Increased risk for non-autoimmune hypothyroidism in young patients with congenital heart defects

Hypothyroidism in Patients with Down Syndrome: Prevalence and Association with Congenital Heart Defects

This population-based study aimed to assess the prevalence of congenital hypothyroidism (CH) and overt hypothyroidism (OH) and their association with congenital heart defects (CHDs) in patients with Down syndrome (DS). The population included all live births residing in Tuscany (Italy) diagnosed with DS recorded in the Registry of Congenital Defects and in the Registry of Rare Diseases of Tuscany in the years 2003-2017. The prevalence of CH and OH in DS patients was calculated by sex and by period. The association of CH and OH with CHDs in DS patients was assessed using multivariate logistic regression. The cohort included 228 subjects. The prevalence of CH and OH was 11.4% (95%CI: 7.4-16.7%) and 12.7% (95%CI: 8.5-12.3%), respectively, with no significant difference by sex. A significant increase in the prevalence of CH (p < 0.0001) was found in the years 2010-2017 compared to the previous period, and among preterm infants (p = 0.009). The presence of CH was associated with a higher prevalence of CHDs (adjusted OR = 2.24, p = 0.082). A significant association between ventricular septal defects (VSDs) and the occurrence of OH (adjusted OR = 3.07, p = 0.025) was also observed. This study confirmed the higher prevalence of both CH and OH in DS compared to the general population. Furthermore, the risk of association between DS and CHDs was higher in the presence of CH, while VSDs are associated with OH, providing relevant insights into the epidemiology of hypothyroidism in DS and associated anomalies.

High Time to Consider the Role of Thyroid Function in Single Ventricle Heart Disease

Herein we respond to the controversial United States Food and Drug Administration (FDA) recommendation to perform thyroid function testing in children up to 3 years of age within 3 weeks of exposure to iodinated contrast media (ICM). Considering the many effects of thyroid hormone on the cardiovascular system, the increased risk of thyroid disease in patients with congenital heart disease, the hemodynamic consequences of the Fontan circulation on the thyroid gland, and the potential clinical significance of subclinical hypothyroidism, we share our perspective that the cardiovascular effects of thyroid hormone may carry more influence for patients with single ventricle heart disease. In our opinion, the FDA statement prompts us to consider routine thyroid hormone surveillance testing in the long-term management of patients with single ventricle heart disease.

Prospective study of thyroid function in the first year of life in infants with Down syndrome

Current American Academy of Pediatrics (AAP) Guidelines recommend monitoring thyroid function in infants with Down syndrome (DS) at birth, 6 and 12 months, and annually thereafter. This study aimed to determine whether these guidelines are optimal for early diagnosis and treatment of (subclinical) hypothyroidism. Enrolled infants with DS less than age 7 months, born at ≥ 30 weeks gestation to monitor thyroid function test (TFT). A filter paper (FP) blood sample was analyzed for TSH and total T4 at ages 2 and 4 weeks and monthly thereafter until 12 months. Subjects with abnormal FP sample and confirmatory serum TFT for hypothyroidism promptly started treatment. Subjects with thyroid dysfunction identified had thyroid antibodies measured at diagnosis and 12 months. Descriptive statistics determined average time to diagnosis of abnormal TFT. Sixteen (30%) of 54 subjects were diagnosed with a thyroid disorder, the majority with subclinical hypothyroidism (SH) and 1 with hyperthyroidism. Diagnosis occurred in 6 (11%), 9 (17%), and 12 (22.2%) infants in the first 30, 60, and 90 days of life (DOL), respectively. Eight infants had an abnormal NBS and half were diagnosed with a thyroid disorder by DOL 8 and the remainder prior to 4 months. Among subjects with a normal NBS, four were diagnosed at a mean of 104 days and three at a mean of 101 days prior to the 6-month and 12-month routine screens, respectively.  Conclusion: Based on current AAP guidelines, thyroid disorder diagnosis would have been delayed in nearly 20% of the subjects. An additional TFT screen at 1 and 3 months can lead to earlier diagnosis and treatment. What is Known: • Current American Academy of Pediatrics (AAP) Guidelines recommend thyroid function tests (TFT) in infants with Down syndrome (DS) at birth and 6 and 12 months. • Peer- reviewed retrospective studies report an increased incidence of hypothyroidism in infants with DS undetected by the newborn screen (NBS) and prior to 6 months. What is New: • This prospective study monitored TFT in infants with DS at age 2 weeks and monthly throughout the first year of life. • The findings in this study support additional TFT screens at 1 and 3 months in infants with DS.

Approach to the Patient With Congenital Hypothyroidism

Congenital hypothyroidism (CH) is the most frequent neonatal endocrine disorder and the most common preventable cause of development delay and growth failure if diagnosed and treated early. The thyroid is the first endocrine gland to develop during embryonic life and to be recognizable in humans. Thyroid development and maturation can be divided into 2 phases: a first phase of embryogenesis and a second phase of folliculogenesis and differentiation with thyroid hormone production at the final steps. Regulation of the thyroid function requires normal development of the hypothalamic-pituitary-thyroid axis, which occurs during the embryonic and neonatal period. Defects in any of steps of thyroid development, differentiation, and regulation lead to permanent CH. Newborn screening programs, established in only one-third of countries worldwide, detect CH and are cost-effective and highly sensitive and specific. During the last decade, epidemiology of CH has changed with increased frequency of thyroid in situ in primary CH. Advances in molecular testing have expanded knowledge and understanding of thyroid development and function. However, a molecular cause is identified in only 5% of CH due to thyroid dysgenesis. The purpose of this article is to describe the clinical approach to the child with CH, focusing on diagnostic work-up and future challenges on optimizing thyroid replacement therapy and regenerative medicine. The review is written from the perspective of the case of 2 girls referred for CH after newborn screening and diagnosed with thyroid ectopy. The genetic work-up revealed novel mutations in TUBB1 gene, associated with large platelets and abnormal platelet physiology.

Genetics of congenital hypothyroidism: Modern concepts

Congenital hypothyroidism (CH) is the most common neonatal endocrine disorder and one of the most common preventable causes of intellectual disability in the world. CH may be due to developmental or functional thyroid defects (primary or peripheral CH) or be hypothalamic‐pituitary in origin (central CH). In most cases, primary CH is caused by a developmental malformation of the gland (thyroid dysgenesis, TD) or by a defect in thyroid hormones synthesis (dyshormonogenesis, DH). TD represents about 65% of CH and a genetic cause is currently identified in fewer than 5% of patients. The remaining 35% are cases of DH and are explained with certainty at the molecular level in more than 50% of cases. The etiology of CH is mostly unknown and may include contributions from individual and environmental factors. In recent years, the detailed phenotypic description of patients, high‐throughput sequencing technologies, and the use of animal models have made it possible to discover new genes involved in the development or function of the thyroid gland. This paper reviews all the genetic causes of CH. The modes by which CH is transmitted will also be discussed, including a new oligogenic model. CH is no longer simply a dominant disease for cases of CH due to TD and recessive for cases of CH due to DH, but a far more complex disorder.

[Genetic of congenital hypothyroidism]

Congenital hypothyroidism (CH) is the most frequent neonatal endocrine disorder. CH is due to thyroid development or thyroid function defects (primary) or may be of hypothalamic-pituitary origin (central). Primary CH is caused essentially by abnormal thyroid gland morphogenesis (thyroid dysgenesis, TD) or defective thyroid hormone synthesis (dyshormonogenesis, DH). DH accounts for about 35% of CH and a genetic cause is identified in 50% of patients. However, TD accounts for about 65% of CH, and a genetic cause is identified in less than 5% of patients. The pathogenesis of CH is largely unknown and may include the contribution of individual and environmental factors. During the last years, detailed phenotypic description of patients, next-generation sequence technologies and use of animal models allowed the discovery of novel candidate genes in thyroid development and function. We provide an overview of recent genetic causes of primary and central CH. In addition, mode of inheritance and the oligogenic model of CH are discussed.

Targeted Secondary Screening for Congenital Hypothyroidism in High-Risk Neonates: A 9 Year Review in a Large California Health Care System

Secondary screening for missed congenital hypothyroidism (CH) has been introduced sporadically, but its necessity and optimal strategy have not been recognized. We hypothesized that a simple clinical protocol (performed by a medical group without a governmental mandate) targeting infants at high risk for missed CH can identify cases. We performed a 9-year retrospective review of 338,478 neonates within a California health plan following the introduction of thyrotropin (TSH) secondary screening for neonates at high risk for missed CH due to very-low-birthweight (VLBW), hospitalized congenital heart disease (CHD), and same-sex multiples (SSM). Screening performance by day 60 of life was 95% successful for VLBW and >50% for CHD and SSM, leading to an additional 35% CH treated cases despite re-testing only 1.7% of the cohort. Infants with VLBW or CHD were 33 times more likely (190 times more likely for CHD with Down Syndrome) to receive treatment for CH than random infants diagnosed by primary screening (p < 0.001), and 92% of these infants were not found by primary newborn screening. Currently, permanent disease has been documented in 84% of CH by primary screening compared to 27% by secondary screening (p < 0.001). This targeted secondary screening program identifies and treats additional CH cases after TSH-only newborn screening.

Primary thyroid dysfunction after single intravenous iodinated contrast exposure in young children: a propensity score matched analysis

BACKGROUND

Data suggest an increased risk of thyroid dysfunction following iodine-based contrast material (IBCM) in children.

OBJECTIVE

To estimate the prevalence of thyroid stimulating hormone (TSH) abnormalities following exposure to a single dose of intravenous IBCM during computed tomography (CT) in young children.

MATERIALS AND METHODS

Inpatients ≤24 months of age who underwent a single CT with intravenous IBCM (exposed cohort) or abdominal ultrasound (US) (unexposed cohort) examination and had a TSH value obtained within 90 days after imaging between January 2009 to November 2018 were identified. Propensity score matching with 20 variables was performed. Primary thyroid dysfunction was defined by abnormally high or low TSH value. Multivariable logistic regression identified risk factors, including intravenous IBCM, for thyroid dysfunction.

RESULTS

From the eligible 4,215 imaging examinations, 114 unique patients were included in the propensity matched population (n=57 per group). Thyroid dysfunction was identified in 14% (8/57) and 7% (4/57) of the IBCM-exposed and IBCM-unexposed cohorts, respectively. No patient in either cohort was started on thyroid hormone supplementation within the 3 months after imaging. Intravenous IBCM exposure was not a significant predictor of thyroid dysfunction on univariable (odds ratio [OR]=2.16, 95% confidence interval [CI]=0.61-7.64, P=0.23) or multivariable (OR=2.61, 95% CI=0.65-10.55, P=0.18) analyses. Significant independent predictors of post-imaging thyroid dysfunction included height (OR=1.25, P=0.0095) and trisomy 21 (OR=4.04, P=0.019).

CONCLUSION

Hospitalized children ≤24 months of age who received a single dose of intravenous IBCM for CT examination had a similar prevalence of TSH abnormalities compared to a propensity score matched group who underwent abdominal US. One dose of intravenous IBCM likely does not cause prolonged TSH abnormalities; however, larger studies are needed.

New genetics in congenital hypothyroidism

INTRODUCTION

Congenital hypothyroidism (CH) is the most frequent neonatal endocrine disorder and one of the most common preventable forms of mental retardation worldwide. CH is due to thyroid development or thyroid function defects (primary) or may be of hypothalamic-pituitary origin (central). Primary CH is caused essentially by abnormal thyroid gland morphogenesis (thyroid dysgenesis, TD) or defective thyroid hormone synthesis (dyshormonogenesis, DH). TD accounts for about 65% of CH, however a genetic cause is identified in less than 5% of patients.

PURPOSE

The pathogenesis of CH is largely unknown and may include the contribution of individual and environmental factors. During the last years, detailed phenotypic description of patients, next-generation sequence technologies and use of animal models allowed the discovery of novel candidate genes in thyroid development, function and pathways.

RESULTS AND CONCLUSION

We provide an overview of recent genetic causes of primary and central CH. In addition, mode of inheritance and the oligogenic model of CH are discussed.

A prospective randomized clinical study of perioperative oral thyroid hormone treatment for children undergoing surgery for congenital heart diseases

Context :

Thyroid hormone deficiency is known to occur after cardiac surgery and known as nonthyroid illness (NTI). The beneficial role of perioperative thyroid hormone supplementation in children has been debatable more so with oral supplementation.

Aims :

The aim is to evaluate the role of pre-operative oral thyroid hormone therapy in preventing NTI. To assess its effect on post-operative thyroid hormone levels, hemodynamic parameters, and cardiac function of infants and small children undergoing pediatric cardiac surgery.

Settings and Design :

Prospective randomized, double-blinded controlled trial at a tertiary level pediatric cardiothoracic center.

Materials and Methods :

Sixty-five children aged under 18 months undergoing corrective surgeries on cardiopulmonary bypass were included. Patients were randomized into two equal groups: placebo group (given placebo) and thyroxine group (given thyroxine tablet 10 μg/kg) orally once a day starting on the preoperative evening till the fifth postoperative day. The postoperative hemodynamics, inotropic requirement, ventilatory requirement, and cardiac function on echocardiography were observed.

Statistical Tests :

Shapiro–Wilk test, Mann–Whitney/t-test, Chi-square test, ANOVA with Tukey correction were used.

Results:

Serum triiodothyronine and thyroxine levels postoperatively were significantly higher in the thyroxine group than in the placebo group. There was no significant difference in left ventricular ejection fraction, hemodynamic variables, extubation time, and length of intensive care unit (ICU) stay between the two groups.

Conclusions:

In infants and small children undergoing corrective cardiac surgery, perioperative oral thyroid hormone therapy reduces the severity of postoperative NTI. It increases the serum level of thyroid hormones but the therapy does not translate to better hemodynamics, reduced inotropic requirement, reduced ventilatory requirement, improved myocardial function or reduced ICU stay when compared to placebo.

General management of pulmonary arterial hypertension associated with adult congenital heart disease

Over the past 15 years there have been significant improvements in the treatment of pulmonary arterial hypertension due to congenital heart disease. Patients now live for several decades, but morbidity and mortality remain high. This article describes the holistic management of this patient group with an emphasis on both the physical and psychosocial aspects of care, taking into account the consequences of chronic cyanosis, avoiding complications and improving quality of life.

Congenital Heart Disease and Thyroid Dysfunction: Combination, Association, and Implication

BACKGROUND

Patients with congenital heart disease have higher prevalence of thyroid dysfunction due to embryonic and genetic coexistence. Marked changes in cardiac function occur secondary to alternations in thyroid hormone levels. Cardiac catheterizations or cardiac surgeries with cardiopulmonary bypass can cause abnormalities in the circulating hormones, in the absence of primary thyroid disease. Therefore, monitoring of thyroid function should be routinely performed in children with congenital heart disease. Thyroid hormone supplementation has been postulated as a possible therapeutic option; however, the therapeutic decisions should be made based on individual circumstances, symptoms, and the severity of the thyroid dysfunction.

OBJECTIVES

To describe the correlation between congenital heart disease in children and thyroid dysfunction and the debate on monitoring, intervention, and treatment.

METHODS

PubMed, Clinical Key, and the Cochrane Library were searched using keywords relevant to congenital heart disease/surgery, cardiopulmonary bypass, thyroid hormones, sick euthyroid syndrome, and cardiac catheterization. Studies were limited to the English language and to children 0 to 18 years old. Studies in adults with important findings were reviewed as well. All clinical studies believed to have relevance were considered. All relevant studies were reviewed, and the most pertinent data were incorporated in this review.

CONCLUSION

There is lack of significant evidence concerning treatment for thyroid dysfunction in children with a congenital cardiac diagnosis. Adequately powered studies are needed before a uniform recommendation about treatment can be made.

Maternal Graves’ disease and fetal tetralogy of Fallot: a case series

Background

Congenital heart defects have been reported with the use of antithyroid medication with ventricular septal defects (VSD) being the most common. As per the current practice guidelines maternal Graves’ disease (GD) is not an indication for fetal echocardiogram.

Case presentation

We described three neonates with tetralogy of Fallot (TOF) born to mothers with GD. Only one of the mothers was on antithyroid medication. Two of these neonates were diagnosed postnatally when they failed the pulse oximeter congenital cardiac screening and diagnosis was established by postnatal echocardiogram. Two of the mothers had radioactive iodine ablation and were on levothyroxine during pregnancy. The dose of levothyroxine was increased during pregnancy. There was no other complication during pregnancy. The third mother had hyperthyroidism and developed a thyroid storm during pregnancy requiring inpatient admission and treatment with propylthiouracil (PTU), metoprolol and methimazole. All babies had normal thyroid function test postnatally and eventually had successful repair of TOF defect.

Conclusion

We report the largest known case series of children with TOF born to mothers with GD. Apart from the isolated reports of fetal TOF in mothers with GD, there is no clear association between fetal TOF and maternal GD and antithyroid medication. Based on the review of the literature and our case series, there may be an increased incidence of congenital heart defects in maternal GD irrespective of antithyroid medication use. This case series may add to the current knowledge base and support routine fetal echocardiogram screening for all mothers with GD.

Expression, function, and regulation of the embryonic transcription factor TBX1 in parathyroid tumors

Transcription factors active in embryonic parathyroid cells can be maintained in adult parathyroids and be involved in tumorigenesis. TBX1, the candidate gene of 22q11.2-DiGeorge syndrome, which includes congenital hypoparathyroidism, is involved in parathyroid embryogenesis. The study aimed to investigate expression, function, and regulation of the parathyroid embryonic transcription factor TBX1 in human parathyroid adult normal and tumor tissues. TBX1 transcripts were detected in normal parathyroids and were deregulated in parathyroid tumors. Using immunohistochemistry, TBX1 protein was detected, mainly at the nuclear level, in a consistent proportion of cells in normal adult parathyroids, whereas TBX1 immunoreactivity was absent in fetal parathyroids. TBX1-expressing cells were markedly reduced in about a half of adenomas (PAds) and two-thirds of carcinomas and the proportion of TBX1-expressing cells negatively correlated with the serum albumin-corrected calcium levels in the analyzed tumors. Moreover, a subset of TBX1-expressing tumor cells coexpressed PTH. TBX1 silencing in HEK293 cells, expressing endogenous TBX1, increased the proportion of cells in the G0/G1 phase of cell cycle; concomitantly, CDKN1A/p21 and CDKN2A/p16 transcripts increased and ID1 mRNA levels decreased. TBX1 silencing exerted similar effects in PAd-derived cells, suggesting cell cycle arrest. Moreover, in PAd-derived cells GCM2 and PTH mRNA levels were unaffected by TBX1 deficiency, whereas it was associated with reduction of WNT5A, an antagonist of canonical WNT/β-catenin pathway. WNT/β-catenin activation by lithium chloride inhibited TBX1 expression levels both in HEK293 and PAd-derived cells. In conclusion, TBX1 is expressed in adult parathyroid cells and deregulated in parathyroid tumors, where TBX1 deficiency may potentially contribute to the low proliferative nature of parathyroid tumors.

Clinical course of infants with congenital heart disease who developed thyroid dysfunction within 100 days

PURPOSE

We investigated the clinical course of infants with congenital heart disease (CHD) who experienced thyroid dysfunction within 100 days of birth.

METHODS

We performed retrospective medical reviews of 54 CHD patients (24 male patients) who underwent a thyroid function test (TFT) between January 2007 and July 2016. Data were collected on birth history, diagnosis of CHD, underlying chromosomal or genetic abnormalities, medication history, surgery, ventilator care, and exposure to iodine contrast media (ICM). Results of neonatal screening tests (NSTs) and TFTs were reviewed.

RESULTS

A total of 36 patients (29 transient, 7 permanent) showed thyroid dysfunction. Among the seven patients with permanent hypothyroidism, three had an underlying syndrome, three showed abnormal NST results, and one was admitted to the intensive care unit for macroglossia and feeding cyanosis. We found that infants with transient thyroid dysfunction had a lower birth weight and were more commonly exposed to thyroid disrupting medication and/or ICM. However, these risk factors were not significant. A total of 8 patients with a history of ICM exposure showed thyroid dysfunction. Excluding 3 patients with elevated thyroid stimulating hormone before ICM exposure, 5 patients recovered from transient thyroid dysfunction.

CONCLUSIONS

We observed thyroid dysfunction in two-thirds of CHD infants (53.7% transient, 13.0% permanent) who had risk factors and received TFT screening within 100 days, despite normal NSTs. Further studies with larger sample sizes are required to revise the criteria for TFT screening in CHD infants.

Thyroid Hemiagenesis: Incidence, Clinical Significance, and Genetic Background

CONTEXT

Thyroid hemiagenesis (THA) constitutes a rare, congenital disorder that is characterized by an absence of one thyroid lobe. Because the pathogenesis and clinical significance of this malformation remain undefined, specific clinical recommendations are lacking, especially for asymptomatic cases.

EVIDENCE ACQUISITION

The PubMed database was searched (years 1970 to 2017), and the following terms were used to retrieve the results: "thyroid hemiagenesis," "thyroid hemiaplasia," "one thyroid lobe agenesis," and "one thyroid lobe aplasia." Subsequently, reference sections of the retrieved articles were searched.

EVIDENCE SYNTHESIS

There is a noticeable susceptibility of subjects with THA to develop additional thyroid and nonthyroidal pathologies. In pathogenesis of concomitant thyroid pathologies, a chronic elevation in thyroid-stimulating hormone values may play an important role. Thus far, genetic studies failed to find a common genetic background of the anomaly, and the potential underlying cause was identified in a minority of the cases.

CONCLUSIONS

Patients with THA are prone to develop additional thyroid pathologies and theoretically might benefit from l-thyroxine treatment to lower the thyrotropin levels to those observed in the normal population. However, further research should be done to ascertain whether such intervention early in life would prevent development of associated thyroid conditions. At least, increased vigilance should be maintained to reveal all of the concomitant disorders as soon as possible during follow-up examinations. Application of high-throughput technologies enabling a genome-wide search for novel factors involved in thyroid embryogenesis might be the next step to expand the knowledge on THA pathogenesis.

Hypothyroidism in Infants With Congenital Heart Disease Exposed to Excess Iodine

Thyroid hormone is critical for neonatal brain development, and even transient hypothyroidism can cause adverse neurocognitive outcomes. Infants exposed to excess iodine are at risk of developing hypothyroidism, especially those with congenital heart disease (CHD), because they are routinely exposed to excess iodine from intravenous iodinated contrast media and topical antiseptics. The aim of the present study was to identify the proportion of neonates with CHD exposed to iodine who developed hypothyroidism and to identify the associated risk factors. This was a retrospective study of neonates undergoing cardiac catheterization at Boston Children's Hospital during a 3-year period, some of whom also underwent cardiac surgery. Hypothyroidism was defined as an elevated thyroid-stimulating hormone level (>20 mIU/L at 24 to 96 hours of age and >15 mIU/L at >96 hours of age by heel-stick sampling and >9.1 mIU/L at 1 to 20 weeks of age by serum testing). Multivariate logistic regression was performed to predict the odds of developing hypothyroidism. Hypothyroidism was diagnosed incidentally in 46 of 183 infants (25%) with CHD after iodine exposure. Controlling for baseline cardiac risk, postnatal age, and gestational age, we found a fourfold increase in odds of developing hypothyroidism in neonates with serum creatinine >0.9 mg/dL and a fourfold increase in those who underwent more than three procedures. Hypothyroidism in neonates with CHD exposed to excess iodine is associated with multiple procedures and impaired renal function. Routine serial monitoring of thyroid function in these neonates is warranted. Future studies should examine the association between hypothyroidism and neurocognitive function in this population.

Disorders of thyroid morphogenesis

Developmental anomalies of the thyroid gland, defined as thyroid dysgenesis, underlie the majority of cases of congenital hypothyroidism. Thyroid dysgenesis is predominantly a sporadic disorder although a reported familial enrichment, variation of incidence by ethnicity and the monogenic defects associated mainly with athyreosis or orthotopic thyroid hypoplasia, suggest a genetic contribution. Of note, the most common developmental anomaly, thyroid ectopy, remains unexplained. Ectopy may result from multiple genetic or epigenetic variants in the germline and/or at the somatic level. This review provides a brief overview of the monogenic defects in candidate genes that have been identified so far and of the syndromes which are known to be associated with thyroid dysgenesis.

Hypothyroidism associated with parathyroid disorders

Hypothyroidism may occur in association with congenital parathyroid disorders determining parathyroid hormone insufficiency, which is characterized by hypocalcemia and concomitant inappropriately low secretion of parathormone (PTH). The association is often due to loss of function of genes common to thyroid and parathyroid glands embryonic development. Hypothyroidism associated with hypoparathyroidism is generally mild and not associated with goiter; moreover, it is usually part of a multisystemic involvement not restricted to endocrine function as occurs in patients with 22q11 microdeletion/DiGeorge syndrome, the most frequent disorders. Hypothyroidism and hypoparathyroidism may also follow endocrine glands' damages due to autoimmunity or chronic iron overload in thalassemic disorders, both genetically determined conditions. Finally, besides PTH deficiency, hypocalcemia can be due to PTH resistance in pseudohypoparathyroidism; when hormone resistance is generalized, patients can suffer from hypothyroidism due to TSH resistance. In evaluating patients with hypothyroidism and hypocalcemia, physical examination and clinical history are essential to drive the diagnostic process, while routine genetic screening is not recommended.

Endocrinologic Diseases in Pediatric Cardiac Intensive Care

OBJECTIVES

The objectives of this review are to discuss the pathophysiology, clinical impact and treatment of hyperglycemia, and disturbances in thyroid and adrenal function prior to and following cardiac surgery in children.

DATA SOURCE

MEDLINE and PubMed.

CONCLUSIONS

Disturbances in glucose metabolism and thyroid and adrenal function are common in critically ill children with cardiac disease and in particular in children undergoing cardiac surgery for complex congenital heart disease. An understanding of the pathophysiology, clinical impact and treatment of these disturbances is essential for the management of these at risk patients.

Pediatric Cardiac Intensive Care Society 2014 Consensus Statement: Pharmacotherapies in Cardiac Critical Care Hormone Replacement Therapy

OBJECTIVE

To provide an overview of the current literature on the use of hormone replacement therapies in pediatric cardiac critical care.

DATA SOURCES

PubMed, EMBASE, and the Cochrane Library were searched using keywords relevant to the hormonal therapy, with no limits on language but restricting the search to children 0-18 years old.

STUDY SELECTION

All clinical studies believed to have relevance were considered. Where studies in children were sparse, additional evidence was sought from adult studies.

DATA EXTRACTION

All relevant studies were reviewed, and the most relevant data were incorporated in this review.

DATA SYNTHESIS

All authors of this review contributed to the appraisal of the data extracted. Challenges and revisions by the authors were conducted by group e-mail debate.

CONCLUSIONS

Glycemic control: although it is likely that some children could benefit, the routine use of tight glycemic control cannot be recommended in children after cardiac surgery. Thyroid hormone replacement: routine use of thyroid hormone replacement to normalize levels after cardiac surgery cannot be recommended on current evidence. Until further evidence from adequately powered studies is available, therapeutic decisions should be based on individual patient circumstances. Corticosteroids: 1) cardiopulmonary bypass: although studies seem to favor steroid administration during surgery with cardiopulmonary bypass, a large randomized controlled trial is required before strong recommendations can be made; 2) refractory hypotension: the evidence for the use of steroid replacement in refractory hypotension is poor, and no firm recommendations can be made; and 3) abnormal adrenal function after cardiac surgery: there is inadequate evidence on which to make recommendations on the use of corticosteroid replacement in children with critical illness-related corticosteroid insufficiency in children following cardiac surgery.

Iodine-induced hypothyroidism in full-term infants with congenital heart disease: more common than currently appreciated?

CONTEXT

Iodine is a micronutrient essential for thyroid hormone synthesis. Thyroid hormone is critical for normal neurocognitive development in young infants, and even transient hypothyroidism can cause adverse neurodevelopmental outcomes. Both iodine deficiency and excess can cause hypothyroidism. Although iodine-induced hypothyroidism is well recognized in premature infants, full-term neonates have received less attention. Infants with congenital heart disease (CHD) are commonly exposed to excess iodine from administration of iodinated contrast agents during cardiac catheterization as well as topical application of iodine-containing antiseptics and dressings; hence, this is a vulnerable population.

OBJECTIVE

We report three cases of iodine-induced hypothyroidism in full-term neonates with CHD after cardiac angiography and topical application of iodine-containing antiseptics and dressings in the operative setting.

RESULTS

Three neonates with CHD and normal thyroid function at birth developed hypothyroidism after exposure to excess iodine. Two of these infants had transient hypothyroidism, and one had severe hypothyroidism requiring ongoing thyroid replacement therapy. All infants were asymptomatic, with hypothyroidism detected incidentally in the inpatient setting due to repeat newborn screening mandated by the long duration of hospitalization in these infants.

CONCLUSIONS

Iodine-induced hypothyroidism may be under-recognized in infants with CHD exposed to excess iodine. Systematic monitoring of thyroid function should be considered to avoid potential long-term adverse neurodevelopmental effects of even transient thyroid dysfunction in this susceptible population.

Genetics of normal and abnormal thyroid development in humans

The most frequent cause of congenital hypothyroidism is thyroid dysgenesis. Thyroid dysgenesis summarizes a spectrum of developmental abnormalities of the embryonic thyroid ranging from complete absence of the thyroid gland (athyreosis), to a normally located but too small thyroid (hypoplasia), or an abnormally located thyroid gland (ectopy). Although considered a sporadic disease, distinct genetic forms of isolated or syndromic thyroid dysgenesis have been described in recent years. However, genetics of thyroid dysgenesis (TD) are mostly not following simple Mendelian patterns, and beside monogenic, multigenic and epigenetic mechanisms need to be considered. The review will highlight the molecular mechanisms of thyroid organogenesis, clinical and genetic features of the different monogenetic forms of thyroid dysgenesis, the aspects relevant for diagnosis and counseling of affected families and current research strategies to get more insight into the non-Medelian mechanisms of normal and abnormal thyroid development.

Common endocrine issues in the pediatric intensive care unit

Thyroid hormone is central to normal development and metabolism. Abnormalities in thyroid function in North America often arise from autoimmune diseases, but they rarely present as critical illness. Severe deficiency or excess of thyroid hormone both represent life-threatening disease, which must be treated expeditiously and thoroughly. Such deficiencies must be considered, because presentation may be nonspecific.

The ambiguous role of NKX2-5 mutations in thyroid dysgenesis

NKX2-5 is a homeodomain-containing transcription factor implied in both heart and thyroid development. Numerous mutations in NKX2-5 have been reported in individuals with congenital heart disease (CHD), but recently a select few have been associated with thyroid dysgenesis, among which the p.A119S variation. We sequenced NKX2-5 in 303 sporadic CHD patients and 38 families with at least two individuals with CHD. The p.A119S variation was identified in two unrelated patients: one was found in the proband of a family with four affected individuals with CHD and the other in a sporadic CHD patient. Clinical evaluation of heart and thyroid showed that the mutation did not segregate with CHD in the familial case, nor did any of the seven mutation carriers have thyroid abnormalities. We tested the functional consequences of the p.A119S variation in a cellular context by performing transactivation assays with promoters relevant for both heart and thyroid development in rat heart derived H10 cells and HELA cells. There was no difference between wildtype NKX2-5 and p.A119S NKX2-5 in activation of the investigated promoters in both cell lines. Additionally, we reviewed the current literature on the topic, showing that there is no clear evidence for a major pathogenic role of NKX2-5 mutations in thyroid dysgenesis. In conclusion, our study demonstrates that p.A119S does not cause CHD or TD and that it is a rare variation that behaves equal to wildtype NKX2-5. Furthermore, given the wealth of published evidence, we suggest that NKX2-5 mutations do not play a major pathogenic role in thyroid dysgenesis, and that genetic testing of NKX2-5 in TD is not warranted.