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Development of contrast sensitivity in infants with prenatal and neonatal thyroid hormone insufficiencies
Giuseppe Mirabella1, Carol A Westall, Elizabeth Asztalos
1Department of Ophthalmology and Vision Science, The Hospital for Sick Children, Toronto, Ontario M5G 1X8, Canada.
Insights
Thyroid hormone is crucial for infant visual development. Insufficiencies during pregnancy and infancy led to reduced contrast sensitivity, highlighting the importance of thyroid hormone for vision.
Area of Science:
- Neuroscience
- Developmental Biology
- Endocrinology
Background:
- Thyroid hormone is vital for brain development, particularly visual processing structures.
- Animal models show impaired visual development with prenatal thyroid hormone deficiency.
- Human data on the impact of thyroid hormone insufficiency on infant visual development are lacking.
Purpose of the Study:
- To investigate the effects of intrauterine and early postnatal thyroid hormone insufficiencies on infant visual abilities.
- To assess contrast sensitivity and visual acuity in infants exposed to maternal hypothyroidism or congenital hypothyroidism.
- To compare visual development in at-risk infants with typically developing controls.
Main Methods:
- Sweep visual evoked potential (VEP) technique used to assess visual function.
- Evaluated infants with maternal hypothyroidism (HYPO), congenital hypothyroidism (CH), and preterm infants.
- Compared visual acuity and contrast sensitivity at 3, 4.5, and 6 months corrected age.
Main Results:
- Infants in the HYPO and CH groups exhibited significantly reduced contrast sensitivity compared to controls.
- Visual acuity was normal in both HYPO and CH groups.
- Lower contrast sensitivity was observed in HYPO infants with higher maternal TSH levels and in CH infants with absent thyroid glands or very high newborn TSH.
Conclusions:
- Thyroid hormone plays a critical role in the development of human visual function, specifically contrast sensitivity.
- Prenatal and early postnatal thyroid hormone insufficiency can compromise visual development.
- These findings underscore the importance of monitoring and managing thyroid hormone levels during pregnancy and infancy for optimal visual outcomes.
Abstract:
Thyroid hormone is essential for normal brain development including structures critical for visual processing. While chick and rodent models have demonstrated abnormal visual development following prenatal thyroid hormone loss, comparable data do not exist in the human. To determine whether human infants with intrauterine and early postnatal thyroid hormone insufficiencies have compromised visual abilities, we investigated contrast sensitivity and visual acuity development in 13 infant offspring of women with hypothyroidism during pregnancy (HYPO), 16 preterm infants born between 32 and 35 weeks gestation, 12 infants with congenital hypothyroidism (CH), and 20 typically developing infants. All were assessed with the sweep visual evoked potential technique at 3, 4.5, and 6 months (corrected) age. Results showed significantly reduced contrast sensitivity but normal visual acuity in HYPO and CH groups relative to controls (p < 0.003 and p < 0.05 respectively). Stratification of the HYPO group into subgroups based on maternal TSH levels during the first half of pregnancy revealed lower contrast sensitivities for infants whose mothers' TSH values were above than below the median (p < 0.05). In the CH group, those with an absent thyroid gland and/or a newborn TSH value above 200 mIU/L had lower contrast sensitivities than did those with other etiologies or TSH levels below 100 mIU/L (p < 0.05). There were no significant effects involving the preterm group. These results indicate that thyroid hormone is important for human visual development.
