Outcome in three siblings with antibody-mediated transient congenital hypothyroidism

Severe Acquired Hypothyroidism and Van Wyk-Grumbach Syndrome in Two Children

The primary manifestations of chronic hypothyroidism in children include growth arrest, delayed skeletal maturity, and delayed puberty. In 1960, Van Wyk and Grumbach reported three girls with hypothyroidism and a combination of incomplete isosexual precocious puberty (early breast development, menstruation, and absence of pubic hair), galactorrhea, delayed bone age, and pituitary enlargement. All abnormalities regressed after appropriate thyroid hormone replacement therapy. Over the years, an increasing number of reported cases has allowed for a more precise understanding of the clinical, biochemical, and radiological phenotypes of the Van Wyk-Grumbach syndrome (VWGS). These varying clinical manifestations are thought to result from a unique pathophysiological process where the thyroid-stimulating hormone (TSH) is a key element. We describe the cases of two patients (a boy and a girl) with severe autoimmune thyroiditis and VWGS. The clinical, biochemical, and radiological imaging characteristics were similar in both patients and included growth failure, absence of clinical goiter, markedly elevated TSH concentrations >100 mIU/L, undetectable free thyroxine levels, "normal" thyroglobulin levels, high follicle-stimulating hormone (FSH) and prolactin levels, prepubertal levels of luteinizing hormone (LH), delayed bone age, and hyperplasia of the pituitary gland. The two patients displayed differences, especially in the absence of clinical pubertal development, moderate anemia, abnormal renal function, and moderate goiter detected via ultrasonography (in the female patient). Thyroxine replacement therapy reversed the VWGS phenotype and hypothyroidism, with satisfactory growth velocity, strictly normal thyroid function, and normal pituitary size detected via magnetic resonance imaging at the 6-month follow-up visit.

Congenital Anomalies in Infant With Congenital Hypothyroidism: A Review of Pathogenesis, Diagnostic Options, and Management Protocols

Thyroid hormones (TH) regulate growth, nervous system myelination, metabolism, and physiologic functions in nearly every organ system. Congenital hypothyroidism (CH) is one of the most common endocrinopathies in children and has potentially devastating neurologic and developmental consequences. The etiology and clinical manifestations of hypothyroidism in children differ from adults. And hence, pediatric medical care requires a detailed understanding of thyroid function and dysfunction in children. The perinatal risk factors include female sex, preterm birth, low birth weight, postmature birth, additional birth abnormalities, and being delivered in multiple births. In countries where newborn screening is practiced, CH is detected after birth through screening tests. It aids in determining the underlying cause, though some patients may be able to start treatment without these tests. Early detection and treatment prevent irreversible and permanent nervous system damage. Thus, in addition to exploring the development of CH, this article has also covered the epidemiological data, clinical aspects, and management stemming from pediatric hypothyroidism.

Congenital Hypothyroidism

Congenital hypothyroidism (CH) is the commonest preventable cause of mental retardation in human species. It is so important for clinician to know its etiology epidemiology, clinical manifestation and treatment strategies. Since it is one of the rare serious diseases that should not be diagnosed clinically because late clinical features corresponds to advanced mental retardation, the neonatal screening detection is the best and preferable way of early diagnosis of this congenital disease. Confirmatory laboratory and radiological diagnostic tests should be performed immediately after the positive neonatal screening test. In order to prevent mental defects and to maintain long term clinical as well as biochemical euthyroidism in affected children its diagnosis approach, medical treatment and follow-up should be well established knowledge to all pediatricians during the childhood period and later on to general practitioners when these individuals grow up as adults. Congenital hypothyroidism is a potentially serious disease that we need to emphasize on early detection, using proper diagnostic tools and early and planned therapeutic approach.

Transient hypothyroidism in the newborn: to treat or not to treat

Transient congenital hypothyroidism (CH) refers to a temporary deficiency of thyroid hormone identified after birth, with low thyroxine (T4) and elevated thyrotropin (TSH), which later recovers to improved thyroxine production, typically in first few months of infancy. Approximately 17% to 40% of children diagnosed with CH by newborn screening (NBS) programs were later determined to have transient hypothyroidism. Causes of transient CH are prematurity, iodine deficiency, maternal thyrotropin receptor blocking antibodies, maternal intake of anti-thyroid drugs, maternal or neonatal iodine exposure, loss of function mutations and hepatic hemangiomas. The classic clinical symptoms and signs of CH are usually absent immediately after birth in vast majority of infants due to temporary protection from maternal thyroxine. NBS has been largely successful in preventing intellectual disability by early detection of CH by performing thyroid function tests in infants with abnormal screening results. In this review we present the evidence for decision making regarding treatment vs. withholding treatment in infants with transient CH and present a rational approach to identifying transient CH based on American Academy of Pediatrics (AAP) recommendation.

Central hypothyroidism

Central hypothyroidism is defined as hypothyroidism due to insufficient stimulation by thyroid stimulating hormone (TSH) of an otherwise normal thyroid gland. It has an estimated prevalence of approximately 1 in 80,000 to 1 in 120,000. It can be secondary hypothyroidism (pituitary) or tertiary hypothyroidism (hypothalamus) in origin. In children, it is usually caused by craniopharyngiomas or previous cranial irradiation for brain tumors or hematological malignancies. In adults, it is usually due to pituitary macroadenomas, pituitary surgeries or post-irradiation. Fatigue and peripheral edema are the most specific clinical features. Diagnosis is established by the presence of normal to low-normal TSH on the background of low-normal thyroid hormones, confirmed by the thyrotropin releasing hormone stimulation test. Therapy includes use of levothyroxine titrated to improvement in symptomology and keeping free T4 in the upper limit of normal reference range.

Congenital hypothyroidism

Congenital hypothyroidism (CH) occurs in approximately 1:2,000 to 1:4,000 newborns. The clinical manifestations are often subtle or not present at birth. This likely is due to trans-placental passage of some maternal thyroid hormone, while many infants have some thyroid production of their own. Common symptoms include decreased activity and increased sleep, feeding difficulty, constipation, and prolonged jaundice. On examination, common signs include myxedematous facies, large fontanels, macroglossia, a distended abdomen with umbilical hernia, and hypotonia. CH is classified into permanent and transient forms, which in turn can be divided into primary, secondary, or peripheral etiologies. Thyroid dysgenesis accounts for 85% of permanent, primary CH, while inborn errors of thyroid hormone biosynthesis (dyshormonogeneses) account for 10-15% of cases. Secondary or central CH may occur with isolated TSH deficiency, but more commonly it is associated with congenital hypopitiutarism. Transient CH most commonly occurs in preterm infants born in areas of endemic iodine deficiency. In countries with newborn screening programs in place, infants with CH are diagnosed after detection by screening tests. The diagnosis should be confirmed by finding an elevated serum TSH and low T4 or free T4 level. Other diagnostic tests, such as thyroid radionuclide uptake and scan, thyroid sonography, or serum thyroglobulin determination may help pinpoint the underlying etiology, although treatment may be started without these tests. Levothyroxine is the treatment of choice; the recommended starting dose is 10 to 15 mcg/kg/day. The immediate goals of treatment are to rapidly raise the serum T4 above 130 nmol/L (10 ug/dL) and normalize serum TSH levels. Frequent laboratory monitoring in infancy is essential to ensure optimal neurocognitive outcome. Serum TSH and free T4 should be measured every 1-2 months in the first 6 months of life and every 3-4 months thereafter. In general, the prognosis of infants detected by screening and started on treatment early is excellent, with IQs similar to sibling or classmate controls. Studies show that a lower neurocognitive outcome may occur in those infants started at a later age (> 30 days of age), on lower l-thyroxine doses than currently recommended, and in those infants with more severe hypothyroidism.

Intractable neonatal seizures: an unusual presentation of congenital hypothyroidism

Congenital hypothyroidism is the most common treatable cause of mental retardation. We report an unusual case of congenital hypothyroidism presenting as intractable seizures in an infant delivered to a mother known to have autoimmune hypothyroidism and who was noncompliant with therapy. To our knowledge, this rare presentation of congenital hypothyroidism has not been reported previously.

Assessment of thyroid function during the long course of Hashimoto's thyroiditis in children and adolescents

CONTEXT

The prognosis of Hashimoto's thyroiditis (HT) in children and adolescents is not well known and studies reporting long-term outcome of the disease are scarce.

OBJECTIVE

To assess the thyroid hormone status during long-term follow-up and to establish the prognosis of children and adolescents with HT.

PATIENTS

One hundred and twenty-nine patients with HT were re-evaluated for thyroid hormone status after a mean follow-up period of 50 months.

RESULTS

Seventy-seven per cent of the euthyroid patients were still euthyroid, while 21.1% of these patients became hypothyroid at the time of re-evaluation. However, 69.5% of hypothyroid patients remained hypothyroid (overt or subclinical) and 30.5% recovered.

CONCLUSION

HT is a dynamic process. Thyroid functions can show variation during follow-up. Therefore, thyroid function tests should be repeated periodically to detect progression to hypothyroidism in initially euthyroid patients as well as reversibility of hypothyroidism.

Treating fetal thyroid and adrenal disorders through the mother

Advances in imaging techniques and in molecular diagnosis have enabled the identification in the fetus of disorders of thyroid and adrenal function that can potentially be treated in utero through the mother. In women with Graves disease, the rare instances of autoimmune fetal hyperthyroidism can generally be treated in a noninvasive way by optimizing treatment of the mother. For fetal hypothyroidism with goiter leading to hydramnios, repeated intra-amniotic injections of thyroxine have been reported to decrease the size of the fetal thyroid, but experience is limited and the risk of premature labor is raised. In women who have previously borne a child with severe congenital adrenal hyperplasia, attempts to prevent virilization of the external genitalia of further affected female fetuses involves treatment with high doses of dexamethasone from week 7 of gestation to term, which includes the crucial period of organogenesis. Only one of every eight fetuses treated will, however, benefit from this therapy, meaning that seven are unnecessarily exposed to this potentially harmful agent. In this article, we review the rationale and evidence for efficacy of these approaches, and discuss their potential adverse effects as well as the ethical problems that they raise.

Sensory neuron sodium current requires nongenomic actions of thyroid hormone during development

Development of the embryonic nervous system requires thyroid hormone. However, the underlying mechanisms and targets of thyroid hormone action are not well defined. To identify embryonic roles for thyroid hormone we tested for effects on a key neuronal trait, voltage-gated sodium current (I(Na)), in the zebrafish model system. We recorded from Rohon-Beard sensory neurons (RBs) using whole cell voltage-clamp methods. Here, we provide in vivo evidence for thyroid hormone regulation of I(Na). Chronic thyroid hormone application increased RB peak I(Na) density 1.4-fold. However, I(Na) density showed a similar increase within 5 min of an acute hormone application, a time course not expected for a genomic mechanism. Tetraiodothyroacetic acid (tetrac), a thyroid hormone blocker, blocked both chronic and acute effects. Further, the thyroid hormone precursor thyroxine (T4) affected I(Na), yet the traditionally active form triiodothyronine did not. Consequently, we tested for a nonconventional T4 receptor. LM609, a selective antagonist of integrin alphaVbeta3, occluded the rapid effect of T4, implicating a specific integrin dimer as a T4 receptor. Chronic application of either tetrac or LM609 significantly reduced sodium conductance, demonstrating an in vivo requirement for T4-integrin regulation of I(Na). Further, removing endogenous T4 levels via yolkectomy reduced sodium conductance, an effect that was partially rescued by T4 supplementation following surgery. Because RBs mediate the embryonic touch response, we tested for behavioral effects. Tetrac and LM609 significantly reduced the percentage of touch trials eliciting a normal touch response. T4's rapid effect on RB I(Na) highlights the importance of embryonic T4 availability and nongenomic T4 signaling.

General background on the hypothalamic-pituitary-thyroid (HPT) axis

This article reviews the thyroid system, mainly from a mammalian standpoint. However, the thyroid system is highly conserved among vertebrate species, so the general information on thyroid hormone production and feedback through the hypothalamic-pituitary-thyroid (HPT) axis should be considered for all vertebrates, while species-specific differences are highlighted in the individual articles. This background article begins by outlining the HPT axis with its components and functions. For example, it describes the thyroid gland, its structure and development, how thyroid hormones are synthesized and regulated, the role of iodine in thyroid hormone synthesis, and finally how the thyroid hormones are released from the thyroid gland. It then progresses to detail areas within the thyroid system where disruption could occur or is already known to occur. It describes how thyroid hormone is transported in the serum and into the tissues on a cellular level, and how thyroid hormone is metabolized. There is an in-depth description of the alpha and beta thyroid hormone receptors and their functions, including how they are regulated, and what has been learned from the receptor knockout mouse models. The nongenomic actions of thyroid hormone are also described, such as in glucose uptake, mitochondrial effects, and its role in actin polymerization and vesicular recycling. The article discusses the concept of compensation within the HPT axis and how this fits into the paradigms that exist in thyroid toxicology/endocrinology. There is a section on thyroid hormone and its role in mammalian development: specifically, how it affects brain development when there is disruption to the maternal, the fetal, the newborn (congenital), or the infant thyroid system. Thyroid function during pregnancy is critical to normal development of the fetus, and several spontaneous mutant mouse lines are described that provide research tools to understand the mechanisms of thyroid hormone during mammalian brain development. Overall this article provides a basic understanding of the thyroid system and its components. The complexity of the thyroid system is clearly demonstrated, as are new areas of research on thyroid hormone physiology and thyroid hormone action developing within the field of thyroid endocrinology. This review provides the background necessary to review the current assays and endpoints described in the following articles for rodents, fishes, amphibians, and birds.

Risk factors of primary thyroid dysfunction in early infants born to mothers with autoimmune thyroid disease

AIM

To assess whether the state of maternal thyroid function and the pattern of thyroid alterations during gestation would affect the infants' thyroid function and to evaluate the risk factors affecting early infants' thyroid function by means of multiple logistic regression.

METHODS

In a cross-sectional study, 78 neonates born to mothers with Graves disease or Hashimoto thyroiditis were examined and followed clinically and biochemically. Neonates born to healthy mothers during the same period were set as controls. Tests of thyroid function, antithyroid peroxidase antibody (TPOAb), antithyroglobulin antibody (TGAb), anti-TSH receptor antibody (TRAb) and antithyroid-stimulating antibody (TSAb) were performed both in early infants and their mothers. All possible maternal and/or infantile risk factors for thyroid dysfunction during early infancy were analysed by means of multiple-factor logistical regression.

RESULTS

The overall prevalence of underlying subtle thyroid abnormalities in these 78 infants was 52.6%, which was significantly higher than that witnessed among infants from healthy mothers (5.4 per thousand, p<0.01). By using multiple logistic regression analysis, the state of maternal thyroid function in gestation, the type of autoimmune thyroid disease during pregnancy and the level of TRAb in the newborn were significantly correlated with the early infants' thyroid dysfunction.

CONCLUSION

Maternal autoimmune thyroid disease during pregnancy will affect infant thyroid function. Therefore, appropriate management of maternal autoimmune thyroid disease throughout pregnancy is essential in the prevention of undesirable neonatal outcomes.

Hypothetical framework for a relationship between maternal thyroid function, nausea and vomiting of pregnancy, and congenital heart disease

Our objective was to investigate whether a relationship exists among maternal thyroid function, nausea and vomiting of pregnancy, and congenital heart disease. A Medline search from 1966 to the present was conducted to look for reports on the existence of this relationship. The results were supplemented by abstract searches and personal communication with relevant authors. Our search found independent evidence that maternal hyperthyroidism is related to increased rates of nausea and vomiting of pregnancy, which in turn is significantly related to a decrease in the incidence of congenital heart disease. Early evidence indicates that the converse may be true: maternal hypothyroidism and thyroid replacement therapy are associated with an increase in congenital heart disease in children. The potential relationship between maternal thyroid function, nausea and vomiting of pregnancy, and thyroid replacement therapy needs further study. We propose a case-control study of children presenting for echocardiography to elicit specific information regarding the pregnancy.

Congenital hypothyroidism: etiologies, diagnosis, and management

Congenital hypothyroidism is a common preventable cause of mental retardation. The overall incidence is approximately 1:4000; females are affected about twice as often as males. Approximately 85% of cases are sporadic, while 15% are hereditary. The most common sporadic etiology is thyroid dysgenesis, with ectopic glands more common than aplasia or hypoplasia. While the pathogenesis of dysgenesis is largely unknown, some cases are now discovered to be the result of mutations in the transcription factors PAX-8 and TTF-2. Loss of function mutations in the thyrotropin (TSH) receptor have been demonstrated to cause some familial forms of athyreosis. The most common hereditary etiology is the inborn errors of thyroxine (T4) synthesis. Recent mutations have been described in the genes coding for the sodium/iodide symporter, thyroid peroxidase (TPO), and thyroglobulin. Transplacental passage of a maternal thyrotropin receptor blocking antibody (TRB-Ab) causes a transient form of familial congenital hypothyroidism. The vast majority of infants are now diagnosed after detection through newborn screening programs using a primary T4-backup TSH or primary TSH test. Screening test results must be confirmed by serum thyroid function tests. Thyroid scintigraphy, using 99mTc or 123I, is the most accurate diagnostic test to detect thyroid dysgenesis or one of the inborn errors of T4 synthesis. Thyroid sonography is nearly as accurate, but it may miss some cases of ectopic glands. If maternal antibody-mediated hypothyroidism is suspected, measurement of maternal and/or neonatal TRB-Ab will confirm the diagnosis. The goals of treatment are to raise the serum T4 as rapidly as possible into the normal range, adjust the levothyroxine dose with growth to keep the serum T4 (or free T4) in the upper half of the normal range and the TSH normal, and maintain normal growth and development while avoiding overtreatment. An initial starting dose of 10-15 microg/kg per day is recommended; this dose will decrease on a weight basis over time. Serum T4 (or free T4) and TSH should be monitored every 1-2 months in the first year of life and every 2-3 months in the second and third years.

A search for the possible molecular mechanisms of thyroid dysgenesis: sex ratios and associated malformations

Permanent primary congenital hypothyroidism (CH) can be caused by abnormal thyroid differentiation (athyreosis), migration (ectopy), or function (leading to goiter). Goiters follow an autosomal recessive pattern of inheritance, whereas ectopy and athyreosis are considered as a single sporadic entity with a female preponderance. On the other hand, a high prevalence of extrathyroidal malformations has been reported in CH, but without linking specific defects to specific types of CH. On the basis of TSH screening, 273 newborns were referred to an academic pediatric endocrinology clinic in the province of Quebec between 1988 and 1997. Of 230 patients with permanent primary CH who had scintigraphy at diagnosis, 141 had ectopy (104 girls), 36 had athyreosis (21 girls), 42 had goiter (18 girls), 10 (3 girls) had a normal scan, and 1 girl had hemiagenesis. Only in the ectopies was the proportion of girls significantly higher than 0.5 (P<0.001). Isolated cardiac malformations were observed in 7 patients (3.0%), a prevalence 5-fold higher than that in the general population; this was largely due to atrial and ventricular septal defects, which were only observed in ectopy and athyreosis. Our data suggest that the molecular mechanisms that lead to complete absence of thyroid differentiation or defective thyroid migration 1) may be similar, but are modulated by the genetic makeup of the embryo and/or the hormonal milieu of the fetus; and 2) may also be involved in septation of the embryonic heart.

Neonatal hypothyroidism: treatment and outcome

Systematic neonatal screening for congenital hypothyroidism (CH), which was progressively implemented in industrialized countries over the past 15 to 25 years, has been extremely successful in eradicating severe mental deficiency resulting from CH. However, in the first generation of children diagnosed by screening, the concept that CH has a threshold effect on intelligence was confirmed. In spite of earlier diagnosis through screening, children with severe CH (i.e., those with a marked retardation of bone age and/or a low circulating thyroxine [T4] before treatment) still had clinically significant intellectual sequelae, amounting to a loss of 6 to 19 IQ points. Recent studies suggest that this developmental gap may be closed by treating more rapidly after birth (2 weeks instead of 4-5 weeks in the early years of the screening era) and by using a higher initial dose of levothyroxine (10-15 instead of 5-8 microg/kg per day). This regimen induces transient hyperthyroxinemia, but no clinical signs or symptoms of hyperthyroidism. Longer term follow-up of larger numbers of patients remains necessary to confirm the normalization of intellectual development and the absence of untowards effects of the treatment regimen in children with severe CH.