Impact of Maternal Thyroid Function During Pregnancy on Adolescent Brain Microstructure

Overview

This study demonstrates that untreated suboptimal gestational thyroid function (SGTF) is associated with altered white matter microstructure in adolescents, specifically increased mean diffusivity in the inferior longitudinal fasciculus. Levothyroxine treatment during pregnancy may reverse these microstructural changes, highlighting the importance of maternal thyroid management.

Background

Thyroid hormones are critical for fetal neurodevelopment, with overt maternal hypothyroidism linked to severe neurological deficits. The effects of milder, suboptimal gestational thyroid function (SGTF) on brain development are less clear but have been associated with adverse neurobehavioral outcomes such as ADHD. Animal studies suggest thyroid hormone deficiency disrupts neuronal differentiation and myelination, particularly affecting white matter. Advanced neuroimaging techniques like diffusion MRI and quantitative magnetization transfer imaging enable detailed assessment of white matter microstructure and myelin content in humans.

Data Highlights

Key Findings

• Untreated SGTF in pregnancy is linked to increased mean diffusivity in the inferior longitudinal fasciculus in adolescents, indicating reduced axonal integrity.
• Levothyroxine treatment during pregnancy appears to normalize white matter microstructure in children of mothers with SGTF.
• No significant differences in brain macrostructure were observed between groups, suggesting microstructural changes are more sensitive markers.
• Secondary analyses did not find robust associations between maternal thyroid hormone levels and white matter microstructure after multiple comparison corrections.
• No clear relationship was established between white matter microstructure and ADHD symptom scores in this cohort.

Clinical Implications

These findings underscore the importance of screening and treating suboptimal thyroid function during pregnancy to potentially prevent subtle but significant alterations in offspring brain white matter microstructure. Levothyroxine supplementation may mitigate risks associated with untreated SGTF, supporting current clinical guidelines for thyroid management in pregnancy. Further monitoring of neurodevelopmental outcomes in children exposed to SGTF is warranted.

Conclusion

Untreated suboptimal gestational thyroid function is associated with specific alterations in adolescent white matter microstructure, which may be reversible with appropriate levothyroxine treatment during pregnancy. This highlights the critical role of maternal thyroid health in fetal brain development.

References

1. Controlled Antenatal Thyroid Screening Study III -- Impact of Maternal Thyroid Function During Pregnancy on Adolescent Brain Microstructure