Low serum thyroxine concentrations and neural maturation in preterm infants

Area of Science:

• Neonatalogy
• Endocrinology
• Neuroscience

Background:

• Thyroid hormones are crucial for neurodevelopment.
• Very low birthweight infants are at risk for thyroid dysfunction.
• Postnatal progression of motor nerve conduction velocity (NCV) is a marker of neurological development.

Purpose of the Study:

• To investigate the effect of hypothyroxinaemia on the postnatal progression of motor nerve conduction velocity in very low birthweight infants.
• To determine the relationship between thyroid hormone concentrations and motor NCV development.

Main Methods:

• Serum thyroid stimulating hormone, triiodothyronine, and thyroxine levels were measured in 33 very low birthweight infants at birth and on days 3, 7, and 21.
• Motor nerve conduction velocity was assessed in the first week, on day 21, and at 40 weeks' postmenstrual age.
• Infants were categorized based on thyroxine concentrations (≥60 nmol/l vs. <60 nmol/l).

Main Results:

• Twenty-six infants developed hypothyroxinaemia (thyroxine <60 nmol/l).
• Motor nerve conduction velocity was delayed in 13 infants (all with hypothyroxinaemia), with delays noted on day 21 and at 40 weeks' postmenstrual age.
• The delay in NCV progression was associated with prolonged hypothyroxinaemia, especially in infants requiring mechanical ventilation.

Conclusions:

• Hypothyroxinaemia is associated with delayed motor nerve conduction velocity progression in very low birthweight infants.
• Prolonged low thyroid hormone levels, particularly in ventilated infants, negatively impact nerve conduction velocity development.
• Further research is warranted to elucidate the role of thyroid hormone in preterm infant nerve conduction velocity.