Congenital hyperthyroidism: autopsy report

Implication of thyroid hormone signaling in neural crest cells migration: Evidence from thyroid hormone receptor beta knockdown and NH3 antagonist studies

Thyroid hormones (TH) have been mainly associated with post-embryonic development and adult homeostasis but few studies report direct experimental evidence for TH function at very early phases of embryogenesis. We assessed the outcome of altered TH signaling on early embryogenesis using the amphibian Xenopus as a model system. Precocious exposure to the TH antagonist NH-3 or impaired thyroid receptor beta function led to severe malformations related to neurocristopathies. These include pathologies with a broad spectrum of organ dysplasias arising from defects in embryonic neural crest cell (NCC) development. We identified a specific temporal window of sensitivity that encompasses the emergence of NCCs. Although the initial steps in NCC ontogenesis appeared unaffected, their migration properties were severely compromised both in vivo and in vitro. Our data describe a role for TH signaling in NCCs migration ability and suggest severe consequences of altered TH signaling during early phases of embryonic development.

Effects of thyroxine exposure on the Twist 1 +/- phenotype: A test of gene-environment interaction modeling for craniosynostosis

BACKGROUND

Craniosynostosis, the premature fusion of one or more of the cranial sutures, is estimated to occur in 1:1800 to 2500 births. Genetic murine models of craniosynostosis exist, but often imperfectly model human patients. Case, cohort, and surveillance studies have identified excess thyroid hormone as an agent that can either cause or exacerbate human cases of craniosynostosis.

METHODS

Here we investigate the influence of in utero and in vitro exogenous thyroid hormone exposure on a murine model of craniosynostosis, Twist 1 +/-.

RESULTS

By 15 days post-natal, there was evidence of coronal suture fusion in the Twist 1 +/- model, regardless of exposure. With the exception of craniofacial width, there were no significant effects of exposure; however, the Twist 1 +/- phenotype was significantly different from the wild-type control. Twist 1 +/- cranial suture cells did not respond to thyroxine treatment as measured by proliferation, osteogenic differentiation, and gene expression of osteogenic markers. However, treatment of these cells did result in modulation of thyroid associated gene expression.

CONCLUSION

Our findings suggest the phenotypic effects of the genetic mutation largely outweighed the effects of thyroxine exposure in the Twist 1 +/- model. These results highlight difficultly in experimentally modeling gene-environment interactions for craniosynostotic phenotypes. Birth Defects Research (Part A) 106:803-813, 2016. © 2016 Wiley Periodicals, Inc.

The association between neonatal thyroxine and craniosynostosis, Texas, 2004-2007

BACKGROUND

Craniosynostosis (CS), a structural anomaly characterized by premature fusion of cranial sutures, occurs in 1 in 2000 live births. Associations of CS with the thyroid have been reported. Neonatal thyroid hormone (T4) is evaluated nationally at birth by the Newborn Screening Program (NBS). This study evaluated the relationship between NBS T4 levels and craniosynostosis.

METHODS

Live-born singleton babies born in 2004 through 2007 were identified through the Texas Birth Defects Registry (499 cases) and Texas Bureau of Vital Statistics (3570 controls) and successfully linked to analyte data available in the Texas NBS Database. Cases were classified based on the absence of other major defects (isolated cases, n = 382) and suture(s) involved. Mean T4 levels were compared between controls and cases (overall and stratified by classification). T4 levels were stratified by quintiles to evaluate differences between cases and controls within quintiles. The diagnostic utility of NBS T4 was evaluated using receiver operator characteristic (ROC) curves.

RESULTS

Mean T4 levels were lower in isolated cases (16.89 μg/dl) than in controls (17.77 μg/dl; p = 0.0004). This trend persisted for sagittal (16.69 μg/dl; p = 0.002) and metopic (16.83 μg/dl; p = 0.042) CS. When stratified by quintiles, 54% of isolated lambdoid CS were in the first quintile compared to controls (p = 0.012). ROC area under the curve (AUC) was approximately 0.55 for all classifications except lambdoid (AUC = 0.73).

CONCLUSION

NBS T4 levels were slightly lower among cases with nearly half of all lambdoid CS having T4 levels in the lowest quintile. However, overall NBS T4 levels are not suitable for potential screening or diagnostic application.

Maternal thyroid disease, thyroid medication use, and selected birth defects in the National Birth Defects Prevention Study

BACKGROUND

Although thyroid disorders are present in approximately 3% of pregnant women, little is known about the association between maternal thyroid disease and birth defects.

METHODS

We assessed the association between maternal thyroid disease, thyroid medication use, and 38 types of birth defects among 14,067 cases and 5875 controls in the National Birth Defects Prevention Study, a multisite, population-based, case-control study. Infants in this study were born between October 1997 and December 2004. Information on exposures including maternal diseases and use of medications was collected by telephone interview.

RESULTS

We found statistically significant associations between maternal thyroid disease and left ventricular outflow tract obstruction heart defects (1.5; 95% CI, 1.0-2.3), hydrocephaly (2.9; 95% CI, 1.6-5.2), hypospadias (1.6; 95% CI, 1.0-2.5), and isolated anorectal atresia (2.4; 95% CI, 1.2-4.6). Estimates for the association between periconceptional use of thyroxine and specific types of birth defects were similar to estimates for any thyroid disease. Given that antithyroid medication use was rare, we could not adequately assess risks for their use for most case groups.

CONCLUSIONS

Our results are consistent with the positive associations between maternal thyroid disease or thyroid medication use and both hydrocephaly and hypospadias observed in some previous studies. New associations with left ventricular outflow tract obstruction heart defects and anorectal atresia may be chance findings.

Maternal thyroid disease as a risk factor for craniosynostosis

OBJECTIVE

To study the relationship between maternal thyroid disease and craniosynostosis using data from the National Birth Defects Prevention Study, a multisite, case-control study.

METHODS

Case infants (n=431) were identified through population-based birth defects surveillance systems at eight sites and had craniosynostosis verified by radiographic imaging. Control infants (n=4,094) consisted of a random sample of live births with no major birth defects from the same population as the case infants. Information on thyroid disease was based on self-report: mothers who reported either a thyroid disorder or use of a medication to treat a thyroid disorder during pregnancy were considered to have thyroid disease. Using an unconditional logistic regression model, we considered potential confounding factors (maternal age, race or ethnicity, smoking, body mass index, preexisting diabetes, plurality, gravidity, family history, infant sex).

RESULTS

Among case mothers, 19 (4.4%) were classified as having thyroid disease, compared with 65 (1.6%) of control mothers. Maternal thyroid disease was associated with craniosynostosis after controlling for maternal age (adjusted odds ratio 2.47, 95% confidence interval 1.46-4.18), the only factor that remained significant in the final model.

CONCLUSION

These data provide additional evidence that maternal thyroid disease (most likely Graves' disease) or its treatment is associated with craniosynostosis. Given the frequency of maternal thyroid disease, this association warrants further investigation.

LEVEL OF EVIDENCE

II.