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Thyroid function in preterm infants 27-29 weeks of gestational age during the first four months of life: results from
María Clemente1, Pilar Ruiz-Cuevas, Antonio Carrascosa
1Pediatric Endocrine Service, Children's Hospital Vall d'Hebron, Autonomous University of Barcelona, Spain. mclement@vhebron.net
Insights
Thyroid function in very preterm neonates (27-29 weeks) is affected by prematurity and illness. Individual assessment is crucial during the first two months of life for these infants.
Area of Science:
- Neonatal endocrinology
- Perinatal medicine
- Thyroid physiology
Background:
- Thyroid function assessment is critical in preterm neonates (PTN).
- Understanding thyroid hormone dynamics in extremely preterm infants (27-29 weeks gestational age) is essential for clinical management.
- Previous studies have established thyroid function norms for later preterm infants (30-35 weeks).
Purpose of the Study:
- To assess thyroid function in preterm neonates born between 27-29 weeks of gestational age.
- To compare thyroid hormone levels between healthy and sick PTN within this gestational age range.
- To establish reference ranges for thyroid hormones in early preterm infants.
Main Methods:
- Studied 80 preterm neonates (27-29 weeks gestational age), categorized as healthy (n=17) or sick (n=63).
- Measured serum TSH, free T4, T4, T3, and rT3 in mothers, cord blood, and infants at multiple postnatal time points (1 hour to 4 months).
- Compared findings with previously evaluated healthy PTN of 30-35 weeks gestational age.
Main Results:
- TSH peaked at 1 hour and declined in both healthy and sick PTN.
- Healthy PTN showed a free T4 peak at 24 hours, absent in sick neonates.
- Sick PTN exhibited lower TSH and free T4 levels at 24 hours and 1 week compared to healthy PTN (p < 0.05).
- Healthy PTN (27-29 weeks) had lower TSH peaks and hormone levels in the first two months than PTN (30-35 weeks), but remained above -2 SD of controls.
- A significant proportion of sick PTN showed free T4 values above -2 SD of healthy PTN (30-35 weeks) controls at later time points.
Conclusions:
- Prematurity and illness significantly influence thyroid function in preterm neonates (27-29 weeks).
- Individualized thyroid function assessment is necessary for these infants, particularly during the first two months of life.
- The study highlights the variability of thyroid hormone levels in sick preterm infants.
Aim:
Assessment of thyroid function in preterm neonates (PTN) 27-29 weeks of gestational age.
Patients And Methods:
80 PTN, gestational age 27 weeks in 24, 28 weeks in 28, and 29 weeks in 28. Neonates were classified as healthy (n=17) or sick (n=63). Measurement of serum TSH, free T4, T4, T3 and rT3 in the mother and in the cord at the time of delivery, and in the infant at 1 hour, 24 hours, 1 week, 3 weeks, and 2 and 4 months of postnatal age.
Results:
In healthy and sick preterms, TSH values peaked at 1 hour and decreased thereafter. Healthy PTN presented a peak in free T4 values at 24 hours that was not observed in sick neonates. Sick PTN had a lower TSH peak and lower free T4 values at 24 hours and 1 week than healthy ones (p < 0.05). Healthy PTN 27-29 weeks had lower TSH peak at 1 hour and lower free T4, T3 and T4 values during the first 2 months than healthy PTN 30-35 weeks (PTN30-35w) previously evaluated (p < 0.05). However, at all postnatal times healthy preterms had free T4 values above -2 SD of the mean values of healthy PTN30-35w. A wide range of free T4 values was observed in the sick group. Free T4 values above -2 SD of the mean values of healthy PTN30-35w were detected in a high proportion of sick PTN (58.3% at 24 hours, 73.5% at 1 week, 93.9% at 3 weeks, 85.1% at 2 months and 100% at 4 months).
Conclusions:
Prematurity and disease influence thyroid function, and consequently thyroid function should be individually assessed in preterms 27-29 weeks of gestation during the first 2 months of life.
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