Do the Infant Respiratory Distress Syndrome and Presumed Sepsis affect Thyroid Function in Preterm Newborns within the First 10 Days of Life?

Objectives: To investigated whether Preterm Infants (PI) who develop IRDS and/or sepsis in the first 10 days of life exhibit changes in thyroid function. Method: Prospective, longitudinal cohort study included all PI admitted and who required NICU for more than 48 hours and remained hospitalized for 10 days or more, that were divided into four groups: 1. No IRDS orsepsis (CG); 2. With IRDS (IG); 3. With Presumed Sepsis (SG); and 4. With both IRDS and presumed sepsis (ISG). The odds that both TSH and T4 levels would be abnormal, the odds that TSH levels alone would be abnormal (with normal T4), and the odds that T4 concentrations would be abnormal (with normal TSH) at days 3 and 10 of life, as a function of Gestational Age (GA), birth weight, 5-minute Apgar score, presence of IRDS, presence of early-onset sepsis, or presence of both IRDS and sepsis were estimated by stepwise backward regression analysis. Results: Eighty-three PI (22 in CG, 25 in IG, 21 in SG, and 15 in ISG) were included in the study. The odds that TSH and free T4 concentrations would be abnormal on the day 3 of life in PI may be associated with GA and presumed sepsis, but not on the day 10 of life. GA, 5-minute Apgar score, and sepsis were factors capable of altering TSH concentrations on the day 3 of life, with a particular role of Apgar score, but not on the day 10 of life. Free T4 would be abnormal on day 3 and day 10 of life were influenced by GA. Conclusion: PI who had a low 5-minute Apgar score and developed or are suspected to have developed neonatal sepsis, measurement of TSH and T4 concentrations should be postponed until after the day 10 of life, so as to prevent false-positive results of thyroid hormone assessment.