Mutation screening of DUOX2 in Chinese patients with congenital hypothyroidism

Patients with Thyroid Dyshormonogenesis and DUOX2 Variants: Molecular and Clinical Description and Genotype-Phenotype Correlation

Thyroid dyshormonogenesis (THD) is a heterogeneous group of genetic diseases caused by the total or partial defect in the synthesis or secretion of thyroid hormones. Genetic variants in DUOX2 can cause partial to total iodination organification defects and clinical heterogeneity, from transient to permanent congenital hypothyroidism. The aim of this study was to undertake a molecular characterization and genotype-phenotype correlation in patients with THD and candidate variants in DUOX2. A total of 31 (19.38%) patients from the Catalan Neonatal Screening Program presented with variants in DUOX2 that could explain their phenotype. Fifteen (48.39%) patients were compound heterozygous, 10 (32.26%) heterozygous, and 4 (12.90%) homozygous. In addition, 8 (26.67%) of these patients presented variants in other genes. A total of 35 variants were described, 10 (28.57%) of these variants have not been previously reported in literature. The most frequent variant in our cohort was c.2895_2898del/p.(Phe966SerfsTer29), classified as pathogenic according to reported functional studies. The final diagnosis of this cohort was permanent THD in 21 patients and transient THD in 10, according to reevaluation and/or need for treatment with levothyroxine. A clear genotype-phenotype correlation could not be identified; therefore, functional studies are necessary to confirm the pathogenicity of the variants.

Results of neonatal screening for congenital hypothyroidism and hyperphenylalaninemia in Zhejiang province from 1999 to 2022

OBJECTIVES

To analyze the results of neonatal screening for congenital hypothyroidism (CH) and hyperphenylalaninemia (HPA) in Zhejiang province from 1999 to 2022.

METHODS

A total of 11 922 318 newborns were screened from September 1999 and December 2022 in Zhejiang province. The blood thyroid stimulating hormone (TSH) levels were measured by a fluorescence method and blood phenylalanine (Phe) levels were measured by fluorescence method or tandem mass spectrometry. TSH≥9 μIU/mL was considered positive for CH, while Phe>120 μmol/L and/or Phe/Tyr ratio>2.0 were considered positive for HPA. The positive newborns in screening were recalled, and the gene variations were detected by high-throughput sequencing and MassARRAY tests.

RESULTS

The overall neonatal screening rate during 1999-2022 was 89.41% (11 922 318/13 333 929) and the screening rate was increased from 6.46% in 1999 to 100.0% in 2022. A total of 8924 cases of CH were diagnosed among screened newborns with an incidence rate of 1/1336. A total of 563 cases of HPA were diagnosed, including 508 cases of classic phenylketonuria (cPKU) and 55 cases of tetrahydrobiopterin deficiency (BH4D), with an incidence rate of 1/21 176. Ninety-seven out of 8924 cases of CH underwent genetic analysis. Gene mutations were detected in 9 CH related genes, the highest frequency mutations were found in DUOX2 gene (69.0%) with c.3329G>A (p.R1110Q) (18.2%) and c.1588A>T (p.K530X) (17.3%) as the hotspot mutations. There were 81 PAH gene variants detected in a total of 250 cases of cPKU, and c728G>A (p.R243Q) (24.4%), c.721C>T (p.R241C) (15.0%) were the hotspot mutations. Meanwhile 7 novel variants in PAH gene were detected: c.107C>A (p.S36*), c.137G>T (p.G46V), c.148A>G(p.K50E), c.285C>T (p.I95I), c.843-10delTTCC, exon4-7del and c.1066-2A>G. There were 12 PTS gene variants detected in 36 cases of BH4D, and c.259C>T (p.P87S) (31.9%) was the hotspot mutation.

CONCLUSIONS

The incident of CH has increased from 1999 to 2022 in Zhejiang province, and it is higher than that of national and global levels; while the incidence of HPA is similar to the national average. DUOX2 gene variation is the most common in CH patients; c.728G>A (p.R243Q) is the hotspot mutation in cPKU patients, while c.259C>T (p.P87S) is the hotspot mutation in BH4D patients.

Clinical, biochemical characteristics and genotype-phenotype analysis of congenital hypothyroidism diagnosed by newborn screening in China

BACKGROUND

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder worldwide. However, the underlying etiology remains unclear in most patients.

METHODS

The newborn screening was performed for TSH in dried blood spots. Serum TSH, T3, T4, free T3(FT3) and free T4 (FT4) were detected for the recalled children. High-throughput sequencing were applied to detect 29 known CH genes. The statistical analyses were performed to analyze the differences between biochemical data, thyroid volume, clinical prognosis and genetic results for 97 patients who had one or more variants in CH related genes.

RESULTS

DUOX2 gene has the highest variant rate, followed by TG, TPO and TSHR gene. The "DUOX2 biallelic variants" group was associated with "Goiter", while "DUOX2 monoallelic variants" group was associated with "Agenesis". In addition, the TSH levels and initial L-T4 dose were significantly higher in "TPO biallelic variants" group than those in "DUOX2 and TSHR biallelic variants" groups.

CONCLUSIONS

Our study showed dyshormonogenesis (DH) might be the leading pathophysiology of CH in Chinese populations. DUOX2 gene mostly caused goiter, but also could be associated with hypoplasia. TPO might play a more irreplaceable role than DUOX2. The digenic variants combination indicated the complexity of genetic etiology in CH.

Combined genetic screening and traditional newborn screening to improve the screening efficiency of congenital hypothyroidism

Background

Congenital hypothyroidism (CH) is an neonatal endocrine disorder. Traditional newborn screening is the mainstream method of CH screening, so as to ensure the early detection and treatment of CH. This method is limited as it has high rates of false positives and negatives. Genetic screening can be used to address the shortcomings of traditional newborn Screening (NBS); however, the comprehensive clinical value of genetic screening is yet to be systematically studied.

Methods

A total of 3,158 newborns who accepted the newborn screening and genetic screening were recruited for this study. Biochemical screening and genetic screening were performed at the same time. The level of TSH with the DBS was detected by time-resolved immunofluorescence assay. High-throughput sequencing technology based on targeted gene capture was used for genetic screening. The suspected neonatal was recalled and tested serum TSH, and FT4. Finally, the effectiveness of traditional NBS and combined screening was compared.

Results

In this study, 16 cases were diagnosed by traditional NBS. 10 cases of DUOX2 mutation were found in newborn CH-related genetic screening, including 5 homozygous and 5 compound heterozygous variations. We found that the c.1588A > T mutations in DUOX2 constituting the predominant site in the present cohort.Compared with NBS and genetic screening, the sensitivity of combined screening increased by 11.1% and 55.6%, respectively. Compared with NBS and genetic screening, the negative predictive value of combined screening increased by 0.1% and 0.4%, respectively.

Conclusions

Combined traditional NBS and genetic screening reduces the false negative rate of CH screening and improves the early and accurate identification of neonates with CH. Our research explains the mutation spectrum of CH in this region, and provisionally demonstrates the necessity, feasibility and significance of genetic screening in newborns and provides a solid basis for future clinical developments.

Predictive factors for the diagnosis of permanent congenital hypothyroidism and its temporal changes in Sergipe, Brazil - A real-life retrospective study

Objective

Congenital hypothyroidism (CH) can be permanent (PCH) or transient (TCH). While the importance of thyroxine in myelination of the brain is undisputed, the benefits to neurodevelopmental outcomes of TCH treatment are controversial. Our objectives were to determine predictive factors for PCH and verify its prevalence changes over time.

Subjects and methods

A total of 165 children were evaluated at 3 years of age to verify the diagnosis of PCH. 130 were submitted to a two-step cluster analysis, with the aim of grouping them into homogeneous clusters. The mean incidence of PCH and TCH was calculated from 2004 to 2010 and 2011 to 2015.

Results

Sixty-six children were diagnosed with PCH, and 99 were diagnosed with TCH. Eighty-one percent of PCH children and all TCH children with thyroid imaging had glands in situ. Eighty children (61.5%) were in Cluster 1, 8 children (6.2%) were in Cluster 2 and 42 children (32.3%) were in Cluster 3. No children had PCH in Cluster 1, while 87.5% of children in Cluster 2 and all children in Cluster 3 had PCH. The most important predictor for PCH was the initial serum TSH, which was marginally higher in importance than the blood spot TSH, followed by the initial serum free T4. The mean incidence of PCH (odds ratio: 1.95, 95% CI 1.36 to 2.95, p < 0.0001) and TCH (odds ratio 1.33, 95%, CI 1.02 to 1.77, p = 0,038) increased over time.

Conclusion

The most important PCH predictors are the initial serum TSH and the blood spot TSH. The mean incidence of both PCH and TCH in our series increased.

Genetic Factors Causing Thyroid Dyshormonogenesis as the Major Etiologies for Primary Congenital Hypothyroidism: Clinical and Genetic Characterization of 33 Patients

BACKGROUND AND AIMS

Although the significance of primary congenital hypothyroidism (CH) is supported by an increasing amount of evidence, the clinical and genetic characteristics of this condition are still poorly understood. This study aimed to explore the underlying genetic etiologies in a cohort of primary CH patients.

SUBJECTS AND METHODS

The clinical data of 33 patients with primary CH were collected and analyzed via a cross-sectional study. Genetic analysis was performed by high-throughput sequencing and Sanger verification, and the pathogenicity of the novel missense variants was predicted using a variety of comprehensive bioinformatic tools.

RESULTS

Among the 33 patients, 22 (22/33, 66.7%) harbored pathogenic variants in the causative genes of thyroid dysgenesis or dyshormonogenesis, with DUOX2 (15/33, 45.5%) topping the list, followed by TG, TPO, DUOXA2 and PAX8. Four novel genetic variants were detected, including a pathogenic frameshift and three likely pathogenic missense variants. Positive neonatal screening for TSH, neonatal jaundice and abnormal thyroid morphology were the main positive findings among all cases. Although 31 of the total 33 CH patients exhibited normal anthropometric and social performance, the other 2 had poor prognosis in this study.

CONCLUSIONS

This study reported 33 new CH patients bearing four novel genetic variants, which enriched the variant spectrum of CH genes. In this cohort, genetic factors causing thyroid dyshormonogenesis were the main etiologies of CH development. Most patients exhibited a favorable prognosis; however, systematic management remains a challenge in achieving improved clinical outcomes for CH patients.

Correlation of DUOX2 residual enzymatic activity with phenotype in congenital hypothyroidism caused by biallelic DUOX2 defects

DUOX2 is the most frequently mutated gene in patients with congenital hypothyroidism (CH) in China. However, no reliable genotype-phenotype relationship has been found in patients with DUOX2 mutations. In this study, DUOX2 mutations were screened in 266 CH patients, and the enzymatic activity of 89 DUOX2 variants was determined in vitro. Furthermore, the DUOX2 residual activity in 76 CH patients caused by DUOX2 biallelic mutations was calculated. The thyroid-stimulating hormone (TSH) and free thyroxine (FT4) levels were found to be higher and lower in patients with DUOX2 residual activity ≤22%, respectively, compared to patients with residual enzymatic activity >22%. Moreover, we interpreted the pathogenicity of DUOX2 variants by applying the ACMG classification criteria with or without PS3/BS3 evidence. The results indicated that residual DUOX2 enzymatic activity was closely related to the clinical phenotypes of CH patients caused by DUOX2 biallelic mutations. These findings suggest that the residual enzymatic activity of 22% may be a cutoff value for estimating the severity of hypothyroidism in CH patients with biallelic DUOX2 mutations. Well-established functional studies are useful and necessary to evaluate the pathogenicity of DUOX2 variants, improving the accuracy and scope of genetic consultations.

Predictors of transient congenital primary hypothyroidism: data from the German registry for congenital hypothyroidism (AQUAPE "HypoDok")

Neonatal screening for congenital primary hypothyroidism (CH) may not distinguish between transient (TCH) and permanent dysfunction (PCH), causing potential overtreatment and concerns in affected families. To specify the indication for interruption of therapy, we analysed the German registry "HypoDok" for infants with CH, which oversees 1625 patients from 49 participating centres in Germany and Austria from 1997 until today. A total of 357 patients with a thyroid gland in loco typico were identified and retrospectively grouped according to cessation (TCH, n = 24) or continuation (PCH, n = 333) of L-thyroxine (L-T4) treatment at 2 years of age. The receiver operating characteristic (ROC) analysis was performed to identify cutoffs predicting TCH by screening TSH concentrations and L-T4 dosages. Gestational ages, birth weights and prevalence of associated malformations were comparable in both groups. The cutoff screening TSH concentration was 73 mU/L. The cutoff daily L-T4 dosage at 1 year was 3.1 μg/kg (90% sensitivity, 63% specificity; 36 μg/day) and at 2 years of age 2.95 μg/kg (91% sensitivity, 59% specificity; 40 μg/day). At 2 years of age, specificity (71%) increased when both of these parameters were considered together.Conclusion: The decision to continue or cease L-T4 treatment at 2 years of age in CH patients diagnosed in neonatal screening may be based on their screening TSH concentrations and individual L-T4 dosages at 1 and 2 years of age. Thus, TCH and PCH may be distinguished; overtreatment avoided; and affected families reassured. What is Known: • The course of congenital primary hypothyroidism may be transient, causing potential overtreatment. • The dose of l-thyroxine at 1 or 2 years of age may predict a transient course of primary congenital hypothyroidism. What is New: • TSH screening concentration and l-thyroxine dosages at 1 and 2 years of age represent reliable predictors for transient congenital primary hypothyroidism with higher sensitivity and specificity when considered together in order to select eligible patients who qualify for treatment withdrawal.

Identification and analyzes of DUOX2 mutations in two familial congenital hypothyroidism cases

BACKGROUND

Mutations in DUOX2 are the frequent cause of congenital hypothyroidism (CH), a common neonatal metabolic disorder characterized by great phenotypic variability. CH can be traditionally subclassified into two subtypes: thyroid dysgenesis (TD) and thyroid dyshormonogenesis. The objectives of this study were to analyze the genetic data of two familial CH cases, to elucidate the pathogenesis from the perspective of genetics and to review and summarize the previous findings.

METHODS

Targeted regions sequencing (TRS) technology covering all exons and intron-exon boundaries of 35 known and potential CH-related candidate target genes in combination with Sanger sequencing were performed to identify the likely pathogenic mutations of the six patients with familial CH.

RESULTS

In family 1, two DUOX2 missense mutations, namely, c.1060C>T/p.R354W in exon 10 and c.3200C>T/p.S1067L in exon 25, were found. Patient 1 (P1), P2 and P3 were transient CH (TCH) patients with eutopic thyroid glands of normal size and function. In family 2, only the mutation c.3200C>T/p.S1067L was identified. P4, P5, and P6 were diagnosed with permanent CH (PCH), which requires lifelong levothyroxine (L-T4) treatment. Furthermore, both P4 and P5 harbored properly located thyroid glands, whereas P6 had a mildly reduced gland. P1, P3, P6, and other family members carrying monoallelic or biallelic DUOX2 mutations showed no obvious abnormal clinical symptoms or signs, while P2, P4, and P5 showed umbilical hernias.

CONCLUSIONS

The present study suggests that the phenotypic features resulting from DUOX2 mutations vary greatly. The p.R354W and p.S1067L alterations or the combination of the two alterations in DUOX2 are probably only predisposing to CH and DUOX2 may be involved in the morphogenesis of the human thyroid gland. Simultaneously, the compensation of DUOX1 for the loss of DUOX2, undetectable pathogenic mutations, the effects of environmental factors, epigenetic mechanisms and the involvement of multiple genes cannot be excluded in the explanation of these genetic results.

Genotype and phenotype correlation in a cohort of Chinese congenital hypothyroidism patients with DUOX2 mutations

BACKGROUND

This study aimed to explore the relationship between the phenotype and genotype of congenital hypothyroidism (CH) caused by dual oxidase 2 (DUOX2) mutation in Chinese children, and to investigate the genetic causes of permanent and transient hypothyroidism through next-generation genetic testing technology and long-term clinical follow-up data.

METHODS

We recruited 61 patients with thyroid stimulating hormone (TSH) levels of >10 mIU/mL during newborn screening, clinical diagnosis of CH, and L-thyroxine (L-T4) oral treatment within 1 month of birth; they were followed up until the present. All CH infants and their parents were genotyped using whole-exome sequencing (WES); DUOX2 variants were detected in 20 infants, and the longitudinal prognosis, genotype, and phenotype correlations were analyzed.

RESULTS

Biallelic DUOX2 mutations were detected in 20 participants. All of them were born full term. All patients were treated with L-T4 when diagnosed with CH; 9 of them stopped L-T4 eventually before 3 years old; and 2 were treated with a reduced dose of L-T4 (12.5 µg per day). The others were still treated with L-T4 at a dose of 37.5-87.5 µg per day. Of these 20 participants, 5 carried an R1110Q variant and 5 carried K530X variants. A total of 7 novel variants were discovered in our cohort. The variants carried in transient CH patients were located extracellularly and not near the functional domain.

CONCLUSIONS

Most CH patients with DUOX2 mutations were those with transient or subclinical CH. The R1110Q, R885L, and K530X were the most common variants in our Chinese cohort. The R1110Q and K530X variants may play a founder effect in the transient CH. The R885L variant may play a benign role in transient CH. Intracellular variants or those near the functional domain may cause permanent CH.

Mutation spectrum analysis of 29 causative genes in 43 Chinese patients with congenital hypothyroidism

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder with a genetic origin. The purpose of the present study was to analyze the mutation spectrum of CH patients in China. A targeted next-generation sequencing panel covering all exons of 29 CH-related causative genes was used in 43 Han Chinese patients with CH [11 dysgenesis and 32 glands in situ (GIS)]. The functional impact and pathogenicity of detected variants were analyzed using a comprehensive bioinformatics approach and co-segregation studies. A total of 47 rare non-polymorphic variants in 9 target genes associated with thyroid hormone synthesis (DUOX2, DUOXA2, TPO, TG, SLC26A4 and SLC5A5), thyroid stimulating hormone resistance (TSHR) and central hypothyroidism (PROP1 and TRHR) were identified in 31 patients (31/43, 72%). Of these variants, 8 were novel, including 3 in DUOX2, 2 in TPO, 3 in TSHR and 1 in SLC5A5. Variants were mostly affected by DUOX2, TG, TPO and TSHR. Approximately 44% of the patients (19/43) carried DUOX2 variants. The mutation detection rates in patients with GIS were higher compared with patients with dysgenesis [25/32 (78%) vs. 6/11 (54%)]. Oligogenic mutations were detected in 25.6% of the total cases and 35% of the mutated cases. Genetic basis was ascertained in 13 patients, reaching a diagnosis detection rate of 30%. In conclusion, genetic defects in dyshormonogenesis, mainly in DUOX2, were the main genetic cause of CH in the Chinese population. Oligogenicity is highly involved in CH pathogenesis and may thus be an important factor in common phenotypic variability observed in patients with CH.

Complicated Relationship between Genetic Mutations and Phenotypic Characteristics in Transient and Permanent Congenital Hypothyroidism: Analysis of Pooled Literature Data

PURPOSE

Mutations and phenotypic characteristics remain unclear in patients with congenital hypothyroidism (CH), and no study concerning whether the outcome of transient CH (TCH) or permanent CH (PCH) is determined by mutations has been reported.

METHODS

We searched the literature up to April 2019. Eligible studies and data extraction were performed. We estimated the relationship between mutations and phenotypic characteristics in pooled patients with CH.

RESULTS

Two hundred forty-one cases were pooled from 41 eligible studies. The thyroid morphology, classification of mutated genes, and types of mutations were different between 94 patients with TCH and 147 patients with PCH. Heterozygous missense mutations prevailed in PAX8, TSHR, FOXE1, and NKX2-5, and patients with these mutated genes had a higher risk of PCH (OR = 37.38, 95% CI 5.04-277.21, P < 0.001). TCH and PCH have equal shares in patients with mutated DUOX2 or DUOXA2. Dual-site and multisite mutations were frequently detected in DUOX2. High phenotypic heterogeneity was observed in mutated DUOX2 even in the same mutations. However, there was no relationship found between mutations and transient or permanent outcome in patients with mutated DUOX2.

CONCLUSION

Transient or permanent outcomes were influenced by the biological function of mutated genes instead of types of mutations among patients with CH. Patients whose mutations were related to thyroid dysgenesis (TD) were more likely to have PCH. The relationship between mutations and phenotypic characteristics is complicated, and phenotypic characteristics may be affected by mutations and other factors.

DUOX Defects and Their Roles in Congenital Hypothyroidism

Extracellular hydrogen peroxide is required for thyroperoxidase-mediated thyroid hormone synthesis in the follicular lumen of the thyroid gland. Among the NADPH oxidases, dual oxidases, DUOX1 and DUOX2, constitute a distinct subfamily initially identified as thyroid oxidases, based on their level of expression in the thyroid. Despite their high sequence similarity, the two isoforms present distinct regulations, tissue expression, and catalytic functions. Inactivating mutations in many of the genes involved in thyroid hormone synthesis cause thyroid dyshormonogenesis associated with iodide organification defect. This chapter provides an overview of the genetic alterations in DUOX2 and its maturation factor, DUOXA2, causing inherited severe hypothyroidism that clearly demonstrate the physiological implication of this oxidase in thyroid hormonogenesis. Mutations in the DUOX2 gene have been described in permanent but also in transient forms of congenital hypothyroidism. Moreover, accumulating evidence demonstrates that the high phenotypic variability associated with altered DUOX2 function is not directly related to the number of inactivated DUOX2 alleles, suggesting the existence of other pathophysiological factors. The presence of two DUOX isoforms and their corresponding maturation factors in the same organ could certainly constitute an efficient redundant mechanism to maintain sufficient H₂O₂ supply for iodide organification. Many of the reported DUOX2 missense variants have not been functionally characterized, their clinical impact in the observed phenotype remaining unresolved, especially in mild transient congenital hypothyroidism. DUOX2 function should be carefully evaluated using an in vitro assay wherein (1) DUOXA2 is co-expressed, (2) H₂O₂ production is activated, (3) and DUOX2 membrane expression is precisely analyzed.

Newborn Screening and Molecular Profile of Congenital Hypothyroidism in a Chinese Population

is the most gene mutation in Chinese CH patients.

Targeted next-generation sequencing of thirteen causative genes in Chinese patients with congenital hypothyroidism

To identify the spectrum and prevalence of thirteen causative genes mutations in congenital hypothyroidism (CH) patients, we collected blood samples and extracted genomic DNA of 106 CH patients, and designed a customized targeted next-generation sequencing panel containing 13 CH-causing genes to detect mutations. A total of 132 mutations were identified in 65.09% of patients (69/106) on the following nine genes: DUOX2, TG, TPO, TSHR, TTF1, TTF2, NKX2-5, PAX8 and GNAS. 69.70% (92/132) mutations related to thyroid dyshormonogenesis genes, including DUOX2 (n = 49), TG (n = 35), and TPO (n = 8). 21.21% (28/132) mutations related to thyroid dysgenesis genes, including TSHR (n = 19), TTF1 (n = 5), TTF2 (n = 1), PAX8 (n = 2), and NKX2-5 (n = 1). 9.09% (12/132) mutations related to GNAS, which was associated with thyrotropin resistance. No mutation of THRA, TSHB, IYD or SLC5A5 was detected. Among 69 mutations detected patients, 41 (59.42%) patients were two or more mutations detected, and mutations of 30 (43.48%) patients related to two or three genes. According to the pathomechanism of the mutant genes, 57.97% CH patients were classified as thyroid dyshormonogenesis. Overall, DUOX2, TG and TSHR mutations were the most common genetic defects in Chinese CH patients, and thyroid dyshormonogenesis could be the first genetic etiology of CH in Chinese. Besides, multiple mutations accounts for a part of genetic pathogenesis.

Increased risk for inflammatory bowel disease in congenital hypothyroidism supports the existence of a shared susceptibility factor

Loss-of-function mutations in dual oxidase (DUOX) 2 are the most common genetic variants found in congenital hypothyroidism (CH), and similar mutations have been recently reported in few very-early-onset inflammatory bowel disease (IBD) patients without CH. If DUOX2 variants indeed increase susceptibility for IBD, the enrichment of DUOX2 mutation carriers among CH patients should be reflected in higher risk for developing IBD. Using a database containing health insurance claims data for over 230 million patients in the United States, 42,922 subjects with CH were identified based on strict inclusion criteria using diagnostic codes. For subgroup analysis, CH patients with pharmacy records were stratified as transient or permanent CH based on the absence or presence of levothyroxine treatment, respectively. Patients were matched to an equal-sized, age- and gender-matched non-CH group. Compared to controls, CH patients had a 73% higher overall IBD prevalence (0.52% vs 0.30%; P < 0.0001). The CH-associated relative risk was higher for indeterminate or ulcerative colitis than Crohn’s disease. Patients with transient CH had higher odds for IBD (OR 2.39 (95% CI 1.77–3.23) than those with permanent CH (1.69 (95% CI 1.31–2.18). We conclude that patients with CH are at an increased risk of developing IBD. The risk was highest for patients with transient CH, for which partial defects in the DUOX2 system are a particularly common finding.

The genetic characteristics of congenital hypothyroidism in China by comprehensive screening of 21 candidate genes

OBJECTIVE

Congenital hypothyroidism (CH), the most common neonatal metabolic disorder, is characterized by impaired neurodevelopment. Although several candidate genes have been associated with CH, comprehensive screening of causative genes has been limited.

DESIGN AND METHODS

One hundred ten patients with primary CH were recruited in this study. All exons and exon-intron boundaries of 21 candidate genes for CH were analyzed by next-generation sequencing. And the inheritance pattern of causative genes was analyzed by the study of family pedigrees.

RESULTS

Our results showed that 57 patients (51.82%) carried biallelic mutations (containing compound heterozygous mutations and homozygous mutations) in six genes (DUOX2, DUOXA2, DUOXA1, TG, TPO and TSHR) involved in thyroid hormone synthesis. Autosomal recessive inheritance of CH caused by mutations in DUOX2, DUOXA2, TG and TPO was confirmed by analysis of 22 family pedigrees. Notably, eight mutations in four genes (FOXE1, NKX2-1, PAX8 and HHEX) that lead to thyroid dysgenesis were identified in eight probands. These mutations were heterozygous in all cases and hypothyroidism was not observed in parents of these probands.

CONCLUSIONS

Most cases of congenital hypothyroidism in China were caused by thyroid dyshormonogenesis rather than thyroid dysgenesis. This study identified previously reported causative genes for 57/110 Chinese patients and revealed DUOX2 was the most frequently mutated gene in these patients. Our study expanded the mutation spectrum of CH in Chinese patients, which was significantly different from Western countries.

[Advances in genetic research of congenital hypothyroidism in China]

Congenital hypothyroidism (CH), which results from insufficient thyroid hormone biosynthesis, is one of the most common neonatal endocrine disorders. Thyroid dysgenesis and thyroid dyshormonogenesis are the two causes of CH and either one will lead to deficiencies of enzymes during thyroid hormone biosynthesis and insufficient thyroid hormone biosynthesis. Recently, researchers have performed extensive studies on genetics of CH. This paper reviews genes reported to be associated with CH in China.

Mutational Spectrum Analysis of Seven Genes Associated with Thyroid Dyshormonogenesis

OBJECTIVE

Thyroid dyshormonogenesis (DH) is a genetically heterogeneous inherited disorder caused by thyroid hormone synthesis abnormalities. This study aims at comprehensively characterizing the mutation spectrum in Chinese patients with DH.

SUBJECTS AND METHODS

We utilized next-generation sequencing to screen for mutations in seven DH-associated genes (TPO, DUOX2, TG, DUOXA2, SLC26A4, SLC5A5, and IYD) in 21 Chinese Han patients with DH from Xinjiang Province.

RESULTS

Twenty-eight rare nonpolymorphic variants were found in 19 patients (90.5%), including 19, 5, 3, and 1 variants in DUOX2, TG, DUOXA2, and SLC26A4, respectively. Thirteen (62%) patients carried monogenic mutations, and six (28.5%) carried oligogenic mutations. Fifteen (71%) patients carried 2 or more DUOX2 (14) or DUOXA2 (1) variants. The genetic basis of DH in nine (43%) patients harboring biallelic or triallelic pathogenic variants was resolved. Seventeen patients (81%) carried DUOX2 mutations, most commonly p.R1110Q or p.K530X. No correlations were found between DUOX2 mutation types or numbers and clinical phenotypes.

CONCLUSIONS

DUOX2 mutations were the most predominant genetic alterations of DH in the study cohort. Oligogenicity may explain the genetic basis of disease in many DH patients. Functional studies and further clinical studies with larger DH patient cohorts are needed to validate the roles of the mutations identified in this study.

Digenic DUOX1 and DUOX2 Mutations in Cases With Congenital Hypothyroidism

CONTEXT

The DUOX2 enzyme generates hydrogen peroxide (H2O2), a crucial electron acceptor for the thyroid peroxidase-catalyzed iodination and coupling reactions mediating thyroid hormone biosynthesis. DUOX2 mutations result in dyshormonogenetic congenital hypothyroidism (CH) that may be phenotypically heterogeneous, leading to the hypothesis that CH severity may be influenced by environmental factors (e.g., dietary iodine) and oligogenic modifiers (e.g., variants in the homologous reduced form of NAD phosphate-oxidase DUOX1). However, loss-of-function mutations in DUOX1 have not hitherto been described, and its role in thyroid biology remains undefined.

CASE DESCRIPTION

We previously described a Proband and her brother (P1, P2) with unusually severe CH associated with a DUOX2 homozygous nonsense mutation (p.R434*); P1, P2: thyrotropin >100 µU/mL [reference range (RR) 0.5 to 6.3]; and P1: free T4 (FT4) <0.09 ng/dL (RR 0.9 to 2.3). Subsequent studies have revealed a homozygous DUOX1 mutation (c.1823-1G>C) resulting in aberrant splicing and a protein truncation (p.Val607Aspfs*43), which segregates with CH in this kindred.

CONCLUSION

This is a report of digenic mutations in DUOX1 and DUOX2 in association with CH, and we hypothesize that the inability of DUOX1 to compensate for DUOX2 deficiency in this kindred may underlie the severe CH phenotype. Our studies provide evidence for a digenic basis for CH and support the notion that oligogenicity as well as environmental modulators may underlie phenotypic variability in genetically ascertained CH.

Disorders of H2O2 generation

After the identification of thyroid H₂O₂ generation system (DUOX) and of its maturation factors (DUOXA), defects in DUOX2 and/or DUOXA2 were rapidly recognized as the possible cause of congenital hypothyroidism (CH) due to thyroid dyshormonogenesis. The present Review reports data on the prevalence of DUOX2 mutations, which is variable among different series but invariably high, pointing to DUOX2 defects as one of the leading causes of dyshormonogenesis. Differently, DUOXA defects seem to be rarely involved in the pathogenesis of CH. Genotype-phenotype correlations are also reported, highlighting the great intra- and inter-familial phenotype variability which appears to be a constant feature of the defects in the H₂O₂ generation systems. Finally, the hypotheses to explain the phenotypic variability of the DUOX2/A2 mutations are discussed, such as the existence of other H₂O₂ generating systems, the age variability in thyroid hormones requirements, the differences in ethnicity, in iodine intake, and in the methodological approaches.

Exome sequencing identifies SLC26A4, GJB2, SCARB2 and DUOX2 mutations in 2 siblings with Pendred syndrome in a Malaysian family

BACKGROUND

Pendred syndrome (PDS, MIM #274600) is an autosomal recessive disorder characterized by congenital sensorineural hearing loss and goiter. In this study, we describing the possible PDS causal mutations in a Malaysian family with 2 daughters diagnosed with bilateral hearing loss and hypothyroidism.

METHODS AND RESULTS

Whole exome sequencing was performed on 2 sisters with PDS and their unaffected parents. Our results showed that both sisters inherited monoallelic mutations in the 2 known PDS genes, SLC26A4 (ENST00000265715:c.1343C > T, p.Ser448Leu) and GJB2 (ENST00000382844:c.368C > A, p.Thr123Asn) from their father, as well as another deafness-related gene, SCARB2 (ENST00000264896:c.914C > T, p.Thr305Met) from their mother. We postulated that these three heterozygous mutations in combination may be causative to deafness, and warrants further investigation. Furthermore, we also identified a compound heterozygosity involving the DUOX2 gene (ENST00000603300:c.1588A > T:p.Lys530* and c.3329G > A:p.Arg1110Gln) in both sisters which are inherited from both parents and may be correlated with early onset of goiter. All the candidate mutations were predicted deleterious by in silico tools.

CONCLUSIONS

In summary, we proposed that PDS in this family could be a polygenic disorder which possibly arises from a combination of heterozygous mutations in SLC26A4, GJB2 and SCARB2 which associated with deafness, as well as compound heterozygous DUOX2 mutations which associated with thyroid dysfunction.

DUOX2 Mutations Are Frequently Associated With Congenital Hypothyroidism in the Korean Population

Background

Most cases with congenital hypothyroidism (CH) are usually sporadic, while about 20% of the cases are caused by genetic defects. Little information is available regarding the mutation incidence and genetic heterogeneity of CH in Koreans. We aimed to determine the mutation incidence of CH in newborn screenings (NBS) and to evaluate the frequency and spectrum of mutations underlying CH.

Methods

A total of 112 newborns with thyroid dysfunction were enrolled from 256,624 consecutive NBS. Furthermore, 58 outpatients with primary CH were added from an endocrine clinic. All coding exons of TSHR, PAX8, TPO, DUOX2, DUOXA2, and SCL5A5 were sequenced.

Results

The mutation incidence of CH was estimated to be 1 in 6,580 newborns. A total of 36 different mutations were identified in 53 cases. The overall mutation positive rate was 31%. The DUOX2 mutations were the most prevalent in both newborns and outpatients. Seven different recurrent mutations [p.G488R (n=13), p.A649E (n=3), p.R885Q (n=3), p.I1080T (n=2), and p.A1206T (n=2) in DUOX2; p.Y138X (n=9) in DUOXA2; and p.R450H (n=5) in TSHR) were identified as the mutations underlying CH.

Conclusions

The mutation incidence of CH was considerably higher than expected in the Korean newborn population. This study revealed seven different recurrent mutations underlying CH. We conclude that DUOX2 mutations are a frequent cause of CH in the Korean population.

High prevalence of DUOX2 gene mutations among children with congenital hypothyroidism in central China

Congenial hypothyroidism (CH) is the most common congenital endocrine disease and is treatable when recognized early enough. We investigated the genetic variants in 12 children diagnosed with CH by newborn screening in Huangshi area central China. Twelve genes commonly involved in CH development were studied. Genomic DNA from peripheral blood was used to amplify all exons of the selected genes, and the constructed sequencing libraries were subjected to next generation high throughput DNA sequencing (NGS). Analysis of the sequencing results identified rare genetic variants in 11 of the 12 patients (91.7%), and two novel rare variants were found in DUOX2 gene and two in TPO gene. Mutations in DUOX2 gene were identified in 10 patients (83.3%), and all these patients were found to carry bi-allelic, tri-allelic mutations or compound mutations with other genes. Recurrent DUOX2 mutations include K530X, R683L, R1110Q, and L1343F. Truncating, splicing, and proven deleterious DUOX2 missense mutations were detected in 50% of the patients. Mutations in TG gene were identified in four patients, and mutations in TPO, THSR, SLC26A4 genes were identified, one in each patient, respectively. The high prevalence of DUOX2 mutations in this cohort of children with CH appears striking and surprising. The clinical implications were discussed.

Mutation screening of the TPO gene in a cohort of 192 Chinese patients with congenital hypothyroidism

OBJECTIVES

Defects in the human thyroid peroxidase (TPO) gene are reported to be one of the causes of congenital hypothyroidism (CH) due to dyshormonogenesis. The aim of this study was to examine the TPO mutation spectrum and prevalence among patients with CH in the Guangxi Zhuang Autonomous Region of China and to define the relationships between TPO genotypes and clinical phenotypes.

METHODS

Blood samples were collected from 192 patients with CH in the Guangxi Zhuang Autonomous Region, China and genomic DNA was extracted from peripheral blood leucocytes. All exons of the 10 common CH-associated genes including TPO together with their exon-intron boundaries were screened by next-generation sequencing (NGS). The effect of the novel TPO mutation was investigated by 'in silico' studies.

RESULTS

NGS analysis of TPO in 192 patients with CH revealed 3 different variations in 2 individuals (2/192, 1%). Sequencing other CH candidate genes in the patients with TPO variants revealed that patient 1 was homozygous for c.2422delT TPO mutation combined with double heterozygous DUOX2 pathogenic variants (p.R683L/p.L1343F) and patient 2 was triallelic for TPO pathogenic variants (p.R648Q/p.T561M/p.T561M). The present study identified a novel TPO variation c.1682C>T/p.T561M; and four known mutations: c.2422delT/p.C808Afs×24 and c.1943C>T/p.R648Q in TPO, c.2048G>T/p.R683L and c.4027C>T/p.L1343F in DUOX2.

CONCLUSIONS

Our study indicated that the prevalence of TPO mutations was 1% among studied Chinese patients with CH. More than two variations in one or more CH-associated genes can be found in a single patient, and may, in combination, affect the phenotype of the individual. A novel TPO variation c.1682C>T/p.T561M was found, thereby expanding the mutational spectrum of the gene.

Next-generation sequencing analysis of DUOX2 in 192 Chinese subclinical congenital hypothyroidism (SCH) and CH patients

BACKGROUND

Defects in the human dual oxidase 2 (DUOX2) gene are reported to be one of the major causes of congenital hypothyroidism (CH). This study was set to examine the DUOX2 mutation spectrum and prevalence among Chinese CH and subclinical congenital hypothyroidism (SCH) patients and to define the relationships between DUOX2 genotypes and clinical phenotypes.

METHODS

Peripheral venous blood samples were collected from 192 CH/SCH patients in Guangxi Zhuang Autonomous Region of China. All exons and their exon-intron boundary sequences of the 11 known CH associated genes including DUOX2 were screened by next-generation sequencing (NGS).

RESULTS

NGS analysis of DUOX2 revealed 18 rare non-polymorphic variants in 57 CH/SCH patients. Sequencing of other CH candidate genes in the 57 patients revealed 2 thyroglobulin (TG) variants. All variants included 11 known mutations, 8 novel variants in DUOX2 and one novel variant in TG, among which three variants p.K530X, p.L1343F and p.R683L are highly recurrent in our patient cohort. 35 (83%) of the 42 patients with one or two DUOX2 pathogenic variants turned out to be SCH or transient congenital hypothyroidism (TCH), whereas 13 (87%) of the 15 patients with three or more DUOX2 pathogenic variants are associated with permanent congenital hypothyroidism (PCH). The accumulation of defects in DUOX2 contribute to the more severe disease regarding thyroid stimulating hormone (TSH) levels, free thyroxine (FT4) levels and initial dose of l-thyroxine (L-T4).

CONCLUSION

Our study expanded the mutational spectrum of the DUOX2 and TG genes and provided the best estimation of the DUOX2 mutation rate (29%) for CH/SCH patients in Guangxi Zhuang Autonomous Region of China. Most one or two DUOX2 pathogenic variants turned out to be SCH or TCH, whereas patients with three or more DUOX2 pathogenic variants were mostly associated with PCH. The coexistence of multiple pathogenic variants may have contributed to the severity of the hypothyroid condition.

Natural course of congenital hypothyroidism by dual oxidase 2 mutations from the neonatal period through puberty

AIM

We previously reported that biallelic mutations in dual oxidase 2 (DUOX2) cause transient hypothyroidism. Since then, many cases with DUOX2 mutations have been reported. However, the clinical features and prognosis of individuals with DUOX2 defects have not been clarified.

OBJECTIVE

We investigated the prognosis of patients with congenital hypothyroidism (CH) due to DUOX2 mutations.

PATIENTS

Twenty-five patients were identified by a neonatal screening program and included seven familial cases. Their serum TSH values ranged from 18.9 to 734.6  mU/l. Twenty-two of the patients had low serum free thyroxine (fT4) levels (0.17-1.1  ng/dl). Twenty-four of the patients were treated with L-thyroxine.

METHODS

We analyzed the DUOX2, thyroid peroxidase, Na(+)/I(-) symporter, and dual oxidase maturation factor 2 genes of these 25 patients by PCR-amplified direct sequencing. An additional 11 genes were analyzed in 11 of the 25 patients using next-generation sequencing.

RESULTS

All patients had biallelic DUOX2 mutations, and seven novel alleles were detected. Fourteen of the patients were able to discontinue replacement therapy, and seven were receiving reduced L-thyroxine doses. Normalization of thyroglobulin lagged several years behind the completion of treatment. Two patients showed permanent hypothyroidism. Except for one case of a learning disability, growth and psychomotor development were normal.

CONCLUSION

The prognosis of Japanese patients with DUOX2 defects was usually transient CH. Delayed improvement of thyroglobulin indicates that these patients have subclinical hypothyroidism. Hypothyroidism did not recur in patients during the study period (up to 18 years old).