Risk factors of hypothyroxinemia in premature infants

Abstract

Background: Hypothyroxinemia is defined by low levels of thyroxine (T4) despite low or normal levels of thyroid-stimulating hormone (TSH). This study aimed to evaluate the risk factors associated with transient hypothyroxinemia (THOP) in premature newborn.Method: This is a single center, retrospective, case-control study. Premature newborns, between 24-34 weeks of gestation, hospitalised between January 2014-December 2019 in our Newborn Intensive Care Unit (NICU) were analyzed through their medical records. Thyroid function tests were routinely performed between the 10th and 20th days of postnatal life and were evaluated according to the gestational age references. Thirty six risk factors (prenatal and postnatal parameters, medical treatments, clinical diagnoses and applications in NICU) were searched in the patient group with THOP (n=71) and the control group with euthyroid prematures (n=73). The risk factors for THOP were identified by univariate analysis, followed by multivariate analysis. Results: Mean gestational ages of the study and the control groups were 29.7 ± 2.48 and 30.5 ± 2.30 weeks, respectively (p = 0.606). The birth weight, small for gestational age (SGA), intraventricular hemorrhage (IVH), congenital heart disease (CHD) were found to be the risk factors for THOP in the univariate analysis and CHD (p=0.033, odds ratio [OR]:3.7, 95% confidence interval [CI]: 1.1-12.3), BW (p=0.012, OR:0.998, 95% CI: 0.9-1.01) and SGA (p=0.006, OR:5.3, 95% CI: 1.6-17.71) were found to be an independent risk factor for THOP as a result of the multivariate analysis.Conclusıons: Although some treatment practices might have had direct effects on pituitary–thyroid axis, associated with the severity of the newborn clinical conditions, non of them was found to be a risk factor for THOP. However, preterm babies with CHD and SGA could have more risk for THOP.