Intellectual outcome, motor skills and BMI of children with congenital hypothyroidism: a population-based study

Thyroid Deficiency Before Birth Alters the Adipose Transcriptome to Promote Overgrowth of White Adipose Tissue and Impair Thermogenic Capacity

Background: Development of adipose tissue before birth is essential for energy storage and thermoregulation in the neonate and for cardiometabolic health in later life. Thyroid hormones are important regulators of growth and maturation in fetal tissues. Offspring hypothyroid in utero are poorly adapted to regulate body temperature at birth and are at risk of becoming obese and insulin resistant in childhood. The mechanisms by which thyroid hormones regulate the growth and development of adipose tissue in the fetus, however, are unclear. Methods: This study examined the structure, transcriptome, and protein expression of perirenal adipose tissue (PAT) in a fetal sheep model of thyroid hormone deficiency during late gestation. Proportions of unilocular (UL) (white) and multilocular (ML) (brown) adipocytes, and UL adipocyte size, were assessed by histological and stereological techniques. Changes to the adipose transcriptome were investigated by RNA sequencing and bioinformatic analysis, and proteins of interest were quantified by Western blotting. Results: Hypothyroidism in utero resulted in elevated plasma insulin and leptin concentrations and overgrowth of PAT in the fetus, specifically due to hyperplasia and hypertrophy of UL adipocytes with no change in ML adipocyte mass. RNA sequencing and genomic analyses showed that thyroid deficiency affected 34% of the genes identified in fetal adipose tissue. Enriched Kyoto Encyclopedia of Genes and Genomes (KEGG) and Gene Ontology (GO) pathways were associated with adipogenic, metabolic, and thermoregulatory processes, insulin resistance, and a range of endocrine and adipocytokine signaling pathways. Adipose protein levels of signaling molecules, including phosphorylated S6-kinase (pS6K), glucose transporter isoform 4 (GLUT4), and peroxisome proliferator-activated receptor γ (PPARγ), were increased by fetal hypothyroidism. Fetal thyroid deficiency decreased uncoupling protein 1 (UCP1) protein and mRNA content, and UCP1 thermogenic capacity without any change in ML adipocyte mass. Conclusions: Growth and development of adipose tissue before birth is sensitive to thyroid hormone status in utero. Changes to the adipose transcriptome and phenotype observed in the hypothyroid fetus may have consequences for neonatal survival and the risk of obesity and metabolic dysfunction in later life.

[Newborn screening: a prime example for effective secondary prevention]

Newborn screening is a medical population-based preventive measure for the early detection and initiation of therapy for all newborns with treatable endocrine and metabolic diseases. Left untreated, these diseases may lead to severe disabilities or even death. Target diseases have to meet the Wilson and Junger criteria on screening. A high sensitivity and specificity is ensured by an excellent analytic process. High process quality is achieved by offering newborn screening to all newborns and by clarifying pathologic findings very quickly. Therefore, in some federal states tracking centers have been established. Nationwide evaluation of process quality is annually performed and published online. The long-term outcome of diseased children has been investigated on a population-based level in Bavaria and at the University of Heidelberg in other studies. Between 2004 and 2012, 6.1 million children were screened (this is equivalent to 99 % of all newborns). The percentage of pathologic findings was 0.6 %. One out of 1300 children was affected by a target disease. For 90 % of these children, therapy started within the first 2 weeks of life. Studies on the long-term outcome show a positive effect on the course of disease, development of children, and the quality of life. In these studies, further challenges in care such as the first information given to parents regarding a pathologic finding or the care of adolescents with less compliance could also be identified. Newborn screening is an established preventive measure. With regard to ethical criteria and effectiveness, continuous evaluation of the process quality and the long-term outcome assure a high quality of the screening process.

Impaired neuromotor outcome in school-age children with congenital hypothyroidism receiving early high-dose substitution treatment

Congenital hypothyroidism (CH) can lead to intellectual deficits despite early high-dose treatment. Our study aimed to determine whether motor impairments can occur despite early high-dose treatment. Sixty-three children with CH and early (median age of onset of treatment 9 d), high-dose treatment (median starting dose of levothyroxine 14.7 μg/kg/d) were tested with the Zurich Neuromotor Assessment (ZNA) at a median age of 13.8 y (range 7.0-14.2 y). Median z-scores in the children with CH were -0.95 in the pure and -0.56 in the adaptive fine motor component, significantly lower than in the ZNA test norms (p < 0.001 and p = 0.01, respectively). The 26 children with athyreosis were more affected than the 33 children with dysgenesis, particularly in the pure motor (-1.55 versus -0.76, p = 0.03), adaptive fine motor (-1.31 versus 0.13, p < 0.01), and static balance task (-0.47 versus 0.67, p = 0.01). Boys performed worse than girls. Older age at onset of treatment was related to poorer adaptive fine motor performance. Movement quality (assessed by associated movements) was not affected. We conclude that severe CH can cause neuromotor deficits persisting into adolescence. These deficits cannot completely be reversed by postnatal treatment, but earlier age at treatment may reduce the degree of impairment.

Fetal and neonatal thyroid function: review and summary of significant new findings

PURPOSE OF REVIEW

The purpose of this review is to briefly summarize current knowledge of fetal and neonatal thyroid function, and then to summarize the most significant new findings over the last year that add to our knowledge of the cause, diagnosis, and management of fetal and neonatal thyroid disorders.

RECENT FINDINGS

Significant findings from publications in the last year include a report that inadequate iodine intake during pregnancy exists in many parts of the world. Conversely, maternal exposure to iodinated contrast agents did not affect neonatal thyroid function. A small lowering in the screening of thyroid-stimulating hormone cutoff resulted in nearly a doubling of the birth prevalence of congenital hypothyroidism, but more cases had a thyroid gland 'in situ'. Partial iodination defects are relatively common causes of dyshormonogenesis. Tailoring the initial starting levothyroxine dose to severity of hypothyroidism resulted in rapid normalization of thyroid function. Although consensus guidelines recommend an initial starting dose in the 10-15-mug/kg/day range, the Cochrane collaborative did not find sufficient evidence from randomized controlled trials to confirm the high-dose recommendation. Under or overtreatment of childhood hypothyroidism appears to adversely impact adult cardiovascular function. Adults with congenital hypothyroidism are more likely to have quality of life issues.

SUMMARY

Investigations of the impact of iodine and thyroid hormone transfer continue to improve our knowledge of maternal-fetal thyroid relationships. Screening programs to detect and treat newborns with congenital hypothyroidism have resulted in a dramatic improvement in neurocognitive outcome. Nevertheless, debate continues on the optimal screening test approach and thyroid hormone treatment.