Serum free thyroxine concentration is not reduced in premature infants with respiratory distress syndrome

• Published in: The Journal of pediatrics Vol. 131; no. 3; pp. 489 - 492
• Main Authors: Job, Leela, Emery, Janet R., Hopper, Andrew O., Deming, Douglas D., Nystrom, Gerald A., Clark, Sudan J., Nelson, Jerald C.
• Format: Journal Article
• Language: English
• Published: New York, NY Mosby, Inc 01.09.1997; Elsevier
• Subjects: Anesthesia. Intensive care medicine. Transfusions. Cell therapy and gene therapy; Biological and medical sciences; Case-Control Studies; Dialysis; Emergency and intensive care: neonates and children. Prematurity. Sudden death; Female; Gestational Age; Humans; Infant, Newborn; Intensive care medicine; Male; Medical sciences; Pulmonary Surfactants - therapeutic use; Radioimmunoassay; Respiratory Distress Syndrome, Newborn - blood; Respiratory Distress Syndrome, Newborn - drug therapy; Thyrotropin - blood; Thyroxine - blood; Endocrinopathy; Human; Premature; False positive; Respiratory disease; Hypothalamohypophysothyroidal axis; Thyroid diseases; Medical screening; Hypothyroidism; Newborn; Postnatal; Thyroxine; Respiratory distress; Hormonal investigation
• ISSN: 0022-3476; 1097-6833
• DOI: 10.1016/S0022-3476(97)80087-X

We used improved methods of assay to determine whether pituitary-thyroidfunction is altered in premature infants with respiratory distress syndrome (RDS) during the first week of postnatal life. Serum free thyroxine (T 4) was measured by direct equilibrium dialysis, total thyroxine (TT 4) by radioimmunoassay, and thyrotropin by a sensitive immunometric assay in 90 premature infants (45 healthy control subjects and 45 with RDS) during their first week of life after 25 to 30 weeks of gestation. Infants in the RDS group received exogenous surfactant therapy. Free T 4 and thyrotropin concentrations of infants were not significantly differentbetween RDS and control groups. As expected, infants with RDS had significantly lower serum total T 4 concentrations compared with control infants (p < 0.001). This difference was present even after stratification for gestational age (25-to 27-week group, p = 0.012; 28-to 30-week group, p = 0.002). Lower total T 4 concentrations were attributable to lower T 4 binding to serum proteins among infants with RDS compared with control subjects, especially in the 25-to 27-week gestation group (p = 0.0075). These data indicate that pituitary-thyroid function is not altered in prematureinfants with RDS. The low total T 4 state in these premature infants is attributable solely to reduced serum T 4 binding, as is often seen in acute nonthyroidal illnesses.