Prevalence and etiology of congenital hypothyroidism detected through an argentine neonatal screening program (1997-2010)

Genetic etiology in patients diagnosed with congenital hypothyroidism with new-generation sequencing: A single-center experience

AIM

Congenital hypothyroidism (CH) is the most common endocrine disorder of the newborn; it is seen in every 3000-4000 births. Genetic features can guide treatment for patients with in situ glands. The present study aimed to contribute to the literature on CH variants and to show the benefit that genetic analysis can provide to patients in follow-up.

METHOD

A total of 52 patients (47 families) diagnosed with CH were included in the study. Overall, 32 target genes involved in thyroid physiology were investigated by next-generation sequencing (NGS).

RESULTS

In total, 29 (55 %) of the patients were male, and the rate of dysgenesis was 19.2 %. In this study, 29 of 52 patients had at least one variant in one gene involved in CH (n = 29, 33 different variants) (Including likely benign variants and variants of unknown significance). There were 21 patients (40.3 %) with gland in situ. The most common variant was DUOX2 (20 %). The second most common variants were those in the TPO and TG genes (15 % and 15 %, respectively); 41.1 % of these were variants of uncertain significance (VUS), 26.4 % were pathogenic, 23.5 % were likely benign, and 11.7 % were likely pathogenic. On the basis of their zygosity, we identified 73.5 % heterozygous, 17.6 % homozygous, and 8.9 % combined heterozygous variants. There were mutant variants in two genes in six patients and three in one patient.

CONCLUSION

This study found a variant in 55 % of the patients and shed light on the etiology of some cases of CH. The frequency of VUS was high. Although variants were identified in this study, their implication in the etiology of CH is not certain and, for most of the patients, it is also not sufficient for explaining the pathology with the current state of knowledge.

Impact of Lowering TSH Cut-Off on Neonatal Screening for Congenital Hypothyroidism in Minas Gerais, Brazil

A higher incidence of primary congenital hypothyroidism (CH) has been related to increased sensitivity in neonatal screening tests. The benefit of treatment in mild cases remains a topic of debate. We evaluated the impact of reducing the blood-spot TSH cut-off (b-TSH) from 10 (Group 2) to 6 mIU/L (Group 1) in a public neonatal screening program. During the study period, 40% of 123 newborns with CH (n = 162,729; incidence = 1:1323) had b-TSH between 6 and 10 mIU/L. Group 1 patients had fewer clinical signs (p = 0.02), lower serum TSH (p < 0.01), and higher free T4 (p < 0.01) compared to those in Group 2 at diagnosis. Reducing the b-TSH cut-off from 10 to 6 mIU/L increased screening sensitivity, allowing a third of diagnoses, mainly mild cases, not being missed. However, when evaluating the performances of b-TSH cut-offs (6, 7, 8, 9, and 10 mIU/L), the lower values were associated with low positive predictive values (PPVs) and unacceptable increased recall rates (0.57%) for a public health care program. A proposed strategy is to adopt a higher b-TSH cut-off in the first sample and a lower one in the subsequent samples from the same child, which yields a greater number of diagnoses with an acceptable PPV.

Incidence of primary congenital hypothyroidism over 24 years in Finland

BACKGROUND

A 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.

METHODS

Two 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.

RESULTS

Between 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.

CONCLUSIONS

In Finland, the incidence of CH has not changed during the 24-year study period.

IMPACT

As 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.

Cognitive Outcomes in Congenital Hypothyroidism: Impact of Socioeconomic Status - A Case-Control Study

OBJECTIVE

Chile is one of the few high-income countries in Latin America, being a pioneer in implementing a national newborn screening (NBS) program in 1992. Currently, it covers 98% of the population, but no long-term outcomes have been described so far. The aim of this study was to report the neurocognitive outcomes of children with congenital hypothyroidism (CH) diagnosed by the NBS program in Chile between 2005 and 2012 and to identify variables associated with the outcomes.

METHODS

We performed a case-control study in children with CH born in the two largest regions of the country. The Leiter-R and TEVI-R tests were administered at home to 69 children with CH and 68 matched control subjects. Other variables affecting cognition were obtained. Multivariate logistic regression analyses were performed for Leiter-R and TEVI-R tests, using a model for cases alone and another model for cases and controls.

RESULTS

No differences in Leiter-R and TEVI-R results were observed between children with CH and the control group. Children who performed better, regardless of whether they had CH, had a higher family income and more assets.

CONCLUSIONS

These results suggest that the Chilean NBS program strategy results in children with normal language, attention, and memory development. Socioeconomic disadvantage represents a significant detriment in cognitive function.

MECHANISMS IN ENDOCRINOLOGY: The pathophysiology of transient congenital hypothyroidism

Transient congenital hypothyroidism (TCH) refers to congenital hypothyroidism which spontaneously resolves in the first few months or years of life. Currently, there is a paucity of reliable markers predicting TCH at diagnosis, and the diagnosis is established following the withdrawal of levothyroxine therapy around 3 years of age. The incidence of TCH is increasing, and it is a major contributor to the overall increase in the incidence of CH in recent studies. Both genetic factors, in particular mutations affecting DUOX2 and DUOXA2, and environmental factors, for example, iodine deficiency and excess, anti- TSHR antibodies and exposure to antithyroid or iodine-rich medications, may cause TCH. Resolution of TCH in childhood may reflect both normal thyroid physiology (decreased thyroid hormone biosynthesis requirements after the neonatal period) and clearance or cessation of environmental precipitants. The relative contributions and interactions of genetic and environmental factors to TCH, and the extent to which TCH may be prevented, require evaluation in future population-based studies.

Newborn Screening for Congenital Hypothyroidism: the Benefit of Using Differential TSH Cutoffs in a 2-Screen Program

CONTEXT

Analysis of a 2-screen program for congenital hypothyroidism (CH) was performed using differential dried-blood spot thyrotropin (bTSH) cutoffs of 10 mU/L at first screening (all infants) and 5 mU/L at second screening (selected infants).

OBJECTIVES

This work aimed to characterize CH infants identified by the second screening and compare infants with bTSH of 5.0 to 9.9 and 10 mU/L or greater on second screening.

DESIGN AND PATIENTS

Maternal and neonatal clinical features were retrospectively analyzed for 119 CH babies detected on the second screen in the Lombardy region of Italy, 2007 to 2014.

RESULTS

Fifty-two (43.7%) of the 119 CH neonates showed bTSH values ranging from 5.0 to 9.9 mU/L at the second screening (low bTSH group) and 67 (56.3%) bTSH of 10.0 mU/L or greater (high bTSH group). The frequency of thyroid dysgenesis and eutopic gland was similar in both groups, as was the frequency of permanent and transient CH. Moreover, a high frequency of extrathyroidal malformations was found in both groups. The percentage of preterm infants (57.7% vs 23.9%, P < .001) and infants admitted to the neonatal intensive care unit (50.0% vs 17.9%, P < .001) was significantly higher in the low vs the high bTSH group. In addition, maternal treatment with glucocorticoids in pregnancy was significantly more frequent in the low bTSH group than in the high bTSH group (11.5% vs 1.5%, P = .042), as well as maternal hypothyroidism and/or goiter (26.9% vs 10.4%, P = .036).

CONCLUSIONS

This study has demonstrated that a lower TSH cutoff at the second screening can detect additional cases of CH and that a second bTSH cutoff of 5.0 mU/L is appropriate for identifying preterm newborns and babies with associated risk factors.

Assessment of intelligence quotient score in children at the age of six with suspected congenital hypothyroidism: A retrospective cohort study

Background: The clinical suspicion of Congenital Hypothyroidism (CH) is identified by abnormal results in the first test of Thyroid Stimulating Hormone (TSH) (5-9.9 mIU/L), and normal results in re-test (TSH<4 mIU/L). The CH has a contribution to physical and mental health. This study aimed to determine the Intelligence Quotient (IQ) score in children with suspected congenital hypothyroidism.

Methods: This research is a retrospective cohort study conducted in Mashhad, Iran. The IQ scores of 1976 children at the age of 6 were considered as an outcome variable. The history of CH screening for each newborn was assessed, then all suspected CH newborns that diagnosed healthy in re-test were considered as an exposed group, the effects of this situation on IQ score was assessed using logistic regression. All analysis was performed in STATA.

Results: The averages of IQ score (p<0.001), weight (p=0.024), and height (p<0.001) in the exposed group were lower than the unexposed group. The exposed group was related to those whose parental education was less or equal to 12 years (p<0.001). Similarly, the history of CH and maternal education for ≤12 years were detected as risk factors for having an IQ score of <90 in children.

Conclusion: Aside from the link between parental education and clinical suspicion of CH in neonates, our findings underline the possible strong effect of CH status and maternal education for ≤12 years on reducing IQ scores in the next years of child life.

Characterization of patients diagnosed with congenital hypothyroidism at the Hospital Universitario San Ignacio between 2001 and 2017

Introducción.

El hipotiroidismo congénito es una causa prevenible de discapacidad cognitiva. Dada la ausencia de signos y síntomas al nacer, es necesario hacer pruebas de tamización para detectarlo. Su incidencia oscila entre uno de cada 2.500 y uno de cada 6.000 nacidos vivos.

Objetivo.

Describir las características antropométricas y demográficas de los participantes, así como medir la concentración de tirotropina (TSH) en sangre de cordón umbilical y de TSH y tiroxina libre (T4 libre) en el suero de los recién nacidos positivos en la prueba de tamización y de aquellos con hipotiroidismo congénito confirmado.

Materiales y métodos.

Se hizo un estudio observacional retrospectivo de un periodo de 17 años mediante la revisión de los registros de laboratorio clínico y las historias para establecer las características demográficas y antropométricas en el momento del nacimiento.

Resultados.

Se analizaron 41.494 recién nacidos. Se encontraron 217 (0,52 %) recién nacidos con prueba positiva de tamización, 19 (8,76 %) de ellos con diagnóstico confirmado mediante pruebas séricas (TSH y T4 libre), para una incidencia de uno por cada 2.183 nacidos vivos. El 78,95 % de los casos de hipotiroidismo congénito correspondió a nacidos a término, el promedio de la edad gestacional fue de 37,3 semanas, similar al de quienes no lo presentaban. No hubo diferencia en el promedio de peso ni en la talla al nacer entre los afectados y los no afectados. La concentración de TSH en sangre de cordón umbilical fue significativamente mayor en los casos de hipotiroidismo congénito que en los recién nacidos sanos.

Conclusiones.

La incidencia de hipotiroidismo congénito fue similar a la encontrada en los estudios consultados. No hubo diferencias clínicas relevantes entre los casos confirmados y los descartados, lo que resalta la pertinencia de la tamización neonatal para el diagnóstico temprano y el tratamiento oportuno.

Neonatal Screening for Congenital Hypothyroidism: What Can We Learn From Discordant Twins?

CONTEXT

Newborn screening program for congenital hypothyroidism (CH) adopting rescreening in at-risk neonates.

OBJECTIVES

To estimate the concordance rate for CH in twin pairs discordant at the first screening; to verify whether long-term follow-up of healthy cotwins belonging to CH discordant pairs may be useful to diagnose thyroid hypofunction during development; to evaluate the importance of genetic and environmental influences on liability to permanent and transient CH.

DESIGN AND PATIENTS

Forty-seven screening discordant twin pairs were investigated. Proband was defined as the twin in the pair with a positive test at the first screening and a confirmed diagnosis of CH.

RESULTS

Seven screening discordant twin pairs became concordant for CH within the first month of life (pairwise concordance of 14.9%) because seven screening negative cotwins showed high TSH values when retested. During long-term follow-up (range, 3 to 21 years), hypothyroidism was diagnosed in two monozygotic screening negative cotwins at the age of 9 months and 12 years, respectively. Furthermore, the twin analysis showed that 95% of liability to transient CH was explained by genetic factors and 5% by environmental (unshared) factors, whereas 64% of phenotypic variance of permanent CH was explained by common environmental factors (shared during the fetal life) and 36% by unshared environmental factors.

CONCLUSIONS

This study showed that the introduction of rescreening permits the diagnosis of CH in a greater number of twins. It also showed the importance of long-term follow-up in both twins in the pair, and the role of nongenetic factors in the etiology of permanent CH.

The effect of thyroid functions on osteopenia of prematurity in preterm infants

Background It is known that thyroid hormones have effects on bone development. In particular, the effect of thyroid hormones on osteopenia of prematurity (OOP) has not been examined in preterm infants. Our study aimed to examine the relationship between OOP and congenital hypothyroidism (CH) in preterm infants. Methods Very low birth weight infants (VLBW, <1500 g) were included in the study. Thyroid-stimulating hormone (TSH) and free thyroxine (fT4) levels were measured on postnatal day 5. Serum calcium, phosphorus and alkaline phosphatase (ALP) levels were studied as standard screening parameters for OOP at postnatal week 4. Patients with serum ALP level >700 IU/L were included in the OOP group. We intended to figure out the relationship between OOP and CH in infants. Results In our study, OOP frequency was 14.9% among 543 VLBW infants. There was no statistically significant difference between groups with and without CH (21.7% and 14.8%, respectively) in terms of OOP (p=0.632). Gestational age (GA) was significantly lower in infants with diagnosed OOP (p<0.001, p<0.001, respectively). In addition, the prevalence rates of mothers with preeclampsia, small for gestational age (SGA), respiratory support requirement, late-onset neonatal sepsis (LOS), bronchopulmonary dysplasia (BPD) and full enteral feeding time were found to be higher in the OOP group (p<0.05). Conclusions We found that thyroid hormones had no effect on OOP in preterm infants. Therefore, future randomized controlled studies as well as long-term outcome studies are warranted on this topic.

Maternal education and newborn thyroid-stimulating hormone level in a congenital hypothyroidism screening program

Objective: To examine the relationship between neonatal thyroid function and the formal education of mothers.Study design: Participants came from a population-based congenital hypothyroidism (CH) screening program in Tianjin, China.Methods: Of 66,390 registered births in 2015, 60,568 mothers and newborns had complete data. Mothers were categorized into one of four categories based on their educational attainment: (a) midschool or less; (b) high school or equivalent; (c) university; or (d) post graduate. Newborn thyroid-stimulating hormone (TSH) level was measured on day 3-7. Two neonatal groups were created using cutoffs of TSH > 10 μIU/ml and TSH > 20 μIU/ml. Odds ratios (OR) for CH risk by maternal education were estimated from logistic regression models after adjusting for potential confounders.Results: For TSH > 10 μIU/ml, the screen positive incidence rate for CH was 1:201 or 4.98 per 1000 births; for TSH > 20 μIU/ml, the incidence rate was 1:2222 or 0.45 per 1000 births. Screen positive incidence rates decreased with increasing maternal education level. Compared to mothers with a postgraduate education, the ORs (95% CI) for midschool or less, high school or equivalent, and university were 2.09 (1.08, 4.04), 1.45 (0.73, 2.90), and 1.61 (0.85, 3.06) using a cutoff of TSH > 10 μIU/ml. At the higher cutoff of TSH > 20 μIU/ml ORs (95% CI) for midschool or less and high school or equivalent were 3.05 (1.20,7.74) and 3.34 (1.24, 8.97), when compared to a composite reference category of university and postgraduate level education.Conclusion: Maternal education is inversely related to neonatal thyroid function though the mechanism remains unexplained.

Genetics and genomic medicine in Argentina

A historical summary of genetics and genomic medicine in Argentina. We go through the achievements and difficulties in the implementation of genetic and genomic services both in academia and health care.

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

BACKGROUND

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.

METHODS

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.

RESULTS

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.

CONCLUSIONS

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.

Pilot Neonatal Screening Program for Central Congenital Hypothyroidism: Evidence of Significant Detection

BACKGROUND/AIM

Congenital hypothyroidism (CH) is a heterogeneous entity. Neonatal screening programs based on thyrotropin (TSH) determination allow primary CH diagnosis but miss central CH (CCH). CCH causes morbidity, alerts to other pituitary deficiencies, and is more prevalent than previously thought. We aimed at developing a pilot neonatal screening program for CCH detection.

PATIENTS AND METHODS

A prospective 2-year pilot neonatal screening study based on simultaneous dried blood specimen TSH and thyroxine (T4) measurements was implemented in term newborns aged 2-7 days. Those with T4 ≤4.5 µg/dL (-2.3 SDS) and TSH <10 mIU/L were recalled (suspicious of CCH) and underwent clinical and biochemical assessment performed by expert pediatric endocrinologists.

RESULTS

A total of 67,719 newborns were screened. Primary CH was confirmed in 24 (1: 2,821). Forty-four newborns with potential CCH were recalled (recall rate 0.07%) at a mean age of 12.6 ± 4.8 days. In this group, permanent CCH was confirmed in 3 (1: 22,573), starting L-T4 treatment at a mean age of 12.3 ± 6.6 days; 14 boys showed T4-binding globulin deficiency (1: 4,837); 24 had transient hypothyroxinemia (21 non-thyroidal illness and 3 healthy); and 3 died before the confirmation stage. According to initial free T4 measurements, CCH patients had moderate hypothyroidism.

CONCLUSIONS

Adding T4 to TSH measurements enabled the identification of CCH as a prevalent condition and contributed to improving the care of newborns with congenital hypopituitarism and recognizing other thyroidal disorders.

A 7-year study on the prevalence of congenital hypothyroidism in northern Iran

Background

Congenital hypothyroidism (CH) is one of the most common congenital endocrine disorders.

The present study determined the prevalence and demographic characteristics of congenital hypothyroidism in the north of Iran.

Objective

To determine the prevalence of congenital hypothyroidism based on transient and permanent types with demographic characteristics in Mazandaran province in northern Iran.

Methods

This retrospective descriptive survey analyzed the medical records of children with primary diagnosis of CH in health centers in all cities of Mazandaran Province between June 2009 and March 2016. To compare the study groups (CH type) in terms of quantitative and qualitative variables, the t-test and Chi-square test were used, respectively using the SPSS22. P-value <0.05 was considered as significant.

Results

Of 269,088 infants screened during the study period, 548 infants with primary congenital hypothyroidism were identified (a prevalence of 1 per 491 births) and congenital hypothyroidism was definitively diagnosed in 389 children (a prevalence of 1 per 453 births); of them, 169 had permanent CH (a prevalence of 1 per 1043 births) and 220 had transient CH (a prevalence of 1 per 801 births). The female to male ratio in the permanent congenital hypothyroidism group was higher than that in the transient congenital hypothyroidism group (p=0.08). The family relationship between mother and father was stronger in the permanent congenital hypothyroidism group than in the transient congenital hypothyroidism group (p=0.03).

Conclusion

These findings show that congenital hypothyroidism is more prevalent in the north of Iran than in other areas of Iran; the prevalence of transient CH is particularly higher than permanent CH.

Congenital Hypothyroidism

Congenital hypothyroidism is common and can cause severe neurodevelopmental morbidity. Prompt diagnosis and treatment are critical to optimizing long-term outcomes. Universal newborn screening is an important tool for detecting congenital hypothyroidism, but awareness of its limitations, repeated screening in high-risk infants, and a high index of clinical suspicion are needed to ensure that all affected infants are appropriately identified and treated. Careful evaluation will usually reveal the etiology of congenital hypothyroidism, which may inform treatment and prognosis. Early and adequate treatment with levothyroxine results in excellent neurodevelopmental outcomes for most patients with congenital hypothyroidism.

[Advances in genetic research of congenital hypothyroidism in China]

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

Neonatal screening: 9% of children with filter paper thyroid-stimulating hormone levels between 5 and 10μIU/mL have congenital hypothyroidism

OBJECTIVES

To determine the prevalence of congenital hypothyroidism in children with filter-paper blood-spot TSH (b-TSH) between 5 and 10μIU/mL in the neonatal screening.

METHODS

This was a retrospective study including children screened from 2003 to 2010, with b-TSH levels between 5 and 10μIU/mL, who were followed-up during the first two years of life when there was no serum TSH normalization. The diagnosis of congenital hypothyroidism was defined as serum TSH ≥10μIU/mL and start of levothyroxine treatment up to 2 years of age.

RESULTS

Of the 380,741 live births, 3713 (1.04%) had filter paper TSH levels between 5 and 10μIU/mL and, of these, 339 (9.13%) had congenital hypothyroidism. Of these, 76.11% of the cases were diagnosed in the first three months of life and 7.96% between 1 and 2 years of age.

CONCLUSION

The study showed that 9.13% of the children with b-TSH levels between 5 and 10μIU/mL developed hypothyroidism and that in approximately one-quarter of them, the diagnosis was confirmed only after the third month of life. Based on these findings, the authors suggest the use of a 5μIU/mL cutoff for b-TSH levels and long-term follow-up of infants whose serum TSH has not normalized to rule out congenital hypothyroidism.

Are lower TSH cutoffs in neonatal screening for congenital hypothyroidism warranted?

When newborn screening (NBS) for congenital hypothyroidism (CH) using thyroid-stimulating hormone (TSH) as a primary screening test was introduced, typical TSH screening cutoffs were 20-50 U/L of whole blood. Over the years, lowering of TSH cutoffs has contributed to an increased prevalence of detected CH. However, a consensus on the benefit deriving from lowering TSH cutoffs at screening is lacking. The present paper outlines arguments both for and against the lowering of TSH cutoffs at NBS. It includes a review of recently published evidence from Australia, Belgium and Italy. A section focused on economic implications of lowering TSH cutoffs is also provided. One issue that bears further examination is the extent to which mild iodine deficiency at the population level might affect the association of neonatal TSH values with cognitive and developmental outcomes. A debate on TSH cutoffs provides the opportunity to reflect on how to make NBS for CH more effective and to guarantee optimum neurocognitive development and a good quality of life to babies with mild as well as with severe CH. All authors of this debate article agree on the need to establish optimal TSH cutoffs for screening programs in various settings and to ensure the benefits of screening and access to care for newborns worldwide.

Pediatric Hypothyroidism: Diagnosis and Treatment

Thyroid hormone has important physiologic functions in nearly every organ system. The critical role of thyroid hormone in growth and in physical and neurologic development lends particular importance to the prompt diagnosis and appropriate treatment of hypothyroidism in infants and children. Congenital hypothyroidism is common and has potentially devastating neurologic consequences. While the approach to diagnosis and treatment of severe congenital hypothyroidism is well established, data continue to emerge about the genetic causes, clinical significance, and prognosis of the milder forms of congenital hypothyroidism that are increasingly being diagnosed by newborn screening. Similarly, the diagnosis and treatment of severe acquired hypothyroidism is straightforward and clearly of clinical benefit, but uncertainty remains about the optimal management of mild subclinical hypothyroidism. This review summarizes current knowledge of the causes, clinical manifestations, diagnosis, treatment, and prognosis of hypothyroidism in infants and children, with a focus on recent developments and areas of uncertainty in this field.

Detecting congenital hypothyroidism with newborn screening: the relevance of thyroid-stimulating hormone cutoff values

OBJECTIVES

To assess the prevalence of congenital hypothyroidism and the ability of various neonatal thyroid-stimulating hormone (TSHneo) cutoff values to detect this disease.

METHODS

This cohort study was based on the retrospective collection of information available from the Reference Service for Newborn Screening database for all live births from January 1, 2010, to December 31, 2012, assessed using the Newborn Screening Program of a Brazilian state, Brazil. The infants were divided into two groups: I - Control: infants with normal newborn screening tests and II - Study: infants with congenital hypothyroidism. Analysis included comparing the TSHneo levels from both groups. A receiver operating characteristic (ROC) curve was constructed to assess the TSHneo cutoff values.

RESULTS

Using a TSHneo cutoff value of 5.0μIU/mL, 50 out of 111,705 screened infants had diagnosis of congenital hypothyroidism (prevalence 1:2234 live births). The ROC curve showed that TSHneo value of 5.03μIU/mL had 100% sensitivity and the greatest associated specificity (93.7%). The area under the curve was 0.9898 (p<0.0001).

CONCLUSIONS

The ROC curve confirmed that the TSHneo cutoff value of 5.0μIU/mL adopted by the Newborn Screening Program of a Brazilian state was the most appropriate for detecting congenital hypothyroidism and most likely explains the high prevalence that was found.

Next-generation sequencing of NKX2.1, FOXE1, PAX8, NKX2.5, and TSHR in 100 Chinese patients with congenital hypothyroidism and athyreosis

BACKGROUND

The abnormal expression of certain transcription factors (NKX2.1, FOXE1, NKX2.5, and PAX8) and thyroid stimulating hormone receptor (TSHR) genes has been associated with athyreosis, which is a form of thyroid dysgenesis (TD). We aimed to identify candidate gene mutations in CH patients with athyreosis and to establish the genotype-phenotype correlations in a Chinese population.

METHODS

The exons and flanking sequences of NKX2.1, FOXE1, NKX2.5, PAX8, and TSHR were screened by next-generation sequencing and further confirmed by direct Sanger sequencing. The mutation frequencies were calculated and compared against databases. The relationship between genotype and phenotype was also determined.

RESULTS

Seven variants were detected in TSHR-p.P52T, p.G132R, p.M164K, p.R450H, p.C700E, p.A522V, and p.R528S. The p. G132R, p. M164K and p. R528S variants were first identified in public databases. Five variants (p.G44D, p.G360V, p.R401Q, p.L418I, and p.E453Q) were found in NKX2.1 and one variant (p.P243T) was detected in FOXE1. In addition, one variant (p.N291I) was found in NKX2.5 and two variants (p.A355V and c.-26G>A) were detected in PAX8.

CONCLUSIONS

Our study indicated that TSHR mutations have phenotypic variability and has further expanded the mutation spectrum of TSHR. We also revealed that the rate of NKX2.1, FOXE1, NKX2.5, and PAX8 mutations were low in patients with CH and athyreosis, in contrast to the higher rate of TSHR mutations.

Association of iodized salt with goiter prevalence in Chinese populations: a continuity analysis over time

BACKGROUND

Iodine deficiency disorders (IDD) refer to diseases that are caused by insufficient iodine intake, and the best strategy to prevent IDD is the addition of iodine to dietary salt. Because iodine deficiency is a common cause of goiter, the prevalence as effectively controlled after the implementation of universal salt iodization (USI) in China. However, there is substantial controversy as to whether the incidence of thyroid disorders is related to iodized salt intake. Therefore, we aimed to clarify whether the risk of goiter can be promoted by USI.

METHODS

A longitudinal continuous study based on the national monitoring results of IDD in China was performed for 3 consecutive years. We recorded the following indicators of IDD from 31 provinces: goiter number, two degrees of goiter (the degree of goiter severity) and cretinism (three endemic diseases), iodized salt intake, median urinary iodine concentration (UIC), soil iodine content and coverage rates of iodized salt. One-way Analysis of Variance (ANOVA) and linear regression analyses examined the differences between the three groups and correlations, respectively. Data were collected from the Chinese national IDD surveillance data in 2011-2013, and the background values of Chinese soil elements were published in 1990.

RESULTS

A reference male's daily intake of maximum iodine was 378.9 μg, 379.2 μg and 366.9 μg in 2011, 2012, and 2013, respectively. No statistical association between daily iodized salt intake and the three endemic diseases was observed in 2011-2013 (P > 0.05). No association was observed between daily iodized salt intake and the UIC of children in 2011 (P > 0.05). Linear regression revealed no significant correlation between the soil iodine content and three endemic diseases. The present study indicated no difference in the daily iodized salt intake in each province during three years (F = 0.886, P = 0.647). The coverage rate of iodized salt remained above 98.7%, and goiter rates were stable in 2011-2013.

CONCLUSION

There was no significant association between iodized salt intake and the three endemic diseases, suggesting that the current nutrition level of iodized salt did not cause the high goiter prevalence.

Growth development in children with congenital hypothyroidism: the effect of screening and treatment variables-a comprehensive longitudinal study

Investigating the screening and early treatment factors potentially affects the growth status of the patients with congenital hypothyroidism. In a longitudinal study, 760 (45 % girl) neonates born in 2002-2009 with congenital hypothyroidism diagnosed by neonatal screening in Isfahan-Iran were followed up to 5 years from the time of diagnosis (i.e., 3-4 records for the first year of age and 2-3 records after that). During follow-up, height, weight, and head circumferences of the patients were measured. Diagnostic and therapeutic factors included serum thyroxine and thyroid stimulating hormone concentration at diagnosis and after treatment initiation, the age at onset of treatment, the first therapeutic dosage, and age at first normalization of thyroxine and thyroid stimulating hormone. Quantile regression for longitudinal data was used for determining the effects of main factors on growth development. Longitudinal growth in height and weight was significantly correlated with the age at onset of treatment and the first therapeutic dosage (p < 0.01), while head circumference only with first therapeutic dosage (p < 0.05). Growth in weight and head circumference was affected by thyroid stimulating hormone at the time of diagnosis (p < 0.05). Also the age of thyroxine normalization had heterogeneous significant impact over the proposed quantiles on weight (p < 0.05), height (p < 0.01), and head circumference (p < 0.001). Among studied factors, the first therapeutic dosage, age at onset of treatment and age of thyroxine normalization seem to be more important for anthropometric development, suggesting that more optimal outcome might be achievable through earlier treatment and appropriate levothyroxine dosage.

Two novel TSHR gene mutations (p.R528C and c.392+4del4) associated with congenital hypothyroidism

Inactivating mutations of the thyrotropin receptor (TSHR) gene are responsible for non-goitrogenic congenital hypothyroidism (CHNG). This study aimed to investigate mutations in the TSHR gene in 20 children with CHNG. Genomic DNA was extracted from peripheral blood leukocytes and was used for mutation screening by direct sequencing. Analyses of the TSHR gene revealed two novel variants in a 2-year-old boy with thyroid hypoplasia: a missense mutation c.1582C>T (p.R528C) and a splice-site deletion c.392+4del4. Bioinformatics analysis demonstrated that both variants are capable of causing disease. Family members of the patient with two mutations and normal controls were also recruited and investigated. Germline mutations from the proband's family were consistent with an autosomal recessive inheritance pattern. These findings indicate that two novel inactivating mutations (p.R528C and c.392+4del4) in the TSHR gene can cause CHNG.

A Novel c.554+5C>T Mutation in the DUOXA2 Gene Combined with p.R885Q Mutation in the DUOX2 Gene Causing Congenital Hypothyroidism

The coexistence of mutations in the dual oxidase maturation factor 2 (DUOXA2) and dual oxidase 2 (DUOX2) genes is rarely identified in congenital hypothyroidism (CH). This study reports a boy with CH due to a novel splice-site mutation in the DUOXA2 gene and a missense mutation in the DUOX2 gene. A four-year-old boy was diagnosed with CH at neonatal screening and was enrolled in this study. The DUOXA2, DUOX2, thyroid peroxidase (TPO), and thyrotropin receptor (TSHR) genes were considered for genetic defects screening. Genomic DNA was extracted from peripheral blood leukocytes, and Sanger sequencing was used to screen the mutations in the exon fragments. Family members of the patient and the controls were also enrolled and evaluated. The boy harbored compound heterozygous mutations including a novel splice-site mutation c.554+5C>T in the maternal DUOXA2 allele and c.2654G>A (p.R885Q) in the paternal DUOX2 allele. The germline mutations from his parents were consistent with an autosomal recessive inheritance pattern. No mutations in the TPO and TSHR genes were detected. A novel splice-site mutation c.554+5C>T in the DUOXA2 gene and a mutation p.R885Q in the DUOX2 gene were identified in a 4-year-old patient with goitrous CH.

Changes in the incidence and etiology of congenital hypothyroidism detected during 30 years of a screening program in central Serbia

Congenital hypothyroidism (CH) is the most frequent congenital endocrine disorder. The purpose of the present study was to determine the incidence of CH in Central Serbia from 1983 to 2013. Newborn screening for CH was based on measuring neonatal thyroid-stimulating hormone (TSH) using a 30 mU/l cutoff (CO) until 12/1987 (P1), 15 mU/l until 12/1997 (P2), 10 mU/l until 12/2006 (P3), and 9 mU/l thereafter (P4). During the study period, there were 1,547,122 live births screened for CH. Primary CH was detected in 434 newborns, with incidence of 1:3728. With gradual lowering of the CO, the incidences of CH increased from 1:5943 in P1 to 1:1872 in P4 (p < 0.001). Incidence of CH with ectopic and enlarged gland doubled (p < 0.001), while prevalence of athyreosis remained relatively constant. The most prominent finding was the increase in the transient CH from none in P1 to 35 % of all CH patients in P4.

CONCLUSION

The overall incidence of CH in Central Serbia during study period nearly tripled, with a significant increase in almost all etiological categories, and was associated with lowering TSH cutoffs as well as other yet unidentified factors. Further studies are needed to identify other factors associated with increasing incidence of CH.

WHAT IS KNOWN

Congenital hypothyroidism (CH) is the main cause of preventable mental retardation. Recent reports have indicated a progressive increase in the incidence of primary CH throughout the world, partially explained by lowering of the TSH cutoff values.

WHAT IS NEW

During the study period associated with lowering of the TSH cutoffs, the overall incidence of CH in Serbia tripled, including transient CH, ectopy, and dyshormonogenesis, while prevalence of athyreosis remained stable during 30 years. Significant increase in the incidence of both permanent and transient CH was observed, associated with lowering of TSH cutoffs as well as other yet unidentified factors.

Increased incidence of congenital hypothyroidism in France from 1982 to 2012: a nationwide multicenter analysis

PURPOSE

Recent studies have shown an increased incidence of congenital hypothyroidism over the past 2 or 3 decades. The etiology of this change is unknown, but it has been related by several authors to lowering of cutoffs. We sought to determine whether the incidence of congenital hypothyroidism (CH) in France has changed.

METHODS

We analyzed data from the nationwide neonatal screening program for CH during the period 1982-2012. We included all children having thyroid-stimulating hormone values above the threshold and for whom diagnosis of CH confirmed by the pediatrician. We estimated multicentric temporal trends in the annual incidence rates adjusted for screening methods for thyroid dysgenesis and eutopic gland.

RESULTS

We found 6622 cases of CH (28.0 per 100,000 newborns); 1895 had a eutopic gland, and 4727 had thyroid dysgenesis. The incidence of eutopic glands showed a significant annual average increase of (5.1%; 95% confidence interval: 4.3-5.9) regardless of the screening method or screening center. This increase was confirmed in severe cases (thyroid-stimulating hormone ≥ 50: 2.1%; 95% confidence interval, 1.4-2.9). The incidence of dysgenesis remained constant.

CONCLUSIONS

The incidence of eutopic glands increased in France, not only in mild forms but also in severe cases.

Congenital hypothyroidism: recent advances

PURPOSE OF REVIEW

This review summarizes significant recent advances in the epidemiology, pathophysiology, and treatment of congenital hypothyroidism.

RECENT FINDINGS

The apparent incidence of congenital hypothyroidism has more than doubled in recent years because of several factors, including more inclusive diagnostic criteria, shifting demographics, and increasing survival of preterm infants. The greatest increase has occurred in mildly affected patients, many of whom have a eutopic thyroid gland. Congenital hypothyroidism may be transient or persistent, but the natural history cannot be predicted by severity at diagnosis. In premature infants, who are especially vulnerable to hypothyroidism, the rise in thyroid-stimulating hormone may be delayed and therefore detected only by routine follow-up screening. Recent studies of defects in thyroid hormone synthesis have focused on the role of mutations in the dual oxidase system and of a novel apical iodide transporter, anoctamin 1. Finally, emerging data suggest that exposure to excess thyroid hormone may be as harmful as hypothyroidism to long-term cognitive development.

SUMMARY

Although newborn screening has virtually eradicated mental retardation due to congenital hypothyroidism in parts of the world, new information continues to accumulate and new questions to arise about the diagnosis, physiology, and optimal management of this disorder.

Novel genetic variants in the TPO gene cause congenital hypothyroidism

BACKGROUND

Mutations in the dual oxidase maturation factor 2 (DUOXA2) and thyroid peroxidase (TPO) genes have been reported to cause goitrous congenital hypothyroidism (GCH). The aim of this study was to determine the genetic basis of GCH in affected children.

METHODS

Thirty children with GCH were enrolled for molecular analysis of the DUOXA2 and TPO genes. All subjects underwent clinical examination and laboratory testing. Genomic DNA was extracted from peripheral blood leukocytes, and Sanger sequencing was used to screen for DUOXA2 and TPO gene mutations in the exon fragments amplified from the extracted DNA. Family members of those patients with mutations were also enrolled and evaluated.

RESULTS

Analysis of the TPO gene revealed six genetic variants, including two novel heterozygous mutations, c.1970T> C (p.I657T) and c.2665G> T (p.G889X), and four mutations that have been reported previously (c.670_672del, c.2268dup, c.2266T> C and c.2647C> T). Three patients harbored the same mutation c.2268dup. The germline mutations from four unrelated families were consistent with an autosomal recessive inheritance pattern. Conversely, no mutations in the DUOXA2 gene were detected.

CONCLUSION

Two novel inactivating mutations (c.1970T> C and c.2665G> T) in the TPO gene were identified. The c.2268dup mutation occurred frequently. No mutations in the DUOXA2 gene were detected in this study.

The changing epidemiology of congenital hypothyroidism: fact or artifact?

Screening increases prevalence estimates for most diseases and congenital hypothyroidism (CH) is no exception, affecting one in 6700 children by clinical ascertainment and one in 3500 in the first surveys of systematic biochemical screening of newborns. Importantly, screening has resulted in the disappearance of intellectual disability due to CH. A further doubling in prevalence estimates has recently been reported, mostly accounted for by changes in screening algorithms; accordingly, the prevalence of overt CH has remained stable. Population-based registries that distinguish confirmed diagnoses from positive screening results have proved invaluable. These registries should include: etiology of CH based on imaging, ideally technetium scintigraphy; ethnicity; socio-educational data; input from the screening laboratories and pediatric endocrinologists. Efforts should now be directed at increasing the proportion of the world's newborns screened for overt CH (currently 30%) and at determining if neonates with mild hyperthyrotropinemia also benefit from early treatment.