DIAGNOSIS OF ENDOCRINE DISEASE: Congenital hypothyroidism: update and perspectives

Modeling Human Thyroid Development by Fetal Tissue-Derived Organoid Culture

Euthyroidism is of profound importance for lifetime health. However, the early diagnosis or therapeutics of thyroid developmental defects has not been established, mainly due to limited understanding of human thyroid development and a lack of recapitulating research model. Herein, the authors elaborate the cell atlas and potential regulatory signaling of the evolution of heterogeneous thyrocyte population from 12 to 16 gestational weeks. Moreover, they establish a long-term culture of human fetal thyroid organoids (hFTOs) system, which retains the fetal thyroid lineages and molecular signatures, as well as the ability to generate functional human thyroid follicles post mice renal transplantation. Notably, cAMP signaling activation in hFTOs by forskolin boosts the maturation of follicle and thus thyroid hormone T4 secretion, which recapitulates the key developmental events of fetal thyroid. Employing this ex vivo system, it is found that enhanced chromatin accessibility at thyroid maturation genes (such as TPO and TG) loci permits the transcription for hormone production. This study provides the cell atlas of and an organoid model for human thyroid development, which will facilitate thyroid research and prospective medicine.

[Clinical guideline of «congenital hypothyroidism»]

Congenital hypothyroidism is an important issue of pediatric endocrinology at which timely diagnosis and treatment can prevent the development of severe cases of the disease. The developed clinical guidelines are a working tool for a practicing physician. The target audience is pediatric endocrinologists and pediatricians. They briefly and logically set out the main definition of the disease, epidemiology, classification, methods of diagnosis and treatment, based on the principles of -evidence-based medicine.

Fetal and Neonatal Thyroid Dysfunction

Fetal and neonatal dysfunctions include rare serious disorders involving abnormal thyroid function during the second half of gestation, which may persist throughout life, as for most congenital thyroid disorders, or be transient, resolving in the first few weeks of life, as in autoimmune hyperthyroidism or hypothyroidism and some cases of congenital hypothyroidism (CH) with the thyroid gland in situ. Primary CH is diagnosed by neonatal screening, which has been implemented for 40 years in developed countries and should be introduced worldwide, as early treatment prevents irreversible neurodevelopmental delay. Central CH is a rarer entity occurring mostly in association with multiple pituitary hormone deficiencies. Other rare disorders impair the action of thyroid hormones. Neonatal Graves' disease (GD) results from the passage of thyrotropin receptor antibodies (TRAbs) across the placenta, from mother to fetus. It may affect the fetuses and neonates of mothers with a history of current or past GD, but hyperthyroidism develops only in those with high levels of stimulatory TRAb activity. The presence of antibodies predominantly blocking thyroid-stimulating hormone receptors may result in transient hypothyroidism, possibly followed by neonatal hyperthyroidism, depending on the balance between the antibodies present. Antithyroid drugs taken by the mother cross the placenta, treating potential fetal hyperthyroidism, but they may also cause transient fetal and neonatal hypothyroidism. Early diagnosis and treatment are key to optimizing the child's prognosis. This review focuses on the diagnosis and management of these patients during the fetal and neonatal periods. It includes the description of a case of fetal and neonatal autoimmune hyperthyroidism.

Clinical, radiological, and molecular diagnosis of congenital pituitary diseases causing short stature

Short stature in children can be caused by congenital pituitary disorders involving at least one form of growth hormone deficiency. Clinical and radiological evaluations of the index case and family history assessments are essential to guide genetic diagnostic testing and interpret results. The first-line approach is panel testing of genes involved in pituitary development with variants known to be pathogenic in this context. It identifies a genetic cause in less than 10% of cases, however. Whole-exome and whole-genome sequencing techniques may provide original information but also raise new questions regarding the pathophysiological role of identified variants. These new tools can make genetic counselling more complex. The role of clinicians in these interpretations is therefore important. © 2022 French Society of Pediatrics. Published by Elsevier Masson SAS. All rights reserved.

Primary Congenital Hypothyroidism in Children Below 3 Years Old - Etiology and Treatment With Overtreatment and Undertreatment Risks, a 5-Year Single Centre Experience

Worldwide neonatal screening for congenital hypothyroidism (CH) is a gold standard of active surveillance in newborns. Prompt diagnosis, subsequent timely treatment implementation, and proper dosage of levothyroxine (L-T4) are crucial for normal growth and development, especially of the central nervous system. However, overtreatment may have a potential negative impact on further neurodevelopment. We retrospectively analysed data of 99 newborns with CH diagnosis, referred to the Endocrinology Outpatient Clinic of the Institute of Mother and Child in Warsaw, Poland from the CH screening program from 2017 to 2021. We evaluated the diagnostic process and treatment up to the age of 3 years. We compared groups of children from the first and the second screening groups (FSG, SSG) in the neonatal screening with an evaluation of ultrasound examination (thyroid dysgenesis vs. gland in situ, GIS). The overtreatment and undertreatment risks were assessed and an analysis of the new TSH thresholds was performed. Treatment was implemented at a median of 9 days of life (3 - 27); 8 days (3 - 17) in FSG and 19 (6 - 27) in SSG. The dose of L-T4 differed between FSG and SSG at all three analysed time points (start of the therapy, 12 months, and 3 years) with significantly higher doses in FSG. The same was observed for the patients with thyroid dysgenesis vs. GIS. Screening TSH level was ≥ 28mIU/l in 91.7% of patients with thyroid dysgenesis in comparison to 74.0% of patients with GIS (p= 0.038). The optimally treated group (fT4 in the upper half of the reference range, according to the guidelines) was up to 58.0% of the children during the follow-up. The risk for overtreatment was present in 1/5 of the study group after 12 months and 1/4 after 3 years of L-T4 therapy. Analysis of new TSH thresholds showed an increased prevalence of mild hypothyroidism, GIS, and either euthyroid state or overtreatment while treating with lower L-T4 doses in comparison to the rest of the cohort. The study confirmed the general efficacy of the CH diagnostic pathway and the timely implemented L-T4 therapy. The suspected overtreatment after the first 12 months of L-T4 therapy requires consideration of the earlier diagnosis re-evaluation.

Association of recessive c.430G>A (p.(Gly144Arg)) thyroid peroxidase variant with primary congenital hypothyroidism in cats

BACKGROUND

Primary congenital hypothyroidism (CH) is a rare endocrine disorder in cats with a largely unknown genetic cause.

OBJECTIVES

Describe the clinical presentation of CH in 11 affected cats and identify the causal genetic variant.

ANIMALS

Eleven CH-cats from 10 unrelated families, 11 CH-free family members, 21 unrelated CH-free cats, and 155 unrelated nondiagnosed cats from different breeds.

METHODS

Case control study of CH-cats and their siblings (2019-2021). Diagnosis was based on low to low-normal serum thyroxine (T4) concentrations, high thyroid-stimulating hormone (TSH) concentrations and clinical signs compatible with CH. We identified the causal variant using Sanger sequencing, genotyping via PCR-RFLP and variant interpretation using ACMG/AMP guidelines.

RESULTS

All CH-cats (5 weeks-8 years) had disproportionate dwarfism. A goiter was not palpable in all. Thyroid scintigraphy with radiopertechnetate showed abnormally high uptake by thyroid glands, whereas scintigraphy with radioiodine showed abnormally low uptake, compatible with a defect in iodine organification by thyroid peroxidase (TPO). All cases were homozygous for TPO variant XM_006930524.4:c.430G>A(p.(Gly144Arg)), while none of the CH-free cats were. All sampled parents were heterozygous for this recessive variant. This variant was found in 15 cat breeds with an estimated allele frequency of 9%.

CONCLUSIONS AND CLINICAL IMPORTANCE

Disproportionate dwarfism, abnormally high TSH and abnormally low to low-normal T4 concentrations are diagnostic for CH in cats. All cases had dyshormonogenesis demonstrated by thyroid scintigraphy. This novel TPO missense variant (not described in humans) causes CH in cats and awareness of it can assist in diagnosis and breeding.

Congenital Hypothyroidism in Preterm Newborns - The Challenges of Diagnostics and Treatment: A Review

Preterm newborns are forced to adapt to harsh extrauterine conditions and endure numerous adversities despite their incomplete growth and maturity. The inadequate thyroid hormones secretion as well as the impaired regulation of hypothalamus-pituitary-thyroid axis may lead to hypothyroxinemia. Two first weeks after birth are pivotal for brain neurons development, synaptogenesis and gliogenesis. The decreased level of thyroxine regardless of cause may lead to delayed mental development. Congenital hypothyroidism (CH) is a disorder highly prevalent in premature neonates and it originates from maternal factors, perinatal and labor complications, genetic abnormalities, thyroid malformations as well as side effects of medications and therapeutic actions. Because of that, the prevention is not fully attainable. CH manifests clinically in a few distinctive forms: primary, permanent or transient, and secondary. Their etiologies and implications bear little resemblance. Therefore, the exact diagnosis and differentiation between the subtypes of CH are crucial in order to plan an effective treatment. Hypothyroxinemia of prematurity indicates dynamic changes in thyroid hormone levels dependent on neonatal postmenstrual age, which directly affects patient's maintenance and wellbeing. The basis of a successful treatment relies on an early and accurate diagnosis. Neonatal screening is a recommended method of detecting CH in preterm newborns. The preferred approach involves testing serum TSH and fT4 concentrations and assessing their levels according to the cut-off values. The possible benefits also include the evaluation of CH subtype. Nevertheless, the reference range of thyroid hormones varies all around the world and impedes the introduction of universal testing recommendations. Unification of the methodology in neonatal screening would be advantageous for prevention and management of CH. Current guidelines recommend levothyroxine treatment of CH in preterm infants only when the diagnose is confirmed. Moreover, they underline the importance of the re-evaluation among preterm born infants due to the frequency of transient forms of hypothyroidism. However, results from multiple clinical trials are mixed and depend on the newborn's gestational age at birth. Some benefits of treatment are seen especially in the preterm infants born <29 weeks' gestation. The discrepancies among trials and guidelines create an urgent need to conduct more large sample size studies that could provide further analyses and consensus. This review summarizes the current state of knowledge on congenital hypothyroidism in preterm infants. We discuss screening and treatment options and demonstrate present challenges and controversies.

Endocrinopathies in Inborn Errors of Immunity

Inborn errors of immunity (IEI), caused by hereditary or genetic defects, are a group of more than 400 disorders, in which the immune system, including lymphocytes, neutrophils, macrophages, and complements, does not function properly. The endocrine system is frequently affected by IEI as an associated clinical feature and a complex network of glands which regulate many important body functions, including growth, reproduction, homeostasis, and energy regulation. Most endocrine disorders associated with IEI are hypofunction which would be treated with supplementation therapy, and early diagnosis and appropriate management are essential for favorable long-term outcomes in patients with IEI. In this review, we aimed to comprehensively summarize and discuss the current understanding on the clinical features and the pathophysiology of endocrine disorders in IEI. This review is composed with three parts. First, we discuss the two major pathophysiology of endocrinopathy in IEI, autoimmune response and direct effects of the responsible genes. Next, the details of each endocrinopathy, such as growth failure, hypothyroidism, hypoparathyroidism, adrenal insufficiency, diabetes mellitus (DM) are specified. We also illustrated potential endocrinopathy due to hematopoietic stem cell transplantation, including hypogonadism and adrenal insufficiency due to glucocorticoid therapy.

Neonatal outcomes and congenital anomalies in pregnancies affected by hypothyroidism

BACKGROUND

Maternal hypothyroidism has been reported to have concerns over neonatal outcomes, not only in the context of neurocognitive development but also in the short term as birth weight and neonatal jaundice.

PATIENTS AND METHODS

We conducted a cross-sectional retrospective study on 638 cases who delivered live births in the Aga Khan University Hospital after ethical approval. Data were collected on hypothyroid pregnant females who were diagnosed before conception or during their antenatal visits during the year 2008-2016. Neonatal outcomes were noted for birth weight, maturity, and neonatal jaundice, neonatal hypothyroidism, neonatal respiratory distress syndrome, sepsis, hypocalcaemia, congenital anomalies, need for intensive care admission, and neonatal death. Subgroup analysis was performed on the timing of diagnosis of maternal hypothyroidism. Data analysis was performed on Statistical Package for the Social Sciences version 20.0.

RESULTS

Neonatal jaundice was the most common neonatal outcome (37.6%) in our cohort of 662 live births. Nearly 15% required intensive care unit admission, however, neonatal death was very rare. The most common clinically significant congenital anomalies were cardiovascular defects, whereas Mongolian spots were the commonest congenital condition to report. There is a statistically significant association between low birth weight (OR 1.86, 95% CI 1.0-3.2, p ≤ 0.05) and congenital anomalies (OR 2.39, 95% CI 1.4-4.0, p ≤ 0.05) with women diagnosed with hypothyroidism before pregnancy.

CONCLUSION

We report the neonatal outcomes and spectrum of congenital anomalies of hypothyroid pregnancies diagnosed before and during conception for the first time from the region of Pakistan.KEY MESSAGEOverall, none of the neonates of hypothyroid pregnancies developed congenital hypothyroidism.Cardiovascular defects in these neonates imply extensive screening and monitoring during pregnancy.Low birth weight and congenital anomalies are associated with the timings of diagnosis of hypothyroidism in pregnancy.

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Congenital hypothyroidism is one of the common diseases causing delayed intelligence development and growth retardation in children. In 2021, the ENDO-European Reference Network updated the practice guidelines for the diagnosis and management of congenital hypothyroidism. The guidelines give a comprehensive and detailed description of the screening, diagnosis, and management of congenital hypothyroidism in neonates. This article gives an interpretation of the guidelines in order to provide a reference for clinicians in China.

DNA methylation at a nutritionally sensitive region of the PAX8 gene is associated with thyroid volume and function in Gambian children

PAX8 is a key thyroid transcription factor implicated in thyroid gland differentiation and function, and PAX8 gene methylation is reported to be sensitive to the periconceptional environment. Using a novel recall-by-epigenotype study in Gambian children, we found that PAX8 hypomethylation at age 2 years is associated with a 21% increase in thyroid volume and an increase in free thyroxine (T4) at 5 to 8 years, the latter equivalent to 8.4% of the normal range. Free T4 was associated with a decrease in DXA-derived body fat and bone mineral density. Furthermore, offspring PAX8 methylation was associated with periconceptional maternal nutrition, and methylation variability was influenced by genotype, suggesting that sensitivity to environmental exposures may be under partial genetic control. Together, our results demonstrate a possible link between early environment, PAX8 gene methylation and thyroid gland development and function, with potential implications for early embryonic programming of thyroid-related health and disease.

Congenital Hypothyroidism

Congenital hypothyroidism (CH) is a disorder of thyroid hormone deficiency which develops secondary to incomplete thyroid development or inadequate thyroid hormone production. State-mandated newborn screening throughout the United States has increased the detection rate of CH, allowing for early intervention. Although the overall mortality rate of CH is low, delayed or omitted treatment can lead to devastating neurocognitive outcomes. As such, CH is regarded as the leading cause of preventable intellectual disability in children. Early identification, facilitated by astute neonatal nursing and medical care, is contingent upon an active working knowledge of the disease process and awareness of the limitations of the newborn screen.

Defective Levothyroxine Response in a Patient with Dyshormonogenic Congenital Hypothyroidism Caused by a Concurrent Pathogenic Variant in Thyroid Hormone Receptor-β

Background: Pituitary resistance to thyroid hormone (PRTH) is often seen in congenital hypothyroidism (CH), presenting as elevated thyrotropin (TSH) values despite (high-)normal thyroid hormone (TH) values achieved by levothyroxine treatment. In this study, we describe a girl with CH who was referred because of difficulties interpreting thyroid function tests. She was thought to have PRTH associated with CH, but genetic studies discovered a pathogenic variant in THRB, causing resistance to TH (RTH-β). Methods: Clinical, genetic, and biochemical data of the proband's family were collected. Results: The 3-year-old girl was diagnosed with CH due to a homozygous pathogenic c.470del p.(Asn157Thrfs*3) SLC5A5 variant in the neonatal period. She needed a notably high levothyroxine dose to normalize TSH, leading to high free thyroxine levels. There were no signs of hyperthyroidism. Sequencing identified a heterozygous pathogenic c.947G>A p.(Arg316His) THRB variant. Conclusions: To our knowledge, this is the first report of concomitant SLC5A5 and THRB variants causing CH and RTH-β.

Clinical features of autosomal recessive polycystic kidney disease in the Japanese population and analysis of splicing in PKHD1 gene for determination of phenotypes

Background

Autosomal recessive polycystic kidney disease (ARPKD) is caused by mutations in the PKHD1 gene. The clinical spectrum is often more variable than previously considered. We aimed to analyze the clinical features of genetically diagnosed ARPKD in the Japanese population.

Methods

We conducted a genetic analysis of patients with clinically diagnosed or suspected ARPKD in Japan. Moreover, we performed a minigene assay to elucidate the mechanisms that could affect phenotypes.

Results

PKHD1 pathogenic variants were identified in 32 patients (0–46 years). Approximately one-third of the patients showed prenatal anomalies, and five patients died within one year after birth. Other manifestations were detected as follows: chronic kidney disease stages 1–2 in 15/26 (57.7%), Caroli disease in 9/32 (28.1%), hepatic fibrosis in 7/32 (21.9%), systemic hypertension in 13/27 (48.1%), and congenital hypothyroidism in 3 patients. There have been reported that truncating mutations in both alleles led to severe phenotypes with perinatal demise. However, one patient without a missense mutation survived the neonatal period. In the minigene assay, c.2713C > T (p.Gln905Ter) and c.6808 + 1G > A expressed a transcript that skipped exon 25 (123 bp) and exon 41 (126 bp), resulting in an in-frame mutation, which might have contributed to the milder phenotype. Missense mutations in cases of neonatal demise did not show splicing abnormalities.

Conclusion

Clinical manifestations ranged from cases of neonatal demise to those diagnosed in adulthood. The minigene assay results indicate the importance of functional analysis, and call into question the fundamental belief that at least one non-truncating mutation is necessary for perinatal survival.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10157-021-02135-3.

Case Report: Expanding the Digenic Variants Involved in Thyroid Hormone Synthesis-10 New Cases of Congenital Hypothyroidism and a Literature Review

Congenital hypothyroidism (CH) is the most common neonatal metabolic disorder. Although it has been understood to be a monogenic disease, some CH patients are reported to carry two or more variants at different genes. Here, ten permanent congenital hypothyroidism (PCH) patients were retrospectively reviewed, with elevated levels of serum thyroid-stimulating hormone and levothyroxine dependence during follow-up between 2015 and 2019. Each affected individual carried digenic variants, which were heterozygous at two of pathogenic genes. In total, five pathogenic genes, TSHR, TG, TPO, DUOX2 and DUOXA2, were simultaneously identified in subjects that were involved in the same metabolic pathway: thyroid hormone biosynthesis. There were digenic variants at TSHR and DUOX2 combined in three patients, DUOX2 and TG combined in two patients, DUOX2 and DUOXA2 combined in two patients, TG and DUOXA2 combined in two patients, and TG and TPO combined in one patient. Additionally, seven novel variants, TSHR c.679G>A, DUOX2 c.127A>T, c.608-619del, c.959T>C, TG c.2307G>A, and c.6759_6765del, and DUOXA2 c.93T>G, were identified in these PCH patients. Along with a literature review on digenic variants in patients with CH, our findings illustrated the complexity of genetic etiology in CH.

Neonatal heel prick screening TSH concentration in the Netherlands as indicator of iodine status

Background

Neonatal Thyroid Stimulating Hormone (nTSH) is proposed as indicator of iodine deficiency in a population. Population’s iodine sufficiency is indicated by a proportion of the newborns less than 3% having nTSH above 5 mIU/L. The aim of this study was to explore the Dutch neonatal heel prick screening TSH data to assess iodine status in the Netherlands and identify determinants and potential confounders of this assessment.

Methods

All newborns born in the Netherlands between 2007 and 2015 with a heel prick collection at day 3-7 were included (n = 1,435,600), except preterm neonates and baby’s with a low birth weight. Total T4 was measured for all children, nTSH was measured in the ~ 20% children with lowest total T4.

Results

The proportion with nTSH > 5mIU/L fluctuated between 0.6-1.3% in 2007-2015. nTSH was significantly associated with laboratory performing the nTSH assay and age of heel prick sampling. The overall increasing trend in proportion nTSH >1mIU/L was confounded by the laboratories with different and changed assays.

Conclusions

The low proportion neonates with high nTSH suggests a sufficient iodine status in the Netherlands. Whether the increased proportion nTSH>1mIU/L over the years is an early indicator of deterioration of the iodine status remains unclear, due to differences and changes in analytical assays. nTSH might be a valuable and inexpensive way to get crude insight in the (trend in) iodine status, but more research is needed on the validity and potential conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12937-021-00722-4.

Congenital hypothyroidism impairs spine growth of dentate granule cells by downregulation of CaMKIV

Congenital hypothyroidism (CH), a common neonatal endocrine disorder, can result in cognitive deficits if delay in diagnose and treatment. Dentate gyrus (DG) is the severely affected subregion of the hippocampus by the CH, where the dentate granule cells (DGCs) reside in. However, how CH impairs the cognitive function via affecting DGCs and the underlying mechanisms are not fully elucidated. In the present study, the CH model of rat pups was successfully established, and the aberrant dendrite growth of the DGCs and the impaired cognitive behaviors were observed in the offspring. Transcriptome analysis of hippocampal tissues following rat CH successfully identified that calcium/calmodulin-dependent protein kinase IV (CaMKIV) was the prominent regulator involved in mediating deficient growth of DGC dendrites. CaMKIV was shown to be dynamically regulated in the DG subregion of the rats following drug-induced CH. Interference of CaMKIV expression in the primary DGCs significantly reduced the spine density of dendrites, while addition of T3 to the primary DGCs isolated from CH pups could facilitate the spine growth of dendrites. Insights into relevant mechanisms revealed that CH-mediated CaMKIV deficiency resulted in the significant decrease of phosphorylated CREB in DGCs, in association with the abnormality of dendrites. Our results have provided a distinct cell type in hippocampus that is affected by CH, which would be beneficial for the treatment of CH-induced cognitive deficiency.

Analysis of Worldwide Carrier Frequency and Predicted Genetic Prevalence of Autosomal Recessive Congenital Hypothyroidism Based on a General Population Database

To assess how genomic information of the general population reflects probabilities of developing diseases and the differences in those probabilities among ethnic groups, a general population database was analyzed with an example of congenital hypothyroidism. Twelve candidate genes that follow an autosomal recessive inheritance pattern in congenital hypothyroidism (SLC5A5, TPO, TG, IYD, DUOXA2, DUOX2, TSHR, SLC26A7, GLIS3, FOXE1, TSHB, TRHR) in the gnomAD database (v2.1.1) were analyzed. The carrier frequency (CF) and predicted genetic prevalence (pGP) were estimated. The total CF in the overall population was 3.6%. DUOX2 showed the highest CF (1.8%), followed by TG (0.46%), TPO (0.44%), TSHR (0.31%), SLC26A7 (0.144%), DUOXA2 (0.141%), IYD (0.08%), SLC5A5 (0.06%), TRHR (0.059%), GLIS3 (0.059%), TSHB (0.04%), and FOXE1 (0%). The pGP in the overall population was 10.01 individuals per 100,000 births (1:9992). The highest pGP was in the East Asian population at 52.48 per 100,000 births (1:1905), followed by Finnish (35.96), Non-Finnish European (9.56), African/African American (4.0), Latino/Admixed American (3.89), South Asian (3.56), and Ashkenazi Jewish (1.81) groups. Comparing the pGP with the real incidence of congenital hypothyroidism, the pGP in East Asian populations was highly consistent with the real incidence.

Genetics of primary congenital hypothyroidism-a review

PURPOSE

Congenital primary hypothyroidism (CH) is a state of inadequate thyroid hormone production detected at birth, caused either by absent, underdeveloped or ectopic thyroid gland (dysgenesis), or by defected thyroid hormone biosynthesis (dyshormonogenesis). A genetic component has been identified in many cases of CH. This review summarizes the clinical and biochemical features of the genetic causes of primary CH.

METHODS

A literature review was conducted of gene defects causing congenital hypothyroidism.

RESULTS

Mutations in five genes have predominantly been implicated in thyroid dysgenesis (TSHR, FOXE1, NKX2-1, PAX8, and NKX2-5), the primary cause of CH (85%), and mutations in seven genes in thyroid dyshormonogenesis (SLC5A5, TPO, DUOX2, DUOXA2, SLC6A4, Tg, and DEHAL1). These genes encode for proteins that regulate genes expressed during the differentiation of the thyroid, such as TPO and Tg genes, or genes that regulate iodide organification, thyroglobulin synthesis, iodide transport, and iodotyrosine deiodination. Besides thyroid dysgenesis and dyshormonogenesis, additional causes of congenital hypothyroidism, such as iodothyronine transporter defects and resistance to thyroid hormones, have also been associated with genetic mutations.

CONCLUSION

The identification of the underlying genetic defects of CH is important for genetic counseling of families with an affected member, for identifying additional clinical characteristics or the risk for thyroid neoplasia and for diagnostic and management purposes.

[Neonatal screening for congenital hypothyroidism]

Congenital hypothyroidism (CH) is the leading cause of preventable mental retardation. It is mainly due to thyroid dysgenesis or dyshormonogenesis with normally located gland, and detected at birth in developed countries by systematic neonatal screening. The early treatment of patients with CH has successfully improved the prognosis and management of this disease. An increase in the incidence of congenital hypothyroidism with a normally located gland has been reported worldwide over the last three decades. The etiology of CH with a normally located gland remains elusive and about half of them demonstrate spontaneous resolution of CH within a few months (transient CH). They highlight the need to reevaluate thyroid function during follow-up.

Snow White and the Seven Dwarfs: a fairytale for endocrinologists

'Snow White and the Seven Dwarfs', a fairytale that is widely known across the Western world, was originally written by the Brothers Grimm, and published in 1812 as 'Snow White'. Though each dwarf was first given an individual name in the 1912 Broadway play, in Walt Disney's 1937 film 'Snow White and the Seven Dwarfs', they were renamed, and the dwarfs have become household names. It is well known that myths, fables, and fairytales, though appearing to be merely children's tales about fictional magical beings and places, have, more often than not, originated from real facts. Therefore, the presence of the seven brothers with short stature in the story is, from an endocrinological point of view, highly intriguing, in fact, thrilling. The diversity of the phenotypes among the seven dwarfs is also stimulating, although puzzling. We undertook a differential diagnosis of their common underlying disorder based on the original Disney production's drawings and the unique characteristics of these little gentlemen, while we additionally evaluated several causes of short stature and, focusing on endocrine disorders that could lead to these clinical features among siblings, we have, we believe, been able to reveal the underlying disease depicted in this archetypal tale.

Molecular and clinical genetics of the transcription factor GLIS3 in Chinese congenital hypothyroidism

The transcription factor GLIS3 is an important factor in hormone biosynthesis and thyroid development, and mutations in GLIS3 are relatively rare. Deletions of more than one of the 11 exons of GLIS3 occur in most patients with various extrathyroidal abnormalities and congenital hypothyroidism (CH), and only 18 missense variants of GLIS3 related to thyroid disease have been reported. The aim of this study was to report the family history and molecular basis of patients with CH who carry GLIS3 variants. Three hundred and fifty-three non-consanguineous infants with CH were recruited and subjected to targeted exome sequencing of CH-related genes. The transcriptional activity and cellular localization of the variants in GLIS3 were investigated in vitro. We identified 20 heterozygous GLIS3 exonic missense variants, including eight novel sites, in 19 patients with CH. One patient carried compound heterozygous GLIS3 variants (p.His34Arg and p.Pro835Leu). None of the variants affected the nuclear localization. However, three variants (p.His34Arg, p.Pro835Leu, and p.Ser893Phe) located in the N-terminal and C-terminal regions of the GLIS3 protein downregulated the transcriptional activation of several genes required for thyroid hormone (TH) biosynthesis. This study of patients with CH extends the current knowledge surrounding the spectrum of GLIS3 variants and the mechanisms by which they cause TH biosynthesis defects.

Neonatal Dyshormonogenetic Goiter with Hypothyroidism Associated with Novel Mutations in Thyroglobulin and SLC26A4 Gene

Congenital goiter is an uncommon cause of neck swelling and it can be associated with hypothyroidism. We discuss a case of primary hypothyroidism with goiter presenting at birth. Ultrasound showed the enlargement of the gland and thyroid function tests detected marked hypothyroidism. Genetic analysis via next generation sequencing (NGS) was performed finding two mutations associated with thyroid dyshormonogenesis: c.7813 C > T, homozygous in the exon 45 of the thyroglobulin gene (TG) and c.1682 G > A heterozygous in exon 15 of the SLC26A4 gene (pendrin). Sanger sequencing of parents' DNA samples revealed that the first mutation (c.7813 C > T) was inherited from both of them, while the second one (c.1682 G > A) was inherited from the mother. Hormone replacement therapy was started, following which a gradual decrease in the size of the goiter was seen with the normalization of hormonal levels. Normal infant growth status and neurological development were recorded during follow-up. Neonatal dyshormonogenetic goiter with hypothyroidism may represent an unusual cause of neonatal neck mass. Early identification and hormone replacement therapy are crucial for a better neurodevelopmental outcome. Genetic analysis is mandatory in order to reach a specific diagnosis and to elucidate new patterns of thyroid disorder.

Identification of Transient Receptor Potential Channel 4-Associated Protein as a Novel Candidate Gene Causing Congenital Primary Hypothyroidism

BACKGROUND

Congenital primary hypothyroidism (CH) is the most common endocrine disorder in neonates.

METHODS

To identify novel genes, we performed whole exome sequencing (WES) in 6 patients with CH due to thyroid dysgenesis (TD). The potential effects of the most relevant variants were analyzed using in silico prediction tools. The most promising candidate gene, transient receptor potential channel 4-associated protein (TRPC4AP), was sequenced in 179 further patients with TD. Expression of TRPC4AP in human thyroid was investigated using RT-PCR. Trpc4ap- functional analysis was performed in Xenopus laevis using Morpholino (MO) antisense oligomers.

RESULTS

WES identified a likely damaging mutation in TRPC4AP leading to a de novo stop codon p.Q552*. Targeted sequencing of TRPC4AP demonstrated gene variants with predicted damaging potential in 5 patients resulting each in an amino acid exchange (p.P706S, p.F729L, p.S777C, and p.N229S). We demonstrated that TRPC4AP is expressed in human thyroid gland tissue. Using Xenopus laevis, we showed that the volume of the tadpole thyroid anlage was reduced by 20% in Trpc4ap MO knockdowns compared to controls and by 41% in "Clustered Regularly Interspaced Short Palindromic Repeats"/Cas9-mediated gene knockout experiments.

DISCUSSION

A recognized interaction of TRPC4AP and the NF-kappa-B-essential-modulator encoded by IKBKG gene was identified by IPA analysis. IKBKG plays a role in activation of the NF-κB-signaling pathway and regulates genes involved in proliferation and survival of thyrocytes and expression of key enzymes of thyroid hormone synthesis.

CONCLUSION

TRPC4AP was identified as a novel candidate gene in TD, but further studies are needed to validate its role in thyroid function.

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.

Molecular and clinical characteristics of congenital hypothyroidism in a large cohort study based on comprehensive thyroid transcription factor mutation screening in Henan

BACKGROUND

Congenital hypothyroidism (CH), the most common neonatal endocrine disorder worldwide, can be caused by variants in thyroid transcription factor (TTF) genes including NKX2-1, FOXE1, PAX8, NKX2-5 and HHEX. This study aims to perform targeted next-generation sequencing (NGS) panel for comprehensive mutation screening on these genes in a cohort of 606 CH patients with various types from Henan Province, China, to investigate the mutation rate of TTF genes, and to analyze the clinical, biochemical and molecular characteristics of our CH cohort.

METHODS

High-throughput sequencing combined with statistical calculation were applied for mutation screening and analyses of the clinical data.

RESULTS

Twenty-two likely disease-causing monoallelic mutations in the TTF genes were identified in our cohort (3.63%, 22/606). Mutated PAX8 was the most predominant genetic alteration among these TTF mutations. Interestingly, PAX8 defects were only found in TD cases and variants in the five TTF genes were detected in gland in situ (GIS) patients. CH patients with the same genotype may have significant phenotypic variability and permanent CH (PCH) patients in the GIS group were significantly fewer than those in the TD group.

CONCLUSIONS

Our study showed the estimated TTF mutation rate among CH cases was 3.63% in Henan Province and genetic alternations in TTF genes played a role not only in TD but also in GIS, especially in goiter. Although we speculated that the five TTF genes may be involved in certain steps of thyroid hormone biosynthesis, more researches are needed to verify the conclusions of the present study.

Congenital Hypothyroidism: A 2020-2021 Consensus Guidelines Update-An ENDO-European Reference Network Initiative Endorsed by the European Society for Pediatric Endocrinology and the European Society for Endocrinology

Background: An ENDO-European Reference Network (ERN) initiative was launched that was endorsed by the European Society for Pediatric Endocrinology and the European Society for Endocrinology with 22 participants from the ENDO-ERN and the two societies. The aim was to update the practice guidelines for the diagnosis and management of congenital hypothyroidism (CH). A systematic literature search was conducted to identify key articles on neonatal screening, diagnosis, and management of primary and central CH. The evidence-based guidelines were graded with the Grading of Recommendations, Assessment, Development and Evaluation system, describing both the strength of recommendations and the quality of evidence. In the absence of sufficient evidence, conclusions were based on expert opinion. Summary: The recommendations include the various neonatal screening approaches for CH as well as the etiology (also genetics), diagnostics, treatment, and prognosis of both primary and central CH. When CH is diagnosed, the expert panel recommends the immediate start of correctly dosed levothyroxine treatment and frequent follow-up including laboratory testing to keep thyroid hormone levels in their target ranges, timely assessment of the need to continue treatment, attention for neurodevelopment and neurosensory functions, and, if necessary, consulting other health professionals, and education of the child and family about CH. Harmonization of diagnostics, treatment, and follow-up will optimize patient outcomes. Lastly, all individuals with CH are entitled to a well-planned transition of care from pediatrics to adult medicine. Conclusions: This consensus guidelines update should be used to further optimize detection, diagnosis, treatment, and follow-up of children with all forms of CH in the light of the most recent evidence. It should be helpful in convincing health authorities of the benefits of neonatal screening for CH. Further epidemiological and experimental studies are needed to understand the increased incidence of this condition.

Guideline Adherence and Registry Recruitment of Congenital Primary Hypothyroidism: Data from the German Registry for Congenital Hypothyroidism (HypoDok)

Neonatal screening for congenital primary hypothyroidism (CH) is mandatory in Germany but medical care thereafter remains inconsistent. Therefore, the registry HypoDok of the German Society of Pediatric Endocrinology and Diabetology (DGKED) was analyzed to evaluate the implementation of evidence-based guidelines and to assess the number of included patients. Inclusion criteria were (i) date of birth between 10/2001 and 05/2020 and (ii) increased thyroid-stimulating hormone (TSH) at screening and/or confirmation. The cohort was divided into before (A) and after (B) guideline publication in 02/2011, to assess the guideline's influence on medical care. A total of 659 patients were analyzed as group A (n = 327) and group B (n = 332) representing 17.5% and 10.3% of CH patients identified in the German and Austrian neonatal screening program during the respective time period. Treatment start and thyroxine doses were similar in both groups and consistent with recommendations. Regular follow-ups were documented. In the first three years of life, less than half of the patients underwent audiometry; developmental assessment was performed in 49.3% (A) and 24.8% (B) (p < 0.01). Documentation of CH patient care by pediatric endocrinologists seemed to be established, however, it reflected only a minority of the affected patients. Therefore, comprehensive documentation as an important instrument of quality assurance and evidence-based medicine should be legally enforced and officially funded in order to record, comprehend, and optimize care and outcome in patients with rare diseases such as CH.

Incidence of primary congenital hypothyroidism and relationship between diagnostic categories and associated malformations

PURPOSE

The incidence of primary congenital hypothyroidism (CH) has grown progressively and literature data indicate an association between CH and congenital malformations. The purpose of this study is to establish the current incidence of CH in the Italian Region of Piedmont and verify the relationship between CH diagnostic categories and associated malformations.

METHODS

The biochemical and clinical data of 105 newborns with CH diagnosed in the period January 2014 to December 2019 were analyzed.

RESULTS

The incidence of CH in the Italian Piedmont region in the 2014-2019 period increased to 1:1090. Thyroid dysgenesis was responsible for 47.6% (50/105) of all cases, with agenesis in 14.3% (15/105), while ectopia and hypoplasia in 23.8% (25/105) and 9.5% (10/105) of the cases, respectively; dyshormonogenesis defects were found in 52.4% (55/105) of cases. Congenital extra-thyroid anomalies were identified in 33/105 (31.4%) of newborns with CH and mainly involve the cardiac system (17/85, 16.1%), urogenital tract (7/85, 6.7%), gastrointestinal tract (5/105, 4.8%), and the musculoskeletal system (5/105, 4.8%). The highest rate of malformations was observed in patients with thyroid agenesis and dyshormonogenesis, respectively, in 53.5% and 36.4% of cases, while in the presence of thyroid ectopia and hypoplasia, the rate was 12% and 20%, respectively, (p = 0.03).

CONCLUSION

In the Italian region of Piedmont, the incidence of primary CH has been increased over time, with a variation in the percentage of the different forms of CH. Congenital malformations, especially affecting the cardiovascular, urogenital, gastrointestinal, and musculoskeletal systems, seem to be mainly associated with thyroid agenesis or defects in hormonogenesis.

Low free thyroxine and normal thyroid-stimulating hormone in infants and children: possible causes and diagnostic work-up

Screening for hypo- or hyperthyroidism in adults is generally done by measuring the serum thyrotropin (thyroid-stimulating hormone, TSH) concentration. This is an efficient approach in case of suspected acquired thyroid disease. However, in infants and children, congenital hypothalamus-pituitary-thyroid (HPT) axis disorders also need to be considered, including primary and central congenital hypothyroidism, and even rarer thyroid hormone receptor and transporter defects. In primary congenital hypothyroidism, TSH will be elevated, but in the other congenital HPT axis disorders, TSH is usually within the normal range. Free thyroxine (FT4) assessment is essential for the diagnosis in these conditions.Conclusion: Here we discuss a number of rare congenital HPT axis disorders in which TSH is normal, but FT4 is low, and provide a clinical algorithm to distinguish between these disorders. What is Known: • A single thyroid-stimulating hormone (TSH) measurement is an appropriate screening method for primary hypothyroidism. • For central hypothyroidism and rare thyroid hormone receptor and transporter defects a free thyroxine (FT4) measurement is essential for the diagnosis because TSH is usually normal. What is New: • Here we present a new problem-oriented clinical algorithm including a diagnostic flow-chart for low FT4 and normal TSH in infants and children.

Clinical profiles and diagnostic challenges in 1158 children with rare hepatobiliary disorders

BACKGROUND

Diagnosis of rare diseases possesses a great challenge in pediatric hepatology because expert knowledge in the field is extremely insufficient. The study aims to explore new findings and collect diagnostic experience from pediatric rare liver diseases.

METHODS

The large-sample case analysis study included pediatric patients who had liver-involved rare diseases. All cases underwent liver biopsy and/or gene sequencing.

RESULTS

A total of 1158 pediatric patients were identified. Liver-based genetic diseases were most frequent (737 cases), followed by liver damages involved in extrahepatic or systemic disorders (151 cases) and cryptogenic hepatobilliary abnormalities (123 cases). Of note, diagnoses of 16 patients were re-evaluated according to genetic results combined with clinical pointers. In addition, 101 patients who underwent gene sequencing remained undiagnosed. Of them, 55 had negative genetic findings, 30 harbored mutations that failed to meet their typically pathogenic condition, and 16 had detected variants that were inconsistent with clinical pointers.

CONCLUSIONS

As a study involving known largest number of children with rare hepatobiliary disorders, it allows us to accumulate information (especially new findings) on the etiology and diagnosis of these disorders. The results can help to improve the diagnostic quality in the population.

IMPACT

Liver-based genetic diseases were most frequent in clinical profiles of pediatric rare liver diseases. Some novel variants in cases with genetic diseases (for example, two variants of c.3638G>T and c.1435G>C in a patient with progressive familial intrahepatic cholestasis type 2) were identified. As a study involving known largest number of pediatric cases with rare hepatobiliary disorders, it allows us to accumulate information on the etiology and diagnosis of these disorders. The study can help to optimize the diagnostic process and significantly improve the diagnostic quality in the field of pediatric hepatology. Given that clinical variability often exists within rare genetic disease entities and not all rare disorders are genetic, clinicians should not over-depend on the genetic results in the diagnosis.

Genetic and Phenotypic Characteristics of Congenital Hypothyroidism in a Chinese Cohort

BACKGROUND

The molecular etiology and the genotype-phenotype correlation of congenital hypothyroidism (CH) remain unclear.

METHODS

We performed genetic analysis in 42 newborns with CH using whole-exome sequencing. Patients were divided into a single-gene group and a multi-gene group according to the number of affected genes, or divided into a monoallelic group, a biallelic group, and an oligogenic group according to the pattern of the detected variants. The clinical characteristics were compared between groups.

RESULTS

Thyroid dysgenesis (TD) was observed in 10 patients and goiter in 5 patients, whereas 27 patients had normal-sized gland-in-situ (GIS). We identified 58 variants in five genes in 29 patients. The genes with the most frequent variants were DUOX2 (70.7%), followed by TSHR (12.1%), DUOXA2 (10.3%), and TPO (5.2%). Variants in the genes causing dyshormonogenesis (DH) were more common than those in the genes causing TD (87.9% versus 12.1%). Among the patients with detected variants, 26 (89.7%) were harboring a single gene variant (single-gene group), which include 22 patients harboring biallelic variants (biallelic group) and four patients harboring monoallelic variants (monoallelic group). Three (10.3%) patients harbored variants in two or three genes (multi-gene group or oligogenic group). Compared with the single-gene group, the levothyroxine (L-T4) dose at 1 year of age was higher in the multi-gene group (p = 0.018). A controllable reduction in the L-T4 dose was observed in 25% of patients in the monoallelic group and 59.1% of patients in the biallelic group; however, no patients with such reduction in the L-T4 dose were observed in the oligogenic group.

CONCLUSIONS

Patients with normal-sized GIS accounted for the majority of our cohort. Genetic defects in the genes causing DH were more common than those in the genes causing TD, with biallelic variants in DUOX2 being dominant. DH might be the leading pathophysiology of CH in Chinese individuals.

A Novel Homozygous Mutation in the Solute Carrier Family 26 Member 7 Gene Causes Thyroid Dyshormonogenesis in a Girl with Congenital Hypothyroidism

We investigated the genetic cause of thyroid dyshormonogenesis in a girl with congenital hypothyroidism. Genetic analysis showed that she was homozygous for a hitherto not described mutation (c.1432_1433delGT, p.V478KfsX11) in the solute carrier family 26 member 7 (SLC26A7) gene. SLC26A7 is proposed to be an anion transporter in the thyroid gland. The mutation leads to a frameshift and a premature stop codon. The predicted protein is truncated and very likely to be nonfunctional if it was expressed at all. In addition, in silico studies predict the mutation to be pathogenic.

DUOX2 variants are a frequent cause of congenital primary hypothyroidism in Thai patients

OBJECTIVE

To identify the genetic etiologies of congenital primary hypothyroidism (CH) in Thai patients.

DESIGN AND METHODS

CH patients were enrolled. Clinical characteristics including age, signs and symptoms of CH, pedigree, family history, screened thyroid-stimulating hormone results, thyroid function tests, thyroid imaging, clinical course and treatment of CH were collected. Clinical exome sequencing by next-generation sequencing was performed. In-house gene list which covered 62 potential candidate genes related to CH and thyroid disorders was developed for targeted sequencing. Sanger sequencing was performed to validate the candidate variants. Thyroid function tests were determined in the heterozygous parents who carried the same DUOX2 or DUOXA2 variants as their offsprings.

RESULTS

There were 118 patients (63 males) included. Mean (SD) age at enrollment was 12.4 (7.9) years. Forty-five of 118 patients (38%) had disease-causing variants. Of 45 variants, 7 genes were involved (DUOX2, DUOXA2, TG, TPO, SLC5A5, PAX8 and TSHR). DUOX2, a gene causing thyroid dyshormonogenesis, was the most common defective gene (25/45, 56%). The most common DUOX2 variant found in this study was c.1588A>T. TG and TPO variants were less common. Fourteen novel variants were found. Thyroid function tests of most parents with heterozygous state of DUOX2 and DUOXA2 variants were normal.

CONCLUSIONS

DUOX2 variants were most common among Thai CH patients, while TG and TPO variants were less common. The c.1588A>T in DUOX2 gene was highly frequent in this population.

Transcription factor GLIS3: Critical roles in thyroid hormone biosynthesis, hypothyroidism, pancreatic beta cells and diabetes

GLI-Similar 3 (GLIS3) is a member of the GLIS subfamily of Krüppel-like zinc finger transcription factors that functions as an activator or repressor of gene expression. Study of GLIS3-deficiency in mice and humans revealed that GLIS3 plays a critical role in the regulation of several biological processes and is implicated in the development of various diseases, including hypothyroidism and diabetes. This was supported by genome-wide association studies that identified significant associations of common variants in GLIS3 with increased risk of these pathologies. To obtain insights into the causal mechanisms underlying these diseases, it is imperative to understand the mechanisms by which this protein regulates the development of these pathologies. Recent studies of genes regulated by GLIS3 led to the identification of a number of target genes and have provided important molecular insights by which GLIS3 controls cellular processes. These studies revealed that GLIS3 is essential for thyroid hormone biosynthesis and identified a critical function for GLIS3 in the generation of pancreatic β cells and insulin gene transcription. These observations raised the possibility that the GLIS3 signaling pathway might provide a potential therapeutic target in the management of diabetes, hypothyroidism, and other diseases. To develop such strategies, it will be critical to understand the upstream signaling pathways that regulate the activity, expression and function of GLIS3. Here, we review the recent progress on the molecular mechanisms by which GLIS3 controls key functions in thyroid follicular and pancreatic β cells and how this causally relates to the development of hypothyroidism and diabetes.

Validity of Six Month L-Thyroxine Dose for Differentiation of Transient or Permanent Congenital Hypothyroidism

OBJECTIVE

The tendency to reduce thyroid stimulating hormone (TSH) referral cut-off values in congenital hypothyroidism (CH) neonatal screening programs has resulted in an increase in the incidence of CH, but also the referral of infants with mild transient elevation of TSH. Therefore, there is a need to develop markers for differentiation of transient elevated TSH and permanent CH as early as safely possible to avoid unnecessary treatment. The aim was to evaluate sixth-month L-thyroxine (LT4) dose as a predictive marker for differentiation of transient elevated TSH and permanent CH.

METHODS

Data of patients who had been followed after referral from the neonatal screening programme between the year 2010 and 2019 in a tertiary pediatric endocrine centre were examined retrospectively.

RESULTS

There were 226 cases referred, of whom 186 (82.3%) had eutopic thyroid gland, and 40 (17.7%) had dysgenetic gland. In patients with a dysgentic gland there was a non-significant tendency to have lower diagnostic free thyroxine concentration but significantly higher TSH compared with those with eutopic gland (p=0.44 and p=0.023, respectively). Patients with thyroid dysgenesis required higher initial and six month LT4 doses compared with those with eutopic glands (p=0.001). Receiver operator curve analysis showed the optimum cut-off value for LT4 at six months for transient vs. permanent CH was 2 μg/kg/day (sensitivity 77% and specificity 55%), regardless of etiology. Similarly, in patients with eutopic glands the optimum cut-off value for LT4 dose at six months for permanent vs. transient patients was 2 μg/kg/day (sensitivity 72% and specificity 54%).

CONCLUSION

Results suggest that LT4 requirement at six months of therapy may be a good marker for predicting transient TSH elevation in patients with eutopic thyroid gland, thus facilitating the decision to halt LT4 therapy.

Targeted Next-Generation Sequencing for Congenital Hypothyroidism With Positive Neonatal TSH Screening

PURPOSE

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder; however, its molecular etiology remains poorly understood.

METHODS

We performed genetic analysis of 24 causative genes using next-generation sequencing in 167 CH cases, comprising 57 dyshormonogenesis (DH), 32 dysgenesis (TD) and 78 undiagnosed. The pathogenicity of variants was assessed by the American College of Medical Genetics guidelines, inheritance pattern, and published evidence. Furthermore, we compared the oligogenic groups and monogenic groups to examine the correlation between variant dosage and severity.

RESULTS

We identified variants in 66.5% cases (111/167) and 15 genes, DUOX2, TSHR, PAX8, TG, TPO, DUOXA2, JAG1, GLIS3, DUOX1, IYD, SLC26A4, SLC5A5, SECISBP2, DIO1, and DIO3. Biallelic variants were identified in 12.6% (21/167), oligogenic in 18.0% (30/167), and monogenic in 35.9% (60/167); however, 68.5% of variants were classified as variant of unknown significance (VUS). Further examinations showed that 3 out of 32 cases with TD (9.4%) had pathogenic variants (2 of TSHR and 1 of TPO), and 8 out of 57 cases with DH (14.0%) (7 of DUOX2, 1 of TG) had pathogenic variants. In addition, TSH levels at the first visit were significantly higher in the oligogenic group than in the monogenic group.

CONCLUSIONS

The detection rate of pathogenic variants in Japanese CH was similar to that previously reported. Moreover, oligogenic cases were likely to be more severe than monogenic cases, suggesting that CH may exhibit a gene dosage effect. Further analysis of VUS pathogenicity is required to clarify the molecular basis of CH.

Genetics of Gland-in-situ or Hypoplastic Congenital Hypothyroidism in Macedonia

Neonatal screening in Macedonia detects congenital hypothyroidism (CH) with an incidence of 1 in 1,585, and more than 50% of cases exhibit a normally located gland-in-situ (GIS). Monogenic mutations causing dyshormonogenesis may underlie GIS CH; additionally, a small proportion of thyroid hypoplasia has a monogenic cause, such as TSHR and PAX8 defects. The genetic architecture of Macedonian CH cases has not previously been studied. We recruited screening-detected, non-syndromic GIS CH or thyroid hypoplasia cases (n = 40) exhibiting a spectrum of biochemical thyroid dysfunction ranging from severe permanent to mild transient CH and including 11 familial cases. Cases were born at term, with birth weight >3,000 g, and thyroid morphologies included goiter (n = 11), thyroid hypoplasia (n = 6), and apparently normal-sized thyroid. A comprehensive, phenotype-driven, Sanger sequencing approach was used to identify genetic mutations underlying CH, by sequentially screening known dyshormonogenesis-associated genes and TSHR in GIS cases and TSHR and PAX8 in cases with thyroid hypoplasia. Potentially pathogenic variants were identified in 14 cases, of which four were definitively causative; we also detected digenic variants in three cases. Seventeen variants (nine novel) were identified in TPO (n = 4), TG (n = 3), TSHR (n = 4), DUOX2 (n = 4), and PAX8 (n = 2). No mutations were detected in DUOXA2, NIS, IYD, and SLC26A7. The relatively low mutation frequency suggests that factors other than recognized monogenic causes (oligogenic variants, environmental factors, or novel genes) may contribute to GIS CH in this region. Future non-hypothesis-driven, next-generation sequencing studies are required to confirm these findings.

Reference Percentiles and Changes over Time for Total Thyroxine in Preterm Infants: A Retrospective Cohort Study

Hypothyroxinemia of prematurity increases the rate of false-positive results in total thyroxine (tT4)-based screening programs for congenital hypothyroidism. The use of specific cutoff values for preterm infants has been proposed, but data on tT4 reference ranges in this population are limited. The primary aim was to establish reference percentiles for tT4 in dried blood spots among Mexican preterm infants. Secondary aims included a comparison of the change of tT4 concentrations over time according to gestational age and to discuss its impact on tT4-based screening programs. This was a retrospective cohort study; 1561 preterm infants were included. Percentile 10th for tT4 concentration at 24-27, 28-30, 31-34, and 35-36 weeks of gestational age, measured in the first week of life was: 47.6, 56.6, 82.3, and 117.1 nmol/L, respectively. tT4 concentrations were compared in three different time points: first week of life, 2-3 weeks of life, and term-corrected gestational age (38 weeks of gestation), progressively increased in infants below 30 weeks, remained stable in infants from 31 to 34 weeks, and decreased in late preterm newborns (35-36 weeks). This study suggests that preterm infants may require the use of lower tT4 cutoff values in newborn screening.

Management of neonates born to mothers with thyroid dysfunction, and points for attention during pregnancy

Thyroid hormone (TH) is indispensable for normal embryonic and fetal development. Throughout gestation TH is provided by the mother via the placenta, later in pregnancy the fetal thyroid gland makes an increasing contribution. Maternal thyroid dysfunction, resulting in lower or higher than normal (maternal) TH levels and transfer to the embryo/fetus, can disturb normal early development. (Maternal) thyroid dysfunction is mostly caused by autoimmune hypo- or hyperthyroidism, i.e. Hashimoto and Graves disease. Autoimmune hyperthyroidism is caused by stimulating TSH receptor antibodies (TSHR Ab), patients with autoimmune hypothyroidism may have blocking TSHR Ab. Maternal TSHR Ab cross the placenta from mid gestation and may cause fetal and transient neonatal hyper- or hypothyroidism. Anti-thyroid drugs taken for autoimmune hyperthyroidism cross the placenta throughout gestation, and may cause fetal and transient neonatal hypothyroidism. This review focusses on the consequences of maternal hypo- and hyperthyroidism for fetus and neonate, and provides a practical approach to clinical management of neonates born to mothers with thyroid dysfunction.

Hypoprolactinemia as a Clue to Diagnosis of Mild Central Hypothyroidism due to IGSF1 Deficiency

Loss-of-function mutations of IGSF1 are an X-linked cause of central hypothyroidism (CeH) and hypoprolactinemia. A boy who is now 15.2 years old presented at the age of 7.69 years for evaluation of obesity. Previous thyroid function evaluation suggested CeH [FT4 0.6 ng/mL, thyroid-stimulating hormone (TSH) 2.2 mIU/L] but his physician took no action. At presentation he was clinically and biochemically euthyroid, prepubertal and obese. Serum prolactin (PRL) was undetectable. Biochemistry was normal except for mild hypercholesterolemia, total cholesterol 198 mg/dL. Subsequently FT4 and TSH levels fluctuated between 0.72-0.95 ng/dL (normal 0.8-2.0) and 1.94-5.77 mIU/L (normal 0.3-5.0), respectively. Sequencing of IGSF1 gene revealed a novel genetic change c.3805C>T in exon 19; substitution of amino acid Arginine at position 1269 with a premature «stop» codon resulting in an altered protein product. The patient additionally presented delayed adrenarche, low height velocity that resolved spontaneously and normal pubertal onset associated with increased FSH levels. At 14 years-of-age, while the patient was at Tanner stage 4, PRL levels became detectable, rising gradually to 2.3 ng/mL at last examination. Thyroxine replacement therapy resulted in decrease in total cholesterol 103 mg/dL. A high index of suspicion for the disorder is needed since several measurements of thyroid function may be required for CeH to be disclosed. The patient’s normal FT4 levels and normal intelligence would have resulted in a missed diagnosis if the serum PRL levels had not been measured. This case highlights the importance of measuring PRL in a boy with low normal FT4 and normal TSH levels.

The TPO mutation screening and genotype-phenotype analysis in 230 Chinese patients with congenital hypothyroidism

Inborn defects in thyroid hormone biosynthesis contribute to nearly half of congenital hypothyroidism (CH) cases in China. The thyroid peroxidase (TPO) mutation is one of the most frequent mutations that results in thyroid dyshormonogenesis. In this study, 35 non-synonymous mutations in 15 TPO sites, including 6 novel mutations, were identified in 230 Chinese patients with CH. The enzyme activity of the mutations in TPO was investigated in vitro, and patients with less than 15% residual enzyme activity showed severe CH, such as markedly increased thyroid-stimulating hormone (TSH) at diagnosis (>100 μIU/mL) and pronounced goiter, and required a higher dose of L-thyroxine to maintain the euthyroid. However, CH patients with greater than 16% TPO activity showed mild CH, a typical childhood socially without L-thyroxine treatment before 3 years of age, and the appearance of a macroscopic goiter at childhood. The findings indicated that the residual enzymatic activity of TPO was correlated with clinical phenotypes of CH patients with TPO biallelic mutations.

Thyrocyte cell survival and adaptation to chronic endoplasmic reticulum stress due to misfolded thyroglobulin

The large secretory glycoprotein thyroglobulin is the primary translation product of thyroid follicular cells. This difficult-to-fold protein is susceptible to structural alterations that disable export of the misfolded thyroglobulin from the endoplasmic reticulum (ER), which is a known cause of congenital hypothyroidism characterized by severe chronic thyrocyte ER stress. Nevertheless, individuals with this disease commonly grow a goiter, indicating thyroid cell survival and adaptation. To model these processes, here we continuously exposed rat PCCL3 thyrocytes to tunicamycin, which causes a significant degree of ER stress that is specifically attributable to thyroglobulin misfolding. We found that, in response, PCCL3 cells down-regulate expression of the "tunicamycin transporter" (major facilitator superfamily domain containing-2A, Mfsd2a). Following CRISPR/Cas9-mediated Mfsd2a deletion, PCCL3 cells could no longer escape the chronic effects of high-dose tunicamycin, as demonstrated by persistent accumulation of unglycosylated thyroglobulin; nevertheless, these thyrocytes survived and grew. A proteomic analysis of these cells adapted to chronic ER protein misfolding revealed many hundreds of up-regulated proteins, indicating stimulation of ER chaperones, oxidoreductases, stress responses, and lipid biosynthesis pathways. Further, we noted increased phospho-AMP-kinase, suggesting up-regulated AMP-kinase activity, and decreased phospho-S6-kinase and protein translation, suggesting decreased mTOR activity. These changes are consistent with conserved cell survival/adaptation pathways. We also observed a less-differentiated thyrocyte phenotype with decreased PAX8, FOXE1, and TPO protein levels, along with decreased thyroglobulin mRNA levels. In summary, we have developed a model of thyrocyte survival and growth during chronic continuous ER stress that recapitulates features of congenital hypothyroid goiter caused by mutant thyroglobulin.

Oligogenic Origin of Differences of Sex Development in Humans

Sex development is a very complex biological event that requires the concerted collaboration of a large network of genes in a spatial and temporal correct fashion. In the past, much has been learned about human sex development from monogenic disorders/differences of sex development (DSD), but the broad spectrum of phenotypes in numerous DSD individuals remains a conundrum. Currently, the genetic cause of less than 50% of DSD individuals has been solved and oligogenic disease has been proposed. In recent years, multiple genetic hits have been found in individuals with DSD thanks to high throughput sequencing. Our group has been searching for additional genetic hits explaining the phenotypic variability over the past years in two cohorts of patients: 46,XY DSD patients carriers of NR5A1 variants and 46,XY DSD and 46,XX DSD with MAMLD1 variants. In both cohorts, our results suggest that the broad phenotypes may be explained by oligogenic origin, in which multiple hits may contribute to a DSD phenotype, unique to each individual. A search for an underlying network of the identified genes also revealed that a considerable number of these genes showed interactions, suggesting that genetic variations in these genes may affect sex development in concert.

BAZ1B is a candidate gene responsible for hypothyroidism in Williams syndrome

Williams syndrome (WS) is a rare neurodevelopmental disorder associated to a hemizygous deletion of 28 genes located on chromosome 7q11.23. WS affected subjects frequently suffer from several endocrine abnormalities including hypothyroidism due to defects in thyroid morphology. To date, several genes involved in thyroid dysgenesis have been identified, nonetheless, none of them is located in the 7q11.23 region. Thus, the hypothyroidism-linked molecular features in WS are not yet known. In this study we focused on one of the WS deleted gene, BAZ1B, demonstrating that its downregulation in thyroid cells leads to cell viability and survival decrement. Taking together, our results show that BAZ1B could be the mainly responsible for thyroid defects observed in some of WS patients and that these alterations are activated by PTEN-mediated mechanisms.

Glis3 as a Critical Regulator of Thyroid Primordium Specification

Background: GLIS3 (GLI-Similar protein 3) is a transcription factor involved in several cellular processes. Homozygous mutations in the GLIS3 gene have been typically associated with neonatal diabetes and congenital hypothyroidism (CH) in a syndrome called NDH. NDH patients present developmental abnormalities including endocrine pancreas defects and a spectrum of thyroid abnormalities, mainly including thyroid dysgenesis (TD). The mouse models revealed a key role of Glis3 in pancreatic islets but not in early thyroid development, as Glis3 was described to retain a role in regulating thyroid hormone synthesis downstream the thyrotropin (TSH)/TSHR signaling pathway and in postnatal follicle proliferation. Hence, in this study, we have been taking advantage of the zebrafish model to gain insights on the Glis3 activity during thyroid organogenesis. Methods: Transient glis3-knockdown zebrafish embryos (called glis3 morphants) were generated by the microinjection of specific glis3 morpholinos at one- to two-cell stage to analyze the thyroid phenotype in vivo. Several additional analyses (in situ hybridization, immunohistochemistry, and pharmacological treatments) were performed for further molecular characterization. Results: The analysis of thyroid embryonic development revealed that Glis3 is involved in early steps of thyroid specification. glis3 morphants exhibited a reduced expression of the early transcription factors nkx2.4 and pax2a at the thyroid primordium level, which is not caused by changes in proliferation or apoptosis of the pharyngeal endoderm. As a result, the differentiated thyroid tissue in morphants appeared reduced in size with decreased expression of tg and slc5a5, a low number of thyroxine (T4)-producing follicles, associated with an elevation of tshba (homologous of the human TSHβ), thus resembling the clinical and biochemical manifestations of patients with TD. Interestingly, glis3 morphants have pancreatic β-cell defects, but not liver defects. In vitro and in vivo data also demonstrated that Glis3 is an effector of the Sonic Hedgehog (SHH) pathway. Molecular and pharmacological inhibition of SHH reproduced the thyroid defects observed in glis3 morphant. Conclusions: Our results demonstrate that glis3, within the SHH pathway, appears to determine the number of endodermal cells committed to a thyroid fate. This is the first evidence of the involvement of Glis3 in TD, thereby expanding the understanding of the genetic basis of thyroid development and CH.

Thyroid hormone therapy in congenital hypothyroidism and pediatric hypothyroidism

The evaluation and management of hypothyroidism in children are similar to adults, but there are important differences based on the dependence on normal thyroid function for neurocognitive and physical development. In the pediatric population, hypothyroidism is frequently categorized as congenital or acquired hypothyroidism, depending on the age of presentation and the underlying etiology. The evaluation and management of children and adolescents with hypothyroidism are determined by the etiology as well as by the age at diagnosis, severity of the hypothyroidism, and the response to thyroid hormone replacement therapy. Children and adolescents require higher weight-based doses for thyroid hormone replacement than do adults, likely due to a shorter half-life of thyroxine (T4) and triiodothyronine (T3) in children, but weight-based dose requirements decrease as the child advances into adulthood. Multiple gaps in knowledge remains regarding how to optimize the treatment of hypothyroidism in pediatric patients, including (but not limited to) the selection of patients with subclinical hypothyroidism for treatment, and the potential benefit of combined LT3/LT4 therapy for patients with persistent symptoms and/or low T3 on LT4 monotherapy. The life-long impact on growth and development, and potentially on long-term cardiovascular and psychosocial health, are significant and highlight the importance of future prospective studies in pediatric patients to explore these areas of uncertainty.