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The role of transient hypothyroxinemia of prematurity in development of visual abilities
1Department of Psychology, University of Toronto, Toronto, Ontario, Canada. joanne.rovet@sickkids.ca
Insights
Transient hypothroxinemia of prematurity (THOP) may contribute to visual deficits in preterm infants. Lower thyroid hormone levels are linked to poorer visual attention, visuomotor skills, and vision in these vulnerable children.
Area of Science:
- Neonatal Medicine
- Developmental Neuroscience
- Ophthalmology
Background:
- Preterm birth increases the risk of visual impairment, but typical prematurity factors do not fully explain all deficits.
- Transient hypothroxinemia of prematurity (THOP), caused by interrupted maternal thyroid hormone supply, is common in preterm infants.
- Thyroid hormone is crucial for early brain development, including visual processing structures.
Purpose of the Study:
- To investigate the hypothesis that THOP contributes to visual impairments in preterm infants.
- To assess visual abilities in preterm infants with varying perinatal thyroid hormone levels.
Main Methods:
- Utilized clinical assessments and visual-evoked potential techniques.
- Measured thyroid hormone levels in two cohorts of preterm infants (23-35 weeks gestation).
- Evaluated visual attention, visuomotor abilities, contrast sensitivity, and color vision at corrected ages (3-18 months).
Main Results:
- In infants born 30-35 weeks gestation, low thyroid hormone levels correlated with reduced visual attention and visuomotor skills.
- In infants born 23-35 weeks gestation, THOP severity negatively correlated with attention, contrast sensitivity, and color vision.
- Findings indicate a link between thyroid hormone levels and visual development in preterm infants.
Conclusions:
- Thyroid hormone is essential for the development of early visual abilities.
- THOP may be a contributing factor to visual deficits observed in preterm infants.
- Further research into thyroid hormone's role in visual development is warranted.
Abstract:
Preterm birth is associated with an increased risk of visual impairment. However, not all visual deficits can be fully explained by the typical prematurity morbidity factors. In addition, children born preterm often exhibit transient hypothroxinemia of prematurity (THOP) due to premature severing of the maternal supply of thyroid hormones. Because thyroid hormone is critically needed for multiple facets of early brain development, including the structures needed for visual processing, and because the maternal thyroid supply is essential throughout pregnancy, it is possible that THOP contributes to the visual impairments seen in preterm children. To test this hypothesis, we used both clinical tests and visual-evoked potential techniques to assess visual abilities in two cohorts of preterm infants whose thyroid hormone levels were measured in the perinatal period. In the first cohort born 30 to 35 weeks gestation, we found associations between low thyroid hormone levels and reduced visual attention at 3 months corrected age (Study 1) and poor visuomotor abilities at 12 and 18 months corrected age (Study 2). In the second cohort born 23 to 35 weeks gestation, THOP severity was negatively correlated with attention at 3 months corrected age (Study 3) and contrast sensitivity and color vision at 6 months corrected age (Study 4). These findings therefore suggest that thyroid hormone is necessary for the development of early visual abilities and that THOP may partially explain the visual deficits of preterm infants.
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