Abstract
BackgroundTo determine the incidence, etiology, and outcomes of thyroid-stimulating hormone (TSH) elevation in extremely low-birth-weight infants (ELBWIs).MethodsNewborn thyroid screening data of 584 ELBWIs (birth weight, < 1000 g; gestational age, ≥ 23 weeks) were retrospectively analyzed to identify initial (≤ 2 postnatal weeks) and delayed (> 2 weeks) TSH elevations. Growth and neurodevelopmental outcomes at 2 years’ corrected age (CA) were assessed according to levothyroxine replacement.ResultsInitial and delayed TSH elevations were detected at CAs of 27 and 30 weeks, respectively, with incidence rates of 0.9 and 7.2%, respectively. All infants with initial TSH elevations had perinatal asphyxia, and 95% of those with delayed TSH elevation were exposed to various stressors, including respiratory support, drugs, and surgery within 2 weeks before diagnosis of TSH elevation. Free thyroxine (T4) levels were simultaneously reduced in 80 and 57% of infants with initial and delayed TSH elevations, respectively. Both initial and delayed TSH elevations were transient, regardless of levothyroxine replacement. Infants receiving levothyroxine replacement therapy had significantly higher TSH elevations, significantly lower free T4 levels, and significantly reduced mortality, compared to untreated infants. However, levothyroxine replacement had no significant effect on long-term growth and neurodevelopmental outcomes.ConclusionsThe timing of insult superimposition on hypothalamic–pituitary–thyroid axis maturation is a major determinant of initial or delayed TSH elevation in ELBWIs. Levothyroxine replacement did not affect growth or neurodevelopmental outcomes in this population.
Highlights
To determine the incidence, etiology, and outcomes of thyroid-stimulating hormone (TSH) elevation in extremely low-birth-weight infants (ELBWIs)
We retrospectively reviewed the medical records of 584 ELBWIs with gestational ages (GAs) of ≥23 weeks who were born at and admitted to the Samsung Medical Center neonatal intensive care unit between January 2000 and July 2013, and for whom the results of initial thyroid function tests (TFTs) performed within the first 2 postnatal weeks were available
Of the 328 infants with initially lower T4 or free T4 (fT4) levels and normal TSH levels, 39 developed delayed TSH elevation according to the subsequent TFT results
Summary
Etiology, and outcomes of thyroid-stimulating hormone (TSH) elevation in extremely low-birth-weight infants (ELBWIs). Thyroid-stimulating hormone (TSH) level is the preferred screening marker for the identification of infants with congenital hypothyroidism. It remains difficult to interpret TSH levels in extremely low-birth-weight infants (ELBWIs),. Given the paucity of relevant clinical information, many factors remain unclear, including the true incidence of initial and delayed TSH elevation among ELBWIs, the clinical association of this condition with NTI, and the ability of thyroxine supplementation to improve outcomes in these cases. The present retrospective observational study primarily aimed to determine the incidence of initial and delayed TSH elevation in ELBWIs. Secondarily, this study aimed to assess the clinical association of TSH elevation with NTI and to examine the effect of thyroxine supplementation on the growth, neurodevelopmental, and endocrine outcomes of ELBWIs at the corrected age (CA) of 2 years
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