Antenatal glucocorticoids increase early total thyroxine levels in premature infants.
BACKGROUND
Hypothyroxinemia is associated with adverse neonatal outcomes including white matter damage, cerebral palsy, poor neurodevelopment and death. It has become increasingly important to understand the natural history and modifiers of thyroid function in the premature infant. It is standard obstetrical practice to offer antenatal glucocorticoids to pregnant women with threatened preterm delivery. Few studies have investigated the effect of antenatal glucocorticoids on neonatal thyroid function.


OBJECTIVE
To examine the association between antenatal exposure to glucocorticoids and early total thyroxine (T4) levels among extremely premature infants.


METHODS
We studied 521 infants born at 4 medical centers. Entry criteria included a gestational age of 23-28 weeks and a serum thyroxine level obtained in the first postnatal week. Receipt of antenatal glucocorticoids was recorded as none, partial, or complete. A complete course consisted of two doses of betamethasone or four doses of dexamethasone within a 48-hour period between 2 and 7 days of delivery. Early total T4 levels were obtained from state-mandated newborn screening programs.


RESULTS
Controlling for potential maternal, perinatal and neonatal confounding variables, infants exposed to a complete course of antenatal glucocorticoids had total T4 levels 0.8 microg/dl higher than their peers who were not exposed to a complete course of antenatal glucocorticoids (p = 0.03).


CONCLUSIONS
Extremely premature infants who received a complete course of antenatal glucocorticoids had significantly higher total thyroxine levels in the first postnatal week. Maternal, perinatal, and early neonatal variables did not completely explain this association. We speculate that antenatal glucocorticoids influence early neonatal thyroid function.
Martin
Camilia R
CR
Department of Neonatology, Beth Israel Deaconess Medical Center, Division of Newborn Medicine, Boston, MA 02215, USA. cmartin1@bidmc.harvard.edu
Van Marter
Linda J
LJ
Allred
Elizabeth N
EN
Leviton
Alan
A
D000328:Adult; D015331:Cohort Studies; D005260:Female; D005865:Gestational Age; D005938:Glucocorticoids / Q000494:pharmacology*; D006801:Humans; D007231:Infant, Newborn; D007234:Infant, Premature / Q000097:blood*; D007407:Interviews as Topic; D016014:Linear Models; D018811:Maternal Exposure; D015999:Multivariate Analysis; D011247:Pregnancy; D012923:Social Class; D013974:Thyroxine / Q000097:blood*
D005938:Glucocorticoids; D013974:Thyroxine