Mild Congenital Hypothyroidism Research Articles

Congenital Hypothyroidism: Screening and Management.

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Prompt diagnosis by newborn screening (NBS) leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet established in all countries globally. Seventy percent of neonates worldwide do not undergo NBS.The initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism.Newborn screening alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Congenital Hypothyroidism: Screening and Management.

Untreated congenital hypothyroidism (CH) leads to intellectual disabilities. Newborn screening (NBS) for CH should be performed in all infants. Prompt diagnosis by NBS leading to early and adequate treatment results in grossly normal neurocognitive outcomes in adulthood. However, NBS for hypothyroidism is not yet practiced in all countries globally. Seventy percent of neonates worldwide do not undergo NBS. The recommended initial treatment of CH is levothyroxine, 10 to 15 mcg/kg daily. The goals of treatment are to maintain consistent euthyroidism with normal thyroid-stimulating hormone and with free thyroxine in the upper half of the age-specific reference range during the first 3 years of life. Controversy remains regarding the detection of thyroid dysfunction and optimal management of special populations, including preterm or low-birth-weight infants and infants with transient or mild CH, trisomy 21, or central hypothyroidism. NBS alone is not sufficient to prevent adverse outcomes from CH in a pediatric population. In addition to NBS, the management of CH requires timely confirmation of the diagnosis, accurate interpretation of thyroid function testing, effective treatment, and consistent follow-up. Physicians need to consider hypothyroidism in the face of clinical symptoms, even if NBS thyroid test results are normal. When clinical symptoms and signs of hypothyroidism are present (such as large posterior fontanelle, large tongue, umbilical hernia, prolonged jaundice, constipation, lethargy, and/or hypothermia), measurement of serum thyroid-stimulating hormone and free thyroxine is indicated, regardless of NBS results.

Incidence of primary congenital hypothyroidism over 24 years in Finland

BackgroundA rise in the incidence of congenital hypothyroidism (CH) has been reported worldwide. This nationwide study aimed to describe the secular trends and current incidence of CH in Finland.MethodsTwo independent study cohorts, a national and a regional, were collected from national registers and patient records. The national cohort represents all CH cases born in Finland between 1994 and 2017. Birth data, results of the screening test, and the incidence of CH were reviewed.ResultsBetween 1994 and 2017, 1,400,028 children were born in Finland. Of these children, 503 were diagnosed with primary CH (incidence 1:2783). Male-to-female sex ratio was 1:2.0. The nationwide incidence was 33 cases per 100,000 live births between 1994 and 1999, 38 cases per 100,000 live births between 2000 and 2005, 40 cases per 100,000 live births between 2006 and 2011, and 33 cases per 100,000 live births between 2012 and 2017. In the regional cohort (n = 139), the incidence of transient CH was 3.6%. The incidence of mild, moderate, and severe CH remained constant.ConclusionsIn Finland, the incidence of CH has not changed during the 24-year study period.ImpactAs opposed to recent reports worldwide, the incidence of congenital hypothyroidism has not changed between 1994 and 2017 in Finland.The proportions of mild, moderate, and severe congenital hypothyroidism did not change significantly over the study period.Lowering the TSH cut-off limit or increasing immigration did not affect the incidence rate of primary congenital hypothyroidism in Finland.

Prevalence and Determinants of Transient Congenital Hypothyroidism in Children With Eutopic Gland in France: A Retrospective Cohort Study.

The increase in the incidence of congenital hypothyroidism (CH) reported worldwide may partly be explained by an increase in the transient form of CH. We aimed to estimate the proportion of transient CH (TCH) in France, and to identify associated neonatal and young child characteristics. We used probabilistic record linkage to link children with eutopic gland born between 2006 and 2012 recorded in the national French CH registry and the French national health data system (SNDS). Of the 703 children recorded, 484 (68.8%) were linked. We retrospectively examined reimbursement for oral levothyroxine (LT4) between January 1, 2006, and December 31, 2017. Children who had discontinued treatment for 6 months or more before December 31, 2017, were classified as having TCH. We used a Cox model to examine the factors associated with TCH. Among the main study sample (n = 471), 53.5% were female, 14.2% were preterm, and 13.8% had low birth weight. One-quarter (n = 111, 24.3%) had mild CH (thyroid-stimulating hormone [TSH] < 50 mU/L, serum) at diagnosis and a median LT4 dose at treatment initiation of 30 μg/day. One-third (n = 155, 32.9%) had TCH. Premature birth (adjusted hazard ratio = 2.1 [1.0-4.2]), a TSH < 50 mU/L at CH screening (7.4 [3.2-17.1]), LT4 dose received at 12 months of age (0.98 [0.97-0.99, P = 0.003]), congenital cardiac malformations (6.6 [1.5-29.0]), and year of birth (1.2 [1.1-1.4]) were all associated with TCH. One-third of the children had TCH, and it was associated with several characteristics at birth and postpartum. These data are useful for CH medical management and epidemiological surveillance.

Basal Serum Thyroxine Level should Guide Initial Thyroxine Replacement Dose in Neonates with Congenital Hypothyroidism

Objective:Initial high-dose sodium levothyroxine (Na-LT4) (10-15 μg/kg/day) replacement for primary congenital hypothyroidism (CH) is recommended in guidelines. However, high-dose Na-LT4 risks iatrogenic hyperthyroidism. The aim of this study was to investigate the normalizing effect of varying initial doses of Na-LT4 on serum thyroid hormone levels.Methods:Fifty-two patients were analyzed retrospectively. The patients were classified into mild (27/51.9%), moderate (11/21.1%) and severe (14/26.9%) CH, based on initial free thyroxine (fT4) levels. Time taken to achieve target hormone levels was compared within groups.Results:Initial mean Na-LT4 doses for mild, moderate and severe disease were 6.9±3.3, 9.4±2.2 and 10.2±2 μg/kg/day. Serum fT4 levels reached the upper half of normal range (>1.32 ng/dL) in a median of 16, 13 and 16 days in patients with mild, moderate and severe CH with the mean time from initial treatment to first control visit of 14.8±6 days (range 1-36). There was no significant difference in terms of time to achieve target fT4 hormone levels according to disease severity (p=0.478). Seven (25.9%), eight (72.7%) and eight (57.1%) patients experienced hyperthyroxinemia (serum fT4 >1.94 ng/dL) in the mild, moderate, and severe CH groups at the first visit, respectively (p=0.016).Conclusion:Not all patients diagnosed with CH require high-dose Na-LT4. Initial dose of Na-LT4 may be selected on the basis of pretreatment thyroid hormone levels. Some patients with moderate and severe CH, experienced iatrogenic hyperthyroxinemia even though the dose was close to the lower limit of the recommended range in guidelines. We suggest that lower initial doses may be appropriate with closer follow-up within the first week.

Congenital Hypothyroidism: A Review of 2020 European Society for Pediatric Endocrinology and the European Society for Endocrinology Consensus Guidelines

Congenital Hypothyroidism: A Review of 2020 European Society for Pediatric Endocrinology and the European Society for Endocrinology Consensus Guidelines

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.

Epidemiologic Characteristics and Risk Factors for Congenital Hypothyroidism from 2009 to 2018 in Xiamen, China

Objective: Early diagnosis and treatment of children with congenital hypothyroidism (CH) through newborn screening can effectively prevent delayed development. This study was designed to investigate the pathogenesis and factors that influence CH in urban areas of China between 2009 and 2018. Methods: A retrospective analysis of newborn screening data and diagnosis and treatment information for CH diagnosed in the information database of the neonatal disease screening center in one of China's five special economic zones from 2009 to 2018. Results: Of the 947,258 newborns screened between 2009 and 2018, 829 (406 girls) were diagnosed with CH at birth (1 diagnosis/1,136 births). Among the 608 cases of CH diagnosed at birth and re-evaluated at the age of 3 years, 487 were permanent congenital hypothyroidism (PCH, 1/1,429), and 121 were transient congenital hypothyroidism (TCH, 1/5,882). A total of 83.2% of infants with PCH (405/487) underwent thyroid imaging in the neonatal period, of which thyroid dysgenesis accounted for 28.64% (116/405) and functional defects accounted for 71.36% (289/405). The incidence of CH changed significantly in infants with initial serum thyroid-stimulating hormone concentrations of 41 to 100 mIU/L and ≥100 mIU/L, whereas the incidence of mild CH showed a slight increase. The incidence of CH was significantly higher in postterm infants (1/63) and low-birth-weight infants (1/370). Conclusion: In the past decade, the incidence of CH has increased, mainly due to the increase in the incidence of PCH and TCH. The incidence of mild CH has increased slightly. Postterm birth and low birth weight are important factors affecting the incidence of CH. Abbreviations: CH = congenital hypothyroidism; FT4 = free thyroxine; L-T4 = levothyroxine sodium; PCH = permanent congenital hypothyroidism; TCH = transient congenital hypothyroidism; TSH = thyroid-stimulating hormone; TT4 = total thyroxine.

MON-102 Serum Concentrations of FT4 and TSH in the First Six Months of L-Thyroxine Treatment in Infants with Congenital Hypothyroidism: Target Attainment Rates Should Be Improved

Levo-Thyroxine (L-T4) is the medication of choice for treating congenital hypothyroidism (CH). Adequate L-T4 treatment is essential for early neurodevelopment in affected patients. Both under- and overtreatment with L-T4 were associated with long-term adverse neurological outcomes. Based on clinical experience, initial L-T4 dosing does not always result in optimal TSH and FT4 concentrations in all CH patients. The purposes of this study were 1) to quantify FT4 and TSH target attainment rates (TAR) in the first six months of L-T4 treatment in infants with CH, 2) to compare characteristics of patients with FT4 concentrations “OUT of” versus “IN” the target range at first time of monitoring.A multicenter retrospective analysis was conducted in infants born between 1995 and 2018. TSH and FT4 TARs were defined according to the most recent guidelines of the European Society for Paediatric Endocrinology (ESPE), as the percentage of concentrations “in” and “in the upper half” of the corresponding laboratory age-specific reference range for TSH and FT4, respectively.We analyzed a total of 208 TSH and 186 FT4 serum concentrations from 60 patients during the first 6 months of L-T4 treatment. The pretreatment FT4 and TSH serum concentrations (mean±SD) were 8.3±5.7 pmol/L and 338±248 mU/L, respectively. CH severity according to ESPE guidelines was severe, moderate and mild for 32%, 27% and 32% of the patients. Postnatal age (PNA) (mean±SD) at start of treatment was 10±12 days. Starting dose of L-T4 (mean±SD) for severe, moderate and mild CH were 10±4, 10±3, and 7±4 µg/kg/day, respectively. Over the study period, TSH TARs of 63% did not further improve between the first monitoring (mean at 17 days of treatment) and fourth monitoring (mean at 4 months of treatment), while FT4 TARs increased from 22% to 45% paralleled with a decrease of too high FT4 values from 55% to 21%.Comparing patients with FT4 concentrations “OUT of” versus “IN” the target range at first time monitoring (16 versus 18 days after starting treatment; p=0.45), they did not differ in pretreatment FT4 concentrations (p=0.2). In contrast, patients who had FT4 concentrations “OUT of” versus “IN” the target range received first dose of L-T4 at an earlier median PNA (7 versus 16 days; p=0.008), had higher pretreatment mean TSH concentrations (364 versus 181 mU/L; p=0.02) and received a higher mean initial L-T4 dose (10.3 versus 7.1 µg/kg/day; p=0.01).First, our results show that FT4 and TSH target ranges were not reached in all patients in the first six months of treatment. Second, our data suggest that TARs could be improved by individualizing initial L-T4 dosing not only according to pretreatment FT4 but also to pretreatment TSH concentrations. L-T4 dosing optimization is needed in this population.

DUOX2 and DUOXA2 Variants Confer Susceptibility to Thyroid Dysgenesis and Gland-in-situ With Congenital Hypothyroidism.

Background: Thyroid dysgenesis (TD), which is caused by gland developmental abnormalities, is the most common cause of congenital hypothyroidism (CH). In addition, advances in diagnostic techniques have facilitated the identification of mild CH patients with a gland-in-situ (GIS) with normal thyroid morphology. Therefore, TD and GIS account for the vast majority of CH cases.Methods: Sixteen known genes to be related to CH were sequenced and screened for variations by next-generation sequencing (NGS) in a cohort of 377 CH cases, including 288 TD cases and 89 GIS cases.Results: In our CH cohort, we found that DUOX2 (21.22%) was the most commonly variant pathogenic gene, while DUOXA2 was prominent in TD (18.75%) and DUOX2 was prominent in GIS (34.83%). Both biallelic and triple variants of DUOX2 were found to be most common in children with TD and children with GIS. The most frequent combination was DUOX2 with DUOXA1 among the 61 patients who carried digenic variants. We also found for the first time that biallelic TG, DUOXA2, and DUOXA1 variants participate in the pathogenesis of TD. In addition, the variant p.Y246X in DUOXA2 was the most common variant hotspot, with 58 novel variants identified in our study.Conclusion: We meticulously described the types and characteristics of variants from sixteen known gene in children with TD and GIS in the Chinese population, suggesting that DUOXA2 and DUOX2 variants may confer susceptibility to TD and GIS via polygenic inheritance and multiple factors, which further expands the genotype-phenotype spectrum of CH in China.

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.

Mean high-dose L-thyroxine treatment is efficient and safe to achieve a normal IQ in young adult patients with congenital hypothyroidism

Context The optimal levothyroxine (LT4) dose to treat congenital hypothyroidism (CH) remains unclear, with debate over whether higher starting doses (>10 µg/kg) are necessary and safe for a normal intelligence quotient (IQ). Objective To examine psychomotor, metabolic, and quality of life (QoL) outcomes in patients with CH treated with a mean high initial LT4 dose. Design, settings, participants A cross-sectional cohort study of patients with CH identified in the Berlin newborn screening program from 1979 to 2003; 76 patients with CH (mean age, 18 years; mean initial LT4 dose, 13.5 µg/kg) and 40 siblings completed the study. Main outcome measures Psychomotor (Wechsler Intelligence Test, CNS Vital Signs), QoL (short form-36 Health Survey), anthropometric (body mass index, height), and metabolic (intima media thickness, laboratory parameters) outcomes were compared with those of healthy siblings. Mean values and percentage of episodes of elevated thyroxine (T4) and tri-jod-thyronin (T3) and suppressed thyrotropin (TSH) before age 2 years were analyzed. A meta-analysis of CH treatment studies was performed. Results There were no significant differences in IQ, QoL, or other outcome measures in patients with CH compared with controls. Most T4 levels were high before age 2 years and during subsequent testing, but mean T3 and TSH levels remained normal. The meta-analysis showed a significant IQ difference in severe vs mild CH cases only when treatment started with an LT4 dose Conclusions High initial LT4 dosing was effective and safely achieved optimal cognitive development in patients with CH, including those severely affected. Supranormal T4 values during infancy were not associated with impaired IQ in adolescence.

The etiologies and incidences of congenital hypothyroidism before and after neonatal TSH screening program implementation: a study in southern Thailand.

Congenital hypothyroidism (CH) is one of the common causes of intellectual disability which can be prevented by early detection of an elevated thyroid stimulating hormone (TSH) level in the newborn and by treatment with thyroxine. In Thailand, neonatal TSH screening was implemented nationwide in 2005. The objective of the study was to determine the etiologies and the estimated incidences of CH in southern Thailand before and after the implementation of a neonatal TSH screening program in 2005. The medical records of pediatric patients who were diagnosed with primary CH at Songklanagarind Hospital during 1995-2013 were retrospectively reviewed. The study was divided into two time periods: study period 1 (SP1) (1995-2004) and study period 2 (SP2) (2005-2013), the time before and after TSH program implementation. The most common form of CH during SP1 was overt permanent CH (66%), mostly caused by athyreosis or ectopic thyroid. In SP2, the most common form of CH was mild permanent CH (39%) (mostly due to dyshormonogenesis), followed by overt CH (32%) and transient CH (29%). The overall annual estimated incidence of CH per 10,000 live births in Songkhla Province was 1.69 (1:5021) in SP1, increasing to 4.77 (1:2238) in SP2; in all 14 provinces in southern Thailand, the estimated incidence was 1.24 (1:8094) in SP1 and 2.33 (1:4274) in SP2. Neonatal TSH screening has a significant impact on the increased detection of the mild form of permanent and transient CH cases, which may be important for the prevention of brain damage from less severe CH although this remains to be documented.

TSH and FT4 Concentrations in Congenital Central Hypothyroidism and Mild Congenital Thyroidal Hypothyroidism.

In central hypothyroidism (CeH), free thyroxine (FT4) concentrations are low, whereas thyrotropin (TSH) concentrations may be low, normal, or even slightly elevated due to reduced bioactivity. Congenital CeH (CCeH) may be isolated or part of multiple pituitary hormone deficiencies (MPHD). We tested our hypotheses that (1) TSH concentrations have a more U-shaped distribution in children with CCeH compared with children with a normally functioning hypothalamic-pituitary-thyroid axis and (2) TSH concentrations in children with CCeH with MPHD are higher compared with children with isolated CCeH. We also studied whether FT4 levels are helpful in distinguishing CCeH from mild congenital hypothyroidism of thyroidal origin (CH-T). Dutch neonatal screening TSH and first diagnostic TSH and FT4 were analyzed in all children diagnosed with permanent CCeH between 1995 and 2012. Controls were children with T4-binding globulin deficiency. FT4 concentrations in CCeH were compared with those in CH-T with TSH values in the same range as those of CCeH. We studied 120 children with CCeH (isolated CCeH, n = 50; MPHD, n = 70) and 350 control subjects. Screening TSH concentrations were not significantly different (P = 0.055), but diagnostic TSH values were significantly different between the CCeH group and the control group (P = 0.037). TSH was significantly higher in MPHD compared with isolated CCeH (P = 0.004). FT4 concentrations were significantly lower in CCeH compared with mild CH-T (P < 0.0005). TSH values in CCeH have a more U-shaped distribution compared with controls with the highest TSH concentrations in MPHD. FT4 levels were significantly lower in CCeH compared with CH-T.

Mean High-Dose l-Thyroxine Treatment Is Efficient and Safe to Achieve a Normal IQ in Young Adult Patients With Congenital Hypothyroidism.

The optimal levothyroxine (LT4) dose to treat congenital hypothyroidism (CH) remains unclear, with debate over whether higher starting doses (>10 µg/kg) are necessary and safe for a normal intelligence quotient (IQ). To examine psychomotor, metabolic, and quality of life (QoL) outcomes in patients with CH treated with a mean high initial LT4 dose. A cross-sectional cohort study of patients with CH identified in the Berlin newborn screening program from 1979 to 2003; 76 patients with CH (mean age, 18 years; mean initial LT4 dose, 13.5 µg/kg) and 40 siblings completed the study. Psychomotor (Wechsler Intelligence Test, CNS Vital Signs), QoL (short form-36 Health Survey), anthropometric (body mass index, height), and metabolic (intima media thickness, laboratory parameters) outcomes were compared with those of healthy siblings. Mean values and percentage of episodes of elevated thyroxine (T4) and tri-jod-thyronin (T3) and suppressed thyrotropin (TSH) before age 2 years were analyzed. A meta-analysis of CH treatment studies was performed. There were no significant differences in IQ, QoL, or other outcome measures in patients with CH compared with controls. Most T4 levels were high before age 2 years and during subsequent testing, but mean T3 and TSH levels remained normal. The meta-analysis showed a significant IQ difference in severe vs mild CH cases only when treatment started with an LT4 dose <10 µg/kg. High initial LT4 dosing was effective and safely achieved optimal cognitive development in patients with CH, including those severely affected. Supranormal T4 values during infancy were not associated with impaired IQ in adolescence.

Individualized treatment to optimize eventual cognitive outcome in congenital hypothyroidism.

In congenital hypothyroidism (CH), age-specific reference ranges (asRR) for fT4 and thyrotropine (TSH) are usually used to signal over/under-treatment. We compared the consequences of individual fT4 steady-state concentrations (SSC's) and asRR regarding over-treatment signaling and intelligence quotient at 11 y (IQ11) and the effect of early over-treatment with high L-T4 dosages on IQ11. Sixty-one patients (27 severe, 34 mild CH) were psychologically tested at 1.8, 6, and 11 y. Development scores were related to over-treatment in the period 0-24 mo, relative to either individual fT4SSC's or asRR. Three groups were formed, based on severity of over/under-treatment 0-5 mo (severe, mild, and no over/under-treatment). FT4 and TSH asRR missed 41-50% of the over-treatment episodes and consequently 22% of the over-treated patients, classified as such by fT4SSC's. Severe over-treatment 0-5 mo led to lowered IQ11's and to a 5.5-fold higher risk of IQ11 < 85 than other treatment regimes. Under-treatment had no effect on development scores. Initial L-T4 dosages >10 µg/kg resulted in a 3.7-fold higher risk of over-treatment than lower dosages. Data suggest that asRR, compared to fT4SSC's, signal over-treatment insufficiently. Using fT4SSC's and avoiding over-treatment may optimize cognitive outcome. Lowered IQ11's are usually a late complication of severe early over-treatment.

TRα receptor mutations extend the spectrum of syndromes of reduced sensitivity to thyroid hormone

Since 2012, eight different abnormalities have been described in the THRA gene (encoding the TRα1 thyroid hormone receptor) of 14 patients from 9 families. These mutations induce a clinical phenotype (resistance to thyroid hormone type α) associating symptoms of untreated mild congenital hypothyroidism and a near-normal range of free and total thyroid hormones and TSH (the T4/T3 ratio is nevertheless usually low). The phenotype can diversely include short stature (due to growth retardation), dysmorphic syndrome (face and limb extremities), psychoneuromotor disorders, constipation and bradycardia. The identified genetic abnormalities are located within the ligand-binding domain and result in defective T3 binding, an abnormally strong interaction with corepressors and a dominant negative activity against still functional receptors. The identification of patients with consistent phenotypes and the underlying mutations are warranted to better delineate the spectrum of the syndromes of reduced sensitivity to thyroid hormone.

The Missense Alteration A5T of the Thyroid Peroxidase Gene is Pathogenic and Associated with Mild Congenital Hypothyroidism

Congenital hypothyroidism (CH) occurs with a prevalence of approximately 1:4000 live births. Defects of thyroid hormone synthesis account for 15-20% of these cases. Thyroid peroxidase (TPO) gene is the most common cause for dyshormonogenesis. So far, more than 60 mutations in the TPO gene have been described, resulting in a variable decrease in TPO bioactivity. We present an 8-day-old male with mild CH who was identified to have a G to A transition in the fifth codon of the TPO gene (c.13G>A; p.Ala5Thr). The unaffected family members were heterozygous carriers of the mutation, whereas 400 healthy individuals of the same ethnic background did not have the mutation. Mutation analysis of 11 known causative CH genes and 4 of our own strong candidate genes with next-generation sequencing revealed no mutations in the patient nor in any other family members. The results of in silico functional analyses indicated partial loss-of-function (LOF) in the resulting enzyme molecule due to mutation. The patient’s clinical finding s were consistent with the effect of this partial LOF of the mutation. In conclusion, we strongly believe that A5T alteration in the TPO gene is actually pathogenic and suggest that it should be classified as a mutation.

The Role of 123I Imaging in the Evaluation of Infants with Mild Congenital Hypothyroidism

Background/Aims: Controversy exists regarding the diagnosis and treatment of mild congenital hypothyroidism (MCH). We studied the value of ¹²³I imaging in patients with MCH. Methods: Retrospective chart review of infants and children <4 years of age who underwent ¹²³I imaging: group 1 = MCH [thyroid-stimulating hormone (TSH) <25 µIU/ml, normal free T₄/T₃], group 2 = severe congenital hypothyroidism (TSH ≥25 µIU/ml), and group 3 = MCH in infancy imaged after treatment withdrawal at age 3 years. Data collected included 4- and 24-hour ¹²³I uptake, TSH, free T₄/total T₃ at imaging, age at imaging, and levothyroxine (<smlcap>L</smlcap>-T₄) dose at 1 year of. Results: Thirty-six patients underwent ¹²³I imaging. In group 1 (n = 20, median TSH: 8.49 µIU/ml), 85% had abnormal imaging consistent with dyshormonogenesis. Two patients were referred after 1 year of age. The median age at imaging for the remaining 18 patients was 54 days. Median <smlcap>L</smlcap>-T₄ dose at 1 year of age for these 18 patients was 2.8 μg/kg, which is consistent with dyshormonogenesis. Ninety-one percent of group 2 (n = 11, median TSH: 428.03 µIU/ml) had abnormal imaging. The median age at imaging was 13 days. Four patients in group 3 had abnormal ¹²³I imaging and restarted treatment. Conclusion:¹²³I imaging is a valuable tool for evaluation, diagnosis, and treatment of MCH.

The severity of congenital hypothyroidism of central origin should not be underestimated.

Congenital hypothyroidism (CH) may be of thyroidal (CHT) or central origin (CHC). Worldwide, most neonatal screening programs are TSH-based and effectively detect CHT. Only a few screening programs measure total or free T4 and TSH simultaneously or stepwise, enabling detection of CHT as well as CHC. A frequently used argument against screening for CHC is its presumed mild hypothyroid character. In the recently published European Society for Paediatric Endocrinology (ESPE) CH consensus guidelines on screening, diagnosis, and management, severity of CH is classified based on initial free T4 (FT4) concentrations. Our objective was to assess disease severity of CHC compared with CHT in a Dutch cohort of CH patients. Pretreatment FT4 concentrations were analyzed in all children with CH detected by the Dutch neonatal T4+TSH+T4-binding-globulin (TBG) screening between 1995 and 2011. Disease severity was classified using the FT4-based ESPE classification. Between 1995 and 2011, 1288 children were diagnosed with CH. Data of 1200 (143 CHC and 1057 CHT) were available for analysis. Based on FT4 concentrations, 4 children with CHC (2.8%) had severe, 75 (52.4%) moderate, and 64 (44.8%) mild CH. In the CHT group, 280 children (26.5%) had severe, 341 (32.3%) moderate, and 436 (41.2%) mild CH. Our results indicate that, based on initial FT4 values, severe CH was much more prevalent in CHT compared with CHC. However, CHC itself should not be considered as only mild because more than half of CHC patients have moderate CH with initial FT4 below 10 pmol/L (0.78 ng/dl).