Long-term oncological outcomes of follicular thyroid cancer in adolescents and young adults: A nationwide population-based study.

BACKGROUND: Follicular thyroid carcinoma (FTC) in adolescents and young adults (AYAs) is rare and data on long-term oncological outcomes are scarce. This study aimed to describe the long-term recurrence and survival rates of AYAs with FTC, and identify risk factors for recurrence. METHODS: This is a retrospective cohort study combining two national databases, including all patients aged 15-39 years, diagnosed with FTC in The Netherlands between 2000 and 2016. Age, sex, tumor size, focality, positive margins, angioinvasion, pT-stage, and pN-stage were included in a Cox proportional hazard model to identify risk factors for recurrence. RESULTS: We included 192 patients. Median age was 31.0 years (IQR 24.7-36.3) and the male to female ratio was 1:4.1. Most patients presented with a minimally invasive FTC (MI-FTC) (95%). Five patients presented with synchronous metastases (2.6%), including two with locoregional metastases (1%) and three with distant metastases (1.6%). During a median follow-up of 12.0 years, three patients developed a recurrence (1.6%), of which one patient developed a local recurrence (33%), and two patients a distant recurrence (67%). Five patients died during follow-up (2.6%). Cause of death was not captured. A Cox proportional hazard model could not be performed due to the low number of recurrences. CONCLUSIONS: FTC in AYAs is generally characterized as a low-risk tumor, as it exhibits a very low recurrence rate, a high overall survival, and it typically presents as MI-FTC without synchronous metastases. These findings underscore the favorable long-term oncological prognosis of FTC in AYAs.

Cardiac function in paediatric patients with congenital adrenal hyperplasia due to 21 hydroxylase deficiency.

BACKGROUND: Hyperandrogenism and exogenous glucocorticoid excess may cause unfavourable changes in the cardiovascular risk profile of patients with congenital adrenal hyperplasia (CAH). OBJECTIVE: To evaluate the cardiac function in paediatric patients with CAH. PATIENTS AND METHODS: Twenty-seven paediatric patients with CAH, aged 8-16 years, were evaluated by physical examination, electrocardiogram (ECG), conventional echocardiography, tissue Doppler imaging and two-dimensional (2D) myocardial strain (rate) imaging. Results were compared to 27 age- and gender- matched healthy controls. RESULTS: No signs of left ventricular hypertrophy or dilatation were detected on echocardiography. ECG revealed a high prevalence (25.9%) of incomplete right bundle branch block. Left ventricular posterior wall thickness in diastole (LVPWd) was significantly lower in patients with CAH compared to controls (5.55 vs 6.53 mm; P = .009). The LVPWd Z-score was significantly lower in patients with CAH yet within the normal range (-1.12 vs -0.35; P = .002). Isovolumetric relaxation time was significantly lower in patients with CAH (49 vs 62 ms; P = .003). Global longitudinal, radial and circumferential strain was not significantly different compared to controls. Global radial strain rate was significantly higher compared to healthy controls (2.58 vs 2.06 1/s; P = .046). Global longitudinal strain was negatively correlated with 24-hour blood pressure parameters. CONCLUSION: Cardiac evaluation of paediatric patients with CAH showed no signs of left ventricular hypertrophy or ventricular dilatation. LVPWd was lower in patients with CAH than in controls but within the normal range. A shorter isovolumetric relaxation time in patients with CAH may be a sign of mild left ventricular diastolic dysfunction.

Pancytopenia and Hypothyroidism in a Patient With Leukemic Infiltration of the Thyroid as the First Presentation of Acute Lymphoblastic Leukemia.

We report the case of a 16-year-old female patient with hypothyroidism, goiter, and pancytopenia. Biopsy of the thyroid showed leukemic infiltration. After confirmation of the diagnosis of B-lymphoblastic leukemia, treatment was started. Histologic follow-up at day 33 and 79 showed no residual signs of leukemic infiltration. Hypothyroidism persisted despite successful antileukemic treatment. Leukemic infiltration of the thyroid should be considered as a differential diagnosis in patients with hypothyroidism, goiter, and pancytopenia. We suggest that follow-up of thyroid function and histology should be incorporated in the follow-up of rare patients with acute lymphoblastic leukemia with thyroid infiltration.

Disorders of Adrenal Steroidogenesis: Impact on Gonadal Function and Sex Development.

A defect in adrenal steroidogenesis may cause a disorder of sex development (DSD). Importantly, DSD of adrenal origin is not restricted to a genital phenotype but is in most cases accompanied by mild to severe impairment in glucocorticoid and/or mineralocorticoid synthesis. If a patient is suspected of DSD of adrenal origin evaluation of glucocorticoid and mineralocorticoid metabolism is therefore essential to provide adequate medical care in the case of a severe and potentially life-threatening insufficiency. The adrenal steroidogenic defects causing DSD, their clinical features and diagnostic work-up are discussed. In this review we provide an overview of defects in the adrenal steroidogenesis and its impact on gonadal function and sex development.

Characterization of the molecular genetic pathology in patients with 11ß-hydroxylase deficiency.

OBJECTIVE: Steroid 11ß-hydroxylase (CYP11B1) deficiency (11OHD) is the second most common form of congenital adrenal hyperplasia. Nonclassic or mild 11OHD appears to be a rare condition. Our study assessed the residual CYP11B1 function of detected mutations, adding to the spectrum of mild 11OHD, and illustrates the variability of the clinical presentation of 11OHD. PATIENTS AND METHODS: Five patients presented with mild to moderate 11OHD. Two women presented with mild hirsutism and in one case with secondary amenorrhoea. Two men presented with precocious pseudopuberty, gynaecomastia and elevated blood pressure. One 46,XX female patient was diagnosed with virilization of the external genitalia 2 years after birth. Direct DNA sequencing was carried out to perform CYP11B1 mutation analysis. The CYP11B1 mutations were functionally characterized using an in vitro expression system. RESULTS: CYP11B1-inactivating mutations were detected in all patients. Two novel missense mutations (p.P42L and p.A297V) and the previously characterized p.R143W mutation had residual CYP11B1 activities between 10% and 27%. A novel p.L382R and the previously uncharacterized p.G444D mutation both caused complete loss of CYP11B1 enzymatic activity. CONCLUSION: Mutations causing partial impairment of 11ß-hydroxylase activity (residual activity of 10% or above) are associated with a less severe clinical presentation of 11OHD, which can be classified as a nonclassic form. Our data demonstrate that patients with nonclassic 11OHD can present with androgen excess, precocious pseudopuberty and increased blood pressure. Timely diagnosis of nonclassic 11OHD and consequently initiation of personalized treatment is essential to prevent co-morbidities caused by androgen excess and hypertension.

Approach to the Patient: Challenging Cases of Pediatric Thyrotoxicosis.

Graves' disease (GD) is the leading cause of hyperthyroidism in children. However, compared to adults GD in children is a rare condition. In a recent guideline issued by the European Thyroid Association the diagnostic evaluation and treatment of pediatric GD is described extensively. In this article we go beyond the guideline and describe the potential challenges of establishing the right etiology of thyrotoxicosis in children, illustrated by cases of thyroid hormone resistance, autonomous functioning thyroid nodules and subacute thyroiditis with a thyrotoxic phase. In addition, we report therapeutic challenges in pediatric GD such as recurrent immunological flare-ups under anti-thyroid drug (ATD) treatment, innovative ways to improve ATD compliance and the role of definitive treatment in persistent complaints of malaise under ATD treatment.

Iodinated Contrast Induced Hypothyroidism in the Infant After Enteral Contrast Enema: A Case Report and Systematic Review.

Background: Excessive iodine intake triggers the Wolff-Chaikoff effect resulting in downregulation of thyroid hormone synthesis to prevent hyperthyroidism. Failure to escape the Wolff-Chaikoff effect can be seen especially in (premature born) infants and may result in prolonged iodine induced hypothyroidism. We describe a rare case of a preterm infant who developed severe iodinated contrast induced hypothyroidism after the use and prolonged stasis of enteral iodinated contrast media (ICM). In addition a systematic literature search was performed to evaluate all available data on this complication. Methods: A systematic literature search was performed in PubMed and Embase. Studies describing the effect of enteral ICM on thyroid function were considered eligible. The primary outcome was to determine the frequency of contrast induced hypothyroidism in infants after administration of enteral ICM. Results: The premature infant in our center developed severe iodinated contrast induced hypothyroidism after enteral ICM. In total, only two studies met our eligibility data, reporting eight patients. Out of these eight patients, four premature infants developed a contrast induced hypothyroidism after enteral administration of ICM. Conclusion: Data on severity, length and frequency of contrast induced hypothyroidism after exposure to enteral ICM is very scarce. The herein reported case and literature search illustrate the potential severity of the complication and underline the necessity of future studies on this topic. We recommend standardized monitoring of thyroid function after exposure to enteral ICM in newborns to prevent delayed diagnosis of severe contrast induced hypothyroidism until evidence based recommendations can be made.

The Definition of Recurrence of Differentiated Thyroid Cancer: A Systematic Review of the Literature.

Background Recurrence is a key outcome to evaluate treatment effect of differentiated thyroid carcinoma (DTC). However, no consistent definition of recurrence is available in current literature or international guidelines. Therefore, the primary aim of this systematic review was to delineate the definitions of recurrence of DTC, categorized by total thyroidectomy with radioactive iodine ablation (RAI), total thyroidectomy without RAI and lobectomy, to assess if there is a generally accepted definition among these categories. Methods This study adhered to 2020 PRISMA statement. In December 2023, systematic literature search in MEDLINE and EMBASE was performed for studies reporting on recurrence of DTC, from January 2018 to December 2023. Studies that did not provide a definition were excluded. Primary outcome was the definition of recurrence of DTC. Secondary outcome whether studies differentiated between recurrence and persistent disease. Two independent investigators screened titles and abstracts, followed by full-text assessment and data extraction. The study protocol was registered in PROSPERO,CRD42021291753. Results In total, 1450 studies were identified. Seventy studies met inclusion criteria, including 69 retrospective studies and one RCT. Median number of patients in included studies was 438 (range 25 - 2297). Seventeen studies (24.3%) reported on lobectomy, four studies (5.7%) on total thyroidectomy without RAI, and 49 studies (70.0%) with RAI. All studies defined recurrence using one or a combination of four diagnostic modalities: cytology/pathology, imaging studies, thyroglobulin(-antibodies), predetermined minimum tumor-free time span. The most common definition of recurrence following lobectomy was cytology/pathology-proven recurrence (47.1% of this subgroup), following total thyroidectomy with RAI was cytology/pathology-proven recurrence and/or anomalies detected on imaging studies (22.4% of this subgroup). No consistent definition was found following total thyroidectomy without RAI. Nine studies (12.9%) differentiated between recurrence and persistent disease. Conclusion Our main finding is that there is no universally accepted definition for recurrence of DTC in the current studies across any of the treatment categories. The findings of this study will provide the basis for a future, international Delphi-based proposal to establish a universally accepted definition of recurrence of DTC. A uniform definition could facilitate global discussion and enhance the assessment of treatment outcomes regarding recurrence of DTC.

A 15-year-old Girl with a Lateral Neck Mass Turning Out to Be Papillary Thyroid Carcinoma-Lateral Ectopic Papillary Thyroid Carcinoma or Lymph Node Metastasis?

Lateral neck lesions in children are common and involve various infectious or inflammatory etiologies as well as embryological remnants such as branchial cleft cysts. Although unusual, ectopic thyroid tissue can also present as a lateral neck mass. Here, we present an unusual case of a 15-year-old girl treated for an asymptomatic lateral neck mass that after surgical removal was found to be papillary thyroid carcinoma (PTC). However, after removal of the thyroid gland, no primary thyroid tumor was found. The question arose whether the lateral neck lesion was a lymph node metastasis without identifiable primary tumor (at histological evaluation) or rather malignant degeneration of ectopic thyroid tissue. Total thyroidectomy was performed with postoperative adjuvant radioactive iodine ablation. Even though PTC in a lateral neck mass without a primary thyroid tumor has been described previously, pediatric cases have not been reported. In this report we share our experience on diagnosis, treatment and follow-up, and review the existing literature.

[A girl with a tumor at the base of the tongue]. / Een meisje met een zwelling op de tongbasis.

An 8-year-old girl with a lingual thyroid was evaluated because of a tumor at the base of the tongue. Ultrasound showed a hypoechogenic homogeneous parenchymatous structure at the base of the tongue consistent with thyroid tissue. Suboptimal levothyroxine treatment resulted in longstanding TSH stimulation causing a lingual goiter.

The Effect of Pre-Thyroidectomy Calcitriol Prophylaxis on Post-Thyroidectomy Hypocalcaemia in Children.

INTRODUCTION: Transient or persistent hypoparathyroidism is one of the most well-known complications of total thyroidectomy and may lead to symptomatic hypocalcaemia. In children, treatment of post-thyroidectomy hypocalcaemia usually consists of postoperative calcium and/or vitamin D supplementation. In 2013, we implemented prophylactic pre-thyroidectomy calcitriol supplementation for all children undergoing total thyroidectomy at the Amsterdam UMC. The objective of this study was to evaluate the efficacy of this prophylactic calcitriol supplementation in preventing post-thyroidectomy hypocalcaemia in children. METHODS: In a retrospective case study, we included all children (age <18 years), who underwent a total or completion thyroidectomy in the Amsterdam UMC, between 2000 and 2020. Patients were divided into two groups, patients with preoperative calcitriol supplementation and those without (controls). Hypocalcaemia was defined as total serum calcium concentration of <2.0 mmol/L. The primary outcome measure was the occurrence of hypocalcaemia in the first 72 h after surgery. Secondary outcome measures were occurrence of symptomatic hypocalcaemia, need for medical intervention within the first 72 h after surgery, and length of hospitalization. RESULTS: A total of 51 patients were included; 26 with calcitriol prophylaxis and 25 controls. There was no significant difference in occurrence of hypocalcaemia (17/26 prophylaxis group; 18/25 control group). Median postoperative calcium concentrations in the first 72 h were significantly higher in the group with prophylaxis at 30-35 h (2.26 vs. 2.01 mmol/L) and 36-41 h (2.17 vs. 1.92 mmol/L). Occurrence of symptomatic hypocalcaemia, need for medical intervention, and length of hospitalization were not significantly different between the groups. CONCLUSION: Calcitriol prophylaxis resulted in somewhat higher postoperative calcium concentrations but did not reduce the occurrence of hypocalcaemia or affect clinical outcome measures such as occurrence of symptomatic hypocalcaemia and length of postoperative hospitalization.

2022 European Thyroid Association Guideline for the management of pediatric Graves' disease.

Hyperthyroidism caused by Graves' disease (GD) is a relatively rare disease in children. Treatment options are the same as in adults - antithyroid drugs (ATD), radioactive iodine (RAI) or thyroid surgery, but the risks and benefits of each modality are different. The European Thyroid Association guideline provides new recommendations for the management of pediatric GD with and without orbitopathy. Clinicians should be alert that GD may present with behavioral changes or declining academic performance in children. Measurement of serum TSH receptor antibodies is recommended for all pediatric patients with hyperthyroidism. Management recommendations include the first-line use of a prolonged course of methimazole/carbimazole ATD treatment (3 years or more), a preference for dose titration instead of block and replace ATD, and to avoid propylthiouracil use. Where definitive treatment is required either total thyroidectomy or RAI is recommended, aiming for complete thyroid ablation with a personalized RAI activity. We recommend avoiding RAI in children under 10 years of age but favor surgery in patients with large goiter. Pediatric endocrinologists should be involved in all cases.

Pediatric Graves' orbitopathy: a multicentre study.

PURPOSE: Graves' orbitopathy (GO) is a rare condition in children often considered to be a less severe condition than at an older age. The aim of our study was to analyse if there are any factors that distinguish paediatric from adult GO in order to provide guidelines for assessing and managing paediatric GO. METHODS: Study design is a multicentre retrospective observational case series; 115 paediatric patients diagnosed with GO who visited our university medical centres in the Netherlands and Iran between 2003 and 2019 were submitted for complete ophthalmological examinations, serological testing and/or orbital imaging. Main outcome measures focussed on the natural course and clinical picture as well as medical and surgical treatment in paediatric GO. RESULTS: Clinical findings included proptosis (n = 97; 84.3%), eyelid retraction (n = 77; 67%) and diplopia (n = 13; 11.3%). Ninety-two patients (80%) presented with mild disease, 21 (18.3%) with moderate-severe disease and two (1.7%) with severe GO. Five patients (4.3%) underwent intravenous glucocorticoids and 25 patients underwent orbital decompression surgery. Strabismus surgery due to primary involvement of extraocular muscles was performed in two patients (1.7%). Overall, rehabilitative surgical treatment was planned in 31 patients (26.9%) with inactive disease. Two patients experienced reactivation of the disease. CONCLUSION: Despite the fact that paediatric and adult GO are considered two separate entities, they might be the same disease with two different clinical phenotypes. Paediatric GO population presents with a comparable clinical picture regarding both soft tissue involvement and proptosis, which may require surgical intervention. Proptosis was present in the majority of paediatric GO patients. Orbital decompression was performed in 21.7% of patients.

Long-Term Oncological Outcomes of Papillary Thyroid Cancer and Follicular Thyroid Cancer in Children: A Nationwide Population-Based Study.

Introduction: Pediatric thyroid carcinoma is a rare malignancy and data on long-term oncological outcomes are sparse. The aim of this study was to describe the long-term oncological outcomes of pediatric papillary thyroid carcinoma (PTC) and follicular thyroid carcinoma (FTC) in a national cohort, and to identify risk factors for recurrence. Methods: We conducted a nationwide, retrospective cohort study, in which we combined two national databases. Patients aged <18 years, diagnosed with PTC or FTC in the Netherlands between 2000 and 2016, were included. pT-stage, pN-stage, multifocality and angioinvasion were included in a Cox-regression analysis for the identification of risk factors for recurrence. Results: 133 patients were included: 110 with PTC and 23 with FTC. Patients with PTC most often presented with pT2 tumors (24%) and pN1b (45%). During a median follow-up of 11.3 years, 21 patients with PTC developed a recurrence (19%). Nineteen recurrences were regional (91%) and 2 were pulmonary (9%). No risk factors for recurrence could be determined. One patient who developed pulmonary recurrence died two years later. Cause of death was not captured. Patients with FTC most often presented with pT2 tumors (57%). One patient presented with pN1b (4%). In 70%, no lymph nodes were collected. None of the patients with FTC developed a recurrence or died. Conclusion: Pediatric PTC and FTC are two distinct diseases. Recurrence in pediatric PTC is common, but in FTC it is not. Survival for both pediatric PTC and FTC is very good.

Identification of a Novel CYP11B2 Variant in a Family with Varying Degrees of Aldosterone Synthase Deficiency.

Isolated aldosterone synthase deficiency is a rare autosomal recessive disorder caused by pathogenic variants in CYP11B2, resulting in impaired aldosterone synthesis. We report on a neonate with isolated aldosterone synthase deficiency caused by a novel homozygous CYP11B2 variant Chr8:NM_000498.3:c.400G>A p.(Gly134Arg). The patient presented shortly after birth with severe signs of aldosterone deficiency. Interestingly, segregation analysis revealed that the patient's asymptomatic father was also homozygous for the CYP11B2 variant. Biochemical evaluation of the father indicated subclinical enzyme impairment, characterized by elevated aldosterone precursors. Apparently, this homozygous variant led to different clinical phenotypes in two affected relatives. In this manuscript we elaborate on the performed biochemical and genetic work-up and describe potential pitfalls of CYP11B2 sequencing due to its homology to CYP11B2.

Optimizing the Timing of Highest Hydrocortisone Dose in Children and Adolescents With 21-Hydroxylase Deficiency.

CONTEXT: Hydrocortisone treatment of young patients with 21-hydroxylase deficiency (21OHD) is given thrice daily, but there is debate about the optimal timing of the highest hydrocortisone dose, either mimicking the physiological diurnal rhythm (morning), or optimally suppressing androgen activity (evening). OBJECTIVE: We aimed to compare 2 standard hydrocortisone timing strategies, either highest dosage in the morning or evening, with respect to hormonal status throughout the day, nocturnal blood pressure (BP), and sleep and activity scores. METHODS: This 6-week crossover study included 39 patients (aged 4-19 years) with 21OHD. Patients were treated for 3 weeks with the highest hydrocortisone dose in the morning, followed by 3 weeks with the highest dose in the evening (n = 21), or vice versa (n = 18). Androstenedione (A4) and 17-hydroxyprogesterone (17OHP) levels were quantified in saliva collected at 5 am; 7 am; 3 pm; and 11 pm during the last 2 days of each treatment period. The main outcome measure was comparison of saliva 17OHP and A4 levels between the 2 treatment strategies. RESULTS: Administration of the highest dose in the evening resulted in significantly lower 17OHP levels at 5 am, whereas the highest dose in the morning resulted in significantly lower 17OHP and A4 levels in the afternoon. The 2 treatment dose regimens were comparable with respect to averaged daily hormone levels, nocturnal BP, and activity and sleep scores. CONCLUSION: No clear benefit for either treatment schedule was established. Given the variation in individual responses, we recommend individually optimizing dose distribution and monitoring disease control at multiple time points.

Persisting symptoms in patients with Hashimoto's disease despite normal thyroid hormone levels: Does thyroid autoimmunity play a role? A systematic review.

OBJECTIVE: Patients with hypothyroidism due to Hashimoto's disease (HD) may experience persisting symptoms despite normal serum thyroid hormone (TH) levels. Several hypotheses have been postulated to explain these persisting symptoms. We hypothesized that thyroid autoimmunity may play a role. DESIGN: A systematic literature review. METHODS: A PubMed search was performed to find studies investigating the relation between the presence of thyroid autoimmunity and (persisting) symptoms. Included studies were critically appraised by the Newcastle - Ottawa Scale (NOS) and then subdivided into (A) disease-based studies, comparing biochemically euthyroid patients with HD, and euthyroid patients with non-autoimmune hypothyroidism or euthyroid benign goitre, and (B) (general) population-based studies. Due to different outcome measures among all studies, meta-analysis of data could not be performed. RESULTS: Thirty out of 1259 articles found in the PubMed search were included in this systematic review. Five out of seven disease-based studies found an association between thyroid autoimmunity and symptoms or lower quality of life (QoL). Sixteen of 23 population-based studies found a comparable positive association. In total, the majority of included studies reported an association between thyroid autoimmunity and persisting symptoms or lower QoL in biochemically euthyroid patients. CONCLUSION: (Thyroid) autoimmunity seems to be associated with persisting symptoms or lower QoL in biochemically euthyroid HD patients. As outcome measures differed among the included studies, we propose the use of similar outcome measures in future studies. To prove causality, a necessary next step is to design and conduct intervention studies, for example immunomodulation vs. placebo preferably in the form of a randomized controlled trial, with symptoms and QoL as main outcomes.

Methimazole-induced remission rates in pediatric Graves' disease: a systematic review.

Objective: Comparison of studies on remission rates in pediatric Graves' disease is complicated by lack of uniformity in treatment protocols, remission definition, and follow-up duration. We performed a systematic review on remission rates in pediatric Graves' disease and attempted to create uniformity by recalculating remission rates based on an intention-to-treat analysis. Methods: PubMed and Embase were searched in August 2020 for studies on patients with Graves' disease: (i) 2 to 18 years of age, (ii) initially treated with methimazole or carbimazole for at least 18 months, (iii) with a follow-up duration of at least 1 year after cessation of methimazole or carbimazole. All reported remission rates were recalculated using an intention-to-treat analysis. Results: Of 1890 articles, 29 articles consisting of 24 patient cohorts were included with a total of 3057 patients (82.6% female). Methimazole or carbimazole was initially prescribed in 2864 patients (93.7%). Recalculation based on intention-to-treat analysis resulted in an overall remission rate of 28.8% (829/2880). Pooled remission rates based on treatment duration were 23.7, 31.0, 43.7, and 75% respectively after 1.5-2.5 years, 2.5-5 years, 5-6 years (two studies), and 9 years (single study) treatment duration. The occurrence of adverse events was 419 in 2377 patients (17.6%), with major side effects in 25 patients (1.1%). Conclusions: Using a standardized calculation, the overall remission rate in methimazole-treated pediatric GD is 28.8%. A few small studies indicate that longer treatment increases the remission rate. However, evidence is limited and further research is necessary to investigate the efficacy of longer treatment durations.

The Efficacy and Short- and Long-Term Side Effects of Radioactive Iodine Treatment in Pediatric Graves' Disease: A Systematic Review.

BACKGROUND: Graves's disease (GD) is the most common cause of hyperthyroidism. Maximal 30% of pediatric GD patients achieve remission with antithyroid drugs. The majority of patients therefore require definitive treatment. Both thyroidectomy and radioactive iodine (RAI) are often used as definitive treatment for GD. However, data on efficacy and short- and long-term side effects of RAI treatment for pediatric GD are relatively scarce. METHODS: A systematic review of the literature (PubMed and Embase) was performed to identify studies reporting the efficacy or short- and long-term side effects of RAI treatment in pediatric GD. RESULTS: Twenty-three studies evaluating 1,283 children and adolescents treated with RAI for GD were included. The treatment goal of RAI treatment changed over time, from trying to achieve euthyroidism in the past to aiming at complete thyroid destruction and subsequent hypothyroidism in the last 3 decades. The reported efficacy of a first RAI treatment when aiming at hypothyroidism ranged from 42.8 to 97.5%, depending on the activity administered. The efficacy seems to increase with higher RAI activities. When aiming at hypothyroidism, both short- and long-term side effects of treatment are very rare. Long-term side effects were mainly seen in patients in whom treatment aimed at achieving euthyroidism. CONCLUSION: RAI is a safe definitive treatment option for pediatric GD when aiming at complete thyroid destruction. When aiming at hypothyroidism, the efficacy of treatment seems to increase with a higher RAI activity. Prospective studies are needed to determine the optimal RAI dosing regimen in pediatric GD.