Admission Thyroid Evaluation in Very-Low-Birth-Weight Infants: Association with Death and Severe Intraventricular Hemorrhage

Abstract

Objectives

: To determine if thyroxine (T₄) and thyrotropin (TSH) levels, measured at the time of admission to the neonatal intensive care unit, are associated with the outcomes of death and/or severe intraventricular hemorrhage (IVH).

Study design

: Blood for total T₄ and TSH was obtained upon admission to the neonatal intensive care unit in infants with birthweights less than 1500 g. Infants were followed until hospital discharge. Statistical analysis included one-way analysis of variance, Pearson correlation, and logistic regression. Data are expressed as mean ± standard deviation (SD).

Results

: One hundred twenty-two infants were enrolled. The mean gestational age of the study population was 27 ± 2.8 weeks. Both T₄ (R = 0.25,p < 0.01) and TSH (R = 0.39, p < 0.01) at the time of admission correlated with gestational age. Infants who died and/or had severe IVH (n = 31) had lower T₄(5.0 ± 2.1 vs. 8.4 ± 4.1 μg/dL, p < 0.01) and lower TSH (5.5 ± 6.0 vs. 18.1 ± 18.1 μIU/mL, p = 0.03) at the time of admission compared to infants who survived without severe IVH. After controlling for gestational age, low T₄ remained associated with an increased odds of death and/or severe IVH (odds ratio for every 1 μg/dL decrease in T₄: 1.4, 95% confidence interval 1.1-1.7).

Conclusions: Our data show that both low total T₄ and TSH, measured at the time of nursery admission, are associated with death and severe intraventricular hemorrhage. Our data suggest that it may be feasible to design a study of early T₄ supplementation to determine potential benefit in infants with the lowest T₄ values rather than treating based on associated factors such as gestational age.