131I administered for ablation therapy, thyroglobulin levels, age, stage of the disease, presence of local or distant metastases, recurrence, or survival. Diffuse hepatic uptake was therefore not associated with residual normal thyroid or metastases as suggested by some but not all previous investigators.     

Effective Radiation Dose from Radiologic Studies in Pediatric Trauma Patients

Evaluation of the pediatric trauma patient frequently requires radiologic studies. Although low-dose radiation from diagnostic radiology is considered safe, lifetime risks per unit dose of radiation are increased in children compared to adults. The total effective dose of radiation to a typical pediatric trauma patient is unknown. We sought to estimate the total effective dose of radiation related to the radiologic assessment of injured children admitted to a pediatric Level I trauma center. We reviewed the radiology records of all children admitted directly to a trauma center in 2002 and tabulated all plain films, computed tomograms, angiographic/fluoroscopic studies, and nuclear medicine studies. Using age-adjusted effective doses (which incorporate biologic effects of radiation), we computed each patient’s total effective dose of radiation. Of 506 admitted patients, 394 (78%) underwent at least one radiologic study. The mean total effective dose per patient was 14.9 mSv (median: 7.2 mSv; interquartile range: 2.2–27.4 mSv). On average, computed tomography accounted for 97.5% of total effective dose. Age and injury severity score did not predict total effective dose. We conclude that in pediatric trauma patients, the estimated total effective dose of radiation varied widely. Computed tomography contributed virtually the entire total effective dose. Regarding radiographic evaluation of pediatric trauma patients, the risks and benefits of current practices should continue to be evaluated critically, because lifetime risks associated with radiation exposure are inversely proportional to age at exposure.     

Extrathyroidal Uptake from Thyroid Carcinoma on 99mTc-Pertechnetate Scintigraphy

Three cases of imaging with 99mTc-pertechnetate (99mTcO4) and unusual positive lymph node uptake in the neck are reported hereby. Two cases were later diagnosed to be well-differentiated thyroid carcinoma, (DTC) with nodal metastasis. The third was a confirmed case of carcinoma thyroid that had presented with mass in the neck soon after surgery, being prepared for ablative dose of radioactive iodine (131I). All three were young females under 40 years of age. These 3 cases signify that extra thyroidal areas of uptake on a routine thyroid scan with 99mTcO4 can some time be due to thyroid carcinoma with regional metastases. Foci of metastasis in patients with DTC may be incidentlly detected with 99mTcO4 scan. Multinodular goiter with palpable lymph node should always be investigated for exclusion of malignancy. The patients underwent near total thyroidectomy and radical neck dissection; histopathology confirmed the scan findings.     

Mammography and the Risk of Thyroid and Hematological Cancers: A Nationwide Population‐based Study

To investigate the association between thyroid cancer as well as the most radiosensitive hematological cancers and radiation exposure from mammography. This study used information from a random sample of two million persons enrolled in the nationally representative Taiwan National Health Insurance (NHI) Research Database. The exposed group was composed of women aged 18–65 who had undergone diagnostic mammography between 2000 and 2007. The nonexposed control group was composed of women in the NHI database who had never undergone diagnostic mammography. There were 25,362 women in the exposed group and 203,317 women in the nonexposed group. After adjusting for age and comorbidities, the patients who had been exposed to radiation from mammography did not have a significantly higher risk of developing thyroid cancer and hematological cancers (adjusted HR, 1.201; 95% CI, 0.813–1.774 for thyroid cancer and adjusted HR, 1.228; 95% CI, 0.838–1.800 for hematological cancers). The scattered radiation dose delivered by mammography should be cautiously handled, but no additional concerns about the risk of thyroid cancer developing malignancy should be emphasized.     

Occupational exposure from common fluoroscopic projections used in orthopaedic surgery

BACKGROUND: Personnel assisting in or performing fluoroscopically guided procedures may be exposed to high doses of radiation. Accurate occupational dosimetric data for the orthopaedic theater staff are of paramount importance for practicing radiation safety. METHODS: Fluoroscopic screening was performed on an anthropomorphic phantom with use of four projections common in image-guided orthopaedic surgery. The simulated projections were categorized, according to the imaged anatomic area and the beam orientation, as (1) hip joint posterior-anterior, (2) hip joint lateral cross-table 45 degrees, (3) lumbar spine anterior-posterior, and (4) lumbar spine lateral 90 degrees. The scattered air kerma rate was measured on a grid surrounding the operating table. For each grid point, the effective dose, eye lens dose, and face skin dose values, normalized over the tube dose area product, were derived. For the effective dose calculations, three radiation protection conditions were considered: (1) with the exposed personnel using no protection measures, (2) with the exposed personnel wearing a 0.5-mm lead-equivalent protective apron, and (3) with the exposed personnel wearing both an apron and a thyroid collar. Maximum permissible workloads for typical hip, spine, and kyphoplasty procedures were derived on the basis of compliance with effective dose, eye lens dose, and skin dose limits. RESULTS: We found that the effective dose, eye lens dose, and face skin dose to an orthopaedic surgeon wearing a 0.5-mm lead-equivalent apron will not exceed the corresponding limits if the dose area product of the fluoroscopically guided procedure is <0.38 Gy m (2). When protective eye goggles are also worn, the maximum permissible dose area product increases to 0.70 Gy m (2), while the additional use of a thyroid shield allows a workload of 1.20 Gy m (2). The effective dose to the orthopaedic surgeon working tableside during a typical hip, spine, kyphoplasty procedure was 5.1, 21, and 250 micro Sv, respectively, when a 0.5-mm lead-equivalent apron alone was used. The additional use of a thyroid shield reduced the effective dose to 2.4, 8.4, and 96 micro Sv per typical hip, spine, and kyphoplasty procedure, respectively. CONCLUSIONS: The levels of occupational exposure vary considerably with the type of fluoroscopically assisted procedure, staff positioning, and the radiation protection measures used. The data presented in the current study will allow for accurate estimation of the occupational dose to orthopaedic theater personnel.     

The Great Unknown—A systematic literature review about risk associated with intraoperative imaging during orthopaedic surgeries

IntroductionModern techniques in orthopaedic surgery using minimally invasive procedures, and increased use of fluoroscopic imaging present a potential increased risk to surgeons due to ionizing radiation exposure. This article is a systematic review of recent literature on radiation exposure of orthopaedic surgeons.Materials and methodsPubmed and Cochrane searches were performed on intraoperative radiation exposure covering English and German articles published between 1.1.2000 and 11.8.2014. Inclusion criteria were clinical studies and systematic literature reviews focusing on radiation exposure of orthopaedic surgeons during surgical procedures of the musculoskeletal system reporting either effective dose (whole body) or equivalent dose at the organ level.All included articles were reviewed with focus on the surgical specialty, the procedure type, the imaging system used, the radiation measurement method, the fluoroscopy time, the radiation exposure, the use of radiation protection, and any references to specific safety guidelines.ResultsThirty-four eligible publications were identified. However, the lack of well-designed studies focusing on radiation exposure of surgeons prevents pooling of data. Highest exposure and subsequent equivalent doses were reported from spinal surgery (up to 4.8 mSv of equivalent dose to the hand) and intramedullary nailing (up to 0.142 mSV of equivalent dose to the thyroid). Radiation exposure was reduced by 96.9% and 94.2% when wearing a thyroid collar and a lead apron.ConclusionsWith the increasing use of intraoperative imaging, there is a growing need for radiation awareness by the operating surgeon. Strict adherence to radiation protection should be enforced to protect in-training surgeons. Strategies to reduce exposure include C-arm position, distance, protective wear, and new imaging technologies. Radiation exposure is harmful and action should be taken to minimize exposure.     

Scattered radiation during fixation of hip fractures. Is distance alone enough protection?

We measured the scattered radiation received by theatre staff, using high-sensitivity electronic personal dosimeters, during fixation of extracapsular fractures of the neck of the femur by dynamic hip screw. The dose received was correlated with that received by the patient, and the distance from the source of radiation. A scintillation detector and a water-filled model were used to define a map of the dose rate of scattered radiation in a standard operating theatre during surgery. Beyond two metres from the source of radiation, the scattered dose received was consistently low, while within the operating distance that received by staff was significant for both lateral and posteroanterior (PA) projections. The routine use of lead aprons outside the 2 m zone may be unnecessary. Within that zone it is recommended that lead aprons be worn and that thyroid shields are available for the surgeon and nursing assistants.     

Hyperthyroidism due to excess iodine

TWO TYPES: Hyperthyroidism may develop in around 10% of patients in excess iodine. It may reveal an undetected pretoxic thyroid disease (type I) or have been induced by excess iodine in previously normal thyroid gland or in an euthyroid goiter (type II). IODINE EXCESSE REVEALING THYROTOXICOSIS: In the former situation, symptoms appear shortly after the iodine load, thyroid scintigraphy shows significant uptake and therapy includes discontinuation of iodine excess, antithyroid drugs, potassium perchlorate and, if necessary, thyroidectomy or a therapeutic dose of iodide 131. IODINE-INDUCED THYROTOXICOSIS: In the latter situation (type II) hyperthyroidism may occur several years after the initiation of iodine excess, scintigraphy shows very low or no uptake, spontaneous remission is observed within six months, despite the persistence of iodine excess, and treatment is based on corticosteroids.