Are Preterm Newborns Who Have Relative Hyperthyrotropinemia at Increased Risk of Brain Damage?

Abstract

Background We sought to disentangle the contributions of hyperthyrotropinemia (an indicator of thyroid dysfunction) (HTT) and intermittent or sustained systemic inflammation (ISSI) to structural and functional indicators of brain damage. Methods We measured the concentrations of TSH on day 14, and of 25 inflammation-related proteins in blood collected during the first 2 postnatal weeks from 786 infants born before the 28th week of gestation who were not considered to have hypothyroidism. We defined hyperthyrotropinemia (HTT) as a TSH concentration in the highest quartile for gestational age on postnatal day 14 and ISSI was defined as a concentration in the top quartile for gestational age of a specific inflammation-related protein on two separate days a week apart during the first two postnatal weeks. We first assessed the risk of brain damage indicators comparing 1) neonates who had HTT to those without (regardless of ISSI), and 2) neonates with HTT only, ISSI only, or HTT+ ISSI, to those who were exposed to neither HTT nor ISSI. HTT was defined as a TSH concentration in the highest quartile for gestational age on postnatal day 14. Results In univariable models that compared those with HTT to those without, HTT was not significantly associated with any indicator of brain damage. In models that compared HTT only, ISSI only, and HTT+ISSI, to those with neither, children with ISSI only or with HTT+ISSI were at significantly higher risk of ventriculomegaly [odds ratios (OR) ranged from 2–6], while those with HTT only were at significantly reduced risk of a hypoechoic lesion [ORs ranged from 0.2–0.4]. Children with HTT only had a higher risk of quadriparesis and those with ISSI alone had a higher risk of hemiparesis [ORs ranged from 1.6–2.4]. Elevated risk of a very low mental development score was associated with both ISSI only and with HTT+ISSI while a very low motor development score and microcephaly were associated with HTT+ISSI. Conclusions The association of HTT with increased or decreased risk of indicators of brain damage depends upon the presence or absence of ISSI.