Increased neonatal thyrotropin in Down syndrome

Endocrine, auxological and metabolic profile in children and adolescents with Down syndrome: from infancy to the first steps into adult life

Down syndrome (DS) is the most common chromosomal disorder worldwide. Along with intellectual disability, endocrine disorders represent a remarkable share of the morbidities experienced by children, adolescents and young adults with DS. Auxological parameters are plotted on syndrome-specific charts, as growth rates are reduced compared to healthy age- and gender-matched peers. Furthermore, children with DS are at increased risk for thyroid dysfunctions, diabetes mellitus, osteopenia and obesity compared to general population. Additionally, male individuals with DS often show infertility, while women tend to experience menopause at an overall younger age than healthy controls. Given the recent outstanding improvements in the care of severe DS-related comorbidities, infant mortality has dramatically decreased, with a current average life expectancy exceeding 60 years. Accordingly, the awareness of the specificities of DS in this field is pivotal to timely detect endocrine dysfunctions and to undertake a prompt dedicated treatment. Notably, best practices for the screening and monitoring of pediatric endocrine disorders in DS are still controversial. In addition, specific guidelines for the management of metabolic issues along the challenging period of transitioning from pediatric to adult health care are lacking. By performing a review of published literature, we highlighted the issues specifically involving children and adolescent with DS, aiming at providing clinicians with a detailed up-to-date overview of the endocrine, metabolic and auxological disorders in this selected population, with an additional focus on the management of patients in the critical phase of the transitioning from childhood to adult care.

Congenital Hypothyroidism: Screening and Management

ABSTRACT

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

Does Tonsillectomy Increase Obesity Risk in Children with Down Syndrome?

OBJECTIVES

To examine weight changes relative to surgical success in children with Down syndrome and obstructive sleep apnea (OSA).

STUDY DESIGN

Retrospective chart review of children with Down syndrome undergoing tonsillectomy from 2005 to 2016 for OSA at a tertiary care children's hospital. Only patients with pre-and postoperative polysomnogram within 6 months of tonsillectomy were included. Demographics, weight, height, and polysomnogram data were collected. Body mass index (BMI), expressed as a percentage of the 95th percentile (%BMI_p95), was calculated for 24 months prior to and following surgery. Pre-and postoperative OSA severity were also recorded. The postoperative obstructive/hypopnea index identified subjects with resolution of obstruction (obstructive/hypopnea index <2 events/hour) or persistent mild/moderate/severe obstructive apnea. Regression analyses were used to compare %BMI_p95 pre- and post-tonsillectomy with %BMI_p95 by OSA status following tonsillectomy.

RESULTS

A total of 78 patients with Down syndrome whose mean age was 5.29 years at time of tonsillectomy were identified. There was no difference between best-fit curves of %BMI _p95 pre-and post-tonsillectomy. There was no difference between best-fit curves of %BMI _p95 in patients who saw resolution of OSA after tonsillectomy vs patients with residual OSA.

CONCLUSIONS

Tonsillectomy neither alters the BMI trajectory of children with Down syndrome, nor changes differentially the risk for obesity in children whose OSA did or did not resolve after surgery.

Thyroid Disorders in Subjects with Down Syndrome: An Update

Down syndrome (DS) is the commonest chromosomal disorder among live born infants. DS is associated with increased risk of endocrine abnormalities particularly thyroid gland disorders. The spectrum of thyroid dysfunction in patients with DS include congenital hypothyroidism, subclinical hypothyroidism, acquired hypothyroidism (autoimmune - non autoimmune), and hyperthyroidism. This review will focus on the characteristics of the different presentations of thyroid abnormalities in DS, screening and management recommendations. (www.actabiomedica.it)

Down syndrome and nonautoimmune hypothyroidisms in neonates and infants

Down syndrome is characterized by a high prevalence of thyroid dysfunction during childhood. In this paper, we review the different kinds of thyroid dysfunction that occur excluding those of autoimmune origin: congenital hypothyroidism (elevated plasma TSH with low plasma T4 occurring at birth usually detected by neonatal screening), subclinical hypothyroidism (elevated plasma TSH with plasma T4 in the normal range, which can be congenital or acquired) and acquired primary hypothyroidism (elevated plasma TSH and low plasma T4 occurring after birth). These dysfunctions, while not due to autoimmunity, are of thyroidal origin. However, the mechanisms leading to these different thyroidal abnormalities have not been clearly defined; in particular, it is difficult to determine whether the different types of dysfunction have a common cause, or if the causes are distinct. Treatment is prescribed according to the type of thyroidal abnormality.

Ten-year longitudinal study of thyroid function in children with Down's syndrome

BACKGROUND/AIMS

The natural history of thyroid function in children with Down's syndrome is relatively unknown. We hypothesized that in these patients the occurrence of thyroid dysfunction rises during development.

METHODS

Thyroid function was assessed yearly in 145 children with Down's syndrome, all followed from birth up to 10 years of age. Heteroskedastic binary and ordinary logistic regression for repeated measures was used to evaluate the relationship of thyroid function with continuous time.

RESULTS

Congenital hypothyroidism was detected in 7% of cases. The probability of acquired thyroid dysfunction increased from 30% at birth to 49% at 10 years (p < 0.001). The subclinical hypothyroidism was nearly stable during the follow-up. The probability of hypothyroidism increased from 7 to 24% at 10 years (p < 0.001). Positive anti-thyroglobulin antibodies were associated with higher odds of more severe hypothyroidism (odds ratio 3.6). Positive anti-thyroid peroxidase antibodies were a better predictor of more severe hypothyroidism (odds ratio 6.1). Diffuse hypoechogenicity on thyroid ultrasound was found in 34 out of 145 children.

CONCLUSION

The probability of thyroid dysfunction increasing during development is higher than previously reported. Such children should be carefully monitored annually to early identify thyroid dysfunction.

DYRK1A BAC transgenic mouse: a new model of thyroid dysgenesis in Down syndrome

The most common thyroid abnormality among Down syndrome (DS) children corresponds to a mildly elevated TSH, with T4 decreased or in the normal range and thyroid hypoplasia, from the neonatal period onward, which aggravate their mental impairment. Transgenic Dyrk1A mice, obtained by bacterial artificial chromosome engineering (mBACTgDyrk1A), have 3 copies of the Dyrk1A gene. The objective is to determine whether this transgenic Dyrk1A (Dyrk1A(+/++)) mouse is an adequate murine model for the study of thyroid dysgenesis in DS. Embryonic thyroid development from embryonic day 13.5 (E13.5) to E17.5 was analyzed in wild-type (WT) and Dyrk1A(+/++) mice by immunofluorescence with anti-Nkx2-1, anti-thyroglobulin, and anti-T4 antibodies, markers of early thyroid development, hormonogenesis, and final differentiation, respectively. The expression of transcription factors Nkx2-1, Pax8, and Foxe1 involved in thyroidogenesis were studied by quantitative RT-PCR at the same embryonic stages. We then compared the adult phenotype at 8 to 12 weeks in Dyrk1A(+/++) and WT mice for T4 and TSH levels, thyroidal weight, and histological analysis. Regarding thyroidal development, at E15.5, Dyrk1A(+/++) thyroid lobes are double the size of WT thyroids (P = .01), but the thyroglobulin stained surface in Dyrk1A(+/++) thyroids is less than a third as large at E17.5 (P = .04) and their differentiated follicular surface half the size (P = .004). We also observed a significant increase in Nkx2-1, Foxe1, and Pax8 RNA levels in E13.5 and E17.5 Dyrk1A(+/++) embryonic thyroids. Dyrk1A(+/++) young adult mice have significantly lower plasma T4 (2.4 ng/mL versus WT, 3.7 ng/mL; P = 0.019) and nonsignificantly higher plasma TSH (114 mUI/L versus WT, 73mUI/L; P = .09). In addition, their thyroids are significantly heavier (P = .04) and exhibit large disorganized regions. Dyrk1A overexpression directly leads to thyroidal embryogenetic, functional and morphological impairment. The young adult thyroid phenotype is probably a result of embryogenetic impairment. The Dyrk1A(+/++) mouse can be considered a suitable study model for thyroid dysgenesis in DS.

Profile of hypothyroidism in Down's syndrome

OBJECTIVE

Although the association between Down's syndrome (DS) and thyroid dysfunction is well recognized, the cause of this condition is not known.

METHODS

Hospital records of patients with DS and hypothyroidism referred to our clinic were retrospectively reviewed. Initial thyroid hormone and thyrotropin (TSH) levels, age at admission, initial anthropometric measurements, age at the beginning of therapy, initial L-thyroxine (L-T4) doses, time to normalization of the thyroid function tests, and L-T4 dose at last visit were recorded. Thyroid ultrasound imaging was used to measure the size of the gland. Descriptive data were expressed as mean±SD values. Skewed data were shown as median and interquartile ranges (IQR).

RESULTS

There were 62 patients with DS (32 male and 30 female). Median TSH level at the first visit was 10.40 (19.4) µIU/mL and median free T4 level was 1.18 (0.43) ng/dL. There was no statistical difference in terms of age, hormone and antibody levels, thyroid volume and L-T4 doses between boys and girls. Thyroid volumes of 54 patients were measured. Only nine of these patients had a normal-sized thyroid gland. Median total thyroid volume was 0.89 (2.07) mL. Thyroid volume was negatively correlated to L-T4 dose at last visit (p=0.006, r=-0.387).

CONCLUSIONS

We found a high prevalence of thyroid dysgenesis in patients with DS and hypothyroidism. This association has not been reported before. Further studies investigating the thyroid gland size in these patients need to be performed to confirm the results.

Down syndrome and thyroid function

Thyroid dysfunction in children with Down syndrome (DS) can occur as early as birth. As children with DS age, their risk for thyroid autoimmunity manifested as autoimmune hypothyroidism or Graves disease increases. The optimal timing and method for thyroid screening in children with DS remains controversial. The American Academy of Pediatrics recommends annual screening in this population. Consensus is needed to establish working definitions of euthyroidism and mild hypothyroidism in all infants, but especially in those with DS.

Thyroid functions of neonates with Down syndrome

Background

We aimed to evaluate thyroid functions and volumes and detect abnormalities in 80 neonates with Down syndrome.

Methods

Data about free triiodothyronine, free thyroxine, thyroid stimulating hormone, thyroglobulin and urinary iodine levels, and ultrasonographic thyroid volume were collected.

Results

Abnormal thyroid function tests were detected in 53.8% of the patients (n = 50) and these were hyperthyrotropinemia, hypothyroidism, iodine deficiency and iodine overload in 32, 2, 12 and 4 patients, respectively. Thyroid volumes were assessed in 36 patients and a total of 17 abnormalities were detected (7 hypoplasia, 3 agenesis and 7 goiter). In patients with hyperthyrotropinemia mean thyroid volume was significantly greater and mean TSH was significantly higher when compared to the patients without hyperthyrotropinemia.

Conclusion

Neonatal screening by thyroid function tests in Down syndrome should be performed to prevent further intellectual deterioration and improve overall development. In the neonatal period, the risk of hyperthyrotropinemia should be kept in mind.