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Hypothyroxinemia of prematurity and infant neurodevelopment: a pilot study
G Ishaik1, E Asztalos, K Perlman
1Department of Psychology, University of Waterloo, Canada.
Insights
Mildly low thyroxine (T4) levels in preterm infants are linked to poorer neurodevelopment. This study shows lower T4 at 40 weeks postconceptional age predicts challenges in attention and motor skills.
Area of Science:
- Neonatalogy
- Neurodevelopmental Pediatrics
- Endocrinology
Background:
- Premature infants face neurodevelopmental risks.
- Thyroid hormone levels are crucial for infant brain development.
- The impact of mild hypothyroxinemia in preterm infants requires further investigation.
Purpose of the Study:
- To investigate the specific effects of hypothyroxinemia on neurodevelopment in premature infants.
- To correlate thyroid hormone levels at different postconceptional ages with developmental outcomes.
Main Methods:
- Thyroid hormone levels (free T4 and total T4) were measured at 2 weeks and 40 weeks postconceptional age (PCA).
- Neurodevelopment was assessed at 3 months corrected age using the Bayley Scales of Infant Development and the Early Infancy Temperament Questionnaire.
- Fifteen preterm infants (30-35 weeks gestation) and 21 full-term infants were studied.
Main Results:
- Preterm infants exhibited lower sensory thresholds and greater reactivity compared to full-term infants.
- Thyroxine levels declined in preterm infants by 40 weeks PCA.
- Higher free T4 at 40 weeks PCA correlated with better attentiveness and sustained attention.
- Higher total T4 at 40 weeks PCA correlated with better motor skills.
Conclusions:
- Mild hypothyroxinemia is present in preterm infants without neurological risk.
- This condition predicts poorer cognitive and motor abilities in later development.
- Thyroid hormone monitoring in preterm infants may be important for predicting neurodevelopmental outcomes.
Abstract:
To assess whether hypothyroxinemia has specific effects on neurodevelopment in premature infants, thyroid hormone levels were determined at 2 weeks of life and 40 weeks postconceptional age (PCA), and infants were evaluated at 3 months corrected age using the Bayley Scales of Infant Development and Early Infancy Temperament Questionnaire. Additional attention scales were derived from the factor analysis of relevant Bayley items. Fifteen infants born between 30 and 35 weeks and 21 full-term infants were studied. Results indicated no group differences on the Bayley or derived attention scales, whereas the temperament questionnaire revealed lower sensory thresholds and greater reactivity in the preterm group. The preterm group had normal thyroxine (T4) levels at 2 weeks of age, which declined by 40 weeks PCA for both free T4 (p < .01 for reference value and p < .0001 for gestational age-adjusted value) and total T4 (p < .05 for age-adjusted value). Correlations revealed that higher 40-week PCA free T4 levels were associated with better attentiveness ratings (p < .01 for reference and p < .0001 for gestational-age values) and sustained attention (p < .05) and higher 40-week total T4 with better motor skills (p < .05 for gestational-age value). These findings signify that a mild degree of hypothyroxinemia is evident in preterm infants without neurological risk and predicts subsequently poorer cognitive and motor abilities.